Vascular structures and relationship to intramuscular fat in supraspinatus muscle following tendon detachment and reattachment - An experimental study in rabbits

Abstract

Background. Supraspinatus (SSP) tendon tear leads to intramuscular fat accumulation and the mechanisms are unknown. We investigated changes in SSP muscle vascularization and association with intramuscular fat following SSP tendon detachment with or without reattachment. Methods. Sixty-six rabbits underwent SSP tendon detachment. In groups of ten, thirty rabbits were sacrificed 4, 8, and 12 weeks following detachment. In groups of twelve, the remaining thirty-six rabbits underwent SSP tendon reattachment 4, 8, and 12 weeks after detachment and were sacrificed 12 weeks later. Vascularization was quantified using CD31 immunohistochem-istry and tested for correlation with intramuscular fat measurements. Results. Four weeks after SSP tendon detachment, vascularization increased in the distal SSP muscle, reaching significance after 12 weeks of detachment (p = 0.024). Vascularization was correlated with intramuscular fat accumulation after detachment (r = 0.29; p = 0.008). No significant correlation was observed in the SSP tendon reattachment groups (r = 0.06; p = 0.65). Some vascular structures in the reattachment group had thicker vascular walls. Conclusion. Increased vascularization in the distal SSP muscle was observed following tendon detachment but not after surgical reattachment. Both increased vascularization and intra-muscular fat accumulation co-localized to the distal end near the tendon tear site.