Femoral stem sagittal balance - Do we need a new entry point?

Abstract

Objectives: Femoral stem positioning is of great importance in hip arthroplasty. Straight stem sagittal balance gains recently more attention in the literature. Methods: We performed a both clinical and cadaveric study in order to identify a possible ideal stem entry point at the level of the proximal femur, that ensures an optimal sagittal stem centering. We compared the sagittal tilt of 52 patients with femoral stem implantation in post-operative x-rays, dividing them in two groups depending on posterior neck cortex perforation. Subsequently, femoral neck osteotomy was performed in 40 cadaveric femurs. After placing an average straight stem, measurements of stem axis and femoral neck were made, in order to identify a possible area that could be used as a landmark, through which an optimal sagittal centering could be achieved. Results: Based on our results, stem sagittal tilt differed significantly when posterior neck was spared. In cadaveric evaluation, when posterior neck cortex was not perforated, the tip of stem was in contact with the posterior diaphysis cortex, thus malpositioned in the sagittal plane. We additionally found a statistically significant difference between neck centre and a) stem posterior boarder and b) neck posterior cortex distance. Conclusions: We conclude that placing the femoral stem just posteriorly to the posterior neck cortex, seems to be a good technique in order to achieve optimal sagittal balance of the femoral component.