Introduction: A posterior entry point, a neutral tip position and stem alignment are recommended for an even cement mantle and an optimal outcome in total hip arthroplasty (THA). Our aim was to highlight any differences between the two approaches in obtaining a neutral stem tip position, particularly in the saggital plane.

Methods: We examined the post op, digitised radiographs of 100 (50 each group) polished, tapered Exeter THA, inserted via the antero-lateral or posterior approaches. The stem tip position was defined as the distance, in millimetres, between the centre of the femoral canal and the centre of the stem tip, in both the coronal and saggital planes.

Results: There was a significant difference between the two approaches in the saggital stem tip position only (p= 0.01), but not in coronal tip position (p=0.1). When not in neutral, stems inserted by the antero-lateral approach showed a marked deviation towards the posterior cortex. This was not the case with the posterior approach.

Discussion: Our results illustrate that a neutral stem tip position in THA, and subsequently an even cement mantle, is significantly more difficult to obtain with an antero-lateral approach than a posterior approach. A posterior approach to the hip avoids the cuff of glutei that can lever the proximal stem anteriorally causing an anterior entry point and a posterior stem tip position. It also illustrates how the anatomy of the proximal femur in the saggital plane makes a neutral stem alignment difficult to achieve with either approach.