Purpose: Little information is available regarding the healing capacity of in situ and completion repair for the treatment of partial thickness rotator cuff tears. The purpose of the study was to analyze the healing characteristics of both techniques.
Methods: Twenty-four adult Sprague-Dawley rats were operated. Partial thickness bursal side tears were created bilaterally at the supraspinatus tendons. Additional 6 rats were used as the sham group. The right shoulders were repaired in situ, and the left shoulders were repaired using the tear completion technique on the 10th day after detachment surgery. Rats were sacrificed on the 10th and 30th days after repair surgery. Type I collagen, the TNF-α concentrations, the number and diameter of fibroblasts, and neovascularization were examined at two different time points.
Results: The collagen concentration (ng/mg total protein) was significantly increased in both groups at T1 and decreased in the in situ group, whereas completion repair continued to increase at T2 (P < 0.05). The mean fibroblast diameter in the completion repair group continued to increase at both time points (P < 0.05). Neovascularization was significantly increased with tear completion compared with in situ repair (P < 0.05) at T1. No significant (n.s.) differences regarding the TNF-α concentration (pg/mg total protein) were noted for both surgical techniques at T2 (P > 0.05).
Conclusion: Despite the concerns of detaching the intact tendon, the completion repair technique exhibited increased healing characteristics compared with the in situ technique. The reason for this finding might be the refreshing effect of debridement at the chronic degenerated tendon that could improve the healing response.
Keywords: Completion repair; In situ repair; Partial thickness tear; Rotator cuff; Shoulder; Tendon healing.