Histologic case series of human acellular dermal matrix in superior capsule reconstruction.

BACKGROUND: Acellular dermal matrix (ADM) allografts are commonly used in the surgical treatment of complex and irreparable rotator cuff tears. Multiple studies report that superior capsule reconstruction (SCR) using ADM has resulted in short-term clinical success as assessed via radiographic and patient-reported outcomes. However, limited information is available regarding the biologic fate of these grafts in human subjects. This case series describes histologic results from 8 patients who had reoperations, during which the previously implanted ADMs were removed. These explanted ADMs were subjected to histologic analysis with the hypothesis that they would have evidence of recellularization, revascularization, and active remodeling. METHODS: Eight patients, 38-82 years old, underwent reoperation 6-38 months after undergoing SCR. ADM explants were voluntarily shipped to the manufacturer for histologic analysis. Each graft's structure and composition were qualitatively evaluated by 1 or more of the following histologic stains: hematoxylin and eosin, safranin O, and Russell-Movat pentachrome. Pan-muscle actin staining also assessed the level of neovascularization, potential myoblast or myocyte infiltration, and muscle tissue development in the graft, and was analyzed to determine the proportion of graft that had been recellularized in situ. RESULTS: Grafts showed varying levels of gross and microscopic incorporation with the host. An uneven, but high, overall degree of recellularization, revascularization, and active remodeling was observed. The degree of remodeling correlated with implant duration. These results are consistent with successful biologic reconstruction of the superior shoulder capsule. CONCLUSIONS: The present histologic analysis suggests that ADMs used in SCR undergo active recellularization, revascularization, and remodeling as early as 6 months after implantation, and that graft recellularization positively correlates with duration of implantation. These results represent a significant advancement in our knowledge regarding biologic incorporation of ADMs used in SCR.

The Histology of a Healed Superior Capsular Reconstruction Dermal Allograft: A Case Report.

Acellular human dermal allograft commonly is used in the surgical treatment of complex rotator cuff tears, but little information is known about the biological fate of these grafts in human subjects. In this case report, the authors describe a patient who presented with a radiographically healed acellular human dermal allograft superior capsular reconstruction but had humeral head avascular necrosis. The healed superior capsular reconstruction, including graft-bone interfaces, was explanted after 7 months and sent for histologic analysis. A successful biological reconstruction of the superior capsule was found. The graft demonstrated gross and microscopic incorporation with the host, including a tendon-like structure, aligned collagen fibers, fibroblast-like cells, and no clear graft-host distinction. Cellular infiltration ranged from 5% to 14% (central graft) to 65% to 92% (sutured attachment points). Neovascularization and active graft remodeling were confirmed histologically. LEVEL OF EVIDENCE: V, case report.