Computer-Assisted Navigation in Total Knee Replacement: Results of an Initial Experience in Thirty-five Patients

The success of total knee replacement surgery depends on several factors, including proper patient selection, appropriate implant design, correct surgical technique, and effective perioperative care. The outcome of total knee replacement surgery is particularly sensitive to variations in surgical technique 1-9. Incorrect positioning or orientation of the implant and improper alignment of the limb can lead to accelerated implant wear and loosening as well as suboptimal functional performance. A number of studies have suggested that alignment errors of >3° are associated with more rapid failure and less satisfactory functional results after total knee arthroplasty 1,10-20. Recent studies have also emphasized that the most common cause for revision total knee replacement is error in surgical technique. Mechanical alignment guides have improved the accuracy with which implants can be inserted. Although mechanical alignment systems are continually being refined, errors in implant and limb alignment continue to occur. It has been estimated that errors in tibial and femoral alignment of >3° occur in at least 10% of total knee arthroplasties, even when performed by experienced surgeons using mechanical alignment systems of modern design. Mechanical alignment systems have fundamental problems that limit their ultimate accuracy. The accuracy of preoperative planning is limited by the errors inherent in standard radiographs. It is difficult to determine accurately, with standard instrumentation, the correct location of crucial alignment landmarks (e.g., the center of the femoral head, the center of the ankle). Moreover, mechanical alignment and sizing devices presume a standardized bone geometry that may not apply to a specific patient. Even the most elaborate mechanical instrumentation systems rely on visual inspection to confirm the accuracy of limb and implant alignment and stability at the conclusion of the total knee replacement procedure. Computer-based alignment systems have been developed to address the …