Strain of the anterior band of the inferior glenohumeral ligament during capsule failure.

Efficacious surgical treatment of glenohumeral instability requires a combination of anterior band origin repair and capsuloligamentous plication. The purpose of this article was to determine anterior band of the inferior glenohumeral ligament stretching at the time of glenohumeral failure. Thirteen fresh-frozen cadaver glenohumeral joints were thawed and dissected of soft tissue except for the capsuloligamentous structures. Testing was performed with a material testing system device, simulating the anterior instability apprehension position of the shoulder with 90 degrees of shoulder abduction and the humerus externally rotated until the bicipital groove was aligned with the supraglenoid tubercle. The length of each anterior band of the inferior glenohumeral ligament was obtained, and a variable reluctance transducer was applied to the anterior band midsubstance. Tensile testing at a strain rate of 100%/sec ensued until complete capsular failure occurred. Mid-substance strain of the anterior band of the inferior glenohumeral ligament at the time of capsular failure averaged 7.23% +/- 2.25% (mean +/- SD) with a range of 3.68% to 10.68%. Load to failure was 712.9 +/- 238.2 N (range 363.6 to 1136.9 N). All of the glenohumeral capsules failed at the glenoid origin, simulating a Bankart lesion, except for one that failed at the humeral insertion. When the intact capsuloligamentous tissue of the glenohumeral joint is tensile-tested in the apprehension position, there is only slight anterior band strain and failure occurring, predominantly at the glenoid insertion site. This has implications for the success of surgical procedures designed for acute repair of Bankart lesions.

Electromyographic and nerve block analysis of the subscapularis liftoff test.

The inability to perform the "liftoff" test has been attributed to a subscapularis muscle or tendon injury. The goals of this study were to evaluate the activity of the glenohumeral muscles during performance of the "liftoff" maneuver and to identify the most effective initial upper extremity placement that isolates the subscapularis musculotendinous unit. In the first phase of this study 15 subjects accomplished four proposed versions to the "liftoff" test while their intramuscular electromyographic activity in select glenohumeral muscles was recorded. The second phase of this study assessed the ability of five subjects with a nonfunctional subscapularis musculotendinous unit to perform the same proposed versions. On the basis of electromyographic data none of the proposed versions to the "liftoff" maneuver isolated the upper and lower subscapularis muscle from either the teres major, latissimus dorsi, posterior deltoid, or rhomboid muscles (p > 0.05). In the presence of a nonfunctional subscapularis musculotendinous unit, the subjects were able to perform all of the proposed versions of the "liftoff" maneuver except one: elevation of the dorsum of the hand from the posterior-inferior border of the scapula (maximum internal rotation test). Although significant electromyographic activity was generated in the potentially confounding shoulder girdle muscles during the maximum internal rotation "liftoff" test, a successful test appears to be dependent on the isolated glenohumeral internal rotation function of the subscapularis muscle.