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The Sonographic Posterolateral Rotatory Stress Test for Elbow Instability: A Cadaveric Validation Study
Accepted Manuscript The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric Validation Study Christopher L. Camp, MD, Shawn W. O’Driscoll, MD PhD, Michael K. Wempe, MD, Jay Smith, MD PII:
S1934-1482(16)30193-9
DOI:
10.1016/j.pmrj.2016.06.014
Reference:
PMRJ 1728
To appear in:
PM&R
Received Date: 24 February 2016 Revised Date:
16 May 2016
Accepted Date: 8 June 2016
Please cite this article as: Camp CL, O’Driscoll SW, Wempe MK, Smith J, The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric Validation Study, PM&R (2016), doi: 10.1016/j.pmrj.2016.06.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric Validation Study
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Christopher L. Camp, MD* Shawn W. O’Driscoll, MD PhD* ¥ Michael K. Wempe, MD ∑ Jay Smith, MD †
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From *Department of Orthopedic Surgery and the Sports Medicine Center, Mayo Clinic, Rochester, Minnesota, U.S.A. ¥ Department of Physical Medicine and Rehabilitation, Nebraska Medical Center, Omaha, NE U.S.A. ∑ Department of Physical Medicine and Rehabilitation, Radiology, and Anatomy, Mayo Clinic, College of Medicine, Rochester, Minnesota, U.S.A.
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†Address correspondence to Jay Smith, M.D. Department of Physical Medicine and Rehabilitation Mayo Clinic 200 First St., SW Rochester MN 55905 Ph: 507-284-2012 Fax: 507-266-1803 [email protected]
Source of Funding: This work was funded in its entirety by internal research funds.
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Device Status: This study does not rely on the usage of any medical devices or instruments that are not approved by the FDA This material was not presented at an AAPM&R Annual Assembly
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ACCEPTED MANUSCRIPT PLRI Ultrasound Evaluation of the Elbow
The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric Validation Study
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Source of Funding: This work was funded in its entirety by internal research funds. Device Status: This study does not rely on the usage of any medical devices or instruments that are not approved by the FDA
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This material was not presented at an AAPM&R Annual Assembly
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The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric
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Validation Study Abstract:
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Background: Although clinical tests can detect posterolateral rotatory instability (PLRI) of the elbow, the
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ability of ultrasound (US) to evaluate PLRI has not been assessed.
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Objective: To determine whether increasing stages of posterolateral rotatory subluxation of the elbow
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could be assessed accurately with a sonographic posterolateral rotatory stress test.
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Design: Cadaveric Study
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Setting: Laboratory
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Patients: Ten, unpaired, cadaveric upper limbs
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Methods: Posterolateral ulnohumeral distance was measured by US at rest and during manual
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sonographic posterolateral rotatory stress testing at four stages of increasing instability: 1) Intact elbow,
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2) Extensor carpi radialis brevis (ECRB) release, 3) ECRB release + Lateral collateral ligament complex
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(LCLC) release to produce a positive posterolateral drawer test, and 4) ECRB release + LCLC and capsule
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release to produce a positive lateral pivot-shift test. Mean values for sonographic resting ulnohumeral
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distance, stressed ulnohumeral distance and laxity were calculated for each stage and compared between
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stages.
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Main Outcome Measures: Posterolateral ulnohumeral laxity
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Results: Mean ulnohumeral laxities were 1, 3, 6 and 10 mm (p<.001) for stages 1-4, respectively. Pairwise
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comparison of mean laxity between the intact elbow (Stage 1) and each pathologic state (Stages 2-4)
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demonstrated differences of 2 mm (Stage 1 vs. 2); 5 mm (Stage 1 vs. 3); and 9 mm (Stage 1 vs. 4)(p<.001).
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The minimal difference in ulnohumeral laxity noted between the intact elbow and an elbow with a
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clinically positive posterolateral rotatory drawer test (Stage 3) was 4 mm.
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Discussion and Conclusions: The sonographic posterolateral rotatory stress test detected increasing
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posterolateral ulnohumeral laxity as a function of increasing clinical PLRI. This test may be used as an
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adjunct to history, examination, and static imaging to assess ulnohumeral laxity in patients with lateral
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elbow pain syndromes. Within the limits of this investigation, sonographic posterolateral ulnohumeral
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laxity of >4 mm should raise suspicion of underlying instability.
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Key Terms: posterolateral rotatory instability, ultrasound, elbow, sonographic posterolateral rotatory
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stress test
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INTRODUCTION Since its initial description in 1991, posterolateral rotatory instability (PLRI) of the elbow has become increasingly recognized as a source of elbow pain and dysfunction.[1] PLRI is the most common
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pattern of elbow instability and typically occurs following a fall onto the outstretched arm during which
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the elbow sustains axial compression, flexion, and valgus torques.[1–3] Although the proximal radioulnar
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joint remains congruent (secondary to the annular ligament), the radial head and ulna collectively rotate
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off the distal humerus in a posterolateral direction.[1] The injury is thought to be more likely to occur with
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the forearm in the supinated position, but it is the ulna and radius in combination that roll off the distal
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humerus rather than the radius supinating in relation to the ulna. Increasing subluxation results in
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sequential disruption, starting laterally with the lateral collateral ligament complex, followed by the
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common extensor tendons, then progressing around anteriorly and posteriorly to involve the capsule and
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eventually part or all of the medial collateral ligament if the elbow dislocates fully.[4] In addition to
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traumatic injury, PLRI can occur secondary to lateral soft tissue attenuation as seen in patients with
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severe common extensor tendinopathy (i.e. “tennis elbow”) or longstanding cubitus varus, or due to
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iatrogenic injury following lateral sided elbow surgery.[5,6] A number of physical examination tests have
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been described to aid in the diagnosis of PLRI, the most well-studied being the posterolateral rotatory
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drawer and lateral pivot-shift tests.[1,7] Although both are valuable examination maneuvers that are
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highly specific for PLRI, the sensitivity of each test is somewhat dependent upon the examiner.[1,7]
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Despite the increased awareness of PLRI, confirming the diagnosis can be difficult based on history and physical exam alone if the examiner is not familiar with the condition and experienced with
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the clinical maneuvers. X-rays may demonstrate associated findings, such as bony avulsions or coronoid
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tip fractures, but are generally not helpful in establishing the diagnosis. Magnetic resonance imaging
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(MRI) can detect lateral collateral ligament complex (LCLC) injuries, but the sensitivity of MRI to detect all
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LCLC injuries has been questioned.[8] Furthermore, as a static test, MRI cannot confirm PLRI in the clinical
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setting. Although dynamic fluoroscopy can be a useful adjunct to detect PLRI, it does not permit soft
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tissue evaluation and exposes the patient and operator to radiation.[9]
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Ultrasound provides a unique combination of high resolution soft tissue imaging, dynamic
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capabilities, portability, lack of radiation exposure, immediacy of results, reduced costs compared to other
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modalities, and lack of contraindications.[9] In recent, years the role of musculoskeletal US (MSK US) in
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sports and musculoskeletal medicine has continued to expand. Multiple studies have documented the
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ability of MSK US to image the soft tissue and bony structures about the lateral elbow, as well as assist in
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the diagnosis and management of lateral elbow disorders affecting the common extensor tendon,
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radiocapitellar joint, and posterior interosseous nerve.[10–12] Although previous studies have reported
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on the sonographic evaluation of the lateral elbow ligaments in both cadavers and healthy volunteers, the
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ability of US to identify PLRI has not been formally investigated.[13–15] In the clinical setting, the authors
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have observed sonographically detectable posterolateral ulnohumeral widening in patients with clinical
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PLRI during posterolateral rotatory stress testing. However, this “sonographic posterolateral rotatory
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stress test” has not been formally evaluated or validated. Consequently, the purpose of this investigation
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was to: 1) determine if PLRI, as evidenced by widening of the posterolateral ulnohumeral joint, can be
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identified by US, 2) determine if US can distinguish between mild and severe cases of clinical PLRI, and 3)
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quantify the amount of sonographically measured PLRI required to produce a positive posterolateral
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rotatory drawer test and lateral pivot-shift test in an unembalmed cadaveric model. We hypothesized
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that clinically unstable elbows would consistently demonstrate sonographically detectable ulnohumeral
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widening during the “sonographic posterolateral rotatory stress test”, and that the extent of ulnohumeral
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widening would increase with the severity of instability.
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MATERIALS AND METHODS
Following approval of the Institutional Review Board and Biospecimens Committee at the
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authors’ institution, ten unpaired, fresh frozen, unembalmed, cadaveric upper limbs were obtained from
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the Department of Anatomical Sciences’ Foundation Bequest Program. Specimens were sectioned at the
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proximal humerus and included the elbow, wrist, and hand. All specimens were completely thawed
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immediately prior to use and were free from deformity, post-traumatic or post-surgical change about the
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elbow, or motion-limiting arthritis. Seven left sided and three right sided specimens were utilized. All 5
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sonographic measures were obtained using a Phillips iU22 ultrasound machine and a 12-5 MHz linear
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array transducer (Phillips Ultrasound Systems, Bothell WA). The sonographic posterolateral rotatory stress test and all US measures were performed by the corresponding author, who had over 13 years of
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experience in diagnostic and interventional musculoskeletal US at the time of this investigation.
