70. CONTACT PRESSURES AND GLENOHUMERAL TRANSLATIONS FOLLOWING SUBACROMIAL DECOMPRESSION: HOW MUCH IS ENOUGH?

Abstract

Purpose: Determine the ideal form of subacromial decompression.

Method: Six cadaveric shoulders with intact rotator cuffs (RTC) underwent “smooth & move (SM),” limited acromioplasty with coracoacromial ligament (CAL) preservation, and CAL resection. Glenohumeral translation was measured in four directions utilizing electromagnetic spatial sensors. Peak RTC pressure was measured during arm abduction utilizing pressure film sensors.

Results: Anterosuperior translation was unchanged after SM or acromioplasty, but increased from 2mm at baseline to 4mm following CAL resection with the arm at 300 abduction (p=0.03). There were no significant changes in other directions of translation following any procedure. In neutral humeral rotation RTC pressure was unchanged after SM (p=1.00). Pressure decreased 64% after a limited acromioplasty (p=0.04), and 72% after CAL resection (p=0.03). There was a trend towards increased abduction at which peak pressure occurred following CAL resection (760 compared to 620;p=0.11) In external rotation, RTC pressure decreased 26% following SM, 52% after limited acromioplasty, and 64% after CAL resection, but values were not statistically changed (p=0.52, p=0.08, and p=0.06). Similarly, abduction angle at which peak pressure was reached increased but was statistically insignificant after SM (720; p=0.75), limited acromioplasty (750; p=0.11), and CAL resection (790; p=0.08). In internal rotation, RTC pressure decreased 32% following the SM, 59% following the limited acromioplasty, and 58% following CAL resection, but none reached statistical significance (p=0.52, p=0.26, p=0.17). Abduction angle of peak pressure was unchanged after SM (670; p=0.63) and limited acromioplasty (670; p=0.63), but increased following CAL resection (620 vs. 790; p=0.04).

Conclusion: A CAL resection leads to increased anterosuperior instability. “Smooth and move” or acromioplasty can safely be performed without increasing translation. Rotator cuff pressure did not significantly decrease after SM. Rotator cuff pressure was significantly decreased to a similar degree following a limited acromioplasty or a CAL resection. A limited acromioplasty with preservation of the CAL may offer the greatest decrease in cuff pressures without the undesirable effect of increased translation. However, statistical significance was affected by high anatomic variability. Therefore, the choice between “smooth & move” and acromioplasty to decrease contact pressure is likely best to be individualized based on acromial morphology.