Location and Magnitude of Capsular Injuries Varies following Multiple Anterior Dislocations of the Shoulder: Implications for Surgical Repair.

Capsular injuriescan occur during multiple shoulder dislocations.The purpose of this study was to evaluate the location and magnitude of glenohumeral capsular injury following multiple dislocations. We hypothesized that the magnitude of capsular injury would increase and the location of peak injury would vary depending on the number of dislocations.Seven fresh-frozen cadaveric shoulders were used. 7 x 11 grid of strain markers were affixed to the anteroinferior capsule.Each jointwas then mounted to a 6 degree-freedom robotic testing system. Marker tracking was performed following 1, 2, 3, 4, 5, and 10 dislocations to determine the non-recoverable strainas capsular injury. Following each dislocation, the magnitude of the maximum principal strain representing the non-recoverable strain in the inferior glenohumeral capsule wasquantified by comparing the strain marker positions following each dislocation.The peak value of non-recoverable strain statistically increased with the number of dislocations in five of seven specimens(p=0.0007).The capsular location that had the peak value of non-recoverable strain varied according to the number of dislocations, and from specimen to specimen.Non-recoverable strain was identified in the posterior capsule andanterior axillary pouch, which increased with the number of dislocations compared to the other regions of the capsule (p= 0.001- 0.012) by up to 16 %. This article is protected by copyright. All rights reserved.