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Influence of the Labrum on Version and Diameter of the Glenoid: A Morphometric Study Using Magnetic Resonance Images
Influence of the Labrum on Version and Diameter of the Glenoid: A Morphometric Study Using Magnetic Resonance Images Joyce Anthony, M.B.B.S., Ibin Varughese, M.B.B.S., Vaida Glatt, Ph.D., Kevin Tetsworth, M.D., F.R.A.C.S., and Erik Hohmann, M.D., Ph.D., F.R.C.S.
Purpose: To use magnetic resonance imaging to determine the influence of the labrum on both the osseous version and effective diameter of the glenoid. Methods: This was a retrospective, cross-sectional study of patients with shoulder pain who underwent MRI between February 2014 and February 2015. The morphology of the glenoid labrum and glenoid was scanned with a 3-T magnetic resonance imaging scanner, and variables were measured by use of IntelliSpace PACS Enterprise. Patients were included if they were aged between 18 and 40 years and the radiologist reported a normal glenohumeral joint or if they were young patients aged less than 30 years with acute traumatic isolated partial- or fullthickness tears of the rotator cuff with a history of symptoms of less than 3 months. A pilot study was conducted with 3 observers and 3 repeated measurements at intervals to determine the interobserver and intraobserver reliability. Data analysis included descriptive statistics of measured variables, as well as paired Student t tests to determine the relative difference between labral and osseous morphometric variables. Results: Excellent inter-rater reliability (0.95-0.96) and intrarater reliability (0.93-0.98) were obtained in the pilot study of 20 patients. The study population was composed of 100 patients with a mean age of 37.3 years (standard deviation [SD], 11.8 years), having a gender distribution of 56 male and 44 female patients; there were 53 right and 47 left shoulders. The glenoid osseous version measured 5.7 (SD, 5.3 ), and the labral version measured 10 (SD, 5.5 ); the glenoid osseous diameter measured 28.0 mm (SD, 3.3 mm), and the labral diameter measured 31.9 mm (SD, 3.2 mm). The labrum significantly increased the version by 4.3 (P ¼ .001) and significantly increased the diameter by 3.9 mm (P ¼ .001). Conclusions: The results of this study showed that the labrum increased the effective glenoid version by 75% (4.3 of retroversion) and the effective glenoid diameter by 14% (3.9 mm). Level of Evidence: Level IV, prognostic case series.
M
orphometric variables of the glenohumeral joint, such as glenoid version and diameter, have previously been associated with glenohumeral instability and rotator cuff tears.1 Saha2 showed, over
From the Department of Orthopaedic Surgery, Royal Brisbane Hospital (J.A., K.T.), Herston; School of Medicine (J.A.), Department of Surgery, School of Medicine (K.T.), and Department of Orthopaedic Surgery, Clinical Medical School (E.H.), University of Queensland, Brisbane; Department of Orthopaedic Surgery, The Prince Charles Hospital (I.V.), Chermside; Institute of Health and Biomedical Innovation, Queensland University of Technology (V.G.), Brisbane; Queensland University of Technology (K.T.), Brisbane; and Orthopaedic Research Institute of Australia (K.T.), Sydney, Australia. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received September 4, 2016; accepted January 25, 2017. Address correspondence to Erik Hohmann, M.D., Ph.D., F.R.C.S., Valiant Clinic/Houston Methodist Group, PO Box 414296, United Arab Emirates. E-mail: [email protected] Ó 2017 by the Arthroscopy Association of North America 0749-8063/16855/$36.00 http://dx.doi.org/10.1016/j.arthro.2017.01.045
40 years ago, that osseous glenoid retroversion and an increased glenohumeral index enhanced shoulder stability. More recently, Hohmann and Tetsworth3 reported that patients with less retroversion and increased inferior glenoid inclination are at higher risk of sustaining an anterior shoulder dislocation. Tetreault et al.4 showed that whereas increased retroversion of the glenoid is predictive of subscapularis and supraspinatus tears, increased anteversion of the glenoid is predictive of infraspinatus and supraspinatus tears. Increased retroversion of the osseous and labral glenoid has been implicated in the development of internal impingement in overhead athletes.5 The osseous and soft-tissue morphology of the glenohumeral joint is also associated with the development of osteoarthritis.6 However, literature on the morphology and morphometry of the glenohumeral joint is sparse and is limited to cadaveric and computed tomography (CT) studies. Saha2 showed that 73.5% of the population had a retroverted glenoid, with an average of 7.4 . Similarly,
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Hohmann and Tetsworth3 reported a mean osseous retroversion of 5.8 in a white population, whereas Matsumura et al.7 reported a mean glenoid retroversion of 1 , ranging from 9 to 13 . Jung et al.8 reported a mean osseous diameter of 27.5 mm. The contact area between the humerus and glenoid varies throughout the range of motion, such that the humeral head is most congruent with the glenoid and the contact area is maximized in abduction.9 The glenoid labrum contributes to 50% of the socket depth and serves to deepen the glenoid fossa and provide an antishear bumper effect.10 However, the influence of the labrum on the effective version and diameter of the glenoid is not well understood, possibly because of the high incidence of labral pathology in cadavers and the poor soft-tissue resolution on CT. The purpose of this study was to use magnetic resonance imaging (MRI) to determine the influence of the labrum on both the osseous version and effective diameter of the glenoid. We hypothesized that the glenoid labrum would maintain the osseous version while increasing the effective diameter.
