Primary metal-on-metal total hip arthroplasty with large-diameter femoral heads: a clinical trial of 59 hips

Large-diameter femoral heads with nearly anatomical sizes became available for metal-on-metal total hip arthroplasty after recent advances in metal-on-metal technology. We retrospectively studied the clinical and radiological results in 59 hips of 54 patients (32 women and 22 men, mean age 54.4 years) who underwent cementless metal-on-metal total hip arthroplasty with large-diameter heads. Patients were followed for a mean of 48.6 months. Range of motion improved significantly after surgery (p = 0.001). Harris hip scores improved from 38.5 points to 903 points at latest follow-up. We found no gender-related differences in Harris hip scores, whereas there was a correlation between age and Harris hip scores (p < 0.001), with excellent results being observed predominantly in younger patients. Mean acetabular inclination of the acetabular cup was 42.2 degrees (range: 37-51 degrees). Radiologically, a 1 mm thick radiolucency was detected in three acetabula, which were asymptomatic. One acetabulum was revised because of displacement. Three patients reported squeaking within their hips, which however disappeared in a short time. We did not observe any dislocation, deep infection or loosening. Grade 1 heterotopic ossification was detected in one hip. Although the inherent stability and the functional results of large anatomical heads are encouraging, longer follow-up data and larger series are essential to evaluate the real advantages of this type of prosthesis over conventional femoral heads.