ABSTRACT
PURPOSE: Recently, a mobile ultracongruent polyethylene insert was used to increase joint stability in the posterior cruciate ligament sacrificed total knee arthroplasty with non-posted mobile bearing. However, as yet there have been no reports about this implant. In this study, the clinical and radiological results of surgery using the implant were analyzed through a navigation system. MATERIALS AND METHODS: The subjects included 95 cases of 70 patients to whom the rotating tibial implant was applied after posterior cruciate ligament resection among the patients who underwent total knee arthroplasty from September 2006 to December 2008. The follow-up duration was at least 24 months, and 40 months on average. For clinical evaluation, the knee score and functional scores were measured preoperatively and at the time of final follow-up. With reference to a 5 mm joint line change measurement recorded by the navigation system, which can affect the clinical result, the comparison and evaluation were performed by dividing the subjects into group I (5 mm). Radiological evaluation was performed by measuring the angle of the mechanical axis of the lower extremities and the patella tilting angle preoperatively and at the time of final follow-up using plain radiographs. RESULTS: Seventy subjects (95 cases) were followed up for at least 24 months. According to the clinical results, the mean KSS knee score improved from a preoperative score of 43.4 to a final follow-up score of 90.6 (p<0.0001). In addition, the mean functional score improved from a preoperative score of 51 to a final follow-up score of 88.4 (p<0.0001). Finally, the mean joint line change, which can affect the clinical result, was 5.82 mm, ranging from -1 to 12 mm. The clinical and radiological evaluations were performed by dividing the subjects into two groups in relation to the reference value of 5 mm, but no significant difference was found. The mechanical axis angles of the lower extremities improved from the preoperative value of varus 10.01degrees to the final follow-up value of varus 1.89degrees, and the difference was significant (p<0.0001). The mean patella tilting angles were 8.8degrees and 9.3degrees, respectively, at the time before the operation and after the final follow-up; this difference was not significant (p=0.89). CONCLUSION: Good clinical and radiological results were observed after at least two years of follow-up subsequent to total knee arthroplasty, in which a rotating ultracongruent polyethylene insert was applied after posterior cruciate ligament resection using a navigation system.