Instability after reverse total shoulder replacement

J Shoulder Elbow Surg (2011) 20, 584-590

www.elsevier.com/locate/ymse

Instability after reverse total shoulder replacement Robert A. Gallo, MDa,*, Seth C. Gamradt, MDb, Christopher J. Mattern, MDc, Frank A. Cordasco, MDc, Edward V. Craig, MDc, David M. Dines, MDc, Russell F. Warren, MDc, on behalf of the Sports Medicine and Shoulder Service at the Hospital for Special Surgery, New York, NY a

Bone and Joint Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, PA, USA b Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA c Shoulder and Sports Medicine Service, Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA Background: Despite advances in technique and implant design, instability after reverse total shoulder arthroplasty remains a challenging postoperative complication. Materials and methods: We examined our institutions’ first 57 reverse total shoulder arthroplasties performed during a 3-year period (2004-2006). There were 9 cases of instability, all occurring within the first 6 months after surgery. Results: All 9 patients had compromise of the subscapularis tendon at the time of initial reverse total shoulder implantation. With regard to implant positioning, 2 patients had superiorly inclined metaglenes and 3 had metaglenes positioned superior to the inferior glenoid. Each patient with a dislocation had at least 1 revision surgery, and 4 patients had underlying infection. At most recent follow-up, only 3 patients had a concentrically reduced reverse total shoulder arthroplasty in place whereas 3 remained explanted, 2 chronically dislocated, and 1 chronically subluxated. Conclusions: Early instability after reverse total shoulder arthroplasty can be related to inadequate soft tissue, inadequate deltoid tension, malpositioned implants, and/or infection, and outcomes of treatment of early instability are generally poor. Level of evidence: Level IV, Case Series, Treatment Study. Ó 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Reverse shoulder replacement; instability; revision

The reverse total shoulder replacement has become an accepted and successful treatment for rotator cuff arthropathy and revision shoulder arthroplasty associated with soft-tissue loss.1,2,4,6-8,10,12,14-16,18,20,21 Although initial *Reprint requests: Robert A. Gallo, MD, Bone and Joint Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, 30 Hope Drive, Hershey, PA 17033. E-mail address: [email protected] (R.A. Gallo).

reports have shown marked improvement in pain and function,1-4,6-8,10,12,14-16,18-21 concerns over complication rates ranging from 19% to 50%1-4,6-8,10,12,14-16,18-21 and reoperation rates as high as 33% at 38 months21 have tempered this enthusiasm. Despite advances in our understanding of the reverse shoulder biomechanics and surgical modifications that have resulted in decreased complications such as inferior glenoid notching,9,13,17 dislocation remains a common

1058-2746/$ - see front matter Ó 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. doi:10.1016/j.jse.2010.08.028

Analysis of cause, rationale for treatment

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Figure 1 (A) The angle of inclination of the implant (a) was determined by drawing a line perpendicular to the coronal plane of the glenoid (dotted line) and a line parallel to the center peg of the glenoid baseplate (b). The craniocaudal position of the glenosphere relative to the inferior glenoid rim represents the measurement between the inferior-most point on the glenosphere and the inferior tip of the glenoid. (B) Reverse total shoulder humeral components inserted with intact tuberosity. (C) Reverse total shoulder humeral components inserted without intact tuberosity.

complication12,21 that is difficult both to predict and to treat. We present a series of 9 patients who sustained early instability after reverse total shoulder replacement. The purpose is to review the preoperative, intraoperative, and postoperative factors; treatment; and ultimate outcomes of each patient and review the available literature to treat this dreaded complication.

Materials and methods This retrospective case series was approved by the Hospital for Special Surgery Institutional Review Board (protocol No. 26110). Over a 3-year period (2004-2006), a total of 57 consecutive reverse total shoulder arthroplasties were performed at our institution. The primary indication for surgery was pain associated with limited shoulder range of motion and shoulder pseudoparalysis due to an absence or inefficiency of the rotator cuff tendons. The underlying etiology was rotator cuff tear arthropathy in 36 cases, failure of previous shoulder prosthesis in 18, and proximal humeral fracture and sequelae in 3. The mean age at the time of reverse total shoulder replacement was 69.9 years (range, 40-89 years). Thirty-six DePuy Delta III prostheses (DePuy Orthopaedics, Warsaw, IN) and twenty-one Encore reverse shoulder prostheses (RSP) (Encore Medical, Austin, TX) were implanted based on the preference of each of 7 fellowship-trained shoulder surgeons. Regardless of the implant chosen, a deltopectoral incision with detachment of the subscapularis tendon, if present, was the surgical approach used for the majority of cases. A total of 24 early complications, including 1 death, 8 dislocations, 7 infections, 2 fractures, 2 component malfunctions, 2 nerve palsies, 1 recurrent subluxation, and 1 component loosening, occurred in 16 patients (28.0%). A total of 24 procedures, including 12 revision surgeries, were required in 11 patients (19.2%). The revision procedures were performed in 8 patients (14.0%) at a mean of 9.3 months (range, 0-26 months) after the reverse prosthesis was initially inserted. Whereas recurrent subluxation was seen in only 1 patient, dislocation occurred in