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To assess for posterolateral rotatory instability (PLRI) sonographically, the elbow was placed in approximately 30 degrees of flexion and the transducer positioned to provide the most distinct bony
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margins of the posterolateral ulnohumeral joint. This was accomplished by bridging the US probe from
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lateral epicondyle to the olecranon, about 1 cm distal to the tip of the olecranon, and by orienting the US
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probe approximately perpendicular to the long axis of the ulna. (Figure 1A) The ulnohumeral distance was
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measured using the electronic calipers on the machine (Figure 2A). All measurements were taken to one
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hundredth of a millimeter (mm) but were rounded off to the nearest mm for the purpose of this report.
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Mean and standard deviations were rounded off to the nearest mm for effectiveness of communication
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and clinical relevance.
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The sonographic posterolateral rotatory stress test was performed as follows. While maintaining
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the transducer position as described above with one hand, the examiner used the other hand to supinate
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the forearm with a moderate torque, correlating to that employed clinically during testing for
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posterolateral rotatory instability. (Figure 1B). The amount of torque could be described as sufficient to
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subluxate an elbow that is potentially unstable, but not enough to injure normal anatomic structures.
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During this maneuver the posterolateral ulnohumeral joint widened and the maximal ulnohumeral
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distance in this stressed state was measured and recorded (i.e. “sonographic posterolateral rotatory
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stress test”, Figure 2B). Ulnohumeral laxity was quantified by subtracting the ulnohumeral distance
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measured in the resting state from that of the stressed state (laxity = stress minus rest).
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Sonographic posterolateral rotatory stress testing was repeated for each of the ten specimens in
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four stages of increasing laxity: 1) Intact elbow, 2) complete extensor carpi radialis brevis (ECRB) tendon
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release, 3) complete ECRB release + Lateral collateral ligament complex (LCLC) release to produce a
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positive posterolateral drawer test, and 4) complete ECRB release LCLC + anterior capsule release to
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produce a positive lateral pivot-shift test. For each elbow, posterolateral ulnohumeral laxity (laxity = 6
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stress minus rest) was determined at each stage, generating a total of 40 measures of laxity (four stages
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for ten elbows). All physical exam tests were performed by a single clinical and surgical expert in elbow
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instability (SOD) with over 20 years of experience diagnosing and treating elbow instability. For Stage 1 (Intact Elbow), measures were obtained prior to making any incisions. For Stage 2
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(ECRB Released), an 8 cm incision was made from 1 cm proximal the lateral epicondyle towards the ulna
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about 1 cm anterior to Kocher’s interval so that the US probe could still be placed over “intact’ skin and
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subcutaneous tissues. The common extensor tendon was exposed and the ECRB tendon origin then
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released off the lateral epicondyle, exposing the anterior half of the capitellum when viewing the elbow
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from the lateral side (Figures 3A and B). Sonographic posterolateral ulnohumeral distances were then
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measured in the stressed and relaxed states, and laxity was calculated as described previously. To assess
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clinical stability, posterolateral rotatory drawer and lateral pivot-shift tests were performed. For Stage 3
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(Positive Posterolateral Rotatory Drawer Test), the LCLC was sequentially released (1 mm at a time at the
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level of the radiocapitellar joint) until the posterolateral rotatory drawer test became clinically positive as
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determined by the expert examiner (Figure 3C). Once positive, the release was stopped and sonographic
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measurements re-obtained. For the final stage (Stage 4: Positive Lateral Pivot-Shift test), the remainder of
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the LCLC was sequentially released (1 mm at a time at the level of the radiocapitellar joint towards the
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ulna) until the lateral pivot-shift test became positive (Figure 3D). Of note, in 3 of the specimens, a
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positive lateral pivot-shift did not occur until the entire LCLC and some of the anterior capsule was
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released. Once the lateral pivot-shift test was positive, the US measures were re-obtained in the resting
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and stressed states. In addition to the sonographic measurements, the following measurements were
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obtained with a caliper: proximal to distal diameter (height) of the capitellum, proximal to distal length of
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ECRB release, amount of LCLC release required to generate a positive posterolateral rotatory drawer test,
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and amount of additional release required to produce a positive lateral pivot-shift test.
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Statistical Analysis
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The mean resting posterolateral ulnohumeral distance, stressed posterolateral ulnohumeral
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distance, and posterolateral ulnohumeral laxity measures for each stage were calculated and compared
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using analysis of variance (ANOVA) for comparison of 3 or more groups of normally distributed continuous 7
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variables. When ANOVA testing revealed significance, post ANOVA pairwise subgroup analysis was
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performed using a student t-test to compare means of two groups of normally distributed variables. A
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total of 15 comparisons were completed. As a result, only p values < .003 were considered to represent
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statistical significance after a Bonferroni correction for multiple comparisons was applied (threshold for
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statistical significance= .05 ÷ 15). Where appropriate, results are reported with means, ranges, mean
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differences (MD), standard deviations (SD), and 95% confidence intervals (CI).
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RESULTS
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Stage 1: Intact Elbow
The mean posterolateral ulnohumeral distance for the intact elbow (Stage 1) was 3 mm (range 2-
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6 mm, SD 1) at rest and 4 mm (range 2-7 mm, SD 2) when stressed using the sonographic posterolateral
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rotatory stress test, resulting in a mean laxity (stress – minus rest) of 1mm (range 0-2 mm, SD 1) for the
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intact elbows. The posterolateral rotatory drawer and lateral pivot-shift tests were negative for all ten
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specimens. (Table 1)
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Stage 2: Complete ECRB Release
Prior to performing a complete ECRB release (Stage 2), the mean proximal to distal capitellar diameter was 26 mm (range 22-31; SD 3). (Figure 3A) The mean amount of ECRB released in the proximal
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to distal direction was 12 mm (range 8-14 mm, SD 2). After ECRB release, the mean sonographic
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ulnohumeral distance was 3 mm (range 1 -4 mm, SD 1) at rest and 6 mm (range 4-8 mm, SD 1) with the
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sonographic posterolateral rotatory stress test, resulting in a mean laxity of 3 mm (range 2-4 mm, SD, 1).
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At this stage, one of the ten (10%) elbows exhibited a positive posterolateral rotatory drawer test while
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the lateral pivot-shift test was negative for all specimens. (Table 1)
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Stage 3: LCLC Release to Produce Positive Posterolateral Drawer Test
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The mean height of lateral collateral ligament complex released to produce a positive
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posterolateral rotatory drawer test (Stage 3) was 11 mm (range 0-17 mm, SD 5). For the one specimen 8
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that demonstrated a positive posterolateral rotatory drawer following ECRB release (specimen #10),
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addition LCLC was not released between Stages 2 and 3. Once the posterolateral drawer test was positive,
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the mean ulnohumeral distances at rest and with the sonographic posterolateral rotatory stress test were
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3 mm (range 1-4 mm, SD 1) and 8 mm (range 5-12 mm, SD 2) respectively. This produced a mean laxity of
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6 mm (range 4-9 mm, SD 1). In Stage 3, all elbows (10 of 10, 100%) demonstrated a positive posterolateral
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rotatory drawer test while 0 of 10 (0%) had a positive lateral pivot-shift test. (Table 1)
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Stage 4: Additional Release of LCLC ± Part of Capsule to Produce Positive Lateral Pivot-Shift Test
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In order to produce a positive lateral pivot-shift (Stage 4), an additional 12 mm (range 5-25 mm, SD 6) release of the lateral collateral ligament complex was required. This resulted in a mean total LCLC
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release of 23.2 mm (range 16-36 mm, SD 6 ). Despite this, three (30%) elbows still had a negative lateral
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pivot-shift and required partial release of the anterior capsule off the anterior humerus to create a
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positive lateral pivot-shift. Release of the posterior capsule was not required. The magnitude of anterior
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capsule released was difficult to quantify, precluding formal measurement. However, only the minimal
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amount required to produce a positive lateral pivot-shift was released. In Stage 4, the mean ulnohumeral
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distances at rest and with the sonographic posterolateral rotatory stress test were 3 mm (range 2-4 mm,
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SD 1) and 13 mm (range 7 – 16 mm, SD 2) respectively. Mean laxity was 10 mm (range 5-13 mm, SD 2). At
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this stage, the posterolateral rotatory drawer and the lateral pivot-shift tests were positive for all
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specimens. (Table 1)
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When comparing Stages 1-4, there were minimal differences in mean ulnohumeral distances at
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rest (3 vs. 3 vs. 3 vs. 3 mm for Stages 1-4 respectively; p=.58). (Table 2) In comparison, the ulnohumeral
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distances during the sonographic posterolateral rotatory stress test increased with increasing stage (4 vs.