Methods Study Design Patients who underwent MRI between February 2014 and February 2015 at a single institution were retrospectively identified. This study was conducted as a retrospective, cross-sectional study of the glenoid and its labrum. The IMPAX radiography database (Agfa HealthCare, Greenville, SC) was searched, and once subjects were identified, the medical chart of the individual was reviewed by an independent research associate (J.A.). The inclusion criteria for the study were defined as follows: patients who presented to the emergency department or general orthopaedic clinic with shoulder pain and who underwent MRI of the glenohumeral joint, age between 18 and 40 years at the time of MRI, and no apparent pathology of the glenohumeral joint as reported by the radiologist. However, we also included young patients aged less than 30 years with acute traumatic isolated partial- or full-thickness tears of the rotator cuff and a short history of symptoms of less than 3 months. It was assumed that these patients did not have any chronic changes to the glenoid, which are more often observed in patients with chronic complaints.4,11 Patients were excluded if there was evidence of any of the following: injury to the biceps anchor, posterior labrum lesion, humeral avulsion of the glenohumeral ligament, anterior labroligamentous periosteal sleeve avulsion, rotator cuff injury, previous fracture-dislocation, bony Bankart lesion, glenoid or humeral chondral damage, previous surgery on the glenoid or proximal humerus, or a history of atraumatic and habitual dislocations. In addition,
patients were excluded if they reported a history of surgical or nonsurgical management of pathology pertaining to the glenohumeral joint. The version and diameter of the glenoid were measured on magnetic resonance (MR) images, by first assessing only the osseous component and then repeating these measures to include the labrum. Imaging Technique and Follow-Up Patients were scanned with a Siemens Magnetom Verio 3-T MRI scanner, and variables were measured with the IMPAX system. All MRI studies were performed by the same radiology technician using a pre-established protocol and reported by a consultant radiologist with a subspecialty interest in musculoskeletal imaging. The radiologist was not involved with measurement or analysis of the study parameters. Images were obtained with the patient supine and the arm placed on the side of the body, with the forearm supinated and the hand under the hip, to maintain humeral position during the examination. The MRI study included sagittal, axial, and coronal oblique images. The coronal oblique images were taken in a plane parallel to the supraspinatus tendon. All patients underwent review at the orthopaedic outpatient clinic within 3 months after MRI to discuss the results and provide consent for inclusion in this study. Morphometric Variables The morphometric variables of the glenohumeral joint that were studied included osseous version, labral version, osseous diameter, and labral diameter. Osseous and labral glenoid diameter, as well as osseous and labral glenoid version, was established by use of the techniques described by Friedman et al.12 and Tetreault et al.4 The axial image immediately inferior to the supraspinatus muscle, where the posterior border of the scapular neck was first clearly visible, was selected. The distance between the anterior and posterior osseous margins of the glenoid denoted the osseous glenoid diameter, and the distance between the anterior and posterior labral margins denoted the labral glenoid diameter (Fig 1). A reference line drawn through the midpoint of the horizontal diameter of the glenoid articular surface and the medial border of the scapular blade defined the axis of the scapula, and a reference line drawn perpendicular to the axis of the scapula at the midpoint of the horizontal diameter of the glenoid articular surface defined the axis of the glenoid. The angle formed by the line joining the anterior and posterior osseous margins of the glenoid and the axis of the glenoid then determined the osseous glenoid version (Fig 2). Similarly, the angle formed by the line joining the anterior and posterior labral margins of the glenoid and the axis of the glenoid determined the labral glenoid version (Fig 2). Given the
GLENOID LABRUM EFFECT ON VERSION AND DIAMETER
Fig 1. The distance between the anterior and posterior labral margins (line 1) was measured by use of the specific work tools within the IMPAX software program (Agfa HealthCare) and denoted the osseous diameter. Similarly, the distance between the anterior and posterior osseous margins of the glenoid (line 2) was measured and denoted the labral glenoid diameter.
comparative nature of the project, all measurements were performed by the independent research associate (J.A.). To establish interobserver and intraobserver reliability (interclass correlation coefficient), 20 random images were selected. Two investigators (J.A. and I.V.) used the described measurement methods, and interobserver and intraobserver correlation coefficients were calculated. Statistical Analysis An a priori sample size analysis was performed by use of the pilot data from the interclass correlation coefficient assessment. The study was designed to detect a difference of 2.5 (standard deviation [SD], 5 ) between osseous and labral version and a difference of 2 mm (SD, 3 mm) between osseous and labral diameter. The sample size based on these assumptions, with a ¼ .05 and power of 90%, indicated that 84 images were needed for version and 65 images were required for diameter. Means and SDs were calculated for all variables, and paired-sample t tests were used to compare osseous version with labral version and osseous diameter with labral diameter. In all tests, P < .05 was considered statistically significant. All analyses were conducted with STATA SE for Windows (version 12.0; StataCorp, College Station, TX).
Results A total of 106 participants underwent MRI between February 2014 and February 2015 and satisfied the inclusion criteria of the study. However, 6 participants had to be excluded from the study based on the
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exclusion criteria: 2 had undergone prior surgical management, and 4 had persistent pain. All of the remaining 100 MRI studies from patients with a mean age of 37.3 years (SD, 11.8 years) were examined to measure the morphometric variables. There were 56 male and 44 female patients; the right shoulder was involved in 53 patients and the left in 47. The reported diagnostic indication for MRI in the study population included acromioclavicular joint injury (n ¼ 8), supraspinatus tendon tears (n ¼ 4), long biceps tendon tears (n ¼ 6), calcific tendinitis (n ¼ 10), ganglion cysts (n ¼ 2), impingement, (n ¼ 31), nonspecific shoulder pain (n ¼ 27), and trauma (n ¼ 12). Excellent inter-rater reliability and intrarater reliability for both glenoid version and diameter were noted. The interobserver reliability was 0.95 for version and 0.96 for diameter. The intraobserver reliability was 0.93 for version and 0.98 for diameter. The mean glenoid osseous version was 5.7 (SD, 5.3 ) of retroversion, and the mean labral version was 10.0 (SD, 5.5 ) of retroversion. The mean osseous diameter was 28.6 mm (SD, 3.3 mm), and the mean labral diameter was 31.9 mm (SD, 3.2 mm). Further descriptive statistics based on gender and site are shown in Table 1. The labrum significantly increased the effective glenoid retroversion by 4.3 (P ¼ .001) and the effective diameter by 3.9 mm (P ¼ .001).
Fig 2. A reference line (line 3) drawn through the midpoint of the horizontal diameter of the glenoid articular surface and the medial border of the scapular blade defined the axis of the scapula, and a reference line (line 4) drawn perpendicular to the axis of the scapula at the midpoint of the horizontal diameter of the glenoid articular surface defined the axis of the glenoid. The angle formed by the line joining the anterior and posterior osseous margins of the glenoid and the axis of the glenoid then determined the osseous glenoid version (lines 2 and 4). Similarly, the angle formed by the line joining the anterior and posterior labral margins of the glenoid and the axis of the glenoid determined the labral glenoid version (lines 1 and 4).
