Posterior Shoulder Instability
ABSTRACT & COMMENTARY
Synopsis: Posterior shoulder instability is an uncommon problem requiring careful patient selection and attention to correction of anatomic labral and capsular abnormalities.
Source: Antoniou J, et al. Capsulolabral augmentation for the management of posteroinferior instability of the shoulder. J Bone Joint Surg Am 2000;82(9):1220-1230.
This prospective evaluation of capsulolabral augmentation for posteroinferior instability of the shoulder evaluated 41 patients undergoing an arthroscopic posterior capsular shift. All patients presented with a positive jerk test and failed a six-month period of rehabilitation. In an attempt to produce a true outcome study, Antoniou and colleagues used a pre- and postoperative SF-36, the Simple Shoulder Test, and a treatment outcome questionnaire. One of four types of surgical findings of the posterior capsular labral complex were noted in more than 83% of patients, and almost an equal number presented with a history of trauma. Surgery included repair or augmentation of the posterior capsulolabral complex to restore the depth of the glenoid cavity. In addition, plication with arthroscopic sutures was performed to tighten the redundant posteroinferior capsule and to close the rotator interval in patients with generalized ligamentous laxity.
Antoniou et al noted improvement in mean scores of the simple shoulder test, but only two of eight of the SF-36 parameters improved significantly at a minimum one-year follow-up. However, those patients on worker’s compensation insurance had no improvement for any of the parameters on SF-36 evaluation. Physical exam findings improved in all patients with regards to stability, but subjectively only 35 of 41 patients described improved stability of the shoulder. Interestingly, 28 of 41 patients complained of residual stiffness, whereas the mean score on flexibility examination had not changed significantly compared to preoperative evaluation.
Comment by Robert C. Schenck, Jr., MD
This interesting study looks at the rare and often overlooked shoulder instability pattern of posteroinferior instability. Doug Harryman, now deceased, had tremendous insight and ingenuity in problems about the shoulder throughout his orthopaedic career. This paper is no different. As with most clinical orthopaedic studies, this paper contrasts the objective findings of a surgical procedure with that of patient satisfaction and outcomes. Using the SF-36 and the Simple Shoulder Test, Antoniou et al note the discrepancies between good objective findings (stable shoulder, good range of motion, minimal pain) and patient satisfaction. All patients with worker’s compensation insurance claims had no improvement on SF-36 parameters despite objective findings otherwise. As noted by other investigators, the SF-36 is frequently difficult to administer despite its universal usage. Furthermore, the ability of the SF-36 to differentiate outcomes with orthopaedic procedures has been questioned.
The described surgical technique is all-arthroscopic and requires an experienced sports surgeon to perform such a plication. They conclude that posteroinferior instability is associated with well-defined lesions of the glenolabral complex that are amenable to repair, thereby restoring the depth of the glenolabral cavity. In addition, capsular plication is necessary to address the redundant capsular laxity. Although Antoniou et al did not detail their complications, such a procedure requires cadaveric lab experience or fellowship training to minimize pitfalls. The final question remaining involves patient selection with posteroinferior instability. In the 19 patients receiving worker’s compensation, only six returned to work. Although the follow-up was only 28 months (range, 12-69 months), Antoniou et al describe a successful arthroscopic technique with good objective findings postoperatively. However, insurance companies reading no improvement on the SF-36 outcome measure may interpret it otherwise, especially in the area of worker’s compensation claims.
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