Abstract
Objectives:
Direct comparisons between the direction of shoulder instability as it pertains to clinical and demographic risk factors are lacking. The purpose of this study is to identify and compare demographic, clinical, and peri-operative variables in patients receiving arthroscopic treatment for anterior and posterior shoulder instability.
Methods:
A retrospective chart review was performed for consecutive patients who underwent primary arthroscopic labral repair surgery for anterior and posterior shoulder instability with a minimum 2-year follow-up. Surgeries were performed by six surgeons at a single institution between 2012-2020. Patients with prior shoulder instability surgeries of any kind were excluded. Demographics and operative variables included sex, body mass index (BMI), Contact/collision sports, tobacco use, ASA grade, number of dislocations (<1, 1, 2, >2), tear size (120, 240, and 360 degrees), age, time from first dislocation to surgery, number of anchors, and concomitant procedures. Study groups were compared using student’s t-tests and Mann-Whitney U test for continuous variables and Chi-Square or Fisher’s Exact tests for discrete variables with a significance of 0.05.
Results:
Five hundred and twenty-four (524) patients met inclusion criteria. Overall, there were 133 females (25.4%) and 291 males (74.6%) with a mean age of 27.1 years at the time of surgery (SD ± 9.9) and a BMI of 26.6 (SD ± 5.6). Posterior instability patients were less likely to have experienced a dislocation (15.1% without prior dislocation) than patients with anterior instability (3.4%). Additionally, posterior instability patients that did experience a dislocation (22.6%) were less likely to have greater than two dislocations when compared to anterior instability patients (53.6%). Posterior instability was more frequently associated with males (85%), higher BMI (mean = 28.25), and contact/collision sports (41%). Posterior instability patients were more likely than anterior instability patients to have concomitant procedures performed at the time of labral repair, including capsular plication, (31.6%) biceps tenodesis (14%), and distal clavicle excision (8.8%). Lastly, posterior instability patients typically required fewer anchors (3.4) than anterior instability patients (3.98) at the time of labral repair.
Conclusions:
Despite having fewer instability events or dislocations, patients that receive a posterior labral repair are more likely to have additional injuries in their shoulder requiring treatment when compared to patients that have received an arthroscopic anterior labral repair. Interestingly, posterior labral repair patients are more commonly male, and contact athletes, as well. With posterior shoulder instability being less common, we speculate that these findings could correlate with a more significant amount of energy/mechanism involved when a shoulder does dislocate posteriorly, thus leading to injuries to additional shoulder structures. It also correlates with the repetitive microtrauma mechanism that can happen with posterior labral tears. Whereas patients may be more likely to experience symptoms over a longer period of time without ever having a full instability event and additional shoulder structures become injured.