Abstract
Introduction
A recent report based on the NARA database (Nordic Arthroplasty Register Association) found that the 10-year survivorship of patients under 50 with traditional total hip arthroplasty was only 83% in 14,600 cases. The purpose of this study was to compare our experience using metal-on-metal hip resurfacing arthroplasty (HRA) to treat these patients.
Methods
from May 2001 to Feb 2012, a single surgeon performed 1029 metal-on-metal HRA in 855 patients younger than 50 years old. Three different implants were used in consecutive groups of patients, first the Corin hybrid HRA (182); then the Biomet hybrid HRA (306); and finally the Biomet uncemented HRA (541). The primary diagnoses were OA (707); dysplasia (125); osteonecrosis (98); post-trauma (28); Legg-Calve-Perthes (27) and others (44). The average age was 43±6 years; 74% were men; the average BMI was 27±4; mean femoral component size was 50±4 (range 40–62); the average T-score was 0±1. 37% of our patients reported a UCLA Activity level of 9 or 10 (impact sports). Six died with causes unrelated to their HRAs. The rate of follow-up was 94%. Our patients were not selected by any criteria except the surgeon's technical ability to perform an HRA.
Results
There were a total 42 failures: acetabular component loosening in 15 cases (8 before two years) femoral component loosening in 9 cases; femoral neck fracture in 5 cases; adverse wear related failure (AWRF) in 4 cases; deep infection in 3 cases; recurrent dislocation in 1 case; other causes in 5 cases. With revision of any component as the end point, the Kaplan-Meier survivorship rate was 94.9% at 8 years and 92.5% at 10 years for the entire group. We compared survivorship between groups at shorter follow-up intervals to determine if results were improving. The survivorship rate at 8 years for Biomet Hybrid group was 95.8%, which was significantly better than 89.1% for the earlier Corin Hybrid group; the survivorship rate at 5 years for the latest Biomet Uncemented HRA group was 98.7%, also better than 96.5% for the prior Biomet Hybrid group. (P=0.0001)
Conclusion
Metal-on-metal hip resurfacing has less than half the 10-year failure rate of THR in young patients. As HRA technology and experience improve, our data suggests that the results further improve. HRA currently meets the NICE criteria for 10-year survivorship of implants while THR doesn't in young patients. Our HRA patients are allowed unrestricted activity, while THR patients are typically restricted. AWRF (0.4%) is a minor problem that has been blown far out of proportion to its significance. Patient selection against HRA in certain subgroups (women, small bearings, history of metal allergy) may not be advisable based on our results.
