The use of optical tracking systems in computer assisted surgical navigation requires the rigid fixation of a dynamic reference base to the target bone to be navigated. This report presents the results of a new approach to optical tracker fixation in the distal femur. Four embalmed cadavers were evaluated for pin placement. It was found that placement of pins from medial to lateral parallel to the transepicondylar axis placed the pins well posterior to the center of the intramedullary canal and away from neurovascular structures. Eighty-six consecutive patients underwent total knee arthroplasty using this new technique. All procedures were successful for performing a navigation-assisted total knee replacement. Obesity was not a factor, nor was there any loosening of the pin array during the procedure. There were no wound-healing problems in any patient. At one year follow-up, no patient could identify subjective symptoms related to either the medial epicondylar area or the stab wound portals. No direct neurovascular injuries were noted and no patient developed a fracture of the femur related to the pin sites.
A new technique is described that facilitates pin placement for minimally invasive approaches while eliminating complications. Sagittal plane optical array orientation simplifies the surgical technique.