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6 vs. 8 vs. 13 mm for Stages 1-4 respectively, p< .001), as did laxity (1 vs. 3 vs. 6 vs. 10 mm for Stages 1-4
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respectively, p< .001). (Figure 4) Since ANOVA revealed significance for the multi-group comparisons for
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stressed measures and laxity across all groups, post-ANOVA pairwise subgroup analysis was performed for
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these categories. Mean ulnohumeral distances with the sonographic posterolateral rotatory stress test 9
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did not differ significantly between Stages 1 and 2 (4 vs. 6 mm, MD 1 mm, 95% CI 0 - 3, p=.60), but laxity
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measures did (1 vs. 3 mm, MD 2 mm, 95% CI 1 - 2, p<.001). Significant differences of progressively
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increasing stress distances and laxity measures were noted when comparing all other subsequent stages
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of instability to one another (Stage 2 vs. 3, and Stage 3 vs. 4). (Table 3)
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DISCUSSION
The most important finding of the current investigation is that PLRI can be sonographically
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detected by evaluating the posterolateral ulnohumeral joint during manual posterolateral rotatory stress
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testing. Consequently, our results suggest that US may be a valid tool for identifying PLRI of the elbow as
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demonstrated in this model. We developed this sonographic posterolateral rotatory stress test in patients
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in our clinic, and although soft tissue laxity in cadavers probably differs from that in patients, the relative
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changes in laxity correlated well with increasing stages of instability in the present study. This suggests
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validity of the relative values reported, although clinical studies will be required to establish absolute
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values.
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resolution imaging of elbow tendons, nerves, ligaments and accessible joint recesses. Furthermore, US
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can dynamically assess tendon motion, nerve instability or snapping, and joint laxity. [9–16]Although prior
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research has documented the ability to sonographically identify the LCLC, assessment of lateral side
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laxity/instability has been limited to non-quantified and nonvalidated descriptions of sonographic varus
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stress testing.[13–15] Furthermore, most patients with PLRI do not have demonstrable varus instability,
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nor does sonographic varus stress testing capture the three-dimensional instability pattern of PLRI.
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Consequently, we developed the sonographic posterolateral rotatory stress test in our clinical practice
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and validated the test in an unembalmed cadaveric model. Using a clinically positive posterolateral
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drawer test as the gold standard, specimens demonstrating PLRI exhibited a mean posterolateral
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ulnohumeral laxity 5 mm greater than in the intact elbow (6 mm for Stage 3 vs. 1 mm for Stage 1, p <
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.001) during manual posterolateral rotatory stress testing. Furthermore, the minimum ulnohumeral laxity
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(stress minus rest) among the 10 specimens demonstrating a clinically positive posterolateral drawer test
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was 4 mm. Based on this initial investigation, ulnohumeral laxity of > 4 mm should raise the index of
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suspicion for PLRI. In addition to identifying PLRI, dynamic ultrasound may also distinguish between various degrees
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of instability. The mean laxity in the intact elbow was 1 mm, and increased to 6 mm when the
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posterolateral rotatory drawer test was positive, and 10 mm when the lateral pivot-shift test was positive
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(p < .001). (Table 2 and Figure 4) In each of the ten individual specimens, ulnohumeral laxity progressively
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increased as a function of increasing instability. Clinically, not all patients with PLRI have sufficient
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instability for the lateral pivot-shift test to be positive, which is in agreement with the observations of this
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study.
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have clinical evidence of PLRI.[17] In our experience the co-existence of common extensor tendinopathy
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and PLRI typically occurs in the setting of at least high grade partial thickness tearing of the common
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extensor tendon, often accompanied by volume loss. In the current investigation we sought to simulate
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this clinical scenario to determine whether the sonographic posterolateral rotatory stress test could
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detect laxity differences between isolated ECRB tearing and isolated ECRB tearing with associated
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capsuloligamentous injury producing clinical instability. An average increase of 2 mm in laxity was
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measured after isolated ECRB release (Stage 1), but the posterolateral rotatory drawer test remained
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negative in 9 of the 10 elbows (90%). However, in the setting of severe ECRB tendon damage combined
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with LCLC complex insufficiency (Stage 3 in the current investigation), 10/10 elbows exhibited a positive
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posterolateral drawer accompanied by an average laxity of 6 mm. Clinically, these findings suggest that
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PLRI in the setting of “tennis elbow” may require attenuation of both the ECRB and the LCLC. This is
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consistent with our experience in the clinic in which we have identified occult PLRI in multiple patients
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with refractory “tennis elbow” and sonographic evidence of severe common extensor tendinosis and LCLC
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attenuation. Further formal clinical investigation with respect to the sonographic posterolateral rotatory
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stress test in the setting of tennis elbow is warranted.
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This work confirms what had previously been written regarding the relationship between the posterolateral rotatory drawer test and the lateral pivot-shift test.[1,7] O’Driscoll described the 11
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posterolateral rotatory drawer as the most sensitive for PLRI, and the lateral pivot-shift test as less
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sensitive and more difficult to perform. In 10 of 10 (100%) specimens in the present study, the
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posterolateral rotatory drawer became positive prior to the lateral pivot-shift test. In fact, an average of
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12 mm (range 5 – 25 mm) of additional LCLC and capsule had to be released to progress from a positive
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posterolateral rotatory drawer to a positive lateral pivot-shift test. Ultimately, ultrasound was able to
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distinguish between the two degrees of clinical PLRI and may therefore have a role in subclassifying PLRI
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according to degree of instability. However, this latter application requires further investigation.
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Several study limitations warrant further discussion. First, practitioners should exercise
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appropriate caution when extrapolating the results of this cadaveric investigation to clinical populations.
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We recognize that the tissue characteristics of cadaveric specimens may not reflect those of live humans,
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and cadaveric specimens are not susceptible to “guarding” as may be encountered in patients. Although
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our methodology controlled for these limitations in part by basing the surgical releases on a clinical gold
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standard, the quantitative laxity observed in patients susceptible to guarding during the sonographic
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posterolateral rotatory stress test may be less than observed in our cadaveric specimens.[1,7] Second, we
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only assessed laxity with the elbow in a single position of 30 degrees of flexion. Although this position
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was chosen to simulate the position used during the posterolateral drawer and pivot-shift tests, it is
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possible that the results of sonographic posterolateral rotatory stress testing would be dependent on
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elbow flexion angle. Third, the current study did not compare the sonographic posterolateral rotatory
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stress test to a sonographic varus stress test as this was not the primary purpose of the investigation.
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Based on our limited but evolving experience, we believe that the sonographic posterolateral rotatory
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stress test is more sensitive than the varus stress test as it assesses the rotatory component of PLRI.
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However, further investigation is required. Fourth, all sonographic testing was performed by a single,
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experienced examiner. This was necessary to ensure standardization of technique. Although the use of a
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single examiner might limit generalizability to other practitioners, we have successfully taught the
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sonographic posterolateral rotatory stress test to other physicians facile with US. Fifth, we chose to
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perform the sequential release starting with the ECRB. Although we recognize that post-traumatic PLRI
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may result from relatively isolated injury to the LCLC, the current study was primarily designed to reflect
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PLRI occurring in the setting of soft tissue attrition as may occur in “tennis elbow”, particularly following
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surgery or multiple injections. In our experience, the sonographic posterolateral rotatory stress test has
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been most useful in detecting unsuspected PLRI in patients with refractory “tennis elbow” and we
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therefore designed the study to reflect this clinical population. Finally, all of our elbows were free from
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trauma, deformity or osteoarthritis. It is assumed that the presence of these entities may represent the
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sonographic assessment of the posterolateral ulnohumeral joint, as well as distance and laxity measures.
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CONCLUSION
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The sonographic posterolateral rotatory stress test detected increasing posterolateral ulnohumeral laxity as a function of increasing clinical PLRI. The sonographic posterolateral rotatory stress
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test may be used as an adjunct to history, examination, and static imaging to assess ulnohumeral laxity in
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patients with lateral elbow pain syndromes. Within the limits of this cadaveric investigation, sonographic
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posterolateral ulnohumeral laxity of >4 mm should raise suspicion of underlying instability. Further
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validation of the sonographic posterolateral rotatory stress test in clinical populations is warranted.
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REFERENCES
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O’Driscoll SW, Bell DF, Morrey BF. Posterolateral rotatory instability of the elbow.
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O’Driscoll SW. Classification and evaluation of recurrent instability of the elbow. Clin Orthop Relat Res 2000:34–43.
