A prospective randomised double-blind study of functional outcome and range of flexion following total knee replacement with the NexGen standard and high flexion components

Abstract

Modifications in the design of knee replacements have been proposed in order to maximise flexion. We performed a prospective double-blind randomised controlled trial to compare the functional outcome, including maximum knee flexion, in patients receiving either a standard or a high flexion version of the NexGen legacy posterior stabilised total knee replacement. A total of 56 patients, half of whom received each design, were assessed pre-operatively and at one year after operation using knee scores and analysis of range of movement using electrogoniometry. For both implant designs there was a significant improvement in the function component of the knee scores (p < 0.001) and the maximum range of flexion when walking on the level, ascending and descending a slope or stairs (all p < 0.001), squatting (p = 0.020) and stepping into a bath (p = 0.024). There was no significant difference in outcome, including the maximum knee flexion, between patients receiving the standard and high flexion designs of this implant.

Range of motion and function are similar in patients undergoing TKA with posterior stabilised and high-flexion inserts

“…Our study and five others in the literature [14,20,22,27,29] failed to prove an increase in flexion with the use of HF TKAs. However, there is evidence that suggests that HF TKA designs may improve intraoperative passive ROM and postoperative maximum weight-bearing flexion.…”

“…Despite the previously mentioned concerns, the use of HF TKA designs has become popular, and the literature reporting on their clinical and biomechanical aspects is encouraging (Table 5). Though intuitively patient satisfaction following surgery may be associated with the achievement of high flexion, the literature has proven otherwise [10,13,14,29,31]. Park et al analysed ROM and clinical outcomes as measured by KSS, WOMAC, and SF-36 in 207 Korean patients (333 knees) one year following TKA.…”

“…The literature results comparing HF and PS TKA designs continue to be inconclusive and are probably design and surgeon dependent [6,10,13,18,20,21,28,29,38]. Table 5 outlines results from different studies comparing PS and HF TKA designs.…”

“…The design changes aim at facilitating flexion by improving the TKA kinematics in high flexion. It remains debatable whether the design changes in the so called HF TKA will not only facilitate but also increase postoperative flexion and diminish the manipulation rate [1, 8,10,14,17,18,22,27,29,37].…”

2009 Marshall Urist Young Investigator Award: How Often Do Patients with High-Flex Total Knee Arthroplasty Use High Flexion?

“…A third study reported no difference in average postoperative knee flexion in 50 patients who underwent bilateral TKAs (138°for NexGen 1 LPS-Flex versus 135°for NexGen 1 LPS) [26]. To date, three of nine clinical studies suggest patients have increased postoperative flexion with highflexion prostheses [6,19,20,23,26,38,42,44,45]. One of these studies reported patients with maximum flexion greater than 135°had a better functional WOMAC Osteoarthritis Index score than patients with maximum flexion of 135°or less (17.5 versus 14.3) [45].…”