A prospective comparative study of hip resurfacing arthroplasty and large-diameter head metal-on-metal total hip arthroplasty in younger patients-a minimum of five year follow-up.

INTRODUCTION: Both hip resurfacing arthroplasty (HRA) and large-diameter head metal-on-metal total hip arthroplasty (LDH MoM THA) are generally used for young and active patients. A number of comparative studies of HRA and total hip arthroplasty have been published in the literature. However, studies that have compared HRA with LDH MoM THA are rare. The purpose of this study is to compare the mid-term results of HRA with those of LDH MoM THA in young patients.

PATIENTS AND METHODS: Between 2007 and 2011, 68 patients were enrolled in the study and randomized into two groups: HRA group (28 hips) and LDH MoM THA group (40 hips). Peri-operative data including blood loss, surgery duration, size of the implant, and post-operative complications were recorded. All patients were assessed clinically and radiologically at six weeks; one, three and five years; and at the time of final review. Functional outcome were assessed using Harris hip (HHS), University of California Los Angeles (UCLA) and Oxford hip (OHS) scores. The mean follow-up for all patients was 7.4 years (5 to 9).

RESULTS: Patient groups matched similarly in age, percent female, body mass index, preoperative HHS, and follow-up time. No differences were observed between the two groups in blood loss or in head size or acetabular inclination angle. HRA group had significantly longer surgery duration but less blood loss. The two groups had comparable HHS, UCLA, and OHS at the latest follow-up. Major complications, such as fracture, dislocation, infection, and adverse reactions to the metal debris (ARMD) were not found in the two groups. Only one case in LDH MoM THA group underwent revision surgery due to unexplained pain.

CONCLUSION: Comparison of HRA and LDH MoM THA shows similar mid-term clinical results. HRA may be preferable due to the well-preserved bone stock and restoration of the native anatomy. LDH MoM THA may be used with caution due to the excessive metal ion release.