Repair of bone defects in revision hip arthroplasty by implantation of a new bone-inducing material comprised of recombinant human BMP-2, Beta-TCP powder, and a biodegradable polymer: an experimental study in dogs.

A recombinant BMP-2-retaining putty-form implant in combination with a hip prosthesis was used to reconstruct a canine hip joint with defects similar to those encountered in revision total hip arthroplasty (THA). The bone defects were made by resecting the medial half of the proximal femur and the superior acetabular bone with inner iliac wall perforation in 10 dogs. In five dogs, hip prostheses were implanted with the putty material consisting of a synthetic polymer (poly D,L-lactic acid-polyethylene glycol block copolymer), beta-tricalcium phosphate powder, and recombinant human BMP-2 in each defect (BMP/Polymer/TCP group). In the remaining five dogs, the same material without rhBMP-2 (control group) was implanted. In the BMP/Polymer/TCP group, new radiopaque shadows began to appear 4 weeks after surgery at the defects around the hip prostheses on both the femoral and acetabular sides. At 12 weeks, the defects were completely filled with new bone in contact with the prosthesis. On histology, the rhBMP-2/Polymer/beta-TCP composite putty implants had been completely resorbed and replaced by new bone. Repair of the bone defects was not seen in the control group. The ability of this material to restore bone effectively eliminates the dependency on bone grafts of autogeneic or allogeneic origin for revision hip arthroplasty and thus opens up a potential new treatment approach in hip cases requiring this type of surgery.