Risk factors for dislocation during the first 3 months after primary total hip replacement.

The prevalence of dislocation of a total hip replacement during the first 3 postoperative months was determined for a series of 315 patients who underwent a unilateral primary total hip operation. All operations were performed by 1 surgeon using a standardized posterior approach with a complete capsulectomy. All of the patients had a femoral component made by 1 manufacturer that had the same 28-mm modular head, the same femoral neck diameter, and the same offset for each size implant. One cementless acetabular component was used for all patients. All of the patients followed the same postoperative rehabilitation program. Of 315 patients, 14 sustained a dislocation, resulting in a prevalence of 4%. There were 13 posterior dislocations and 1 anterior dislocation. Because the surgeon, the surgical approach, the femoral component design, and the rehabilitation protocol were identical for all of these patients, the only variables that could affect the risk of dislocation were the size of the acetabular component and the femoral neck length, the type of fixation of the femoral component, the orientation of the acetabular component, and the characteristics of each patient. The patient characteristics that were studied included age; gender; height; weight; preoperative diagnosis; and a category termed cerebral dysfunction, which included a state of confusion during the hospital stay, a prior history of excessive alcohol consumption, or both of these conditions. Statistical analysis demonstrated 1 variable that was associated with a higher dislocation rate, the presence of cerebral dysfunction. There was a trend toward increased age as a risk factor. None of the other patient or component variables were found to be significant risk factors.