71. THE EFFECT OF POSTERIOR CAPSULAR TIGHTNESS ON PRESSURE IN THE SUBACROMIAL SPACE

Abstract

Purpose: Subacromial impingement syndrome is a painful condition which occurs during overhead activities as the rotator cuff is compressed between the greater tuberosity and the acromion. Unrecognized secondary causes of impingement syndrome may lead to treatment failure. Posterior capsular tightness, believed to alter shoulder joint kinematics, is often cited as a secondary cause but scientific evidence is lacking. The objective of this study was to evaluate the effect of posterior capsular tightness on pressure in the subacromial space.

Method: Ten fresh-frozen cadaver shoulder specimens were mounted on a custom testing apparatus. With the scapula fixed, the deltoid and cuff muscles were loaded statically with a constant ratio to elevate the humerus in the scapular plane under physiologic loading conditions. For each treatment (intact capsule, 1cm and 2cm plication), pressure in the subacromial space and glenohumeral kinematics were recorded during elevation. The treatment order was randomly assigned to each specimen. Peak pressure and translation of the humeral head center were compared using a repeated measures ANOVA.

Results: Peak subacromial pressures (mean±sd) were similar between treatment groups: 345±152 kPa, 410±213 kPa and 330±164 kPa for the intact, 1cm and 2cm plication respectively (p> 0.05). No significant differences were found for superior or antero-posterior translations of the humeral head at the peak pressure position (p> 0.05).

Conclusion: Posterior capsular tightness, as a sole variable, did not contribute significantly to increased pressure in the subacromial space or to increased anterior or superior humeral head translation during abduction. Clinically, posterior capsular tightness may occur in association with impingement syndrome but may not play a significant role in causation.