Joint line changes after navigation-assisted mobile-bearing TKA.

The purpose of this study was to analyze the clinical results of patients who underwent navigation-assisted cruciate ligament retention-type mobile-bearing total knee arthroplasty (TKA) according to joint line changes. From September 2004 to January 2006, cruciate ligament retention-type mobile-bearing TKAs were performed using a navigation system (OrthoPilot; B. Braun Aesculap, Tuttlingen, Germany) on 50 knees in 45 patients (2 men, 43 women). The mean follow-up period was 46 (range, 39-55 months), and patient mean age was 65 years. There was 1 case of rheumatic arthritis; all others were of degenerative arthritis. Proximal tibia resection was performed at the sclerotic level of the medial tibial plateau. The distance from the lowest point of lateral tibial plateau (registered point) to the proximal resection plane was measured. Clinical outcomes (range of motion, Knee Society Score) were compared for joint line elevations of > or =3 mm (20 cases) and <3 mm (30 cases). Mean joint line elevation was 1.93 mm (range, -1-5 mm). Joint line change was not found to be associated with difference of clinical results (P>.05). The findings of this study suggest that joint line changes in the range of -1 to 5 mm after cruciate ligament retention-type mobile-bearing TKA do not affect clinical outcome.