Femoral Stem Version in Primary Hip Arthroplasty: Challenges and Advances in 3D Planning.

» Native femoral version (NFV) demonstrates inconsistent correlation with prosthetic femoral version (PFV) and should not be relied upon in isolation for femoral version planning in cementless total hip arthroplasty (THA). » Final stem version is strongly influenced by intramedullary canal morphology, fixation mechanics, and stem design philosophy. Straight, tapered wedge, and diaphyseal-engaging stems demonstrate greater variability in PFV, whereas anatomic and calcar-guided short stems may better preserve NFV. » Current planning methods inadequately characterise three-dimensional canal anatomy and fail to simulate canal-stem interaction, limiting accurate prediction of PFV. » Intraoperative estimation methods remain inconsistent and highly dependent on surgeon experience. Robotic-assisted THA enables real-time PFV measurements and supports femur-first strategies to optimise combined anteversion, although current systems still rely on computed tomography templating without true canal-stem interaction modelling. » Reliable PFV prediction will likely require next-generation planning platforms integrating internal canal anatomy, statistical shape modelling and artificial intelligence-driven modelling into planning workflows.