Abstract
Purpose
The NexGen® legacy posterior stabilized (LPS)-Flex total knee system (Zimmer, Warsaw, IN) is designed to provide 150° of flexion following total knee arthroplasty (TKA). But, recent reports found a high incidence of loosening of the femoral component related to the deep flexion provided. We evaluated 9- to 12-year clinical and radiological follow-up results after NexGen® LPS-Flex TKA.
Materials and Methods
A retrospective evaluation was undertaken of 209 knees in 160 patients (21 males, 139 females) who were followed up for more than 9 years after Nexgen®LPS-Flex TKA. Evaluations included preoperative and postoperative range of motion(ROM), Knee Society(KS) knee score, function scores, tibiofemoral angle and assessment of postoperative complications.
Results
The NexGen® LPS-Flex TKA resulted in a significant ROM increase from a mean flexion contracture of 9°(range 0°–20°) and further flexion of 117°(range 80° –155°) to a mean flexion contracture of 2°(range 0° –10°) and a further flexion of 131°(range 95° –155°). The KS knee and function scores significantly improved from 52 and 38 before surgery to 87 and 82 after surgery, respectively. The tibiofemoral angle significantly improved from varus 5.7° to valgus 5.4°. Progressive radiolucent lines around the femoral component on radiographs were observed in 39 knees(18.7%, 34 patients), and more of those knees, could squat than non-radiolucent knees(74.4% vs. 25.6%; P<0.05). Twelve knees(5.7%, 11 patients) were revised at a mean 53 months after the index operation due to loosening of the femoral component. Other causes of revision included 3 knees of infection(1.4%) and 3 knees of instability(1.4%).
Conclusion
While NexGen® LPS-Flex TKA satisfactorily improved ROM, it was associated with a relatively high incidence of loosening of the femoral components. This might be associated with passive-maximal flexion activity, such as squatting or kneeling. The clinical relevance of this study is that squatting or kneeling, common activity in Asian, may not be allowed after NexGen® LPS-Flex TKA.
