5. LONGER LIFE

10-year patient survivorship is 20% better for HRA patients.

For patients matched for age, sex, diagnosis, economic status, and medical comorbidities there is a 20% lower mortality in the HRA group than the THR group. The best study was an analysis of the British Registry data by Kendall from Oxford University. It has been confirmed in another independent analysis of the same data as well as by data from the Australian Registry.

Calculation of implant survivorship was explained above. We are discussing patient survivorship here. In large population-based studies, the survivorship of patients who have had a THR is about the same as those that haven’t. When HRA is compared to THR in a controlled fashion, fewer deaths occur in 10 years in the HRA group. The first impulse is that HRA patients are generally younger – so this makes sense. But these studies have controlled for age as well as many other factors that might explain the difference.

The mean age for an HRA patient in my practice is 54 years. Using very approximate numbers, if the chance that anyone of this age will die within 10 years is about 5%, then the person who has an HRA has a 20% lower incidence, which means 4% rather than 5%. These are small but strongly statistically significant numbers from a very large database. The only explanation I can hypothesize is that HRA patients are more able or likely to exercise than THR patients. Regular and vigorous exercise promotes longevity. More importantly, this data helps to dispel the concept that many total joint surgeons promote, that metal ion release from hip resurfacing implants is a significant health risk.