8 patients (15.1%), with concomitant infection in 4. All dislocations were anterior and confirmed radiographically. The medical records of these 9 patients who had instability after reverse shoulder replacement were reviewed for the following information: patient’s age at the time of the initial reverse shoulder replacement surgery, the nature of previous surgical procedures, and underlying etiology requiring reverse total shoulder replacement. Initial postoperative radiographs were examined for (1) inclination angle between the glenosphere and scapular neck, (2) craniocaudal position of the glenosphere relative to the inferior glenoid rim, and (3) presence of the greater tuberosity (Fig. 1). The proposed mechanism and treatment of each dislocation and the eventual outcome were obtained through review of surgical notes and clinical follow-up, respectively. Special notation was made of the implant type and sizes of each component at revision procedures.

Results The mean age at the time of initial reverse total shoulder replacement was 66 years (range, 54-80 tears). Seven patients, including five patients who had previous shoulder arthroplasty, had prior surgical procedures performed in the affected shoulder. The mean number of procedures for each patient before reverse total shoulder replacement was 2.1 (range, 0-5). None of the 9 patients died or were lost to follow-up. The mean time from reverse total shoulder replacement to most recent follow-up was 18.8 months. Several perioperative abnormalities were identified among this cohort of patients. All 9 had an abnormality of the subscapularis tendon found at the time of reverse total shoulder implantation (Fig. 2). Whereas 3 patients had an absent subscapularis tendon, the others had intact or partially intact tendons of moderate or poor quality. With regard to implant positioning, 2 had superiorly angled metaglenes and 3 had metaglenes positioned superior to the

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Figure 2 The subscapularis tendon was irregular in all 9 instability cases, including this patient with a significantly atrophied subscapularis tendon on CT scan.

inferior edge of the glenoid (Fig. 3). Only 5 of 9 had intact, well-reduced greater tuberosities; the remaining 4 had a compromised tuberosity because of either fracture sequelae or previous hemiarthroplasty (or both). Table I provides the background information and original surgical information for all 9 patients. Instability developed within the first 6 months in all patients in our cohort. Each patient with a dislocation had at least 1 revision surgery to treat the reverse total shoulder instability. Four cases were complicated by infection. At most recent follow-up, only 3 patients have concentrically located reverse total shoulder replacements. Whereas 3 remain explanted because of poor-quality bone and/or infection, 2 are chronically dislocated and another has recurrent subluxation. Table II lists each patient’s revision procedures and ultimate outcome.

Discussion The reverse total shoulder replacement has been an effective option to restore function among those with shoulder pseudoparalysis. Despite its success, this procedure has been associated with a relatively high complication rate. Most series, particularly those with a large proportion of revision cases, have reported cases of instability after reverse total shoulder replacement,12,21 yet few discuss methods of prevention and treatment. Instability of a reverse total shoulder implant remains a difficult problem to solve. In our series, despite each patient undergoing revision surgery, only 3 prostheses were concentrically located at the time of most recent follow-up. Often, revision cases are limited by poor bone stock and inadequate soft-tissue envelopes from the underlying disease and/or previous procedures. Furthermore, many patients undergoing reverse shoulder replacements are elderly, medically fragile, and unable to tolerate major

Figure 3 A metaglene positioned superior to the inferior edge of the glenoid was among the most common technical errors that occurred in this series of instability.

surgical revisions. Therefore, the savvy shoulder surgeon must be able to recognize the cause of instability and determine a treatment plan that restores stability while limiting adverse outcomes. The preliminary step in any workup for instability after arthroplasty is to determine whether the joint has become infected and whether the components have loosened or dislodged. Although we had only 1 case of early loosening among our institution’s first 57 reverse total shoulder patients, instability was accompanied by infection in 44% of our cases. Among the 4 cases of instability associated with infection, only 1 involved a patient who had a previous shoulder replacement; the others had cuff tear arthropathy as the underlying etiology. All 3 non-revision cases were treated surgically to correct the reverse shoulder replacement instability before the discovery of an infection, which involved Propionibacterium acnes as the causative agent in each case. For those cases with a well-fixed implant and no evidence of an infection, the cause of instability should be sought. Knowledge of the mechanism of dislocation guides the surgical treatment plan. In our experience, noninfectious instability can result from either inadequate tensioning of the deltoid or impingement of the components. Inadequate tensioning of the deltoid after reverse total shoulder replacement was first described by Grammont. In his sentinel article, he discussed ‘‘global decoaptation,’’ a condition in which the lack of sufficient tension in the deltoid muscle causes the formation of a space between the ball and the socket.1,7 Intraoperatively, there is little to

