Biomechanical Evaluation of Multidirectional Glenohumeral Instability and Repair

Abstract

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.

Effects of combined anterior and posterior plication of the glenohumeral ligament complex for the repair of anterior glenohumeral instability: a biomechanical study

“…The finding of a posterior and inferior shift of the humeral head when the joint was externally rotated has also been found in similar studies evaluating anterior arthroscopic repair 2 and capsulorrhaphy for multidirectional instability. 17 This finding of a posterioreinferior shift has been previously implicated to lead to arthropathy after nonanatomic open stabilization procedures. 1 The hypothesis that adding a posterior plication would help reestablish the normal kinematics was not proven in this study.…”

“…The stretch was applied slowly to the specimen over a period of 10 to 15 minutes to achieve the 20% stretch without rupturing the capsule. 2,17,18 Once the 20% stretch was obtained, the humerus was locked and the specimen was held in this position for 30 minutes.…”

Biomechanical evaluation of a coracoclavicular and acromioclacicular ligament reconstruction technique utilizing a single continuous intramedullary free tendon graft

“…18 Translational testing was carried out per previously established methods. 3,6,16 The setpoint of the Microscribe was set with the AC joint anatomically reduced.…”

Capsule function following anterior dislocation: Implications for diagnosis of shoulder instability

“…19,20 Strain distributions in the anteroinferior capsule have also been examined to understand the capsule function and the manner in which it transmits loads from the humerus to the scapula. 9,16,[21][22][23][24] While experimental models have quantified non-recoverable strain, 22 its relation to changes in capsule and joint function are not well understood.…”