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.
One of the authors (AB) developed and has patented the device investigated in this study. There are no further commercial
associations (eg, consultancies, stock ownership, equity interest, etc) that might pose a conflict of interest in connection
with the submitted article.
Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations
were conducted in conformity with ethical principles of research, and that informed consent for participation in the study
was obtained.