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 degrees 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 degrees 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 degrees . Mean medial laxity was 3.5+/-1.4 degrees , mean lateral laxity was 4.4+/-2.2 degrees 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.