Optimal implant placement in Primary Total Hip Arthroplasty (THA) aims to restore physiological hip function. Three-Dimensional Computed-Tomography (3D-CT) and Patient-Specific Instrumentation (PSI) can guide implant positioning in THA. Despite growing evidence of preferable results compared to conventional templating, these tools remain underused in clinical practice. This thesis aimed to assess the role of 3D-CT planning and PSI in terms of femoral stem implantation through pre- and post-operative 3D-CT image analysis in primary THA. 3D-CT planning accurately predicted the femoral stem size (96% within one size) and femoral offsets in uncemented THA. Predicting Prosthetic Femoral Version (PFV) proved to be the unmet need given the limited surgical control of uncemented femoral stems to avoid an insufficient or retroverted PFV associated with THA instability. An insufficient PFV (