A new technique for determining proper mechanical axis alignment during total knee arthroplasty : Progress toward computer-assisted TKA

• Published in: Orthopedics (Thorofare, N.J.) Vol. 22; no. 7; pp. 698 - 702
• Main Authors: KRACKOW, K. A, SERPE, L, PHILLIPS, M. J, BAYERS-THERING, M, MIHALKO, W. M
• Format: Journal Article
• Language: English
• Published: Thorofare, NJ Slack 01-07-1999; SLACK INCORPORATED
• Subjects: Arthroplasty, Replacement, Knee - methods; Biological and medical sciences; Biomechanical Phenomena; Bone Malalignment - prevention & control; Cadaver; Follow-Up Studies; Humans; Knee Joint - diagnostic imaging; Knee Joint - surgery; Medical sciences; Monitoring, Intraoperative - instrumentation; Observer Variation; Radiography; Range of Motion, Articular; Sensitivity and Specificity; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Technology. Biomaterials. Equipments; Therapy, Computer-Assisted - methods; Treatment Outcome; Performance evaluation; Knee; Human; Medical equipment; Prosthesis; Thigh; Diseases of the osteoarticular system; Lower limb; Technical assistance; Optimization; Leg; Alignment; Surgery
• ISSN: 0147-7447; 1938-2367

Successful total knee arthroplasty (TKA) relies on proper positioning of prosthetic components to restore the mechanical axis of the lower extremity. This report presents and analyzes a new noninvasive method using the Optotrack (Northern Digital Inc, Ontario, Canada) to accurately determine the center of the femoral head. This method, together with direct digitization of the bony landmarks of the knee and ankle intraoperatively, permits placement of the lower extremity in proper alignment intraoperatively. It also permits the surgeon to follow all the angles of movement or rotation and all displacements that occur at each step of the operative procedure. knee intraoperatively via a customized Windows-based program. In addition to presenting our first case, which, importantly, represents the first computer-assisted TKA in a patient, we report on the accuracy and reproducibility of the technique for locating the center of the femoral head obtained during an extensive series of cadaver studies. Location of the femoral head, a major aspect of effecting neutral mechanical axis alignment, appears to be possible to within 2-4 mm, which corresponds to an angular accuracy of better than 1 degree. This method requires no computed tomography scans or other preliminary marker placement. The only basic requirement other than the instrumentation described is a freely mobile hip, which is generally present in TKA patients.