The geometry of the bone structure associated with total hip arthroplasty

Close adaptation of the prosthesis to the bone is the key to achieving optimal stability and fixation for total hip arthroplasty (THA). However, there have been no adequate studies of bone morphology, especially in different races. The aim of this study was to analyze the geometry of the acetabulum and proximal femur of people from South China, based on three-dimensional reconstruction, and to detect differences between different population subsets. CT scans were performed on 80 healthy volunteers (160 hips) from South China, comprising 40 males (80 hips) and 40 females (80 hips). The images were imported into Mimics 10.01 to perform 3D reconstruction. THA-associated anatomical parameters were measured and compared with other published data. In comparison with published data, it seemed that people from South China have smaller acetabular abduction angle, larger acetabular supro-inferior diameter, larger neck-shaft angle, smaller offset, thinner femoral shaft and more proximal isthmus, which needed to be further confirmed. There were significant differences between the genders in most parameters. As significant differences in canal flare index (CFI) and distal canal flare index (DCFI) were found between genders, it was concluded the most significant differences lay in the isthmus of the femur. Among the femora, according to Noble's classification we identified more normal types and fewer stovepipe and champagne-flute types than expected from the literature, indicating that uncemented prostheses would be suitable for most people from South China. Our findings reveal that simply choosing the smallest of a series of prostheses would not necessarily provide a good fit, due to the different trends from the proximal to the distal part of the femur. Significant variation exists in THA-associated anatomy between genders and population subsets. It is therefore imperative that each patient receives individual consideration rather than assuming all patients have the same anatomy, especially for different races.