296. AMBULATORY DRILLING FOR NECROSIS OF THE FEMORAL HEAD: INTERMEDIARY RESULTS OF A RANDOMIZED STUDY EVALUATING CONTRIBUTION OF AUTOLOGOUS BONE MARROW WITH AND WITHOUT BMP

Abstract

Purpose of the study: Drilling along yields disappointing results for osteonecrosis of the femoral head due to the high failure rate despite prolonged rest and also because of the risk of fracture. To prevent these problems, we have developed a new drilling technique which was evaluated prospectively.

Material and methods: The procedure performed percutaneously uses a lateral cortical orifice measuring 5mm, non-concentrated autologous bone marrow was injected after drilling. Osteoinductive protein (BMP7) was associated in random fashion (groups BMP+ and BMP−). Ficat stage 1 and 2 necrosis was included. Outcome was the rate or revision for prosthesis.

Results: Forty hips (36 patients) were included and assessed at mean four years (range 2–6). The necrosis was related to: alcoholism (n=5), cortisone (n=25), barotraumas (n=2), metabolic disease (n=4), idiopathic condition (n=4). Group BMP- (drilling+bone marrow) included 24 hips and group BMP+ (drilling+bone marrow+BMP7) 16 hips. The groups were comparable regarding necrosis stage (15% stage 3, 65% stage 2, 20% stage 1) and mean Koo index (27 BMP+ vs 34 BMP-; NS). There were no infections and no fractures despite immediate and complete weight-bearing. The revision rate for prosthesis was higher in the BMP- group (67%) than in the BMP+ group (43%) but the difference did not reach significance (p=0.10). The failure rate was not affected by the severity of the necrosis in the BMP+ group: all stage 3 hips were revised in the BMP- group versus none in the BMP+ group. The only variable predictive of revision for prosthesis was the Koo index (p=0.02).

Discussion: Adjunction of BMP did not improve significantly the success rate of drilling with bone marrow adjunction but adding BMP appeared to limit the unfavourable impact of server necrosis observed in the BMP- group. To reach a statistical power of 80%, 40 cases would be needed in each arm. This threshold has not yet been reached. It can be noted however that the proposed method does ensures early weight bearing without the risk of complications. Similarly, since it is a percutaneous procedure, later arthroplasty is not compromised. The principle confounding factor, the richness of the bone marrow, was not assessed, motivating a new randomized trial with measurement of CFU-F.