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Table 1. Distribution of Mean Values of Morphometric Variables Based on Gender and Site Osseous Version, Gender Male Female Site Right Left Total
Labral Version,
Osseous Labral Diameter, mm Diameter, mm
6.5 (5.5) 10.6 (5.2) 4.6 (4.9) 9.2 (5.9)
30.1 (2.8) 25.4 (1.8)
34.1 (2.0) 29.2 (2.0)
5.4 (5.1) 9.6 (5.6) 6.0 (5.5) 10.4 (5.5) 5.7 (5.3) 10.0 (5.5)
27.9 (3.4) 28.3 (3.3) 28.0 (3.3)
31.6 (3.1) 32.4 (3.2) 31.9 (3.2)
NOTE. Data are presented as mean (standard deviation).
Discussion The most important findings of this study are that the glenoid labrum increased the effective glenoid version by 75% (4.3 ) whereas the effective glenoid diameter also increased by 14% (3.9 mm). The morphology of the glenoid fossa has been described as a pear-shaped structure or reverse commaeshaped structure.8 The version of the glenoid decreases from superior to inferior.13 For this project, a standardized technique to measure the glenoid osseous version was used, which has been previously described by both Tetreault et al.4 and Friedman et al.12 Tetreault et al. showed that the correlation between MR and CT images was almost perfect, with a Pearson correlation moment of 0.98. Given the excellent inter-rater and intrarater reliability for both version and diameter in our study, the measures are most likely accurate, reliable, and valid. The version of the osseous glenoid has been previously investigated using cadavers and CT images, with varying published results ranging from a mean of 1 to 7.4 of retroversion.2,3,7,13 Our study found a mean osseous retroversion of 5.7 , consistent with these prior studies. Similarly, this study found a mean osseous diameter of 28 mm, which is also consistent with prior studies that have reported means ranging from 22.00 mm in an Asian population to 29 mm in a white population.14,15 The glenoid labrum is a roughly circular fibrous structure that contributes to 50% of the total depth of the glenoid socket. Detachment therefore reduces this depth by approximately 50%, from 5 to 2.4 mm.10 Howell and Galinat10 suggested that these anatomic observations provide some evidence that the labrum, as well as the resulting socket, may be a critical factor in shoulder stability, and this may have clinical implications. Surgical repair and restoration of the glenoid-labrum complex increase the height of the labrum and may be important for clinical outcome and recurrence rates.16,17 Most current surgical techniques use an arthroscopic repair, with suture anchors used to reattach the labrum to the glenoid.18 However, different surgical techniques may result in better restoration of labral height and provide increased
stability to the glenohumeral construct.19,20 In addition, labral height and thickness are directly related to strain behavior, in which a thinner labrum results in increased strain.21 Glenoid version may also be a risk factor for anterior shoulder dislocation, and in fact, a recent publication by Hohmann and Tetsworth3 reported that patients with less retroversion were at higher risk of sustaining an anterior shoulder dislocation. In contrast, Owens et al.22 could not show that glenoid version, width, or index was associated with shoulder instability. Arthroscopic labral repair may therefore serve 2 purposes. The increase in glenoid retroversion may possibly result in subtle changes in kinematics and reduce anterior translation, with the glenohumeral center of rotation and translation shifting posteriorly.23 It could be postulated that increasing osseous diameter, socket depth, and the contact area with the humeral head may be less important than previously thought and that the creation of a soft-tissue bumper reduces anterior translation.23 Alberta et al.23 effectively placed suture anchors medial to the intact labrum and increased labral height and thickness. However, Yamamoto et al.24 showed that there was no difference in translational forces, whether a bumper was created or not. Nevertheless, a major limitation of this study was that the bumper created by reattaching the labrum to the glenoid was not large enough to make a significant difference. The mean size of the bumper was only 2.2 mm compared with 2.4 mm in the intact shoulder, effectively reducing labral height. In a later study, Yamamoto et al.25 showed that glenoid defects of less than 30% have no effect on glenohumeral joint contact pressures provided that the labrum was reconstructed, confirming that there might be a critical loss of effective glenoid diameter. The findings of Yamamoto et al.25 may explain why the 14% increase in effective glenoid diameter caused by the labrum in our series has possibly no effect on stability. Alternatively, the significant increase in retroversion by 75% may be a more important factor for shoulder stability. A possible relation between glenoid version and posterior instability has been previously described by Brewer et al.26 They showed a direct relation between excessive retroversion of the glenoid and posterior nontraumatic dislocation. More recently, Gottschalk et al.27 have also shown that patients with posterior instability have a higher incidence of a retroverted glenoid. In contrast, the only study describing a possible relation between glenoid version and anterior instability was published by Hohmann and Tetsworth3 in 2015. In this comparative study, they showed that among patients who had sustained an anterior shoulder dislocation, the glenoid retroversion was 2 compared with 6 in the control group. Eichinger et al.28 showed that changes in glenoid version can reduce dislocation
GLENOID LABRUM EFFECT ON VERSION AND DIAMETER
forces significantly. Spontaneous anterior dislocations occurred in 25% of specimens with an anterior glenoid version of 10 , whereas posterior dislocations occurred in 62% of specimens with glenoid retroversion exceeding 15 . These findings strongly suggest a causal relation between glenoid version and shoulder instability. Glenoid version is only one of the static stabilizing factors, and there are both static and dynamic variables that also contribute to stability. Although anterior glenohumeral instability is common among young athletes, the risk factors for injury are still poorly understood.22 The results of our basic morphologic study have shown that the labrum increases effective glenoid retroversion by 75% but only contributed to a 14% increase in the effective glenoid diameter. Limitations This study has several limitations. This is a retrospective, cross-sectional study of MRI studies performed for patients who presented with shoulder pain without any demonstrable pathology, as determined by a consultant radiologist, with the patients’ complaints resolving spontaneously in 3 months without any surgical intervention. This sample may not be representative of the normal healthy population and could potentially introduce bias. Moreover, performing patient recruitment from a single institution, as opposed to performing a multicenter study, may weaken the external validity of the study. However, closer examination shows that the osseous morphometric variables appear to reflect the results of prior studies, representing a normal healthy population and preserving the external validity of the study.2,3,7,14,15 Moreover, stringent inclusion and exclusion criteria were used to minimize the risk of selection of pathologic glenohumeral joints, but sampling bias cannot be entirely excluded. Measurement of morphometric variables was performed by a single investigator and could potentially introduce measurement bias. However, given the high intrarater correlation coefficient, the decision to not involve multiple observers was made to minimize interobserver measurement errors. This study did not account for pivotal variables such as gender, age, and site; other factors such as race and professional involvement in throwing sports could confound the results of this study.5,7,15 Regardless, not limiting participation in the study to a particular race or activity level further improves the external validity of the study.