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Sanchez-Sotelo J, Morrey BF, O’Driscoll SW. Ligamentous repair and reconstruction for posterolateral rotatory instability of the elbow. J Bone Joint
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al. Tardy posterolateral rotatory instability of the elbow due to cubitus varus. J
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O’Driscoll SW, Spinner RJ, McKee MD, Kibler WB, Hastings 2nd H, Morrey BF, et
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O’Driscoll SW. Elbow instability. Acta Orthop Belg 1999;65:404–15.
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Terada N, Yamada H, Toyama Y. The appearance of the lateral ulnar collateral ligament on magnetic resonance imaging. J Shoulder Elbow Surg 2004;13:214–6.
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Smith J, Finnoff JT. Diagnostic and Interventional Musculoskeletal Ultrasound: Part 1. Fundamentals. PM R 2009;1:64–75. doi:10.1016/j.pmrj.2008.09.001.
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2004;33:63–79. doi:10.1007/s00256-003-0680-7.
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Finlay K, Ferri M, Friedman L. Ultrasound of the elbow. Skeletal Radiol
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[11]
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Lin CW, Chen YH, Chen WS. Application of Ultrasound and Ultrasound-Guided Intervention for Evaluating Elbow Joint Pathologies. J Med Ultrasound
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2012;20:87–95. doi:10.1016/j.jmu.2012.04.007.
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antebrachial cutaneous nerve. Clin Anat 2015;28:872–7. doi:10.1002/ca.22601.
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[13]
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Jacobson J a., Chiavaras MM, Lawton JM, Downie B, Yablon CM, Lawton J. Radial Collateral Ligament of the Elbow: Sonographic Characterization With Cadaveric
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Cesmebasi A, O’driscoll SW, Smith J, Skinner JA, Spinner RJ. The snapping medial
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Dissection Correlation and Magnetic Resonance Arthrography. J Ultrasound Med 2014;33:1041–8. doi:10.7863/ultra.33.6.1041.
[14]
Stewart B, Harish S, Oomen G, Wainman B, Popowich T, Moro JK. Sonography of
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the lateral ulnar collateral ligament of the elbow: Study of cadavers and healthy
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volunteers. Am J Roentgenol 2009;193:1615–9. doi:10.2214/AJR.09.2812.
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[15]
Gondim Teixeira PA, Omoumi P, Trudell DJ, Ward SR, Lecocq S, Blum A, et al. Ultrasound assessment of the lateral collateral ligamentous complex of the
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elbow: Imaging aspects in cadavers and normal volunteers. Eur Radiol
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2011;21:1492–8. doi:10.1007/s00330-011-2076-8.
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Smith J, Finnoff JT, O’Driscoll SW, Lai JK. Sonographic evaluation of the distal
biceps tendon using a medial approach: the pronator window. J Ultrasound Med
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2010;29:861–5.
[17]
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Kalainov DM, Cohen MS. Posterolateral rotatory instability of the elbow in
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association with lateral epicondylitis. A report of three cases. J Bone Joint Surg
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Am 2005;87:1120–5. doi:10.2106/JBJS.D.02293.
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FIGURES
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Figure 1: Ultrasound probe position during the Sonographic Posterolateral Rotatory Stress Test in an
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unembalmed cadaveric specimen. The probe is placed in the anatomic axial plane bridging the lateral
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epicondyle to the olecranon (A). To perform the Sonographic Posterolateral Rotatory Stress test, the
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examiner uses the opposite hand to apply a supination torque at the wrist, eliciting PLRI subluxation
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indicated by the gap in the posterolateral ulnohumeral joint (B).
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Figure 2: Sonographic posterolateral ulnohumeral distance at rest (A) and during the sonographic
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posterolateral rotatory stress test (B). Although still pictures can be obtained in both the resting and
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stressed states, the authors recommend capturing videos and obtaining resting and stress measurement
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from the videos. This allows the examiner to maintain transducer stability during testing. Images
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obtained with transducer positioned as in Figure 1. Hum: humerus.
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Figure 3: Lateral view of the right elbow demonstrating measurement of capitellar diameter (A). The
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Extensor Carpi Radialis Brevis (ECRB) release for Stage 2 is also shown (A and B). For Stage 3, the lateral
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collateral ligament complex (LCLC) was sequentially released at the level of the radiocapitellar joint until
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the posterolateral rotatory drawer test became positive (C). Finally, this release was continued through
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the lateral collateral ligament complex (LCLC) and anterior capsule until the lateral pivot-shift test become
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positive (D). ECRB: extensor carpi radialis brevis; LCL: lateral collateral ligament; LCLC: lateral collateral ligament complex; RC:
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radiocapitellar.
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Figure 4: Sonographic Posterolateral Ulnohumeral Laxity with Progressive Instability
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Stage 1: Intact Elbow; Stage 2: ECRB released; Stage 3: Positive posterolateral rotatory drawer test; Stage
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4: Positive lateral pivot-shift test. Stages 3 and 4 represent clinical instability. Values are means in mm
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with bars indicating +/- standard deviation (SD). *Indicates a statistically significant difference (p<.003)
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between groups.
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TABLES
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Table 1: Individual results of the clinical and sonographic exam for each specimen at each stage of
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progressive instability.
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Table 2: Multi-group comparisons of mean sonographic ulnohumeral distances and laxities across all
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stages of instability.
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Table 3: Pairwise comparisons of mean sonographic ulnohumeral distances between sequential
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pathologic states of instability (Stages 1 vs. 2, 2 vs. 3, and 3 vs. 4).
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The Sonographic Posterolateral Rotatory Stress Test: Cadaveric Validation TABLES
(+)?
(+)?
Ultrasound Exam (mm)
(+) ?
PS
Rest
Stress
Laxity
PLRD
PS
Rest
Stress
Laxity
PLRD
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
3 2 4
3 4 5
1 2 1
6 6 5
3 4 2
4 4 7
2 1 1
2 4 4
5 6 8
3 3 4
3 2 2
5 2 3
2 0 1
6 4 4
3 2 3
6
7
1
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
3 2 3
2 3 6
(-) (-) (-) (-) (-) (-) (-) (-) (-) +
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4
+ + + + + + + + + +
Mean: Min: Max: StDev:
3
4
1
3
6
3
2 6
2 7
0 2
1 4
4 8
2 4
3 2 1 3
Ultrasound Exam (mm)
Stage 4 (+) Lateral Pivot-Shift Clinical Exam (+)?
Ultrasound Exam (mm)
PS
Rest
Stress
Laxity
PLRD
PS
Rest
Stress
Laxity
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
3 2 3
9 11 8
6 9 5
14 16 12
12 13 9
7 7 9
6 5 5
2 3 4
11 12 15
9 9 11
3 2 1
9 6 5
5 4 4
2 2 2
14 7 12
11 5 10
4
12
7
+ + + + + + + + + +
2 2 3
1 3 4
+ + + + + + + + + +
3
15
12
3
8
6
3
13
10
1 4
5 12
4 9
2 4
7 16
5 13
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PLRD
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Table 1: Individual results of the clinical and sonographic exam for each specimen at each stage of progressive instability. Stage 1 Stage 2 Stage 3 Intact Elbow ECRB Released (+) Posterolateral Rotatory Drawer Specimen Clinical Exam Ultrasound Exam Clinical Exam Clinical Exam
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1.47 1.59 0.52 0.90 1.29 0.70 1.00 1.98 1.49 0.60 2.42 2.27 PLRD: posterolateral rotatory drawer test; PS: lateral pivot-shift test; + indicates the clinical test was positive; (-) indicates that the clinical test was negative, min: minimum; max: maximum; StDev: standard deviation
Rest (mm) Stress (mm) Laxity (mm)
1 3 4 1
2 3 6 3
Mean Values for All stages 3 4 p-value* 3 3 0.58 8 13 < 0.001 6 10 < 0.001
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Table 2: Multi-group comparison of mean sonographic ulnohumeral distances and laxities across all stages of instability.
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*Calculated by ANOVA. P< 0.003 considered to represent statistical significance
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Table 3: Pairwise comparisons of mean sonographic ulnohumeral distances between sequential pathologic states of instability (Stages 1 vs. 2, 2 vs. 3, and 3 vs. 4).
Rest (mm) Stress (mm) Laxity (mm)
1 3 4 1
2 3 6 3
Diff 1 1 2
Stage 1 vs. 2 p-value* 0.60 <0.001
95% CI 0.1 to 2.7 1.2 to 2.4
2 3 6 3
3 3 8 6
Diff 0 3 3
Stage 2 vs. 3 p-value* <0.001 <0.001
95% CI 1.2 to 4.4 1.7 to 3.9
3 3 8 6
4 3 13 10
Diff 0 4 4
Stage 3 vs. 4 p-value* <0.001 <0.001
95% CI 2.3 to 6.5 2.7 to 6.3
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S1934-1482(16)30193-9
DOI:
10.1016/j.pmrj.2016.06.014
Reference:
PMRJ 1728
To appear in:
PM&R
Received Date: 24 February 2016 Revised Date:
16 May 2016
Accepted Date: 8 June 2016
Please cite this article as: Camp CL, O’Driscoll SW, Wempe MK, Smith J, The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric Validation Study, PM&R (2016), doi: 10.1016/j.pmrj.2016.06.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric Validation Study
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Christopher L. Camp, MD* Shawn W. O’Driscoll, MD PhD* ¥ Michael K. Wempe, MD ∑ Jay Smith, MD †
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From *Department of Orthopedic Surgery and the Sports Medicine Center, Mayo Clinic, Rochester, Minnesota, U.S.A. ¥ Department of Physical Medicine and Rehabilitation, Nebraska Medical Center, Omaha, NE U.S.A. ∑ Department of Physical Medicine and Rehabilitation, Radiology, and Anatomy, Mayo Clinic, College of Medicine, Rochester, Minnesota, U.S.A.
