Biomechanical evaluation of multidirectional glenohumeral instability and repair.

The purpose of the current study was to create a multidirectional glenohumeral instability model and compare anterior capsulolabral reconstruction with inferior capsular shift with respect to their effects on glenohumeral translation and rotational range of motion. Ten fresh frozen cadaveric shoulders were used with a custom shoulder translation testing jig. To create the multidirectional instability model the capsule was stretched an additional 20% from the initial rotational range of motion in apprehension and neutral positions. Shoulders were repaired using anterior capsulolabral reconstruction (n = 5) or an inferior capsular shift (n = 5). Anterior, posterior, inferior, and superior translations were measured along with the rotational range of motion for intact, stretched, and repaired conditions. All specimens showed increased translations and rotations after stretching. Both repair techniques significantly reduced anterior, posterior, and inferior translation. The inferior capsular shift was more effective in reducing inferior translation in the apprehension position; however, postoperative rotational range of motion was restricted significantly when compared with anterior capsulolabral reconstruction, and posterior subluxation of the humeral head was seen in all specimens. These results indicate that a vertical capsulorrhaphy with a medial to lateral shift of the glenohumeral capsule, as in the inferior capsular shift repair, significantly reduces rotational range of motion when compared in vitro with the horizontal shift of the anterior capsulolabral reconstruction.