Background: Several studies have demonstrated positive relationships between high hospital volume and improved outcome following total knee replacement. To our knowledge, it has not been demonstrated whether improved outcomes are causally determined by selective referral to high-volume hospitals. We therefore evaluated the effect of a national regulation regarding minimum hospital volume for total knee replacement on two short-term outcome parameters.
Methods: We performed a comparison of the years before (2004, 2005) and after (2006) the implementation of a national regulation on minimum hospital volume for total knee replacement through a secondary analysis of a national database on the quality of inpatient care in Germany as reflected by the number of cases per hospital and the postoperative rates of wound infection and wound hematoma or secondary hemorrhage.
Results: We analyzed 110,349 cases from 2004, 118,922 cases from 2005, and 125,322 cases from 2006. Implementation of the regulation had a significant effect on the number of cases per hospital. Of the hospitals that had performed one to forty-nine cases in 2005, 35.6% moved to higher-volume categories and 21.2% dropped out in 2006. Multiple logistic regression analysis adjusting for patient characteristics demonstrated risk reductions of 22.5% (odds ratio, 0.775; 95% confidence interval, 0.700 to 0.857) for postoperative wound infection and of 44% (odds ratio, 0.562; 95% confidence interval, 0.531 to 0.596) for wound hematoma or secondary hemorrhage from 2005 to 2006. For wound infection, approximately half of the improvement was attributable to the effects of the minimum-volume regulation. For wound hematoma and secondary hemorrhage, the improvement could not be explained by the minimum-volume regulation.
Conclusions: Implementation of the minimum-volume regulation for total knee replacement resulted in more patients being managed at higher-volume hospitals than expected. Following the implementation of a minimum-volume regulation, effects on two short-term outcome parameters were observed, but definite conclusions could only be made regarding wound infection, with the minimum-volume regulation resulting in a decreased rate of infection.