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 heads were taken at 3 weeks postoperatively and at 1-month intervals thereafter. The specimens were studied histologically with a hemotoxylin and eosin staining technique. Bone biopsies showed no microscopic evidence of rejection, and only minimal evidence of necrosis. Patency of the microvascular anastomosis was confirmed with bone scanning, using technitium 99m phosphate, arteriograms, and by Doppler flowmeter. All animals had an uneventful postoperative course, with achievement of full weight-bearing status by postoperative day 10, and normal activity by 1 month postoperatively. There were no infections or hip dislocations. One animal sustained a femoral neck fracture and was sacrificed at 4 months. At 6 months, the remaining animals were sacrificed. At necropsy, the experimental animals and the normal dog showed viable chondrocytes and osteocytes, with minimal bone necrosis. No dislocations or allograft rejections were observed. Based on this small series, a successful technique has been developed for orthotopic transplantation of a vascularized hip joint in a canine model.