Commentary & Perspective

Commentary & Perspective on
"Loss of Chondrolabral Containment of the Glenohumeral Joint in Atraumatic Posteroinferior Multidirectional Instability"
by Seung-Ho Kim, MD, et al.

Commentary & Perspective by
Ken Yamaguchi, MD*,
Shoulder and Elbow Service, Washington University School of Medicine, St. Louis, MO

An evolving understanding of pathophysiology has greatly aided the development of successful treatment strategies for instability about the shoulder. For example, the anatomic derangements that have been shown to be associated with anteroinferior instability include labral detachment, inferior capsular stretching, and anterior bone loss¹. The proper identification and surgical treatment of these lesions has led to reliable success.

With regard to posterior instability, however, relatively sparse pathophysiologic information has been available. While few have debated that capsular attenuation is a primary factor associated with recurrent posterior instability, other potentially important sources of pathology, such as glenoid retroversion or loss of glenoid concavity, have been relatively less studied^2-6. The absence of this information may be partly responsible for the higher failure rates that have been associated with both the open and the arthroscopic surgical techniques that are currently employed in the treatment of posteroinferior instability^7,8.

In this issue of The Journal, the article by Kim, Noh, Park, Ryu, and Oh represents an important contribution to our understanding of the noncapsular processes that may be involved in posterior instability. In this well-written and thoughtfully conducted study, the authors employed the use of high-resolution magnetic resonance-arthrography to investigate both the soft-tissue and osseous abnormalities that were associated with a loss of glenoid concavity. Measured variables included the version of osseous and chondrolabral portions of the glenoid, labral height, and glenoid depth. Thirty-three patients with atraumatic posteroinferior instability were compared with thirty-three normal subjects. To the authors' credit, strict inclusion and exclusion criteria were imposed, an appropriate power analysis was performed, and radiographic analysis for accuracy was determined with intra and interobserver agreement analysis.

The authors demonstrated that shoulders with posteroinferior multidirectional instability were significantly different from normal shoulders with respect to anatomy that may be important to stability. Shoulders with instability had more retroversion of both the osseous and chondrolabral portions of the glenoid. Additionally, the height of the posterior labrum was decreased, contributing to a finding of decreased glenoid depth. All of these parameters were significantly different for only the middle and inferior planes of the glenoid. The loss of potentially important contributors to glenoid-based, humeral-head containment was a consistent finding.

In presenting these findings, the authors were careful to state that their results do not distinguish whether the loss of glenoid-based containment was a cause or a consequence of recurrent instability. While this is certainly true, given the limitations of this study, the results were certainly compelling regarding an important role for loss of containment in the progression of posterior instability. The results are biomechanically plausible and make intuitive sense. The findings also help explain why, in the authors' experience, modern arthroscopic procedures that directly address both capsular laxity and "labral augmentation" have been demonstrated to have high success rates in the treatment of posterior instability⁹. The results also suggest that restoring the soft-tissue component to glenoid containment was even more important in the treatment of individuals with osseous-based retroversion.

The authors are to be congratulated for this important study. Their findings strongly suggest that capsulolabroplasty of the posterior inferior labrum and capsule would be a more reliable means to restore stability than capsular shift alone.

*The author did not receive grants or outside funding in support of the research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Flatow EL, Warner JI. Instability of the shoulder: complex problems and failed repairs: part I. Relevant biomechanics, multidirectional instability, and severe glenoid loss. Instr Course Lect. 1998;47:97-112.
2. Neer CS 2nd, Foster CR. Inferior capsular shift for involuntary inferior and multidirectional instability of the shoulder. A preliminary report. J Bone Joint Surg Am. 1980;62:897-908.
3. Hurley JA, Anderson TE, Dear W, Andrish JT, Bergfeld JA, Weiker GG. Posterior shoulder instability. Surgical versus conservative results with evaluation of glenoid version. Am J Sports Med. 1992;20:396-400.
4. Lazarus MD, Sidles JA, Harryman DT 2nd, Matsen FA 3rd. Effect of a chondral-labral defect on glenoid concavity and glenohumeral stability. A cadaveric model. J Bone Joint Surg Am. 1996;78:94-102.
5. Weishaupt D, Zanetti M, Nyffeler RW, Gerber C, Hodler J. Posterior glenoid rim deficiency in recurrent (atraumatic) posterior shoulder instability. Skeletal Radiol. 2000;29:204-10.
6. Gerber C, Ganz R, Vinh TS. Glenoplasty for recurrent posterior shoulder instability. An anatomic reappraisal. Clin Orthop. 1987;216:70-9.
7. Wirth MA, Groh GI, Rockwood CA Jr. Capsulorrhaphy through an anterior approach for the treatment of atraumatic posterior glenohumeral instability with multidirectional laxity of the shoulder. J Bone Joint Surg Am. 1998;80:1570-8.
8. Pollock RG, Bigliani LU. Recurrent posterior shoulder instability. Diagnosis and treatment. Clin Orthop. 1993;291:85-96.
9. Kim SH, Kim HK, Sun JI, Park JS, Oh I. Arthroscopic capsulolabroplasty for posteroinferior multidirectional instability of the shoulder. Am J Sports Med. 2004;32:594-607.

Copyright © 2005 by the The Journal of Bone and Joint Surgery, Inc.