Can version of the proximal femur be used for CT planning uncemented femoral stems?

Three-Dimensional Computed Tomography (3D-CT) planning can predict the prosthetic femoral size in unce-mented primary Total Hip Arthroplasty (THA). Correct sizing usually results in optimal varus/valgus femoral alignment; however, its effect on the Prosthetic Femoral Version (PFV) is poorly understood. Most 3D-CT planning systems use Native Femoral Version (NFV) to plan PFV. We aimed to assess the relationship between PFV and NFV in primary uncemented THA using 3D-CT analysis. Pre-and post-operative CT data was retro-spectively collected from 73 patients (81 hips) undergoing primary uncemented THA with a straight-tapered stem. 3D-CT models were used to measure PFV and NFV. The clinical outcomes were evaluated. The discrep-ancy between PFV and NFV was low (<5 degrees) in 43%, moderate (5-10 degrees) in 40%, high (10-15 degrees) in 11% and very high (>15 degrees) in 6% of the cases. We found that NFV is not a useable guide for planning PFV. The 95% limits of agreement were both high at 17 degrees and 15 degrees, respectively. Satisfactory clinical outcomes were recorded. The discrepancy was large enough to recommend against the use of NFV for planning PFV when using straight -tapered uncemented stems. Further work should focus on the internal bony anatomy and the influence of stem design when planning uncemented femoral stems.

Automated summary

Three-Dimensional Computed Tomography planning can predict prosthetic femoral size in un-cemented primary Total Hip Arthroplasty. However, the relationship between Prosthetic Femoral Version and Native Femoral Version is not well understood. This study aimed to assess this relationship using 3D-CT analysis.