A comparison of RhBMP-7 (OP-1) and autogenous graft for metaphyseal defects after osteotomy of the distal radius

Abstract

SUMMARY AIM: The aim of the study was to demonstrate whether RhBMP-7 is an effective alternative to autogenous bone graft in the healing of metaphyseal defects in the distal radius following corrective osteotomies for symptomatic malunion after distal radial fractures. Thirty patients were entered into the study and were randomised to receive either RhBMP-7 or autogenous bone graft harvested from the ipsilateral iliac crest. Stabilisation of the osteotomy was either carried out with non- bridging external fixation or the pi-plate. Clinical, radiographic and functional review were carried out at regular intervals up to 1 year. The first 10 patients were treated using non-bridging external fixation of the osteotomy. Two of the 4 patients treated with RhBMP-7 developed excessive osteolysis around the osteotomy site resulting in loss of the corrected position and non-union of the osteotomy. The other 2 patients healed at 13 weeks. The 6 patients treated with autogenous bone graft all healed at an average of 7 weeks, without any complications. It was postulated that the osteolysis was related to instability of the osteotomy site, and the use of external fixation was abandoned and replaced with internal fixation with a dorsal pi-plate. In the pi-plate group of patients, 10 were treated with autogenous bone graft and 10 with RhBMP-7. The bone graft patients healed at 7 weeks compared to 18 weeks for the RhBMP-7 patients, which was statistically significant (p = 0.019). The patients who received bone graft had complete filling of the metaphyseal defect radiologically. Five patients treated with RhBMP-7 healed at the volar cortex with a dorsal defect remaining at 1 year. Two patients developed non-union radiologically. Ten patients (3 in the RhBMP-7 and 7 in the bone graft groups) required plate removal for soft tissue complications. RhBMP-7 does not confer the same stability as bone graft, allowing shear forces across the osteotomy site when used in conjunction with non-bridging external fixation, reducing the capacity for healing and resulting in osteolysis. Using the RhBMP-7 with a pi-plate resulted in healing of the osteotomy, but at a slower rate than autogenous bone graft.