FUNCTIONAL OUTCOMES OF TOTAL JOINT REPLACEMENT IN PATIENTS SUFFERING PERI-OPERATIVE MYOCARDIAL INFARCTION

There were more than 574,000 primary lower limb total joint arthroplasties performed in the United States in 2002 and 48,000 in Canada over approximately the same period. The incidence of clinically apparent myocardial infarction following lower limb arthroplasty has been previously reported at 1.8% (Gandhi et al, 2006). The functional outcome of patients suffering post-operative myocardial infarctions has never been reported to our knowledge. Our hypothesis is that functional scores of patients undergoing total joint arthroplasty that suffer peri-operative myocardial infarction will be lower than in our control patients. Patients were retrospectively identified from a prospectively collected database of total joint arthroplasties performed at one center. Six surgeons performed 3320 primary lower limb arthroplasties over a period of seven years. Patients of interest were identified via discharge summaries to have suffered a myocardial infarction diagnosed clinically and confirmed by biochemical assay. These patients were then case matched for demographics, risk factors and pre-operative functional score. Sixty-two patients (twenty six hips and thirty six knees) were identified as having suffered a post-operative myocardial infarction. There was an overall mortality of 13% and only thirty-four of the sixty-two (55%) completed follow-up to one year. The clinical course of the remaining patients remains uncertain. Statistically significant differences have been observed in Oxford hip scores at six weeks post operatively. Any differences disappear by six months. No statistically significant differences in outcomes were seen in knee outcomes. It would appear that those patients who are well enough to return for follow-up do just as well as those patients who did not suffer myocardial infarctions. There may be some differences in the rate of recovery from the surgery, but it appears that overall functional outcome of the patients that survive remain good.