Conclusions The results of this study showed that the labrum increased the effective glenoid version by 75% (4.3 of retroversion) and the effective glenoid diameter by 14% (3.9 mm).
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References 1. Lewis GS, Armstrong AD. Glenoid spherical orientation and version. J Shoulder Elbow Surg 2011;20:3-11. 2. Saha AK. Dynamic stability of the glenohumeral joint. Acta Orthop Scand 1971;42:491-505. 3. Hohmann E, Tetsworth K. Glenoid version and inclination are risk factors for anterior shoulder dislocation. J Shoulder Elbow Surg 2015;24:1268-1273. 4. Tetreault P, Krueger A, Zurakowski D, Gerber C. Glenoid version and rotator cuff tears. J Orthop Res 2004;22: 202-207. 5. Drakos MC, Barker JU, Osbahr DC, et al. Effective glenoid version in professional baseball players. Am J Orthop 2010;39:340-344. 6. Walch G, Badet R, Boulahia A, Khoury A. Morphologic study of the glenoid in primary glenohumeral osteoarthritis. J Arthroplasty 1999;14:756-760. 7. Matsumura N, Ogawa K, Kobayashi S, et al. Morphologic features of humeral head and glenoid version in the normal glenohumeral joint. J Shoulder Elbow Surg 2014;23:1724-1730. 8. Jung HJ, Jeon IH, Ahn TS, et al. Penetration depth and size of the nonarthritic glenoid: Implications for glenoid replacement. Clin Anat 2012;25:1043-1050. 9. Warner JJ, Bowen MK, Deng XH, Hannafin JA, Arnoczky SP, Warren RF. Articular contact patterns of the normal glenohumeral joint. J Shoulder Elbow Surg 1998;7: 381-388. 10. Howell SM, Galinat BJ. The glenoid-labral socket. A constrained articular surface. Clin Orthop Relat Res 1989;243:122-125. 11. Bishop JL, Kline SK, Aalderink KJ, Zauel R, Bey MJ. Glenoid inclination in rotator cuff patients and associations with superior glenohumeral joint translation. J Shoulder Elbow Surg 2009;18:213-236. 12. Friedman RJ, Hawthorne KB, Genez BM. The use of computerized tomography in the measurement of glenoid version. J Bone Joint Surg Am 1992;74: 1032-1037. 13. Bouchaib J, Clavert P, Kempf JF, Kahn JL. Morphological analysis of the glenoid version in the axial plane according to age. Surg Radiol Anat 2014;36:579-585. 14. De Wilde LF, Berghs BM, Audenaert E, Sys G, Van Maele GO, Barbaix E. About the variability of the shape of the glenoid cavity. Surg Radiol Anat 2004;26:54-59. 15. Phonphok P, Kulkamthorn N. Assessment of approximate glenoid size in Thai people. J Med Assoc Thai 2014;97: S14-S18 (suppl 2). 16. Park JY, Lee SJ, Lhee SH, Oh JH. Change in labrum height after arthroscopic Bankart repair: Correlation with preoperative tissue quality and clinical outcome. J Shoulder Elbow Surg 2012;21:1712-1720. 17. Green MR, Christensen KP. Arthroscopic Bankart procedure: Two- to five year followup with clinical correlation to severity of glenoid labral lesion. Am J Sports Med 1995;23:276-281. 18. Balke M, Shafizadeh S, Bouillon B, Banerjee M. Management of shoulder instability: The current state of treatment among German orthopaedic surgeons. Arch Orthop Trauma Surg 2016;136:1717-1721.
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19. Hagstrom LS, Marzo JM. Simple versus horizontal anchor repair of Bankart lesions: Which better restores labral anatomy? Arthroscopy 2013;29:325-329. 20. Okamura K, Takiuchi T, Aoki M, Ishii S. Labral shape after arthroscopic Bankart repair: Comparisons between the anchor and Caspari methods. Arthroscopy 2005;21:194-199. 21. Drury NJ, Ellis BJ, Weiss JA, McMahon PJ, Debski RE. The impact of glenoid labrum thickness and modulus on labrum and glenohumeral capsule function. J Biomech Eng 2010;132:121003. 22. Owens BD, Campbell SE, Cameron KL. Risk factors for anterior glenohumeral instability. Am J Sports Med 2014;42:2591-2596. 23. Alberta FG, Elattrache NS, Mihata T, McGarry MH, Tibone JE, Lee TQ. Arthroscopic anteroinferior suture plication resulting in decreased glenohumeral translation and external rotation. Study of a cadaver model. J Bone Joint Surg Am 2006;88:179-187. 24. Yamamoto N, Muraki T, Sperling JW, et al. Does the “bumper” created during Bankart repair contribute to
25.
26.
27.
28.
shoulder stability? J Shoulder Elbow Surg 2013;22: 828-834. Yamamoto A, Massimini DF, Di Stefano J, Higgins LD. Glenohumeral contact pressure with simulated anterior labral and osseous defects in cadaveric shoulders before and after soft tissue repair. Am J Sports Med 2014;42: 1947-1954. Brewer BJ, Wubben RC, Carrera GF. Excessive retroversion of the glenoid cavity. A cause of non-traumatic posterior instability of the shoulder. J Bone Joint Surg Am 1986;68:724-731. Gottschalk MB, Ghasem A, Todd D, Daruwalla J, Xerogeanes J, Karas S. Posterior shoulder instability: Does glenoid retroversion predict recurrence and contralateral instability? Arthroscopy 2015;31:488-493. Eichinger JK, Massimini DF, Kim J, Higgins LD. Biomechanical evaluation of glenoid version and dislocation direction on the influence of anterior shoulder instability and development of Hill-Sachs lesions. Am J Sports Med 2016;44:2792-2799.
