Learning curve effect of navigated total knee replacement

摘要

Introduction: All orthopaedics procedures have a learning curve, whereas some procedures have a steep and difficult curve, some are relatively safe. Computer assisted total knee arthroplasty is a developing technique for improving the alignment of the leg and orientation of components in TKA. Restoration of the neutral alignment of the leg is an important factor affecting the long term results of total knee arthroplasty (TKA). We tried to evaluate the learning curve effect in navigated total knee replacement. Methods: We reviewed 50 patients who underwent computer assisted total knee arthroplasty by five orthopaedic surgeons in Kings College Hospital. The main objective of the study was to evaluate alignment of the leg and the orientation of components on post-operative long-leg coronal films. Results: The results confirmed that computer assisted TKA has much better results even in the hands of dedicated knee surgeons who are not doing computer assisted orthopaedic surgery routinely. The patients were evaluated using long leg coronal films. Coronal femoral component angle, coronal tibial component angle, mechanical orientation of femoral component and mechanical femoro-tibial axis were calculated. In our study of 50 cases only 12 percent of the cases had their alignment outside the recommended normal range, when initial 10 cases are not included only 2.5 percent of cases was outside the recommended normal range. These values were statistically significant at p-value less than 0.05. The blood loss during the procedure was average 933 ml which was much less than the conventional jig based surgery. There were only two patients with superficial infections and none of the patients had deep infections. The tourniquet time was about 105 minutes in average but it decreased as the surgeons got used to the instrumentation.