Clinical Performance of The Optetrak® Total Knee Prosthesis

Minimum two year follow-up

As presented at the European Federation of National Associations of Orthopaedics and Traumatology, June 1999.

Ivan A. Gradisar, Jr., M.D.*,  Michael Askew, Ph.D.*,  and Albert H. Burstein, Ph.D.**
*The Crystal Clinical and Clinical Professor, Northeastern Ohio School of Medicine, Akron, OH USA. **Professor Emeritus, Hospital for Special Surgery and Cornell University.

Purpose

This report details the performance of the Optetrak^® total knee system, a knee replacement design introduced in 1994. The femoral/tibial articulation is a bi-concave “sphere on sphere” geometry. Precise femoral/tibial articular matching is designed into the system, eliminating potential mismatch that might compromise polyethylene contact stresses.  Patellar flange geometries are optimized to reduce lateral retinacular tissue tension. This report is confined to posterior cruciate retaining prostheses of the system, which is used only in primary cases. All reconstructions were performed using: a bio-ingrowth femoral prosthesis; a cemented modular, polyethylene, metal-backed tibial prosthesis; and a cemented, all polyethylene patellar prosthesis.

Patients and Methods

Two hundred of the first 773 arthroplasties performed to the date of this report have undergone the two-year evaluation.  This group consisted of 159 patients, 41 of them with bilateral arthroplasties. There were 66 males and 93 females whose average age was 71 years (48-86 years). The mean weight of the group was 90 kilograms (52-139 kg) and the mean height was 167 centimeters (143-196 cm). Pre- and post-operative evaluation of all patients included patient satisfaction, patellar alignment, the Hospital for Special Surgery score and the Knee Society knee score. Surgical technique, including criteria for lateral patellar releasing, remained constant throughout the study. A two-year post-operative range of motion evaluation, determined using the traditional supine position, was available for 108 patients in the group.

Results

Two years following surgery, the average Hospital for Special Surgery score was 88. The average Knee Society knee score was 81 and the average Knee Society function score was 84. All patellae were resurfaced and all of the knees had at least partial retention of the posterior cruciate ligament. Only eight (4 percent) lateral patellar releases were required. Post-operative skyline views revealed an average patellar tilt of only 0.2 degrees to the medial side. There was no clinically evident mal-tracking of the patella.  Patients exhibited 113 degrees total range of motion with no lag.

Discussion and Conclusion

Total knee arthroplasty performed using the Optetrak^® cruciate retaining prosthesis achieved excellent functional results and patellar performance at the two-year evaluation point. Range of motion was increased over previous designs used, based on historical data from the author’s clinical practice. The most intriguing design advance, favorable polyethylene interfacial load transfer, must await long term observation to validate the potential benefit of a more durable arthroplasty.

Acknowledgement: Mark Kovacik, B.S.