The Tension Required to Repair the Supraspinatus Tendon to Bone Rapidly Increases following Injury
Authors: Gerald R Williams Jr, MD Philadelphia PA
References: AAOS 2005
The objective of this study was to determine the relationship between rotator cuff repair tension and time from injury in a rat model.
Increased rotator cuff repair tension is associated with poor results and is thought to occur because of muscle fibrosis and fatty replacement. The changes in repair tension with time from injury are unknown. Therefore, the objective of this study was to determine the relationship between rotator cuff tendon repair tension and time from injury in a rat model.
A full-thickness supraspinatus tendon tear was surgically created by releasing the insertion site and allowing complete retraction in 41 rat shoulders. Repair tension was measured following complete musculotendinous mobilization at 0, 2, 4, 9, and 16 weeks post-injury using a tensiometer and a standardized protocol. Comparisons were made using an ANOVA (*p<0.05 vs. 0wk, data as mean (sd)).
Repair tension rapidly increased after injury followed by a progressive, but less dramatic, increase with additional time. Specifically, the tension increased from 0.4(0.1) N at 0 weeks to 1.5(0.7)*, 1.8(0.6)*, 2.4(0.7)*, and 2.6(0.5)* N at 2, 4, 9, and 16 weeks.
The increase in repair tension at 2 weeks post-injury was more than half the overall increase in repair tension at 16 weeks. This suggests that increased repair tension may be the result of something other than fatty replacement and fibrosis of the muscle belly. Moreover, these findings suggest that early rotator cuff repair will be associated with lower repair tension and that additional time from injury to repair in a tear that is already chronic may not lead to dramatically increased repair tension.