Survival of Microvascular Physeal Allograft Transplants Following Withdrawal of Short-Term Postoperative Immunosuppression

• Published in: Journal of bone and joint surgery. American volume Vol. 86; no. 2; pp. 281 - 289
• Main Authors: Bray, Peter W, Neligan, Peter C, Bowen, C. Vaughan A, Boyer, Martin I
• Format: Journal Article
• Language: English
• Published: Boston, MA Copyright by The Journal of Bone and Joint Surgery, Incorporated 01.02.2004; Journal of Bone and Joint Surgery Incorporated; Journal of Bone and Joint Surgery AMERICAN VOLUME
• Edition: American volume
• Subjects: Animals; Biological and medical sciences; Cyclosporine - administration & dosage; Female; Graft Survival; Growth Plate - blood supply; Growth Plate - transplantation; Immunosuppressive Agents - administration & dosage; Medical sciences; Microcirculation; Orthopedic surgery; Postoperative Care; Rabbits; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Time Factors; Short term; Postoperative; Prognosis; Diseases of the osteoarticular system; Rheumatology; Homograft; Rabbit; Transplantation; Lagomorpha; Survival; Vertebrata; Immunosuppression; Experimental disease; Mammalia; Treatment; Surgery; Animal; Orthopedics; Graft; Bone
• ISSN: 0021-9355; 1535-1386
• DOI: 10.2106/00004623-200402000-00010

BackgroundPhyseal necrosis following vascularized allograft transplantation occurs because of vascular rejection. The effect of immunosuppression withdrawal on physeal viability after bone-healing to the recipient site was investigated with use of a validated model for heterotopic microvascular transplantation of rabbit tibial physeal allografts. Our hypothesis was that an allograft survives after withdrawal of immunosuppression only if bone-healing, and therefore epiphyseal and metaphyseal vascular continuity, occurs between the transplanted physis and the recipient bone.MethodsPhyseal grafts with adjacent exposed epiphyseal and metaphyseal bone were transplanted to allogeneic recipients. Graft circulation was restored microsurgically. The immunosuppression regimen consisted of cyclosporine, administered for six weeks, followed by withdrawal of immunosuppression for four weeks. The animals were killed at ten weeks postoperatively. Group I consisted of twelve allografts that were transferred with bone contact between the transplanted graft and the iliac crest recipient site, whereas group II consisted of twelve allografts transplanted without bone contact. Control groups had identical surgical procedures without immunosuppression. Longitudinal growth was assessed by fine-detail radiography, and osseous union was evaluated histologically. Transplanted physes were evaluated histologically, and cellular viability was quantified by bromodeoxyuridine uptake. Two-way analysis of variance was used to compare physeal viability between groups.ResultsFollowing immunosuppression withdrawal, the physeal grafts with bone contact had significantly greater viability indices (16.0 ± 2.9 compared with 0.0 ± 0.0, p < 0.005) and decreased longitudinal growth (5.1 ± 1.9 mm compared with 10.3 ± 3.5 mm, p < 0.05), and they demonstrated histological features that were consistent with continued viability associated with mild rejection compared with grafts transplanted without bone contact. Abnormalities of physeal architecture, however, were seen routinely. All control physes transferred without immunosuppression were nonviable and did not grow.ConclusionsThe viability of physeal allograft transplants is preserved following the withdrawal of immunosuppression, provided that the graft design and recipient site preparation allow for epiphyseal and metaphyseal neovascularization mediated by bone-healing between graft and recipient.Clinical RelevanceShort-term use of systemic immunosuppression might prove to be acceptable ethically and useful clinically following vascularized physeal allotransplantation if continued viability and longitudinal growth of the physis could be ensured.