Uncemented femoral stem orientation and position in total hip arthroplasty: A CT study

BELZUNCE, MARTIN A.; HENCKEL, JOHANN; DI LAURA, ANNA; HART, ALISTER

JOURNAL OF ORTHOPAEDIC RESEARCH

JOHN WILEY & SONS INC

Año: 2020 vol. 38 p. 1486 - 1496

0736-0266

In total hip arthroplasty (THA), accurate positioning of components is important for functionality and long life of the implant. Femoral component version has been under‐investigated when compared to the acetabular cup. Accurate prediction of the femoral version on the preoperative plan is particularly important because a well‐fitting uncemented stem will, by definition, press‐fit into a version that is dictated by the anatomy of the proximal femur. A better understanding of this has recently become an unmet need because of the increased use of uncemented stems and of preoperative image‐based planning. We present the first, three‐dimensional (3D) comparison between the planned and achieved orientation and position of the femoral components in THA. We propose a comparison method that uses the 3D models of a, CT‐generated, preoperative plan and a postoperative CT to obtain the discrepancy in the six possible degrees of freedom. We ran a prospective study (level 2 evidence) of 30 patients undergoing uncemented THA to quantify the discrepancy between planned and achieved femoral stem orientation and position. The discrepancy was low for: femoral stem vertical position and leg length; and varus‐valgus and anterior‐posterior orientation. The discrepancy was higher for femoral version with a mean(±SD) of ‐1.5 ± 7.8 deg. Surgeons should be aware of the variability of the eventual position of uncemented stems in THA and acknowledge the risk of achieving a less‐than‐optimal femoral version, different to the pre‐operative 3D‐CT plan.