Metal-on-Metal Total Hip Arthroplasty for Crowe I and II Dysplastic Hips: Short-term Results of 66 Patients

Objectives: This retrospective study was designed to evaluate outcome of patients with coxarthrosis secondary to low grade hip dysplasia treated with large head Metal-on-Metal (MoM) hip arthroplasty. Patients and methods: Seventy–six dysplastic hips of sixty-six patients were managed with large head MoM cementless total hip arthroplasty and they had a mean of 51 months (range, 42-62 months) follow-up after surgery. The mean age was 44.5 years and 51 (77.2%) of the patients were female. There were 46 Crowe I hips and 30 Crowe II hips. While ten patients had bilateral dysplastic hips, 2 of them had left sided type I and right sided type II dysplasia. The functional evaluation was done with Harris hip scoring system whereas radiological evaluation was done according to Pagnano, Gruen and DeLee and Charnley. Results and Conclusion: No dislocation or signs of early aseptic loosening was detected in our patients. Patients whom were operated for bilateral hip dysplasia showed a mean functional score of 89.4±0.4 points beside the unilateral cases which was 96.3±0.7 points (p<0.005). No major complication due to surgery was detected. Only in one patient, a periprosthetic fracture was occured and it was satisfactorly treated by internal fixation without implant revision. MoM articulations with large head size have been used to decrease the dislocation rate by increasing the range of motion available prior to impingement and jumping distance before dislocation. Nevertheless, beside such manageable properties, some debate exists about metal ion release in case of these articulations. Our results indicate that large head MoM hip arthroplasty is a good choice for low grade dysplastic hips with good-excellent short-term results without any toxicity according to ion release. Its design can decrease dislocation rate and the propensity for wear debris with a potentially lower rate of failure.