A novel cadaveric model for anterior-inferior shoulder dislocation using forcible apprehension positioning

Abstract

Abstract-A novel cadaveric model for anterior-inferior shoulder dislocation using forcible apprehension positioning is presented. This model simulates an in vivo mechanism and yields capsulolabral lesions. The scapulae of 14 cadaveric entire upper limbs (82 ± 9 years, mean ± standard deviation) were each rigidly fixed to a custom shoulder-testing device. A pneumatic system was used with pulleys and cables to simulate the rotator cuff and the deltoid muscles (anterior and middle portions). The glenohumeral joint was then positioned in the apprehension position of abduction, external rotation, and horizontal abduction. A 6-degree-of-freedom load cell (Assurance Technologies, Garner, North Carolina) measured the joint reaction force that was then resolved into three orthogonal components of compression force, anteriorly directed force, and superiorly directed force. With the use of a thrust bearing, the humerus was moved along a rail with a servomotor-controlled system at 50 mm/s that resulted in horizontal abduction. Force that developed passively in the pectoralis major muscle was recorded with an independent uniaxial load cell. Each of the glenohumeral joints dislocated anterior-inferior, six with avulsion of the capsulolabrum from the anterior-inferior glenoid bone and eight with capsulolabral stretching. Pectoralis major muscle force as well as the joint reaction force increased with horizontal abduction until dislocation. At dislocation, the magnitude of the pectoralis major muscle force, 609.6 N ± 65.2 N was similar to the compression force, 569.6 N ± 37.8 N. A cadaveric model yielded an anterior dislocation with a mechanism of forcible apprehension positioning when the appropriate shoulder muscles were simulated and a passive pectoralis major muscle was included. Capsulolabral lesions resulted, similar to those observed in vivo.

Effect of deltoid tension and humeral version in reverse total shoulder arthroplasty: a biomechanical study

“…3,22,25,34 Active muscle contraction, proprioceptive control, and dynamically changing muscle lines of action could not be simulated by mechanical actuators and static loads. Similarly, a reduced set of muscles spanning the glenohumeral joint included only the rotator cuff and deltoid.…”

“…The middle deltoid pulley was positioned 5 mm lateral to the acromion, midway between the anterolateral and posterolateral corners. 18,25,36 The posterior deltoid pulley was positioned 5 mm superior to the scapular spine midway along the insertion of the posterior deltoid. Anatomic landmarks were located by palpation.…”

Biomechanical effects of glenoid retroversion in total shoulder arthroplasty

“…Using specific markings for shoulder positioning, the shoulder testing system permitted highly accurate and precise positioning of the shoulder in a repeatable manner. 3,12,13,15,21 The long axis of the humerus was aligned parallel to the floor, achieving a total of 90°of shoulder abduction (30°of scapular inclination and 60°of glenohumeral abduction). The humerus was rotated, with alignment of the proximal-most portion of the biceps tendon with the anterior-most edge of the acromion; this was defined as 90°of external rotation.…”

Development and Performance Evaluation of a Multi-PID Muscle Loading Driven In Vitro Active-Motion Shoulder Simulator and Application to Assessing Reverse Total Shoulder Arthroplasty

“…In the case of the shoulder, few simulators have been devel oped. The majority of these systems have focused on evaluating biomechanics while the shoulder is statically positioned, or when passive motions are externally applied with or without muscle loading [1][2][3][4][5][6][7][8][9][10]. However, Kedgley et al showed that simulators using continually variable muscle forces to drive shoulder motion (as is the case in vivo) produce motions with higher repeatability than passive systems, and thus greater statistical power [11].…”