Body mass index as a risk factor for mis-seating of ceramic liners in total hip arthroplasty

Background A retrospective radiographic review was undertaken to determine the prevalence of mis-seated ceramic liners in primary total hip arthroplasty and the association between body mass index and mis-seating risk. Methods Patients with primary implantation of the Trident (Stryker, Mahwah, NJ) uncemented ceramic acetabular component were identified from a prospective database of 2227 primary total hip arthroplasties and radiographically reviewed. All procedures were performed at one center between 1999–2006. The mis-seating angle and location were determined. The risk of mis-seating by body mass index was calculated using logistic regression models. Results A total of 411 primary total hip arthroplasties were identified. Mis-seating occurred in 81 patients (19.7%). Of the 411 total hip arthroplasties, 83 (20.2%) were performed in patients with a body mass index of less than 25.0 defined as underweight to normal, 133 (32.4%) in patients who were overweight with a body mass index between 25.0–29.9, and 195 (47.4%) in patients who were obese with a body mass index of over 30.0. Adjustment for case mix revealed a significant association between body mass index and risk of mis-seating of ceramic components. Patients who were overweight at the time of total hip arthroplasty (body mass index 25.0–29.9) were at increased risk of mis-seating (adjusted odds ratio 2.52, 95% confidence interval (1.24-5.12, P=0.01). Conclusions Mis-seating of ceramic acetabular systems in total hip arthroplasty was a frequent occurrence. Patients who were overweight were more than two times more likely to suffer mis-seating than those who were underweight, of normal weight, or obese.