Purpose: To use magnetic resonance imaging to determine the influence of the labrum on both the osseous version and effective diameter of the glenoid. Methods: This was a retrospective, cross-sectional study of patients with shoulder pain who underwent MRI between February 2014 and February 2015. The morphology of the glenoid labrum and glenoid was scanned with a 3-T magnetic resonance imaging scanner, and variables were measured by use of IntelliSpace PACS Enterprise. Patients were included if they were aged between 18 and 40 years and the radiologist reported a normal glenohumeral joint or if they were young patients aged less than 30 years with acute traumatic isolated partial- or fullthickness tears of the rotator cuff with a history of symptoms of less than 3 months. A pilot study was conducted with 3 observers and 3 repeated measurements at intervals to determine the interobserver and intraobserver reliability. Data analysis included descriptive statistics of measured variables, as well as paired Student t tests to determine the relative difference between labral and osseous morphometric variables. Results: Excellent inter-rater reliability (0.95-0.96) and intrarater reliability (0.93-0.98) were obtained in the pilot study of 20 patients. The study population was composed of 100 patients with a mean age of 37.3 years (standard deviation [SD], 11.8 years), having a gender distribution of 56 male and 44 female patients; there were 53 right and 47 left shoulders. The glenoid osseous version measured 5.7 (SD, 5.3 ), and the labral version measured 10 (SD, 5.5 ); the glenoid osseous diameter measured 28.0 mm (SD, 3.3 mm), and the labral diameter measured 31.9 mm (SD, 3.2 mm). The labrum significantly increased the version by 4.3 (P ¼ .001) and significantly increased the diameter by 3.9 mm (P ¼ .001). Conclusions: The results of this study showed that the labrum increased the effective glenoid version by 75% (4.3 of retroversion) and the effective glenoid diameter by 14% (3.9 mm). Level of Evidence: Level IV, prognostic case series.
M
orphometric variables of the glenohumeral joint, such as glenoid version and diameter, have previously been associated with glenohumeral instability and rotator cuff tears.1 Saha2 showed, over
From the Department of Orthopaedic Surgery, Royal Brisbane Hospital (J.A., K.T.), Herston; School of Medicine (J.A.), Department of Surgery, School of Medicine (K.T.), and Department of Orthopaedic Surgery, Clinical Medical School (E.H.), University of Queensland, Brisbane; Department of Orthopaedic Surgery, The Prince Charles Hospital (I.V.), Chermside; Institute of Health and Biomedical Innovation, Queensland University of Technology (V.G.), Brisbane; Queensland University of Technology (K.T.), Brisbane; and Orthopaedic Research Institute of Australia (K.T.), Sydney, Australia. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received September 4, 2016; accepted January 25, 2017. Address correspondence to Erik Hohmann, M.D., Ph.D., F.R.C.S., Valiant Clinic/Houston Methodist Group, PO Box 414296, United Arab Emirates. E-mail: [email protected] Ó 2017 by the Arthroscopy Association of North America 0749-8063/16855/$36.00 http://dx.doi.org/10.1016/j.arthro.2017.01.045
40 years ago, that osseous glenoid retroversion and an increased glenohumeral index enhanced shoulder stability. More recently, Hohmann and Tetsworth3 reported that patients with less retroversion and increased inferior glenoid inclination are at higher risk of sustaining an anterior shoulder dislocation. Tetreault et al.4 showed that whereas increased retroversion of the glenoid is predictive of subscapularis and supraspinatus tears, increased anteversion of the glenoid is predictive of infraspinatus and supraspinatus tears. Increased retroversion of the osseous and labral glenoid has been implicated in the development of internal impingement in overhead athletes.5 The osseous and soft-tissue morphology of the glenohumeral joint is also associated with the development of osteoarthritis.6 However, literature on the morphology and morphometry of the glenohumeral joint is sparse and is limited to cadaveric and computed tomography (CT) studies. Saha2 showed that 73.5% of the population had a retroverted glenoid, with an average of 7.4 . Similarly,
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Hohmann and Tetsworth3 reported a mean osseous retroversion of 5.8 in a white population, whereas Matsumura et al.7 reported a mean glenoid retroversion of 1 , ranging from 9 to 13 . Jung et al.8 reported a mean osseous diameter of 27.5 mm. The contact area between the humerus and glenoid varies throughout the range of motion, such that the humeral head is most congruent with the glenoid and the contact area is maximized in abduction.9 The glenoid labrum contributes to 50% of the socket depth and serves to deepen the glenoid fossa and provide an antishear bumper effect.10 However, the influence of the labrum on the effective version and diameter of the glenoid is not well understood, possibly because of the high incidence of labral pathology in cadavers and the poor soft-tissue resolution on CT. The purpose of this study was to use magnetic resonance imaging (MRI) to determine the influence of the labrum on both the osseous version and effective diameter of the glenoid. We hypothesized that the glenoid labrum would maintain the osseous version while increasing the effective diameter.
