Abstract
Background
Hip resurfacing arthoplasty (HRA) showed promising early and mid-terms results at the beginning of the new millennium. Adverse local tissue reactions associated with metal debris considerably slowed down the implantation of HRA which use is now limited to a few specialized centers. The long term success of this procedure, however, is still largely unknown. This study aimed to provide the clinical results of a series of 400 consecutive HRA with a minimum follow-up of 20 years.
Methods
All patients treated with Conserve®Plus HRA between November 1996 and November 2000 were retrospectively selected and 355 patients (400 hips) were included. The clinical results of this series was previously reported in 2004 at a follow up of 2 to 6 years[1]. There were 96 women (27%) and 259 men (73%). Mean age at surgery was 48.2 ± 10.9 years. Long-term survivorship was assessed with Kaplan-Meier survival estimates. UCLA hip scores and SF-12 quality of life scores were collected at follow-up visits. Radiographic positioning of the acetabular component was assessed with the computation of the contact patch to rim (CPR) distance. Radiolucencies about the metaphyseal stem and around the acetabular component were recorded to assess the quality of the component fixation.
Results
The mean time of follow up was 16.3 ± 5.5 years including 183 hips beyond 20 yrs. Nine hips were lost to follow up (2.2%) Thirty-three patients (35 hips,8.8%) died of causes unrelated to the surgery at a mean 11.9 ± 5.3 years after surgery The mean UCLA hip scores at last follow-up were 9.3 ± 1.0, 9.1 ± 1.4, 9.0 ± 1.8, and 6.9 ± 1.7 for pain, walking, function, and activity, respectively. Post-operative SF-12 scores were 48.4 ± 10.3 for the physical component and 48.5 ± 15.5 for the mental component and did not differ from those of the general US population. Fifty-five patients (60 hips) underwent revision surgery at a mean time of 9.3 ± 5.8 years. Indications for revision surgery included acetabular component loosening (12 hips), femoral component loosening (31 hips), femoral neck fracture (6 hips), wear (6 hips), sepsis (2 hips), recurrent dislocations (1 hip), acetabular component protrusion after over-reaming (1 hip) and unknown (1 hip which was revised in another center). Using any revision as an endpoint, the Kaplan-Meier survivorship was 95.2% at 5 years, 91.2% at 10 years, 87.3% at 15 years, and 83.2% at 20 years. A multivariate model for risk factor analysis showed a diagnosis of developmental dysplasia (p=0.020) and a low body mass index (typically associated with higher levels of activity) (p=0.032), to be significantly related to revision for any reason. Female sex was not a risk factor after adjustment for hip dysplasia and component size was made (Table 1). There was only 1 femoral failure (a late neck fracture 19 years after surgery) among the hips reconstructed with a cemented metaphyseal stem (n=59). Five of the 6 hips (1.5%) with wear-related failures all had mal-positioned sockets (CPR distance <10mm) and were therefore preventable. There were no cases with a high score of aseptic lymphocytic vasculitis-associated lesions (ALVAL)[2], suggesting metal sensitivity. X-ray analysis showed excellent persisting fixation in all but one hip.
Conclusions
In this group of patients operated over 20 years ago, HRA keeps providing excellent pain relief and quality of life to the patients. Subsequent progress in the preparation of the femoral head has considerably reduced the failure rate on the femoral side which was the main mode of failure in this initial series[3, 4]. The 83.1% 20 year survivorship of this initial series surpasses that of total hip arthroplasties in use 20 years ago in this young patient population[5]. Life-long durability of the device is anticipated for most of the remaining patients. The established benefits of this procedure, such as a low dislocation rate, an anatomic reconstruction with physiologic loading of the proximal femur, the absence of taper corrosion, and an easy conversion if ever necessary, make HRA a preferable alternative to THA in young and active patients.
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