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†Address correspondence to Jay Smith, M.D. Department of Physical Medicine and Rehabilitation Mayo Clinic 200 First St., SW Rochester MN 55905 Ph: 507-284-2012 Fax: 507-266-1803 [email protected]
Source of Funding: This work was funded in its entirety by internal research funds.
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Device Status: This study does not rely on the usage of any medical devices or instruments that are not approved by the FDA This material was not presented at an AAPM&R Annual Assembly
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The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric Validation Study
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Source of Funding: This work was funded in its entirety by internal research funds. Device Status: This study does not rely on the usage of any medical devices or instruments that are not approved by the FDA
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This material was not presented at an AAPM&R Annual Assembly
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The Sonographic Posterolateral Rotatory Stress Test For Elbow Instability: A Cadaveric
13
Validation Study Abstract:
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Background: Although clinical tests can detect posterolateral rotatory instability (PLRI) of the elbow, the
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ability of ultrasound (US) to evaluate PLRI has not been assessed.
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Objective: To determine whether increasing stages of posterolateral rotatory subluxation of the elbow
18
could be assessed accurately with a sonographic posterolateral rotatory stress test.
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Design: Cadaveric Study
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Setting: Laboratory
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Patients: Ten, unpaired, cadaveric upper limbs
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Methods: Posterolateral ulnohumeral distance was measured by US at rest and during manual
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sonographic posterolateral rotatory stress testing at four stages of increasing instability: 1) Intact elbow,
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2) Extensor carpi radialis brevis (ECRB) release, 3) ECRB release + Lateral collateral ligament complex
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(LCLC) release to produce a positive posterolateral drawer test, and 4) ECRB release + LCLC and capsule
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release to produce a positive lateral pivot-shift test. Mean values for sonographic resting ulnohumeral
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distance, stressed ulnohumeral distance and laxity were calculated for each stage and compared between
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stages.
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Main Outcome Measures: Posterolateral ulnohumeral laxity
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Results: Mean ulnohumeral laxities were 1, 3, 6 and 10 mm (p<.001) for stages 1-4, respectively. Pairwise
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comparison of mean laxity between the intact elbow (Stage 1) and each pathologic state (Stages 2-4)
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demonstrated differences of 2 mm (Stage 1 vs. 2); 5 mm (Stage 1 vs. 3); and 9 mm (Stage 1 vs. 4)(p<.001).
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The minimal difference in ulnohumeral laxity noted between the intact elbow and an elbow with a
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clinically positive posterolateral rotatory drawer test (Stage 3) was 4 mm.
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Discussion and Conclusions: The sonographic posterolateral rotatory stress test detected increasing
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posterolateral ulnohumeral laxity as a function of increasing clinical PLRI. This test may be used as an
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adjunct to history, examination, and static imaging to assess ulnohumeral laxity in patients with lateral
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elbow pain syndromes. Within the limits of this investigation, sonographic posterolateral ulnohumeral
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laxity of >4 mm should raise suspicion of underlying instability.
40 Level of Evidence: II
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Key Terms: posterolateral rotatory instability, ultrasound, elbow, sonographic posterolateral rotatory
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stress test
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INTRODUCTION Since its initial description in 1991, posterolateral rotatory instability (PLRI) of the elbow has become increasingly recognized as a source of elbow pain and dysfunction.[1] PLRI is the most common
48
pattern of elbow instability and typically occurs following a fall onto the outstretched arm during which
49
the elbow sustains axial compression, flexion, and valgus torques.[1–3] Although the proximal radioulnar
50
joint remains congruent (secondary to the annular ligament), the radial head and ulna collectively rotate
51
off the distal humerus in a posterolateral direction.[1] The injury is thought to be more likely to occur with
52
the forearm in the supinated position, but it is the ulna and radius in combination that roll off the distal
53
humerus rather than the radius supinating in relation to the ulna. Increasing subluxation results in
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sequential disruption, starting laterally with the lateral collateral ligament complex, followed by the
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common extensor tendons, then progressing around anteriorly and posteriorly to involve the capsule and
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eventually part or all of the medial collateral ligament if the elbow dislocates fully.[4] In addition to
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traumatic injury, PLRI can occur secondary to lateral soft tissue attenuation as seen in patients with
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severe common extensor tendinopathy (i.e. “tennis elbow”) or longstanding cubitus varus, or due to
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iatrogenic injury following lateral sided elbow surgery.[5,6] A number of physical examination tests have
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been described to aid in the diagnosis of PLRI, the most well-studied being the posterolateral rotatory
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drawer and lateral pivot-shift tests.[1,7] Although both are valuable examination maneuvers that are
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highly specific for PLRI, the sensitivity of each test is somewhat dependent upon the examiner.[1,7]
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Despite the increased awareness of PLRI, confirming the diagnosis can be difficult based on history and physical exam alone if the examiner is not familiar with the condition and experienced with
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the clinical maneuvers. X-rays may demonstrate associated findings, such as bony avulsions or coronoid
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tip fractures, but are generally not helpful in establishing the diagnosis. Magnetic resonance imaging
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(MRI) can detect lateral collateral ligament complex (LCLC) injuries, but the sensitivity of MRI to detect all
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LCLC injuries has been questioned.[8] Furthermore, as a static test, MRI cannot confirm PLRI in the clinical
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setting. Although dynamic fluoroscopy can be a useful adjunct to detect PLRI, it does not permit soft
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tissue evaluation and exposes the patient and operator to radiation.[9]
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Ultrasound provides a unique combination of high resolution soft tissue imaging, dynamic
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capabilities, portability, lack of radiation exposure, immediacy of results, reduced costs compared to other
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modalities, and lack of contraindications.[9] In recent, years the role of musculoskeletal US (MSK US) in
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sports and musculoskeletal medicine has continued to expand. Multiple studies have documented the
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ability of MSK US to image the soft tissue and bony structures about the lateral elbow, as well as assist in
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the diagnosis and management of lateral elbow disorders affecting the common extensor tendon,
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radiocapitellar joint, and posterior interosseous nerve.[10–12] Although previous studies have reported
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on the sonographic evaluation of the lateral elbow ligaments in both cadavers and healthy volunteers, the
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ability of US to identify PLRI has not been formally investigated.[13–15] In the clinical setting, the authors
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have observed sonographically detectable posterolateral ulnohumeral widening in patients with clinical
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PLRI during posterolateral rotatory stress testing. However, this “sonographic posterolateral rotatory
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stress test” has not been formally evaluated or validated. Consequently, the purpose of this investigation
83
was to: 1) determine if PLRI, as evidenced by widening of the posterolateral ulnohumeral joint, can be
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identified by US, 2) determine if US can distinguish between mild and severe cases of clinical PLRI, and 3)
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quantify the amount of sonographically measured PLRI required to produce a positive posterolateral
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rotatory drawer test and lateral pivot-shift test in an unembalmed cadaveric model. We hypothesized
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that clinically unstable elbows would consistently demonstrate sonographically detectable ulnohumeral
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widening during the “sonographic posterolateral rotatory stress test”, and that the extent of ulnohumeral
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widening would increase with the severity of instability.
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MATERIALS AND METHODS
Following approval of the Institutional Review Board and Biospecimens Committee at the
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authors’ institution, ten unpaired, fresh frozen, unembalmed, cadaveric upper limbs were obtained from
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the Department of Anatomical Sciences’ Foundation Bequest Program. Specimens were sectioned at the
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proximal humerus and included the elbow, wrist, and hand. All specimens were completely thawed
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immediately prior to use and were free from deformity, post-traumatic or post-surgical change about the
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elbow, or motion-limiting arthritis. Seven left sided and three right sided specimens were utilized. All 5
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sonographic measures were obtained using a Phillips iU22 ultrasound machine and a 12-5 MHz linear
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array transducer (Phillips Ultrasound Systems, Bothell WA). The sonographic posterolateral rotatory stress test and all US measures were performed by the corresponding author, who had over 13 years of
101
experience in diagnostic and interventional musculoskeletal US at the time of this investigation.
