OUR EXPERIENCE USING CAS FOR TOTAL KNEE REPLACEMENT

Total knee arthroplasty is well documented to be a very successful operation, proper alignment and soft tissue balancing is important. Computer navigation for TKA has been available for more than 10 years. This paper reviews our outcomes and the lessons learned from CAS. October 1, 2001 we preformed the first clinical case of a navigated TKA in North America. We tracked our early results at with 1 year of follow up of 150 navigated knee cases and compared there data to 50 non- navigated knees. Long standing lower extremity x-rays were measured to determine mechanical alignment. In 2011 we reviewed all cases to date to determine if there were pin site problems. In 2012 we looked at are recurvatum data. Oct 2011 was our 10 th year using the computer navigation system for TKA. We reviewed what we have learned and assess our outcome data on patients who were at least 9.5 years post surgery. All patients received long standing lower extremity x-rays pre-operatively and at 10 year follow up. Any problems or revisions were noted. Our early results will be compared to our 10 year results. Our 1 year results showed no difference in clinical outcome or range of motion compared to the non-navigated group. The navigated knee group had better alignment; 52% were in neutral alignment, vs. 23% in the non-navigated group. Overall the navigated group, 80% of all alignment was within 1.5 degrees of neutral while the non-navigated groups 80 % of cases were between 5° valgus and 4° varus. Our data for 10 year follow up (range 9.5–10.5 years) is the similar to our early results. We have seen 42 patients, 44 knees. The alignment from long standing lower extremity x-rays, 53% were neutral or +/− 1°. Twenty eight knees of 43 were +/− 3°. There were 3 revisions in this small group. One was revised for a loose tibial base plate with osteolysis on the tibia and femur. The revision was 10 years after the index surgery. There were 2 other revisions, both for infection, were treated with a poly exchange and wash out. To date we have done 2030 navigated knee cases and our data shows that 13.9% demonstrate genu recurvatum. The range was 0.5° to 30°, 104 patients, 5.1% had more than 5° recurvatum. In the literature recurvatum rates are reported at about 1%. After reviewing all case to date in we did not observe any pin site problems. CAS is still the main objective measure we have in the operating room to date. The advantages of CAS are it provides real time assessment of the true varus/valgus deformity, initial extension and medial/lateral soft tissue imbalance and anticipates final trial reduction. We are performing less soft tissue releases most likely because our tibia and femoral cuts are more precise. Our 10 year follow up data while encouraging requires more investigation.