Correlation between femoral neck version and strain on the femur after insertion of femoral prosthesis.

Stress analysis on the femur after insertion of a femoral prosthesis with a modular interchangeable neck with adjustable neck version was performed using in vitro experimental procedures and cemented strain gauges. Although strain on the anterior and posterior aspects was less than on the medial and lateral aspects, it was more markedly affected by adjusting the interchangeable neck from straight to anteverted (or retroverted) than strain on the medial and lateral aspects, particularly around the stem tip. There was a highly significant correlation between compressive strain on the side toward which the prosthetic neck was oriented and the extent of neck version, whether anteverted or retroverted. Insertion of a femoral implant in excessive anteversion (or retroversion) may cause noticeably increased stress on the anterior and posterior aspects of the proximal femoral shaft.