Delayed tendon reattachment does not reverse atrophy and fat accumulation of the supraspinatus – an experimental study in rabbits

Muscle atrophy and fat accumulation occur after rotator cuff tearing. Whether these changes are reversible after a successful repair is still unknown. Imaging allows only a semi-quantitative assessment of muscle atrophy and fat deposition. As only experimental studies permit a quantification of both, a unilateral detachment and wrapping in a polyvinylidine fluoride membrane of the supraspinatus was done in 22 rabbits. After 12 weeks, the polyvinylidine fluoride membrane was removed in 10 rabbits and the tendon inserted into a bony trough. The opposite shoulder served as control. All rabbits were killed at 24 weeks. Accumulation of fat on the muscle surface as well as between the muscle fascicles and occasionally in the sarcoplasm was increased in both experimental groups when compared to controls (non-reattached 12.8%, reattached 23.5% vs controls 5.4%; all p