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To assess for posterolateral rotatory instability (PLRI) sonographically, the elbow was placed in approximately 30 degrees of flexion and the transducer positioned to provide the most distinct bony
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margins of the posterolateral ulnohumeral joint. This was accomplished by bridging the US probe from
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lateral epicondyle to the olecranon, about 1 cm distal to the tip of the olecranon, and by orienting the US
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probe approximately perpendicular to the long axis of the ulna. (Figure 1A) The ulnohumeral distance was
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measured using the electronic calipers on the machine (Figure 2A). All measurements were taken to one
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hundredth of a millimeter (mm) but were rounded off to the nearest mm for the purpose of this report.
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Mean and standard deviations were rounded off to the nearest mm for effectiveness of communication
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and clinical relevance.
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The sonographic posterolateral rotatory stress test was performed as follows. While maintaining
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the transducer position as described above with one hand, the examiner used the other hand to supinate
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the forearm with a moderate torque, correlating to that employed clinically during testing for
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posterolateral rotatory instability. (Figure 1B). The amount of torque could be described as sufficient to
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subluxate an elbow that is potentially unstable, but not enough to injure normal anatomic structures.
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During this maneuver the posterolateral ulnohumeral joint widened and the maximal ulnohumeral
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distance in this stressed state was measured and recorded (i.e. “sonographic posterolateral rotatory
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stress test”, Figure 2B). Ulnohumeral laxity was quantified by subtracting the ulnohumeral distance
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measured in the resting state from that of the stressed state (laxity = stress minus rest).
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Sonographic posterolateral rotatory stress testing was repeated for each of the ten specimens in
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four stages of increasing laxity: 1) Intact elbow, 2) complete extensor carpi radialis brevis (ECRB) tendon
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release, 3) complete ECRB release + Lateral collateral ligament complex (LCLC) release to produce a
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positive posterolateral drawer test, and 4) complete ECRB release LCLC + anterior capsule release to
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produce a positive lateral pivot-shift test. For each elbow, posterolateral ulnohumeral laxity (laxity = 6
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stress minus rest) was determined at each stage, generating a total of 40 measures of laxity (four stages
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for ten elbows). All physical exam tests were performed by a single clinical and surgical expert in elbow
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instability (SOD) with over 20 years of experience diagnosing and treating elbow instability. For Stage 1 (Intact Elbow), measures were obtained prior to making any incisions. For Stage 2
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(ECRB Released), an 8 cm incision was made from 1 cm proximal the lateral epicondyle towards the ulna
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about 1 cm anterior to Kocher’s interval so that the US probe could still be placed over “intact’ skin and
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subcutaneous tissues. The common extensor tendon was exposed and the ECRB tendon origin then
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released off the lateral epicondyle, exposing the anterior half of the capitellum when viewing the elbow
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from the lateral side (Figures 3A and B). Sonographic posterolateral ulnohumeral distances were then
134
measured in the stressed and relaxed states, and laxity was calculated as described previously. To assess
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clinical stability, posterolateral rotatory drawer and lateral pivot-shift tests were performed. For Stage 3
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(Positive Posterolateral Rotatory Drawer Test), the LCLC was sequentially released (1 mm at a time at the
137
level of the radiocapitellar joint) until the posterolateral rotatory drawer test became clinically positive as
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determined by the expert examiner (Figure 3C). Once positive, the release was stopped and sonographic
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measurements re-obtained. For the final stage (Stage 4: Positive Lateral Pivot-Shift test), the remainder of
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the LCLC was sequentially released (1 mm at a time at the level of the radiocapitellar joint towards the
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ulna) until the lateral pivot-shift test became positive (Figure 3D). Of note, in 3 of the specimens, a
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positive lateral pivot-shift did not occur until the entire LCLC and some of the anterior capsule was
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released. Once the lateral pivot-shift test was positive, the US measures were re-obtained in the resting
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and stressed states. In addition to the sonographic measurements, the following measurements were
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obtained with a caliper: proximal to distal diameter (height) of the capitellum, proximal to distal length of
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ECRB release, amount of LCLC release required to generate a positive posterolateral rotatory drawer test,
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and amount of additional release required to produce a positive lateral pivot-shift test.
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Statistical Analysis
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The mean resting posterolateral ulnohumeral distance, stressed posterolateral ulnohumeral
150
distance, and posterolateral ulnohumeral laxity measures for each stage were calculated and compared
151
using analysis of variance (ANOVA) for comparison of 3 or more groups of normally distributed continuous 7
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variables. When ANOVA testing revealed significance, post ANOVA pairwise subgroup analysis was
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performed using a student t-test to compare means of two groups of normally distributed variables. A
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total of 15 comparisons were completed. As a result, only p values < .003 were considered to represent
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statistical significance after a Bonferroni correction for multiple comparisons was applied (threshold for
156
statistical significance= .05 ÷ 15). Where appropriate, results are reported with means, ranges, mean
157
differences (MD), standard deviations (SD), and 95% confidence intervals (CI).
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RESULTS
160
Stage 1: Intact Elbow
The mean posterolateral ulnohumeral distance for the intact elbow (Stage 1) was 3 mm (range 2-
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6 mm, SD 1) at rest and 4 mm (range 2-7 mm, SD 2) when stressed using the sonographic posterolateral
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rotatory stress test, resulting in a mean laxity (stress – minus rest) of 1mm (range 0-2 mm, SD 1) for the
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intact elbows. The posterolateral rotatory drawer and lateral pivot-shift tests were negative for all ten
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specimens. (Table 1)
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Stage 2: Complete ECRB Release
Prior to performing a complete ECRB release (Stage 2), the mean proximal to distal capitellar diameter was 26 mm (range 22-31; SD 3). (Figure 3A) The mean amount of ECRB released in the proximal
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to distal direction was 12 mm (range 8-14 mm, SD 2). After ECRB release, the mean sonographic
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ulnohumeral distance was 3 mm (range 1 -4 mm, SD 1) at rest and 6 mm (range 4-8 mm, SD 1) with the
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sonographic posterolateral rotatory stress test, resulting in a mean laxity of 3 mm (range 2-4 mm, SD, 1).
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At this stage, one of the ten (10%) elbows exhibited a positive posterolateral rotatory drawer test while
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the lateral pivot-shift test was negative for all specimens. (Table 1)
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Stage 3: LCLC Release to Produce Positive Posterolateral Drawer Test
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The mean height of lateral collateral ligament complex released to produce a positive
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posterolateral rotatory drawer test (Stage 3) was 11 mm (range 0-17 mm, SD 5). For the one specimen 8
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that demonstrated a positive posterolateral rotatory drawer following ECRB release (specimen #10),
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addition LCLC was not released between Stages 2 and 3. Once the posterolateral drawer test was positive,
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the mean ulnohumeral distances at rest and with the sonographic posterolateral rotatory stress test were
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3 mm (range 1-4 mm, SD 1) and 8 mm (range 5-12 mm, SD 2) respectively. This produced a mean laxity of
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6 mm (range 4-9 mm, SD 1). In Stage 3, all elbows (10 of 10, 100%) demonstrated a positive posterolateral
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rotatory drawer test while 0 of 10 (0%) had a positive lateral pivot-shift test. (Table 1)
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Stage 4: Additional Release of LCLC ± Part of Capsule to Produce Positive Lateral Pivot-Shift Test
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In order to produce a positive lateral pivot-shift (Stage 4), an additional 12 mm (range 5-25 mm, SD 6) release of the lateral collateral ligament complex was required. This resulted in a mean total LCLC
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release of 23.2 mm (range 16-36 mm, SD 6 ). Despite this, three (30%) elbows still had a negative lateral
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pivot-shift and required partial release of the anterior capsule off the anterior humerus to create a
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positive lateral pivot-shift. Release of the posterior capsule was not required. The magnitude of anterior
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capsule released was difficult to quantify, precluding formal measurement. However, only the minimal
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amount required to produce a positive lateral pivot-shift was released. In Stage 4, the mean ulnohumeral
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distances at rest and with the sonographic posterolateral rotatory stress test were 3 mm (range 2-4 mm,
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SD 1) and 13 mm (range 7 – 16 mm, SD 2) respectively. Mean laxity was 10 mm (range 5-13 mm, SD 2). At
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this stage, the posterolateral rotatory drawer and the lateral pivot-shift tests were positive for all
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specimens. (Table 1)
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When comparing Stages 1-4, there were minimal differences in mean ulnohumeral distances at
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rest (3 vs. 3 vs. 3 vs. 3 mm for Stages 1-4 respectively; p=.58). (Table 2) In comparison, the ulnohumeral
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distances during the sonographic posterolateral rotatory stress test increased with increasing stage (4 vs.
