PRELIMINARY CLINICAL OUTCOMES OF A POROUS METAL IMPLANT FOR INTERVENING IN FEMORAL HEAD OSTEONECROSIS

Abstract

Introduction: The purpose of this study was to review the preliminary clinical outcomes of a clinical study of a new implant for intervening in Stage I & II femoral head osteonecrosis.

Materials & Methods: The porous tantalum (Hedrocel® Trabecular Metal, Zimmer Inc./Implex Corp.) is 80% porous with a modulus of elasticity similar to bone. The implant is 10 mm in diameter, offered in 70 – 130 mm lengths in 5 mm increments, and possesses threads for engagement of the lateral cortex. The investigation is an FDA regulated, prospective IDE study of the implant in comparison to core decompression for patients with Stage I or II osteonecrosis (Steinberg-UPenn). Patients exhibiting unilateral disease are randomized to an implant or core decompression (50–50 chance). All patients exhibiting bilateral disease receive the implant. Clinical outcome measures include HHS and SF-12 scored pre-op, at 6, 12, and 24 months, and radiographic data is collected at these same times, and at 6 and 12 weeks.

Results: Prior to the clinical study, a custom case was performed in 1998, and a second in 1999. Since the study began in June 2000, 12 surgeries have been performed with the implant. All 14 patients are reportedly doing well. Radiographic review shows no evidence of abnormal bone density and no evidence of radiolucencies. All lesions appear similar to the pre-op condition. In one case, at 3-months, there is radiographic evidence that the implant has stabilized a slightly collapsed subchon-dral plate, and that new bone has formed in proximity to the tip of the implant. This patient exhibited mild pain at 8 weeks, which has since subsided.

Discussion: The preliminary clinical experience with this implant is encouraging and suggests that mechanically supporting the subchondral plate with this implant is a viable method of intervening in the early stages of osteonecrosis.