THE RATE OF HETEROTOPIC OSSIFICATION IN HIP RESURFACING COMPARED TO TOTAL HIP ARTHROPLASTY

Abstract

There is little in the literature reporting on the incidence of heterotopic ossification (HO) after hip resurfacing arthroplasty. HO has long been recognized as a complication of THA, with a reported incidence that ranges between 5 – 90 %. We investigated the incidence of HO in a group of hip resurfacing patients, and compared this against the incidence of HO in a comparable group of patients managed with a conventional THA. We retrospectively reviewed patients who had a hip resurfacing procedure from January 2004 to December 2007 carried out by a single surgeon. To act as our comparative group, we selected a closely matched group of patients in terms of age and sex who underwent a THA over the same time period, under the same surgeon. 47 cases of resurfacing, 23 were female and 24 male. The 47 cases of the selected THA group consisted of 24 females and 23 males. Therefore the two groups were of a similar sex make up. Within the resurfacing group of patients, the ages ranged from 31 to 68 years, with the mean being 55.4 years, and the median being 56.5 years. The THA group possessed an age range of from 31 to 68 years, with the mean being 55.4 years, and the median being 56.5 years. The resurfacing group of patients had 5 cases showing HO, giving an overall rate of 10.6 percent. 3 were of the grade I variety, while 2 were grade II. The THA group had 6 cases showing HO, giving an overall rate of 12.8 percent. 5 of these were of the grade I variety, while 1 was of the grade III variety. We used a two tailed Fischer’s Exact test set at the 5th percentile significance level to compare the overall rate of HO occurrence between the 2 groups, namely 10.6 percent versus 12.8 percent. This gave a p value of 0.238. Therefore we can state that there is no significant difference in the rate of HO formation between the resurfacing and THA patients.