Abstract
Background
Total hip replacement (THR) and total knee replacement (TKR) are usually effective at relieving pain; however, 7–23% of patients experience chronic post-surgical pain. These trials aimed to investigate the effect of local anaesthetic wound infiltration on pain severity at 12 months after primary THR or TKR for osteoarthritis.
Methods
Between November 2009 and February 2012, 322 patients listed for THR and 316 listed for TKR were recruited into a single-centre double-blind randomised controlled trial. Participants were randomly assigned (1:1) to receive local anaesthetic infiltration and standard care or standard care alone. Participants and outcomes assessors were masked to group allocation. The primary outcome was pain severity on the WOMAC Pain scale at 12 months post-surgery. Analyses were conducted using intention-to-treat and per-protocol approaches. Ethics approval was obtained from Southampton and South West Hampshire Research Ethics Committee.
Results
In the hip trial, patients in the intervention group had significantly less pain at 12 months post-operative than patients in the standard care group (differences in means 4.74; 95% CI 0.95, 8.54; p=0.015), although the difference was not clinically significant. Post-hoc analysis found that patients in the intervention group were more likely to have none to moderate pain than severe pain at 12 months than those in the standard care group (odds ratio 10.19; 95% CI 2.10, 49.55; p=0.004). In the knee trial, there was no strong evidence that the intervention influenced pain severity at 12 months post-operative (difference in means 3.83; 95% CI −0.83, 8.49; p=0.107).
Conclusions
In conclusion, routine use of infiltration could be beneficial in improving long-term pain relief for some patients after THR.
Level of evidence
Randomised controlled trial
Funding
This article presents independent research funded by the National Institute for Health Research (NIHR) in England under its Programme Grants for Applied Research programme (RP-PG-0407-10070). The views expressed in this article are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. The research team acknowledge the support of the NIHR, through the Comprehensive Clinical Research Network.
