Sequential volume reduction with capsular plications: relationship between cumulative size of plications and volumetric reduction for multidirectional instability of the shoulder.

PURPOSE: To quantify the relationship between the amount of shoulder capsule imbricated with a simple stitch and the degree of glenohumeral volume reduction in a multidirectional instability model. Secondary purposes were to identify the number of arthroscopic plication stitches required to reduce the shoulder volume equal to that of an open lateral-based inferior capsular shift and to compare volume reductions between suture anchor and suture-only capsular plication stitches. STUDY
DESIGN: Controlled laboratory study.
METHODS: Twelve fresh-frozen cadaveric shoulders (mean age, 64.4 years) were dissected to the level of the rotator cuff. A viscous liquid was injected into each joint, and measurements were taken before and after six 1-cm arthroscopic capsular plication stitches were performed. The sizes of the capsular plications were measured to quantify the amount of capsule imbricated with each simple stitch. A repeated random-intercept regression model was fitted for each outcome, with significance set at P = .05.
RESULTS: There was a near-linear relationship, with each 1 cm of total plication equaling 10% volume reduction up to 4.0 cm. After this, each additional 1-cm plication stitch resulted in 2% to 6% more reduction (mean, 4%). Five simple plication stitches reduced the volume by 52% in the suture anchor group and 49% in the suture-only group. The suture anchor achieved 3% greater volumetric reduction than the suture-only plication stitches, but this effect was not statistically significant (P = .06). Conclusion/ CLINICAL RELEVANCE: A 1-cm capsular plication stitch results in a roughly 10% volume reduction of the glenohumeral joint. Five simple capsular plication stitches result in a volume reduction equivalent to an open lateral-based capsular shift.