Changes in Femoral Version During Implantation of Anatomic Stems: Implications on Stem Design.

Abstract

Component positioning in total hip arthroplasty (THA) is among the primary indicators for longevity and success. Acetabular component positioning has been discussed in literature at length; however, femoral component positioning is also important as it contributes to combined anteversion. In this study, we examined the changes in femoral anteversion after the implantation of anatomic stem ABG II. A cadaveric study, a computed tomography-based computer modeling study, and a clinical study using a navigation system were conducted to document these changes. These studies demonstrated that the anatomic stem ABG II increased the postimplantation femoral version by approximately 7°. The postimplantation versions followed a bimodal distribution. The computed tomography and navigation data also highlighted that the patient population may roughly be divided into 2 groups: the first group that needs anteverted stem and the second group that needs little or no anteversion in the stem to recreate the desired version and offset. Based upon our data, we propose a new anatomic stem design that is offered in 2 version angles of 0° and 7° to help create the desired version and offset.