In vivo stability of total knee arthroplasty using a navigation system

The aim of this study was to evaluate in vivo stability for mediolateral laxity in extension and anteroposterior laxity in 90° of flexion and to correlate these and the range of motion (ROM) in 42 total knee arthroplasties (TKA) performed using a navigation system, with a minimum 1-year follow-up. The following parameters were measured at the final follow-up: mediolateral laxity in extension and anteroposterior laxity in 90° of flexion as determined by stress radiographs and a Telos arthrometer, modified HSS scores (excluding laxity and range of motion) and the range of motion (ROM). The mean modified HSS score was 82% of 82 maximum allowable points, and the mean postoperative ROM was 128.1±10.4°. Mean medial laxity was 3.5±1.4°, mean lateral laxity was 4.4±2.2° and mean anteroposterior laxity was 7.1±4.1 mm. We found no significant correlation between mediolateral laxity and postoperative ROM. However, a significant correlation was found between postoperative ROM and anteroposterior laxity. In conclusion, the use of a navigation system in TKA assists the surgeon to achieve good in vivo stability. Short-term clinical results are promising.