Fresh osteochondral allografts for posttraumatic knee defects: long-term followup

Abstract

Fresh osteochondral allograft transplantation has been an effective treatment option with promising long-term clinical outcomes for focal posttraumatic defects in the knee for young, active individuals. We examined histologic features of 35 fresh osteochondral allograft specimens retrieved at the time of subsequent graft revision, osteotomy, or TKA. Graft survival time ranged from 1 to 25 years based on their time to reoperation. Histologic features of early graft failures were lack of chondrocyte viability and loss of matrix cationic staining. Histologic features of late graft failures were fracture through the graft, active and incomplete remodeling of the graft bone by the host bone, and resorption of the graft tissue by synovial inflammatory activity at graft edges. Histologic features associated with long-term allograft survival included viable chondrocytes, functional preservation of matrix, and complete replacement of the graft bone with the host bone. Given chondrocyte viability, long-term allograft survival depends on graft stability by rigid fixation of host bone to graft bone. With the stable osseous graft base, the hyaline cartilage portion of the allograft can survive and function for 25 years or more.

Figures

Fig. 1A–C

(A) A radiograph shows traumatic loss of a medial femoral condyle in a 17-year-old girl. (B) A radiograph shows the same knee 10 years postreconstruction with FOCA. (C) A radiograph shows the same knee 20 years posttransplantation. There is now bicompartmental osteoarthritis.

Fig. 2A–E

The histopathologic findings of this patient at 20 years posttransplantation are shown. (A) A photograph shows a cross-section of the cartilage graft. Note preservation of graft thickness and integration of graft bone with host bone. (B) A photomicrograph shows the surface and superficial zone of the cartilage allograft (Stain, hematoxylin and eosin; original magnification, ×10). Note focal fallout of chondrocytes in the superficial zone and preservation of chondrocytes in the upper zone. The chondrocytes normally oriented “radially” are aligned more horizontally. (C) A photomicrograph shows the superficial zone of the cartilage allograft (Stain, safranin O [light green stain]; original magnification, ×10). The superficial cartilage matrix shows proteoglycan depletion. The deeper layer shows intense staining indicative of high proteoglycan concentration. (D) A photomicrograph shows the deep zone of the cartilage allograft (Stain, hematoxylin and eosin; original magnification, ×10). Note preservation of graft chondrocytes and tidemark. The bone subjacent to the tidemark is a mixture of necrotic graft bone and viable host bone. (E) A photomicrograph shows viable host appositional bone growing on necrotic graft trabecular bone (Stain, hematoxylin and eosin; original magnification, ×20).