The minimal invasive total knee arthroplasty has demonstrated shorter hospital stays, less postoperative blood loss, and less pain associated with these techniques but concerns are raised about inaccurate implant alignment due to limited visibility. The combination of computer assisted arthroplasty and MIS could aid in the improvement of the accuracy of implantation.

This prospective randomized study presents the initial results of the first 25 cases of two different imageless computer-assisted arthroplasty, the Orthopilot(B. Braun-Aesculap, Tuttlingen, Germany) and the Ci navigation system(DePuy, Munich, Germany). The same surgeon performed all TKA procedures using the minimidvastus approach. Coronal and sagittal alignments of the femoral and tibial components were determined using postoperative full length radiographs.

Comparison of the 2 groups demonstrated no difference in postoperative limb alignment, femoral and tibial coronal alignment, and sagittal tibial alignment. The sagittal alignment between the 2 groups showed different results. The Orthopilot group showed a tendency toward flexion of the femoral components, and the Ci navigation group showed a tendency toward extension of the femoral components. The tourniquet time was longer by an average of 16minutes in the Ci navigation group. One complication of femoral fracture through the pin site occurred in the Orthopilot group. Combined CAS and MIS has he advantage in improving the accuracy of component alignment but caution is needed for improving sagittal femoral component alignment.