Dislocation after total hip arthroplasty among patients with developmental dysplasia of the hip.

The precise relationship between developmental dysplasia of the hip and dislocation among patients after total hip arthroplasty has not been well clarified. A total of 820 patients with developmental dysplasia of the hip who underwent total hip arthroplasty from January 2000 to December 2009 were categorized according to Crowe classification, and postoperative dislocation rates were analyzed among subgroups. The overall dislocation rate was 2.93%. No statistically significant differences in dislocation rates were observed between these with and without subtrochanteric osteotomy. Femoral head size was the only factor with significant difference between the dislocated and stable groups, especially when femoral head diameter increased from 28 to 32 mm. Of all dislocations, 69.6% were anterior dislocation, and the degree of cup anteversion and combined anteversion of anterior dislocators was higher than that of the posterior dislocators (P = .0082 and P = .001).