Methods Study Design Patients who underwent MRI between February 2014 and February 2015 at a single institution were retrospectively identified. This study was conducted as a retrospective, cross-sectional study of the glenoid and its labrum. The IMPAX radiography database (Agfa HealthCare, Greenville, SC) was searched, and once subjects were identified, the medical chart of the individual was reviewed by an independent research associate (J.A.). The inclusion criteria for the study were defined as follows: patients who presented to the emergency department or general orthopaedic clinic with shoulder pain and who underwent MRI of the glenohumeral joint, age between 18 and 40 years at the time of MRI, and no apparent pathology of the glenohumeral joint as reported by the radiologist. However, we also included young patients aged less than 30 years with acute traumatic isolated partial- or full-thickness tears of the rotator cuff and a short history of symptoms of less than 3 months. It was assumed that these patients did not have any chronic changes to the glenoid, which are more often observed in patients with chronic complaints.4,11 Patients were excluded if there was evidence of any of the following: injury to the biceps anchor, posterior labrum lesion, humeral avulsion of the glenohumeral ligament, anterior labroligamentous periosteal sleeve avulsion, rotator cuff injury, previous fracture-dislocation, bony Bankart lesion, glenoid or humeral chondral damage, previous surgery on the glenoid or proximal humerus, or a history of atraumatic and habitual dislocations. In addition,
patients were excluded if they reported a history of surgical or nonsurgical management of pathology pertaining to the glenohumeral joint. The version and diameter of the glenoid were measured on magnetic resonance (MR) images, by first assessing only the osseous component and then repeating these measures to include the labrum. Imaging Technique and Follow-Up Patients were scanned with a Siemens Magnetom Verio 3-T MRI scanner, and variables were measured with the IMPAX system. All MRI studies were performed by the same radiology technician using a pre-established protocol and reported by a consultant radiologist with a subspecialty interest in musculoskeletal imaging. The radiologist was not involved with measurement or analysis of the study parameters. Images were obtained with the patient supine and the arm placed on the side of the body, with the forearm supinated and the hand under the hip, to maintain humeral position during the examination. The MRI study included sagittal, axial, and coronal oblique images. The coronal oblique images were taken in a plane parallel to the supraspinatus tendon. All patients underwent review at the orthopaedic outpatient clinic within 3 months after MRI to discuss the results and provide consent for inclusion in this study. Morphometric Variables The morphometric variables of the glenohumeral joint that were studied included osseous version, labral version, osseous diameter, and labral diameter. Osseous and labral glenoid diameter, as well as osseous and labral glenoid version, was established by use of the techniques described by Friedman et al.12 and Tetreault et al.4 The axial image immediately inferior to the supraspinatus muscle, where the posterior border of the scapular neck was first clearly visible, was selected. The distance between the anterior and posterior osseous margins of the glenoid denoted the osseous glenoid diameter, and the distance between the anterior and posterior labral margins denoted the labral glenoid diameter (Fig 1). A reference line drawn through the midpoint of the horizontal diameter of the glenoid articular surface and the medial border of the scapular blade defined the axis of the scapula, and a reference line drawn perpendicular to the axis of the scapula at the midpoint of the horizontal diameter of the glenoid articular surface defined the axis of the glenoid. The angle formed by the line joining the anterior and posterior osseous margins of the glenoid and the axis of the glenoid then determined the osseous glenoid version (Fig 2). Similarly, the angle formed by the line joining the anterior and posterior labral margins of the glenoid and the axis of the glenoid determined the labral glenoid version (Fig 2). Given the
GLENOID LABRUM EFFECT ON VERSION AND DIAMETER
Fig 1. The distance between the anterior and posterior labral margins (line 1) was measured by use of the specific work tools within the IMPAX software program (Agfa HealthCare) and denoted the osseous diameter. Similarly, the distance between the anterior and posterior osseous margins of the glenoid (line 2) was measured and denoted the labral glenoid diameter.
comparative nature of the project, all measurements were performed by the independent research associate (J.A.). To establish interobserver and intraobserver reliability (interclass correlation coefficient), 20 random images were selected. Two investigators (J.A. and I.V.) used the described measurement methods, and interobserver and intraobserver correlation coefficients were calculated. Statistical Analysis An a priori sample size analysis was performed by use of the pilot data from the interclass correlation coefficient assessment. The study was designed to detect a difference of 2.5 (standard deviation [SD], 5 ) between osseous and labral version and a difference of 2 mm (SD, 3 mm) between osseous and labral diameter. The sample size based on these assumptions, with a ¼ .05 and power of 90%, indicated that 84 images were needed for version and 65 images were required for diameter. Means and SDs were calculated for all variables, and paired-sample t tests were used to compare osseous version with labral version and osseous diameter with labral diameter. In all tests, P < .05 was considered statistically significant. All analyses were conducted with STATA SE for Windows (version 12.0; StataCorp, College Station, TX).
Results A total of 106 participants underwent MRI between February 2014 and February 2015 and satisfied the inclusion criteria of the study. However, 6 participants had to be excluded from the study based on the
3
exclusion criteria: 2 had undergone prior surgical management, and 4 had persistent pain. All of the remaining 100 MRI studies from patients with a mean age of 37.3 years (SD, 11.8 years) were examined to measure the morphometric variables. There were 56 male and 44 female patients; the right shoulder was involved in 53 patients and the left in 47. The reported diagnostic indication for MRI in the study population included acromioclavicular joint injury (n ¼ 8), supraspinatus tendon tears (n ¼ 4), long biceps tendon tears (n ¼ 6), calcific tendinitis (n ¼ 10), ganglion cysts (n ¼ 2), impingement, (n ¼ 31), nonspecific shoulder pain (n ¼ 27), and trauma (n ¼ 12). Excellent inter-rater reliability and intrarater reliability for both glenoid version and diameter were noted. The interobserver reliability was 0.95 for version and 0.96 for diameter. The intraobserver reliability was 0.93 for version and 0.98 for diameter. The mean glenoid osseous version was 5.7 (SD, 5.3 ) of retroversion, and the mean labral version was 10.0 (SD, 5.5 ) of retroversion. The mean osseous diameter was 28.6 mm (SD, 3.3 mm), and the mean labral diameter was 31.9 mm (SD, 3.2 mm). Further descriptive statistics based on gender and site are shown in Table 1. The labrum significantly increased the effective glenoid retroversion by 4.3 (P ¼ .001) and the effective diameter by 3.9 mm (P ¼ .001).
Fig 2. A reference line (line 3) drawn through the midpoint of the horizontal diameter of the glenoid articular surface and the medial border of the scapular blade defined the axis of the scapula, and a reference line (line 4) drawn perpendicular to the axis of the scapula at the midpoint of the horizontal diameter of the glenoid articular surface defined the axis of the glenoid. The angle formed by the line joining the anterior and posterior osseous margins of the glenoid and the axis of the glenoid then determined the osseous glenoid version (lines 2 and 4). Similarly, the angle formed by the line joining the anterior and posterior labral margins of the glenoid and the axis of the glenoid determined the labral glenoid version (lines 1 and 4).
