Geographical variation in incidence of primary total hip arthroplasty: a population-based analysis of 34,642 replacements

Abstract

Background: Considerable variation in total hip arthroplasty (THA) incidence between regions has been described. The aim of this study was to evaluate geographical variation in the incidence of primary THA for OA in Finland and to analyze variables associated with this variation.

Methods: Using Hospital Discharge Register, 34,642 THAs performed for primary OA over the 1998 and 2005 period were identified. Incidence indices for 21 hospital administrative regions were determined. Logistic regression analysis and generalized linear models were used for studying the association of potential explanatory factors for the variation in the incidence of THA.

Results: Incidence indices of THA varied from 1.9- to 3.0-fold during the study period. A high ratio of primary THA for primary OA to primary THA for any reason was associated with a high absolute incidence of primary THA (P < 0.001). Neither average incomes nor morbidity were associated with the incidence of THA.

Interpretation: When hip surgery was performed on a larger scale, threshold for performing THAs due to primary OA was higher. Socio-economic status had no apparent effect on THA rate. Surgeon decision-making related factors influence THA rates when there are only a few surgeons responsible for performing THAs in a region.