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. 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.Background
Methods
Regardless of their expectations concerning level of pain following TKR, those participants who perceived an improvement in pain as a result of their TKR were less likely to expect a cure for their residual pain and were either very well or reasonably well adjusted to the pain. Nevertheless, those who had moderate expectations of outcome were more likely to perceive an improvement than those with high expectations. Those individuals who reported having held high expectations of TKR outcome and subsequently experienced increased pain were likely to experience distress in relation to their pain; those who also felt that a cure for their current pain may be possible experienced particularly high levels of distress.
