Prevalence and patterns of neuropathic pain in people with chronic post-surgical pain after total knee arthroplasty

Aim
To describe the prevalence and patterns of neuropathic pain over one year of follow-up in a cohort of patients with chronic post-surgical pain at three months after total knee replacement (TKR).
Methods
Between 2016 and 2019, 363 patients with troublesome pain, defined as score of ≤14 on Oxford Knee score pain subscale, at three months after TKR from eight UK NHS hospitals were recruited into the Support and Treatment After Replacement (STAR) clinical trial. Self-reported neuropathic pain and postoperative pain trajectory was assessed at three, nine and fifteen months after surgery using the painDETECT and Douleur Neuropathique 4 (DN4) collected by postal survey.
Results
Neuropathic pain was common amongst those reporting chronic pain at three months post-operative, with half reporting neuropathic pain on painDETECT (191/363; 53%) and 74% (267/359) on DN4. Of those with neuropathic pain at three months, half continued to have symptoms over the next twelve months (148/262, 56%), a quarter had improved (67/262, 26%), or their neuropathic symptoms fluctuated over time (24/262, 9%). However, a subgroup of participants reported new, late onset neuropathic symptoms (23/262, 9%). Prevalence of neuropathic symptoms was similar between the screening tools when the lower cut-off painDETECT (score≥13) was applied. Overall, mean neuropathic pain scores improved between three and 15 months after TKR.

Conclusion
Neuropathic pain is common amongst patients with chronic pain at three months after TKR. Although neuropathic symptoms improved over time, up to half continued to report painful neuropathic symptoms at fifteen months after TKR. Postoperative care should include screening, assessment, and treatment of neuropathic pain in patients with early chronic postoperative pain after TKR.