Accuracy of intramedullary femoral alignment in total knee replacement: intraoperative assessment of alignment rod position

Current knee replacement techniques favour intramedullary (IM) alignment instrumentation for the guidance of distal femoral resection. Accurate femoral resection depends on the IM alignment guide lying along the line of the anatomical femoral axis, any discrepancy will affect the placement of the femoral cutting jig causing an inaccuracy of the femoral component position in the coronal plane. This study recorded the intra-operative alignment rod position prior to femoral resection. A variation of 5.3° (1.6° varus to 3.7° valgus) was found in relation to the true femoral anatomical axis. This study reveals that IM femoral alignment techniques often place the femoral resection jig in 1–2° more valgus than anticipated which reflects distal femoral anatomy.