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6 vs. 8 vs. 13 mm for Stages 1-4 respectively, p< .001), as did laxity (1 vs. 3 vs. 6 vs. 10 mm for Stages 1-4
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respectively, p< .001). (Figure 4) Since ANOVA revealed significance for the multi-group comparisons for
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stressed measures and laxity across all groups, post-ANOVA pairwise subgroup analysis was performed for
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did not differ significantly between Stages 1 and 2 (4 vs. 6 mm, MD 1 mm, 95% CI 0 - 3, p=.60), but laxity
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measures did (1 vs. 3 mm, MD 2 mm, 95% CI 1 - 2, p<.001). Significant differences of progressively
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increasing stress distances and laxity measures were noted when comparing all other subsequent stages
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of instability to one another (Stage 2 vs. 3, and Stage 3 vs. 4). (Table 3)
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DISCUSSION
The most important finding of the current investigation is that PLRI can be sonographically
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detected by evaluating the posterolateral ulnohumeral joint during manual posterolateral rotatory stress
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testing. Consequently, our results suggest that US may be a valid tool for identifying PLRI of the elbow as
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demonstrated in this model. We developed this sonographic posterolateral rotatory stress test in patients
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in our clinic, and although soft tissue laxity in cadavers probably differs from that in patients, the relative
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changes in laxity correlated well with increasing stages of instability in the present study. This suggests
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validity of the relative values reported, although clinical studies will be required to establish absolute
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values.
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resolution imaging of elbow tendons, nerves, ligaments and accessible joint recesses. Furthermore, US
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can dynamically assess tendon motion, nerve instability or snapping, and joint laxity. [9–16]Although prior
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research has documented the ability to sonographically identify the LCLC, assessment of lateral side
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laxity/instability has been limited to non-quantified and nonvalidated descriptions of sonographic varus
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stress testing.[13–15] Furthermore, most patients with PLRI do not have demonstrable varus instability,
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nor does sonographic varus stress testing capture the three-dimensional instability pattern of PLRI.
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Consequently, we developed the sonographic posterolateral rotatory stress test in our clinical practice
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and validated the test in an unembalmed cadaveric model. Using a clinically positive posterolateral
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drawer test as the gold standard, specimens demonstrating PLRI exhibited a mean posterolateral
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ulnohumeral laxity 5 mm greater than in the intact elbow (6 mm for Stage 3 vs. 1 mm for Stage 1, p <
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.001) during manual posterolateral rotatory stress testing. Furthermore, the minimum ulnohumeral laxity
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(stress minus rest) among the 10 specimens demonstrating a clinically positive posterolateral drawer test
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was 4 mm. Based on this initial investigation, ulnohumeral laxity of > 4 mm should raise the index of
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suspicion for PLRI. In addition to identifying PLRI, dynamic ultrasound may also distinguish between various degrees
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of instability. The mean laxity in the intact elbow was 1 mm, and increased to 6 mm when the
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posterolateral rotatory drawer test was positive, and 10 mm when the lateral pivot-shift test was positive
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(p < .001). (Table 2 and Figure 4) In each of the ten individual specimens, ulnohumeral laxity progressively
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increased as a function of increasing instability. Clinically, not all patients with PLRI have sufficient
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instability for the lateral pivot-shift test to be positive, which is in agreement with the observations of this
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study.
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have clinical evidence of PLRI.[17] In our experience the co-existence of common extensor tendinopathy
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and PLRI typically occurs in the setting of at least high grade partial thickness tearing of the common
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extensor tendon, often accompanied by volume loss. In the current investigation we sought to simulate
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this clinical scenario to determine whether the sonographic posterolateral rotatory stress test could
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detect laxity differences between isolated ECRB tearing and isolated ECRB tearing with associated
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capsuloligamentous injury producing clinical instability. An average increase of 2 mm in laxity was
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measured after isolated ECRB release (Stage 1), but the posterolateral rotatory drawer test remained
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negative in 9 of the 10 elbows (90%). However, in the setting of severe ECRB tendon damage combined
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with LCLC complex insufficiency (Stage 3 in the current investigation), 10/10 elbows exhibited a positive
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posterolateral drawer accompanied by an average laxity of 6 mm. Clinically, these findings suggest that
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PLRI in the setting of “tennis elbow” may require attenuation of both the ECRB and the LCLC. This is
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consistent with our experience in the clinic in which we have identified occult PLRI in multiple patients
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with refractory “tennis elbow” and sonographic evidence of severe common extensor tendinosis and LCLC
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attenuation. Further formal clinical investigation with respect to the sonographic posterolateral rotatory
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stress test in the setting of tennis elbow is warranted.
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This work confirms what had previously been written regarding the relationship between the posterolateral rotatory drawer test and the lateral pivot-shift test.[1,7] O’Driscoll described the 11
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posterolateral rotatory drawer as the most sensitive for PLRI, and the lateral pivot-shift test as less
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sensitive and more difficult to perform. In 10 of 10 (100%) specimens in the present study, the
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posterolateral rotatory drawer became positive prior to the lateral pivot-shift test. In fact, an average of
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12 mm (range 5 – 25 mm) of additional LCLC and capsule had to be released to progress from a positive
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posterolateral rotatory drawer to a positive lateral pivot-shift test. Ultimately, ultrasound was able to
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distinguish between the two degrees of clinical PLRI and may therefore have a role in subclassifying PLRI
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according to degree of instability. However, this latter application requires further investigation.
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Several study limitations warrant further discussion. First, practitioners should exercise
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appropriate caution when extrapolating the results of this cadaveric investigation to clinical populations.
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We recognize that the tissue characteristics of cadaveric specimens may not reflect those of live humans,
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and cadaveric specimens are not susceptible to “guarding” as may be encountered in patients. Although
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our methodology controlled for these limitations in part by basing the surgical releases on a clinical gold
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standard, the quantitative laxity observed in patients susceptible to guarding during the sonographic
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posterolateral rotatory stress test may be less than observed in our cadaveric specimens.[1,7] Second, we
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only assessed laxity with the elbow in a single position of 30 degrees of flexion. Although this position
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was chosen to simulate the position used during the posterolateral drawer and pivot-shift tests, it is
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possible that the results of sonographic posterolateral rotatory stress testing would be dependent on
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elbow flexion angle. Third, the current study did not compare the sonographic posterolateral rotatory
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stress test to a sonographic varus stress test as this was not the primary purpose of the investigation.
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Based on our limited but evolving experience, we believe that the sonographic posterolateral rotatory
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stress test is more sensitive than the varus stress test as it assesses the rotatory component of PLRI.
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However, further investigation is required. Fourth, all sonographic testing was performed by a single,
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experienced examiner. This was necessary to ensure standardization of technique. Although the use of a
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single examiner might limit generalizability to other practitioners, we have successfully taught the
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sonographic posterolateral rotatory stress test to other physicians facile with US. Fifth, we chose to
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perform the sequential release starting with the ECRB. Although we recognize that post-traumatic PLRI
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may result from relatively isolated injury to the LCLC, the current study was primarily designed to reflect
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PLRI occurring in the setting of soft tissue attrition as may occur in “tennis elbow”, particularly following
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surgery or multiple injections. In our experience, the sonographic posterolateral rotatory stress test has
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been most useful in detecting unsuspected PLRI in patients with refractory “tennis elbow” and we
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therefore designed the study to reflect this clinical population. Finally, all of our elbows were free from
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trauma, deformity or osteoarthritis. It is assumed that the presence of these entities may represent the
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sonographic assessment of the posterolateral ulnohumeral joint, as well as distance and laxity measures.
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CONCLUSION
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The sonographic posterolateral rotatory stress test detected increasing posterolateral ulnohumeral laxity as a function of increasing clinical PLRI. The sonographic posterolateral rotatory stress
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test may be used as an adjunct to history, examination, and static imaging to assess ulnohumeral laxity in
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patients with lateral elbow pain syndromes. Within the limits of this cadaveric investigation, sonographic
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posterolateral ulnohumeral laxity of >4 mm should raise suspicion of underlying instability. Further
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validation of the sonographic posterolateral rotatory stress test in clinical populations is warranted.
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REFERENCES
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[1]
[2]
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J Bone Joint Surg Am 1991;73:440–6.
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O’Driscoll SW, Bell DF, Morrey BF. Posterolateral rotatory instability of the elbow.
Anakwenze O a., Kancherla VK, Iyengar J, Ahmad CS, Levine WN. Posterolateral Rotatory Instability of the Elbow. Am J Sports Med 2013;42:485–91.
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doi:10.1177/0363546513494579.
Orthop Surg 2004;12:405–15.
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[4]
O’Driscoll SW. Classification and evaluation of recurrent instability of the elbow. Clin Orthop Relat Res 2000:34–43.
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Mehta JA, Bain GI. Posterolateral rotatory instability of the elbow. J Am Acad
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[5]
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Sanchez-Sotelo J, Morrey BF, O’Driscoll SW. Ligamentous repair and reconstruction for posterolateral rotatory instability of the elbow. J Bone Joint
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Surg Br 2005;87:54–61. doi:10.1016/S0276-1092(08)70516-9.
