Abstract
Background
To investigate whether the interaction between pre-operative widespread hyperalgesia and radiographic osteoarthritis (OA) was associated with pain severity before and after total hip replacement (THR) and total knee replacement (TKR).
Methods
Data were analysed from 232 patients receiving THR and 241 receiving TKR. Pain was assessed pre-operatively and at 12 months post-operatively using the WOMAC Pain Scale. Widespread hyperalgesia was assessed through forearm pressure pain thresholds (PPTs) measured using an algometer. The severity of radiographic OA was evaluated using the Kellgren and Lawrence scheme. Statistical analysis was conducted using linear regression and multilevel models, and adjusted for confounding variables.
Results
Pre-operative
In knee patients, there was weak evidence that the effect of PPTs on pain severity was greater in patients with more severe OA compared to patients with less severe OA (Grade 3 OA: ß=0.96 vs Grade 4 OA: ß=4.03). However, in hip patients, the effect of PPTs on pain severity did not differ with the extent of radiographic OA (Grade 3 OA: ß=3.95 vs Grade 4 OA: ß=3.67).
Post-operative
Patients undergoing TKR with less severe OA who had lower PPTs (greater widespread hyperalgesia) benefitted less from surgery than patients with higher PPTs (Grade 3 OA: ß=2.28). Conversely, patients undergoing THR with more severe OA who had lower PPTs benefited more from surgery than patients with higher PPTs (Grade 4 OA: ß=−2.92).
Conclusion
Central sensitisation may be a determinant of how much patients benefit from joint replacement, but the effect varies by joint and severity of structural joint changes.
Level of Evidence
2
Approvals
The APEX trials were registered as an International Standardised Randomised Controlled Trial (96095682), approved by Southampton and South West Hampshire Research Ethics Committee (09/H0504/94) and all participants provided informed written consent.
