Large skeletal defects resulting from tumors, infection, or failed arthroplasty present
a reconstructive challenge. Available methods have limitations. Structural allografts
are incompletely revascularized, and are prone to nonunion and late stress fracture.
Vascularized autografts provide the ability to heal and remodel with stress, but are
frequently of insufficient size and strength. Prosthetic replacement of diaphyseal
bone may fail, loosen, or produce periprosthetic fractures. Transplantation of living
allogenic bone would provide a replacement closely matched to the dimensions and mechanical
properties of the resected bone, combined with the desirable healing properties of
a vascularized autograft. Vascularized bone allotransplantation without the health
risks of immunosuppressive drugs or tolerance induction would be an important advance.
The authors proposed a novel method by which this may be accomplished: microsurgical
bone transfer with development of a new host-derived osseous blood supply. Immunosuppression
needs only to allow sufficient time for angiogenesis to occur.
Two groups of 30 PVG rats underwent microsurgical femoral transplantation from DA
donors. The femoral vessels were anastomosed and the contralateral saphenous artery
and vein were implanted longitudinally through the medullary canal as an arteriovenous
pedicle. This was ligated proximal to the bone in 15 rats. A reinforced silicone membrane
was wrapped around the bone to prevent angiogenesis from surrounding tissues. FK-506
was administered daily for 14 days. At 18 weeks, skin grafts from DA, PVG, and Lewis
rats were placed. At 21 weeks, blood flow in the cortex of the bone grafts was measured
using the hydrogen washout method.
Blood flow in the patent a∕v pedicle group was 3.2 ± 2.0 ml∕min∕100 g; no flow values
could be obtained in the ligated group (p = 0). All PVG skin grafts healed (94 ± 6%
area); all DA and Lewis grafts were rejected (100% area). Capillary density measurements
were correlated with blood flow values (r = 0.70; p < 0.0001). Two a∕v pedicles were
thrombosed at sacrifice (93% patency rate).
Neoangiogenesis from implanted blood vessels of donor origin maintains blood flow
in a vascularized bone allograft after removal of immunosuppression and in the absence
of tolerance. Implanted a∕v pedicles maintain patency in a small animal model.