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Table 1. Distribution of Mean Values of Morphometric Variables Based on Gender and Site Osseous Version, Gender Male Female Site Right Left Total
Labral Version,
Osseous Labral Diameter, mm Diameter, mm
6.5 (5.5) 10.6 (5.2) 4.6 (4.9) 9.2 (5.9)
30.1 (2.8) 25.4 (1.8)
34.1 (2.0) 29.2 (2.0)
5.4 (5.1) 9.6 (5.6) 6.0 (5.5) 10.4 (5.5) 5.7 (5.3) 10.0 (5.5)
27.9 (3.4) 28.3 (3.3) 28.0 (3.3)
31.6 (3.1) 32.4 (3.2) 31.9 (3.2)
NOTE. Data are presented as mean (standard deviation).
Discussion The most important findings of this study are that the glenoid labrum increased the effective glenoid version by 75% (4.3 ) whereas the effective glenoid diameter also increased by 14% (3.9 mm). The morphology of the glenoid fossa has been described as a pear-shaped structure or reverse commaeshaped structure.8 The version of the glenoid decreases from superior to inferior.13 For this project, a standardized technique to measure the glenoid osseous version was used, which has been previously described by both Tetreault et al.4 and Friedman et al.12 Tetreault et al. showed that the correlation between MR and CT images was almost perfect, with a Pearson correlation moment of 0.98. Given the excellent inter-rater and intrarater reliability for both version and diameter in our study, the measures are most likely accurate, reliable, and valid. The version of the osseous glenoid has been previously investigated using cadavers and CT images, with varying published results ranging from a mean of 1 to 7.4 of retroversion.2,3,7,13 Our study found a mean osseous retroversion of 5.7 , consistent with these prior studies. Similarly, this study found a mean osseous diameter of 28 mm, which is also consistent with prior studies that have reported means ranging from 22.00 mm in an Asian population to 29 mm in a white population.14,15 The glenoid labrum is a roughly circular fibrous structure that contributes to 50% of the total depth of the glenoid socket. Detachment therefore reduces this depth by approximately 50%, from 5 to 2.4 mm.10 Howell and Galinat10 suggested that these anatomic observations provide some evidence that the labrum, as well as the resulting socket, may be a critical factor in shoulder stability, and this may have clinical implications. Surgical repair and restoration of the glenoid-labrum complex increase the height of the labrum and may be important for clinical outcome and recurrence rates.16,17 Most current surgical techniques use an arthroscopic repair, with suture anchors used to reattach the labrum to the glenoid.18 However, different surgical techniques may result in better restoration of labral height and provide increased
stability to the glenohumeral construct.19,20 In addition, labral height and thickness are directly related to strain behavior, in which a thinner labrum results in increased strain.21 Glenoid version may also be a risk factor for anterior shoulder dislocation, and in fact, a recent publication by Hohmann and Tetsworth3 reported that patients with less retroversion were at higher risk of sustaining an anterior shoulder dislocation. In contrast, Owens et al.22 could not show that glenoid version, width, or index was associated with shoulder instability. Arthroscopic labral repair may therefore serve 2 purposes. The increase in glenoid retroversion may possibly result in subtle changes in kinematics and reduce anterior translation, with the glenohumeral center of rotation and translation shifting posteriorly.23 It could be postulated that increasing osseous diameter, socket depth, and the contact area with the humeral head may be less important than previously thought and that the creation of a soft-tissue bumper reduces anterior translation.23 Alberta et al.23 effectively placed suture anchors medial to the intact labrum and increased labral height and thickness. However, Yamamoto et al.24 showed that there was no difference in translational forces, whether a bumper was created or not. Nevertheless, a major limitation of this study was that the bumper created by reattaching the labrum to the glenoid was not large enough to make a significant difference. The mean size of the bumper was only 2.2 mm compared with 2.4 mm in the intact shoulder, effectively reducing labral height. In a later study, Yamamoto et al.25 showed that glenoid defects of less than 30% have no effect on glenohumeral joint contact pressures provided that the labrum was reconstructed, confirming that there might be a critical loss of effective glenoid diameter. The findings of Yamamoto et al.25 may explain why the 14% increase in effective glenoid diameter caused by the labrum in our series has possibly no effect on stability. Alternatively, the significant increase in retroversion by 75% may be a more important factor for shoulder stability. A possible relation between glenoid version and posterior instability has been previously described by Brewer et al.26 They showed a direct relation between excessive retroversion of the glenoid and posterior nontraumatic dislocation. More recently, Gottschalk et al.27 have also shown that patients with posterior instability have a higher incidence of a retroverted glenoid. In contrast, the only study describing a possible relation between glenoid version and anterior instability was published by Hohmann and Tetsworth3 in 2015. In this comparative study, they showed that among patients who had sustained an anterior shoulder dislocation, the glenoid retroversion was 2 compared with 6 in the control group. Eichinger et al.28 showed that changes in glenoid version can reduce dislocation
GLENOID LABRUM EFFECT ON VERSION AND DIAMETER
forces significantly. Spontaneous anterior dislocations occurred in 25% of specimens with an anterior glenoid version of 10 , whereas posterior dislocations occurred in 62% of specimens with glenoid retroversion exceeding 15 . These findings strongly suggest a causal relation between glenoid version and shoulder instability. Glenoid version is only one of the static stabilizing factors, and there are both static and dynamic variables that also contribute to stability. Although anterior glenohumeral instability is common among young athletes, the risk factors for injury are still poorly understood.22 The results of our basic morphologic study have shown that the labrum increases effective glenoid retroversion by 75% but only contributed to a 14% increase in the effective glenoid diameter. Limitations This study has several limitations. This is a retrospective, cross-sectional study of MRI studies performed for patients who presented with shoulder pain without any demonstrable pathology, as determined by a consultant radiologist, with the patients’ complaints resolving spontaneously in 3 months without any surgical intervention. This sample may not be representative of the normal healthy population and could potentially introduce bias. Moreover, performing patient recruitment from a single institution, as opposed to performing a multicenter study, may weaken the external validity of the study. However, closer examination shows that the osseous morphometric variables appear to reflect the results of prior studies, representing a normal healthy population and preserving the external validity of the study.2,3,7,14,15 Moreover, stringent inclusion and exclusion criteria were used to minimize the risk of selection of pathologic glenohumeral joints, but sampling bias cannot be entirely excluded. Measurement of morphometric variables was performed by a single investigator and could potentially introduce measurement bias. However, given the high intrarater correlation coefficient, the decision to not involve multiple observers was made to minimize interobserver measurement errors. This study did not account for pivotal variables such as gender, age, and site; other factors such as race and professional involvement in throwing sports could confound the results of this study.5,7,15 Regardless, not limiting participation in the study to a particular race or activity level further improves the external validity of the study.
