Vascularized orthotopic osteochondral transplantation of the canine proximal femur

Osteochondral vascularized proximal femoral allografts were orthotopically transplanted in five adult beagles (four experimental and one control). The experimental animals were placed on 0.1 mg/kg of FK506 intravenously for 7 days, and then converted to 1.0 mg/kg orally. Biopsies of the femoral head s were taken at 3 weeks postoperatively and at 1-month intervals thereafter . The specimens were studied histologically with a hemotoxylin and eosin st aining technique. Bone biopsies showed no microscopic evidence of rejection , and only minimal evidence of necrosis. Patency of the microvascular anast omosis was confirmed with bone scanning, using technitium 99m phosphate, ar teriograms, and by Doppler flowmeter. All animals had an uneventful postope rative course, with achievement of full weight-bearing status by postoperat ive day 10, and normal activity by 1 month postoperatively. There were no i nfections or hip dislocations. One animal sustained a femoral neck fracture and was sacrificed at 4 months. At 6 months, the remaining animals were sa crificed. At necropsy, the experimental animals and the normal dog showed v iable chondrocytes and osteocytes, with minimal bone necrosis. No dislocati ons or allograft rejections were observed. Based on this small series, a su ccessful technique has been developed for orthotopic transplantation of a v ascularized hip joint in a canine model.