Preoperative and immediate postoperative data on initial reverse total shoulder arthroplasty procedure

Patient

Age (y)

Diagnosis

Previous surgery

Reverse implant

Subscapularis integrity

Metaglene inclination

Distance from inferior metaglene to inferior glenoid

Intact greater tuberosity

A

60

Failed arthroplasty

DePuy Delta

Absent

Upward 16

9 mm below

No

B

54

Cuff tear arthropathy

DePuy Delta

Partially intact, moderate quality

Downward 13

3 mm below

Yes

C

69

DePuy Delta

4 mm below

No

67

Intact, moderate quality Intact, poor quality

Downward 5

D

Downward 7

6 mm below

No

E

65

Failed arthroplasty after fracture Failed arthroplasty after fracture Failed arthroplasty

Total shoulder arthroplasty (2) Open rotator cuff repair, lysis of adhesions Arthroscopy, hemiarthroplasty Hemiarthroplasty

Downward 7

9 mm above

Yes

F G

76 65

Cuff tear arthropathy Failed arthroplasty

Partially intact, poor quality Intact, poor quality Absent

Downward 10 Downward 1

8 mm above 2 mm below

Yes No

H

80

Cuff tear arthropathy

Upward 8

4 mm below

Yes

I

54

Cuff tear arthropathy

Partially intact, moderate quality Absent

Downward 5

3 mm above

Yes

DePuy Delta

Hemiarthroplasty (2)

Encore RSP

None Total shoulder arthroplasty, hemiarthroplasty (2) None

DePuy Delta Encore RSP

Open rotator cuff repair (3), latissimus transfer, debridement

Encore RSP DePuy Delta

Analysis of cause, rationale for treatment

Table I

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Table II

Revision reverse total shoulder replacement surgery for instability and outcomes

Patient

Reverse implant

Revision 1

A

DePuy Delta

B

DePuy Delta

Enlarged stem Increased polyethylene thickness Increased glenosphere size Added lateralizer

C D E

DePuy Delta DePuy Delta Encore RSP

F

DePuy Delta

G

Encore RSP

H I

Encore RSP DePuy Delta

Added lateralizer Explanted Increased humeral socket thickness Decreased polyethylene thickness

Revision 2

Increased polyethylene thickness

Increased humeral socket polyethylene thickness

Enlarged stem Increased polyethylene thickness Increased glenosphere size Decreased humeral socket thickness

Added lateralizer

Implanted Encore prosthesis

guide the surgeon in determining the correct amount of tension to place on the deltoid. Boileau et al1 suggested that proper tensioning of the implant can be roughly gauged by the tension generated within the conjoined tendon after reduction of the implant. Often, however, intraoperative assessment of deltoid tension is based on surgeon experience. This determination likely contributes to the learning curve seen during a surgeon’s first 20 reverse shoulder replacements.22 More recently, L€adermann et al11 described a radiographic method of determining optimal deltoid tension based on humeral length. In this method, humeral length of the contralateral limb is measured preoperatively and used to guide the amount of lengthening necessary to restore adequate deltoid tension.11 If ‘‘global decoaptation’’ is the source of instability, offset should be increased to restore proper deltoid tension.1 In most instances, offset can be restored with relatively simple measures, such as increasing the diameter of the glenosphere, placing a humeral neck extension (lateralizer) beneath the polyethylene cup, and/or increasing the thickness of the polyethylene cup.1 The baseplate and stem, which are anchored to the glenoid and humerus, respectively, usually do not need to be revised. However, caution must be paid to avoid deltoid overtensioning, which can result in acromion fracture and brachial plexus neurapraxia. Impingement of the implant requires a more extensive revision of the components, particularly the baseplate and metaglene. In our experience, the implant usually impinges on the inferior scapular neck as the arm is adducted. The mechanism is similar to that responsible for inferior scapular notching. Recently, several manufacturer

Proposed mechanism

Outcome

Impingement

Chronic dislocation

Inadequate tension Impingement Inadequate tension Stem loosening Inadequate tension

Explant

Impingement

Inadequate tension Impingement Inadequate tension Inadequate tension

Concentrically intact Explant Concentrically intact, chronically infected Concentrically intact