Conclusions The results of this study showed that the labrum increased the effective glenoid version by 75% (4.3 of retroversion) and the effective glenoid diameter by 14% (3.9 mm).
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References 1. Lewis GS, Armstrong AD. Glenoid spherical orientation and version. J Shoulder Elbow Surg 2011;20:3-11. 2. Saha AK. Dynamic stability of the glenohumeral joint. Acta Orthop Scand 1971;42:491-505. 3. Hohmann E, Tetsworth K. Glenoid version and inclination are risk factors for anterior shoulder dislocation. J Shoulder Elbow Surg 2015;24:1268-1273. 4. Tetreault P, Krueger A, Zurakowski D, Gerber C. Glenoid version and rotator cuff tears. J Orthop Res 2004;22: 202-207. 5. Drakos MC, Barker JU, Osbahr DC, et al. Effective glenoid version in professional baseball players. Am J Orthop 2010;39:340-344. 6. Walch G, Badet R, Boulahia A, Khoury A. Morphologic study of the glenoid in primary glenohumeral osteoarthritis. J Arthroplasty 1999;14:756-760. 7. Matsumura N, Ogawa K, Kobayashi S, et al. Morphologic features of humeral head and glenoid version in the normal glenohumeral joint. J Shoulder Elbow Surg 2014;23:1724-1730. 8. Jung HJ, Jeon IH, Ahn TS, et al. Penetration depth and size of the nonarthritic glenoid: Implications for glenoid replacement. Clin Anat 2012;25:1043-1050. 9. Warner JJ, Bowen MK, Deng XH, Hannafin JA, Arnoczky SP, Warren RF. Articular contact patterns of the normal glenohumeral joint. J Shoulder Elbow Surg 1998;7: 381-388. 10. Howell SM, Galinat BJ. The glenoid-labral socket. A constrained articular surface. Clin Orthop Relat Res 1989;243:122-125. 11. Bishop JL, Kline SK, Aalderink KJ, Zauel R, Bey MJ. Glenoid inclination in rotator cuff patients and associations with superior glenohumeral joint translation. J Shoulder Elbow Surg 2009;18:213-236. 12. Friedman RJ, Hawthorne KB, Genez BM. The use of computerized tomography in the measurement of glenoid version. J Bone Joint Surg Am 1992;74: 1032-1037. 13. Bouchaib J, Clavert P, Kempf JF, Kahn JL. Morphological analysis of the glenoid version in the axial plane according to age. Surg Radiol Anat 2014;36:579-585. 14. De Wilde LF, Berghs BM, Audenaert E, Sys G, Van Maele GO, Barbaix E. About the variability of the shape of the glenoid cavity. Surg Radiol Anat 2004;26:54-59. 15. Phonphok P, Kulkamthorn N. Assessment of approximate glenoid size in Thai people. J Med Assoc Thai 2014;97: S14-S18 (suppl 2). 16. Park JY, Lee SJ, Lhee SH, Oh JH. Change in labrum height after arthroscopic Bankart repair: Correlation with preoperative tissue quality and clinical outcome. J Shoulder Elbow Surg 2012;21:1712-1720. 17. Green MR, Christensen KP. Arthroscopic Bankart procedure: Two- to five year followup with clinical correlation to severity of glenoid labral lesion. Am J Sports Med 1995;23:276-281. 18. Balke M, Shafizadeh S, Bouillon B, Banerjee M. Management of shoulder instability: The current state of treatment among German orthopaedic surgeons. Arch Orthop Trauma Surg 2016;136:1717-1721.
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19. Hagstrom LS, Marzo JM. Simple versus horizontal anchor repair of Bankart lesions: Which better restores labral anatomy? Arthroscopy 2013;29:325-329. 20. Okamura K, Takiuchi T, Aoki M, Ishii S. Labral shape after arthroscopic Bankart repair: Comparisons between the anchor and Caspari methods. Arthroscopy 2005;21:194-199. 21. Drury NJ, Ellis BJ, Weiss JA, McMahon PJ, Debski RE. The impact of glenoid labrum thickness and modulus on labrum and glenohumeral capsule function. J Biomech Eng 2010;132:121003. 22. Owens BD, Campbell SE, Cameron KL. Risk factors for anterior glenohumeral instability. Am J Sports Med 2014;42:2591-2596. 23. Alberta FG, Elattrache NS, Mihata T, McGarry MH, Tibone JE, Lee TQ. Arthroscopic anteroinferior suture plication resulting in decreased glenohumeral translation and external rotation. Study of a cadaver model. J Bone Joint Surg Am 2006;88:179-187. 24. Yamamoto N, Muraki T, Sperling JW, et al. Does the “bumper” created during Bankart repair contribute to
25.
26.
27.
28.
shoulder stability? J Shoulder Elbow Surg 2013;22: 828-834. Yamamoto A, Massimini DF, Di Stefano J, Higgins LD. Glenohumeral contact pressure with simulated anterior labral and osseous defects in cadaveric shoulders before and after soft tissue repair. Am J Sports Med 2014;42: 1947-1954. Brewer BJ, Wubben RC, Carrera GF. Excessive retroversion of the glenoid cavity. A cause of non-traumatic posterior instability of the shoulder. J Bone Joint Surg Am 1986;68:724-731. Gottschalk MB, Ghasem A, Todd D, Daruwalla J, Xerogeanes J, Karas S. Posterior shoulder instability: Does glenoid retroversion predict recurrence and contralateral instability? Arthroscopy 2015;31:488-493. Eichinger JK, Massimini DF, Kim J, Higgins LD. Biomechanical evaluation of glenoid version and dislocation direction on the influence of anterior shoulder instability and development of Hill-Sachs lesions. Am J Sports Med 2016;44:2792-2799.