[6]
al. Tardy posterolateral rotatory instability of the elbow due to cubitus varus. J
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Bone Joint Surg Am 2001;83-A:1358–69.
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O’Driscoll SW, Spinner RJ, McKee MD, Kibler WB, Hastings 2nd H, Morrey BF, et
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[7]
O’Driscoll SW. Elbow instability. Acta Orthop Belg 1999;65:404–15.
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[8]
Terada N, Yamada H, Toyama Y. The appearance of the lateral ulnar collateral ligament on magnetic resonance imaging. J Shoulder Elbow Surg 2004;13:214–6.
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doi:10.1016/S1058274603003185.
[9]
Smith J, Finnoff JT. Diagnostic and Interventional Musculoskeletal Ultrasound: Part 1. Fundamentals. PM R 2009;1:64–75. doi:10.1016/j.pmrj.2008.09.001.
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[10]
2004;33:63–79. doi:10.1007/s00256-003-0680-7.
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Finlay K, Ferri M, Friedman L. Ultrasound of the elbow. Skeletal Radiol
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[11]
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Lin CW, Chen YH, Chen WS. Application of Ultrasound and Ultrasound-Guided Intervention for Evaluating Elbow Joint Pathologies. J Med Ultrasound
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2012;20:87–95. doi:10.1016/j.jmu.2012.04.007.
[12]
antebrachial cutaneous nerve. Clin Anat 2015;28:872–7. doi:10.1002/ca.22601.
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[13]
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Jacobson J a., Chiavaras MM, Lawton JM, Downie B, Yablon CM, Lawton J. Radial Collateral Ligament of the Elbow: Sonographic Characterization With Cadaveric
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Cesmebasi A, O’driscoll SW, Smith J, Skinner JA, Spinner RJ. The snapping medial
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Dissection Correlation and Magnetic Resonance Arthrography. J Ultrasound Med 2014;33:1041–8. doi:10.7863/ultra.33.6.1041.
[14]
Stewart B, Harish S, Oomen G, Wainman B, Popowich T, Moro JK. Sonography of
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the lateral ulnar collateral ligament of the elbow: Study of cadavers and healthy
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volunteers. Am J Roentgenol 2009;193:1615–9. doi:10.2214/AJR.09.2812.
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[15]
Gondim Teixeira PA, Omoumi P, Trudell DJ, Ward SR, Lecocq S, Blum A, et al. Ultrasound assessment of the lateral collateral ligamentous complex of the
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elbow: Imaging aspects in cadavers and normal volunteers. Eur Radiol
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2011;21:1492–8. doi:10.1007/s00330-011-2076-8.
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[16]
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Smith J, Finnoff JT, O’Driscoll SW, Lai JK. Sonographic evaluation of the distal
biceps tendon using a medial approach: the pronator window. J Ultrasound Med
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2010;29:861–5.
[17]
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Kalainov DM, Cohen MS. Posterolateral rotatory instability of the elbow in
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association with lateral epicondylitis. A report of three cases. J Bone Joint Surg
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Am 2005;87:1120–5. doi:10.2106/JBJS.D.02293.
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FIGURES
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Figure 1: Ultrasound probe position during the Sonographic Posterolateral Rotatory Stress Test in an
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unembalmed cadaveric specimen. The probe is placed in the anatomic axial plane bridging the lateral
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epicondyle to the olecranon (A). To perform the Sonographic Posterolateral Rotatory Stress test, the
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examiner uses the opposite hand to apply a supination torque at the wrist, eliciting PLRI subluxation
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indicated by the gap in the posterolateral ulnohumeral joint (B).
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Figure 2: Sonographic posterolateral ulnohumeral distance at rest (A) and during the sonographic
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posterolateral rotatory stress test (B). Although still pictures can be obtained in both the resting and
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stressed states, the authors recommend capturing videos and obtaining resting and stress measurement
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from the videos. This allows the examiner to maintain transducer stability during testing. Images
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obtained with transducer positioned as in Figure 1. Hum: humerus.
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Figure 3: Lateral view of the right elbow demonstrating measurement of capitellar diameter (A). The
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Extensor Carpi Radialis Brevis (ECRB) release for Stage 2 is also shown (A and B). For Stage 3, the lateral
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collateral ligament complex (LCLC) was sequentially released at the level of the radiocapitellar joint until
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the posterolateral rotatory drawer test became positive (C). Finally, this release was continued through
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the lateral collateral ligament complex (LCLC) and anterior capsule until the lateral pivot-shift test become
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positive (D). ECRB: extensor carpi radialis brevis; LCL: lateral collateral ligament; LCLC: lateral collateral ligament complex; RC:
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radiocapitellar.
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Figure 4: Sonographic Posterolateral Ulnohumeral Laxity with Progressive Instability
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Stage 1: Intact Elbow; Stage 2: ECRB released; Stage 3: Positive posterolateral rotatory drawer test; Stage
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4: Positive lateral pivot-shift test. Stages 3 and 4 represent clinical instability. Values are means in mm
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with bars indicating +/- standard deviation (SD). *Indicates a statistically significant difference (p<.003)
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between groups.
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TABLES
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Table 1: Individual results of the clinical and sonographic exam for each specimen at each stage of
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progressive instability.
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Table 2: Multi-group comparisons of mean sonographic ulnohumeral distances and laxities across all
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stages of instability.
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Table 3: Pairwise comparisons of mean sonographic ulnohumeral distances between sequential
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pathologic states of instability (Stages 1 vs. 2, 2 vs. 3, and 3 vs. 4).
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The Sonographic Posterolateral Rotatory Stress Test: Cadaveric Validation TABLES
(+)?
(+)?
Ultrasound Exam (mm)
(+) ?
PS
Rest
Stress
Laxity
PLRD
PS
Rest
Stress
Laxity
PLRD
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
3 2 4
3 4 5
1 2 1
6 6 5
3 4 2
4 4 7
2 1 1
2 4 4
5 6 8
3 3 4
3 2 2
5 2 3
2 0 1
6 4 4
3 2 3
6
7
1
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
3 2 3
2 3 6
(-) (-) (-) (-) (-) (-) (-) (-) (-) +
7
4
+ + + + + + + + + +
Mean: Min: Max: StDev:
3
4
1
3
6
3
2 6
2 7
0 2
1 4
4 8
2 4
3 2 1 3
Ultrasound Exam (mm)
Stage 4 (+) Lateral Pivot-Shift Clinical Exam (+)?
Ultrasound Exam (mm)
PS
Rest
Stress
Laxity
PLRD
PS
Rest
Stress
Laxity
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
3 2 3
9 11 8
6 9 5
14 16 12
12 13 9
7 7 9
6 5 5
2 3 4
11 12 15
9 9 11
3 2 1
9 6 5
5 4 4
2 2 2
14 7 12
11 5 10
4
12
7
+ + + + + + + + + +
2 2 3
1 3 4
+ + + + + + + + + +
3
15
12
3
8
6
3
13
10
1 4
5 12
4 9
2 4
7 16
5 13
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PLRD
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(mm)
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Table 1: Individual results of the clinical and sonographic exam for each specimen at each stage of progressive instability. Stage 1 Stage 2 Stage 3 Intact Elbow ECRB Released (+) Posterolateral Rotatory Drawer Specimen Clinical Exam Ultrasound Exam Clinical Exam Clinical Exam
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1 2 3 4 5
1.47 1.59 0.52 0.90 1.29 0.70 1.00 1.98 1.49 0.60 2.42 2.27 PLRD: posterolateral rotatory drawer test; PS: lateral pivot-shift test; + indicates the clinical test was positive; (-) indicates that the clinical test was negative, min: minimum; max: maximum; StDev: standard deviation
Rest (mm) Stress (mm) Laxity (mm)
1 3 4 1
2 3 6 3
Mean Values for All stages 3 4 p-value* 3 3 0.58 8 13 < 0.001 6 10 < 0.001
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Table 2: Multi-group comparison of mean sonographic ulnohumeral distances and laxities across all stages of instability.
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*Calculated by ANOVA. P< 0.003 considered to represent statistical significance
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Table 3: Pairwise comparisons of mean sonographic ulnohumeral distances between sequential pathologic states of instability (Stages 1 vs. 2, 2 vs. 3, and 3 vs. 4).
Rest (mm) Stress (mm) Laxity (mm)
1 3 4 1
2 3 6 3
Diff 1 1 2
Stage 1 vs. 2 p-value* 0.60 <0.001
95% CI 0.1 to 2.7 1.2 to 2.4
2 3 6 3
3 3 8 6
Diff 0 3 3
Stage 2 vs. 3 p-value* <0.001 <0.001
95% CI 1.2 to 4.4 1.7 to 3.9
3 3 8 6
4 3 13 10
Diff 0 4 4
Stage 3 vs. 4 p-value* <0.001 <0.001
95% CI 2.3 to 6.5 2.7 to 6.3
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