Abstract
Background: In the UK 80% unicompartmental knee replacements(UKRs) and 10% of total knee replacements(TKRs) use mobile bearings. It is suggested that mobile bearings are more physiological and wear less, however it is still unclear whether patients tolerate mobile bearing knee replacements as well.
Patients and methods: We report four prospective studies,. Two compared fixed with mobile bearings in TKR and two in UKR. The prostheses involved were fixed and mobile variants of the Rotaglide (TKR), Kinemax (TKR) and Uniglide (UKR). In addition the Oxford and St. George Sled UKRs were compared. All except the Uniglide study were randomized prospective trials (RCTs)
611 patients were involved with a mean age of 68 years. Residual pain following surgery was assessed with either the Oxford Knee Score (OKS) or the WOMAC score. The patients were followed up at one and two years postoperatively by a Research nurse and the findings recorded prospectively on the Bristol Knee database.
Results:
| Study 1: | Rotaglide. Prospective RCT. 171 patients. Mean pain score (OKS) Fixed bearing 15.4 v Mobile bearing 13.2. P= 0.012. Fixed bearing prosthesis caused significantly less pain. |
| Study 2: | Kinemax. Prospective RCT. 198 patients. Mean pain score (WOMAC) Fixed bearing 8.9 v Mobile bearing 8.3. P = 0.443. Trend favouring fixed bearing. |
| Study 3: | Uniglide Non-randomised trial. 184 patients. Mean pain score (WOMAC) Fixed bearing 7.6 v Mobile bearing 10.1. P < 0.001. Fixed bearing caused significantly less pain. |
| Study 4: | St. George Sled v Oxford. Prospective RCT. 94 patients. Mean pain score (OKS) 15.8 v 13.9 . P= 0.058. Strong trend suggesting the Sled caused less pain. |
Conclusion: Our data suggests that the fixed bearing knee replacements result in less residual pain than their mobile bearing counterparts, at least in the first two years following surgery.
Correspondence should be addressed to: Tim Wilton, BASK, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
