Allograft-Prosthetic Composite Reconstruction

Allograft-prosthetic composite reconstruction (APC) is a hybrid limb-salvage technique that combines the biological advantages of a structural bone allograft with the immediate stability and load-bearing capacity of a prosthetic implant. Originally developed for pediatric and young adult bone sarcoma patients (where preservation of host bone for future revision is critical) and revision arthroplasty cases with massive proximal femoral or humeral bone loss, APC has become a standard option in orthopedic oncology and complex revision arthroplasty.

Common indications and locations: proximal humerus APC after sarcoma resection (allows reattachment of rotator cuff to allograft tendon insertions—critical for shoulder function), proximal femur APC after sarcoma or massive revision (allows abductor/iliopsoas reattachment, prevents Trendelenburg gait), distal femur and proximal tibia (less common, more often pure endoprosthesis chosen). The composite is fabricated by inserting an endoprosthesis (long-stem hemiarthroplasty or total joint component) into a fresh-frozen size-matched cadaveric allograft segment, then either cementing the prosthesis into the allograft canal or using press-fit; the composite is then implanted at the resection site with cemented or press-fit fixation in the host bone, and a step-cut or transverse osteotomy junction with allograft-host bone.

Technical considerations: meticulous size matching of allograft (CT-based templating), preservation of allograft tendon/ligament insertions for soft-tissue reattachment, secure step-cut osteotomy with plate/screw fixation at allograft-host bone junction, autograft bone or BMP at junction to enhance union, soft-tissue reattachment with non-absorbable sutures and bone tunnels, and meticulous infection prevention. Outcomes: long-term studies show 10-year construct survival 70-85% with revision rates 15-25%; major complications include allograft fracture (10-20%), nonunion at allograft-host junction (10-30%, higher with chemotherapy), deep infection (5-15%, devastating—often requires removal), and prosthesis-allograft loosening; functional outcomes are generally superior to pure endoprosthesis for proximal humerus and femur due to soft-tissue reconstruction capacity. Postoperative protocol includes prolonged protected weight-bearing, restricted ROM initially, and structured rehabilitation.