Outcome implications for the timing of bilateral total knee arthroplasties.

Health Care Financing Administration data from 1985 to 1990 revealed 339,152 total knee arthroplasties of which 62,730 (18.6%) were bilateral procedures (simultaneous 112,922; staged 6 weeks, 4354; staged 3 months, 4524; staged 6 months, 9829; and staged 1 year 31,401). Medicare beneficiaries undergoing bilateral procedures were an average of 73 years of age; demographics revealed that among the various simultaneous and staged groups 57% to 69% were females, 90% were white, 85% to 90% had a diagnosis of osteoarthritis, and 30% to 40% were performed in rural hospitals. Between 1985 and 1990, surgical and vascular complications ranged from 2.4% to 4% and 4.1% to 6.8%, respectively, for all types of bilateral staged and simultaneous total knee arthroplasties. All differences were statistically significant. After controlling statistically for demographic variables and diagnoses, a surrogate for case mix, it was found that individuals electing simultaneous bilateral arthroplasties experienced twice the number of intensive care days than those choosing staged procedures. Days in the intensive care unit were double when done simultaneously instead of staged (0.48 versus 0.21). Nosocomial infections were similar within groups (10% versus 13%); however, wound infections were nearly half when done simultaneously (0.5% versus 1%) versus in a staged fashion. Length of stay and cost were much less for the simultaneous procedure group who were sicker as measured by the number of diagnoses. Mortality at 30 days was highest for the simultaneous procedure group (.99%) versus staged 3 or 6 months (0.30%); however, by 2 years it was close to 4% for all groups. Staging the procedure 3 to 6 months seems to offer the fewest disadvantages, is only slightly more expensive, and has the lowest mortality rate.