Chronic dislocation Chronic subluxation Explant

recommendations regarding the placement of the glenosphere and its baseplate have been made and confirmed biomechanically to reduce contact between the polyethylene cup and the inferior scapular neck.9,13 The recommendations include (1) component placement flush or extending beyond the inferior glenoid rim and (2) 15 downward tilt of the component. These guidelines were not known at the time at which most of the reverse total shoulder replacements in our series were performed and subsequently revised. In addition, a recent study using the Encore RSP (Encore Medical, Austin, TX) recommended a humeral neck-shaft angle of 130 , 10-mm lateral offset, and a glenosphere with a 42-mm diameter to increase the range of impingement-free adduction.9 Because these guidelines were published after our series was performed, no attempt was made to revise the components according to these guidelines. Not unexpectedly, the only revision surgery to correct impingement that was successful involved a revision of the humeral component and glenosphere. The lack of competent, normally functioning subscapularis tendon likely contributes to instability. Edwards et al5 showed that an irreparable subscapularis at the time of reverse total shoulder replacement is the most significant risk factor for dislocation after implantation using a deltopectoral approach. Boileau et al1 suggested that the lack of compromise of the subscapularis tendon in an anterosuperior transdeltoid approach contributes to the lower incidence of instability seen with that approach. Indeed, no dislocations have been reported among the 4 published series (total of 50 patients) that used the subscapularissparing approaches exclusively.4,7,10,19

Analysis of cause, rationale for treatment On the basis of our experience and the available literature, standard workup after a dislocation of a reverse shoulder implant should focus on assessment of modifiable factors such component stability, positioning, version, and inclination; humeral length; and of course, presence of infection. Infection should be evaluated with routine serum markers, such as complete blood count, C-reactive protein level, erythrocyte sedimentation rate, and if warranted, a shoulder aspiration with fluid culture. All cultures should be allowed to grow for a minimum of 10 days to adequately detect P acnes. Once infection has been ruled out, radiographs, including standard shoulder views and bilateral full-length anteroposterior humeral views, should be obtained and analyzed according to standard guidelines for component position and inclination9,13 and humeral length.11 Finally, component version and the presence of an adequate subscapularis are best evaluated with a computed tomography (CT) scan. Evidence of component loosening should be apparent on both radiographs and CT. Given our study’s retrospective nature, it has several weaknesses, especially related to the radiographic interpretation of the images. The determination of inclination we used is prone to error and a high degree of interobserver disagreement; however, this method remained the best option to measure inclination. Unfortunately, there were no accurate determinations of version obtained because postoperative axillary radiographic views and CT images were not routinely ordered postoperatively. Nonetheless, our measurements, though somewhat imperfect, do offer additional insight on possible mechanisms of instability. Although the surgical learning curve likely contributed to some of the instability, the exact role that surgeon experience with the procedure plays in the development of postoperative complications after reverse total shoulder arthroplasty remains unproven. A recent study suggested that there was no significant difference in intraoperative complication and early complication rate between a surgeon’s first and second set of 10 reverse total shoulder replacements.22 It should be noted that all surgeons in this study were fellowship-trained shoulder surgeons with at least 5 years of clinical experience and perform a high volume of shoulder arthroplasty. Reverse total shoulder arthroplasty represents a valuable tool for restoring painless shoulder function in those with rotator cuff arthropathy and failed shoulder replacements with a deficient rotator cuff. However, there is a significant risk of complications, such as instability. In all cases of instability, infection and component loosening should be ruled out. Thereafter, the causedeither inadequate deltoid tension or component impingement (or both)dmust be determined to successfully treat the instability. For cases of ‘‘global coaptation,’’ increasing offset to increase deltoid tension is often successful. Meanwhile, impingement often requires revision of components according to recent guidelines to restore stability.

589

Conclusions Despite advances in technique and implant design, instability after reverse total shoulder arthroplasty remains a challenging postoperative complication. Early instability after reverse total shoulder arthroplasty can be related to inadequate soft tissue, improper tensioning of the deltoid, malpositioned implants, and/or infection. A thorough evaluation of the etiology should be sought and used to guide treatment of early instability after a reverse total shoulder replacement.

Acknowledgment The authors thank John MacGillivray, MD, Stephen Fealy, MD, and Michael Maynard, MD, for contributing patients to the study, as well as Alana Burns and Jessica Lahre for their assistance in facilitating the study.

Disclaimer Robert A. Gallo, Seth C. Gamradt, Christopher J. Mattern, and Frank A. Cordasco, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article. Edward V. Craig has a royalty agreement with Biomet. David M. Dines has royalty agreements with Biomet and Biomimetic Therapeutics; serves as a paid consultant to or is an employee of Biomet, Biomimetic Therapeutics, and Tornier; has stock considerations with Biomimetic Therapeutics; and has received research support from Biomet and Biomimetic Therapeutics. Russell F. Warren has royalty agreements with Biomet and Smith & Nephew, has stock considerations with Zimmer, is a paid consultant for KFx, and receives research support from Smith & Nephew.

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