Prospective randomized controlled trial comparing range of motion after standard and high-flexion posterior stabilized total knee prosthesis

Abstract

INTRODUCTION: There is an increasing demand for a better ROM in patients receiving TKR. The design of the prosthesis has been modified to allow deep flexion to occur. However, there is still controversy whether this can lead to a clinically significant improvement in flexion range. METHODS: A prospective randomized controlled trial comparing ROM after standard and high-flexion designed prosthesis was done in 24 patients receiving one-stage bilateral TKR (high-flexion NexGen LPS Flex in one knee and a standard version NexGen LPS in another knee). All the operations were done by the same surgeon with the same operative and rehabilitation protocol. The maximum knee flexion was measured at the final follow-up. RESULTS: The mean preoperative knee flexion was 106°. There was no difference between the high-flexion designed group and standard version group in terms of the preoperative knee flexion, preoperative mechanical alignment, postoperative mechanical alignment, position of the implanted components in coronal and sagittal plane, change in joint line, flexion gap balance and presence of residual posterior femoral condyle osteophyte. At a minimum follow-up of four years, there was no difference in the maximum knee flexion between the high-flexion designed group (115°) and standard version group (114°) (p=0.606, paired t test; beta error=0.055). CONCLUSION: In a group of patients having a preoperative knee flexion <130°, the use of a TKR of a high-flexion design ex hibited no additional benefit in terms of postoperative knee flexion when compared with a standard version prosthesis.