Mechanistic Pain Profiling of Patients with Osteoarthritis: Current Knowledge and Future Directions

The Osteoarthritis Research International (OARSI) provides clinical guidelines for the treatment of pain in osteoarthritis, and some of the most utilized treatments are Non-Steroidal Anti-Inflammatory Drug (NSAID) plus paracetamol and total joint arthroplasty. Most patients will benefit from these treatments, but some patients are less responsive or showing unwanted side effects, and selecting the right patients for the most optimal treatment would further highlight the opportunities of personalize pain medicine. Quantitative sensory testing (QST) of patients with OA includes measures of widespread pressure hyperalgesia (assessed by pressure pain thresholds, PPTs), temporal summation of pain (TSP), and conditioned pain modulation (CPM). The current dissertation has focus on how assessment of central pain pathways using QST prior to treatment can predict pain and pain reduction after treatment.
The studies presented here found associations between preoperative widespread hyperalgesia (paper 2), facilitated TSP (paper 1, 3, and 4), and impaired CPM (paper 5) and chronic postoperative pain in patients with painful osteoarthritis after total joint arthroplasty. In addition, pre-treatment facilitated TSP was associated with limited analgesic response to 4 weeks of COX-2 inhibitors (paper 6) and 3-weeks of NSAIDs plus paracetamol (paper 7). Finally, impaired CPM was associated to limited analgesic response of 3 weeks of NSAIDs plus paracetamol (paper 8).
A systematic review on all studies related to QST, chronic postoperative pain, and responses to pharmacological interventions is included in this dissertation (paper 9), which highlights that pressure pain stimuli, TSP, and CPM were the most frequently assessed QST modalities, and TSP (50%) and CPM (approx. 44%) were most frequently associated with chronic postoperative pain or response to pharmacological treatments.
Conclusively, these studies (paper 1-8) demonstrate that patients with a pro-nociceptive sensory profile might respond poorly to the standard OA pain treatment as recommended by OARSI, and the systematic review (paper 9) might indicate that this information is useful in other painful disorders than osteoarthritis.