To compare the volume of acetabular bone resection after primary hip arthroplasty with different cup designs and technique of implantation using a computer model.

The factors influencing acetabular bone resection during acetabular cup implantation in THA or hip resurfacing (SRA) include the design of the component and technique of implantation. The impact of these variables on bone resection was simulated with a computer model. A 3-D pelvis was reconstructed from CT scan images. The bony acetabulum circumference was 52.5mm. Implantation of pressfit acetabular component sustaining angles of 165°, 170° and 180° with different wall thicknesses (3.5, 4.0, 5.0mm) at various depths was simulated.

Bone loss of 2742mm3 was calculated for the 165°, 4mm thick, 54mm cup, and deepening of reaming by 1 and 2mm would result in bone loss of 3780mm3 (+38%) and 5076mm3 (+85%), respectively. When oversizing to a 56mm 165° component, 4998mm3 (+82%) of bone was removed. For a 54mm, 5 mm thick component sustaining an angle of 180°, the bone loss would reach 12 410mm3 (+450%).

Acetabular component design has a significant influence on the amount of acetabular bone resection. The surgical technique (avoiding over deepening and oversised components) should minimise bone loss. This knowledge is of particular importance in hip resurfacing since the acetabular component size depends on the selected femoral component size. The knowledge is is also important in THA to minimise bone loss at primary implantation.