A Biomechanical Analysis of Shoulder Stabilization

Abstract

Background: The use of posterior capsular plication to decrease capsular volume and address capsular laxity for treatment of posterior instability, multidirectional instability, or as an additional technique in the treatment of anterior instability is common. Multiple different suturing techniques have been described.

Hypothesis: The simple stitch will have inferior biomechanical properties compared with either the horizontal mattress or figure-of-8 stitches for suture plication of the posteroinferior quadrant of the glenoid.

Study Design: Controlled laboratory study.

Methods: Twenty-one fresh-frozen shoulders with a mean age of 57.7 ± 12.3 years were randomized into capsulolabral plication of the posteroinferior quadrant using either simple stitch configuration, horizontal mattress configuration, or figure-of-8 configuration. Each shoulder was mounted onto a materials testing machine, preloaded to 5 N for 2 minutes, cycled from 5 to 25 N for 100 cycles (1 Hz), and then loaded to failure at 15 mm/min. Capsular displacement from the glenoid was determined using digital video analysis. Data recorded included mode of failure, ultimate load to failure, load at 2 mm of displacement, as well as displacement during cyclical loading (during the entire 100 cycles and during the final cycle only).

Results: There was a statistically significant difference (P < .0001) in mechanism of failure among the 3 groups with the simple stitch group failing more often in the capsular tissue than in the mattress and figure-of-8 sutures, which more commonly failed at the capsulolabral junction. There was no statistically significant difference (P > .05) among the 3 groups in gapping (displacement) after cyclical loading, load at 2 mm of displacement, or in ultimate load to failure.

Conclusion/Clinical Relevance: Based on these results, all 3 stitches can be used effectively for capsular plication, although the simple stitch may be preferred for the capsular plication because of technical ease and decreased trauma to the capsulolabral tissue.