Less Invasive TKA Extramedullary Femoral Reference Without Navigation

Femoral intramedullary canal referencing is used by most knee arthroplasty systems. Fat embolism, activation of coagulation, and bleeding may occur from the reamed canal. The purpose of our study was to evaluate a new extramedullary device that relies on templated data. We randomized 100 consecutive patients undergoing primary total knee arthroplasty through a limited parapatellar approach to use of either standard intramedullary femoral instruments (IM group) or a new extramedullary device (EM group). The extramedullary instrument was calibrated using templated data obtained from a preoperative full-limb weightbearing anteroposterior view of the knee. In both groups, an intraoperative double check was performed using an extramedullary rod referring to the anterosuperior iliac spine. Femoral component coronal alignment was within 0° ± 2° of the mechanical axis in 84% of the IM group and 86% of the EM group. Sagittal alignment of the femoral component was 0° ± 2° in 78% of the IM group and 90% of the EM group. We observed no difference in the average operative time between the two groups. The two groups showed similar postoperative blood loss. Extramedullary reference with careful preoperative templating can be safely used during TKA.

Level of Evidence: Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.