Neer Award 2001: nonrecoverable strain fields of the anteroinferior glenohumeral capsule under subluxation.

Although tears of the glenohumeral capsule have been observed in anteroinferior instability, prefailure, nonrecoverable deformation is suspected but has not been shown to exist after shoulder subluxation. The inferior glenohumeral ligament in the anteroinferior capsule (AIC) is a primary stabilizer in anteroinferior instability. The aim of this study was to examine the nonrecoverable strain field of the AIC due to shoulder subluxation. Nonrecoverable strains were calculated between a nominal strain state and a postsubluxed state. AIC marker coordinates were reconstructed from stereoradiographs, and strains were calculated from these coordinates. Nonrecoverable strain was shown to develop, varying from 3% to 7% through a range of joint subluxation. High strain tended to occur on the glenoid side of the AIC. Interestingly, strains were generally not oriented along major ligamentous bands. This is the first study to quantify planar nonrecoverable strain fields in the glenohumeral joint capsule.