Pain sensitization may predict chronic pain after knee replacement
medwireNews: Preoperative pain sensitization is associated with chronic pain after total knee replacement (TKR), a preliminary study by UK researchers indicates.
The association, if confirmed in larger studies, suggests that patients at high risk for developing chronic pain can make an informed decision about whether to undergo surgery and potentially be targeted with interventions to improve their likelihood for a good outcome.
Vikki Wylde (University of Bristol) and colleagues studied 51 patients who were scheduled to undergo TKR because of osteoarthritis and 50 healthy participants without knee pain (controls). All participants were aged 50 years and over.
Quantitative Sensory Testing (QST) revealed that median preoperative pressure pain thresholds (PPTs) at both knee and forearm were significantly lower in patients than in controls, report Wylde et al in Osteoarthritis and Cartilage. Heat pain thresholds at both sites were comparable between the groups.
Among the TKR patients, the severity of pain in the index knee improved significantly over the study period, from a median of 40 (measured using the Western Ontario and McMaster Universities Osteoarthritis Index Pain subscale) before surgery to 90 at 1-year follow-up.
Wylde et al found that there was a significant positive correlation between patients’ preoperative forearm PPT and pain scores at 1 year after surgery. This suggests that patients with higher preoperative levels of pain sensitization had more severe pain in the replaced knee 1 year after surgery than those with lower preoperative sensitization
Further analysis found that the median postoperative pain score was significantly worse in patients with low (ie, below-median) preoperative forearm PPTs than in those with high (above-median) values, at 85 versus 95.
There was no correlation between preoperative heat pain thresholds and postoperative pain severity, however.
Describing their findings as “novel” but “preliminary,” the researchers call for further investigation into the role of preoperative pain sensitization in predicting chronic post-surgical pain.
“Further research could then evaluate whether the addition of an assessment of preoperative pain sensitization into a predictive model increases its ability to accurately identify who is likely to experience chronic pain after TKR,” they write.
“This would enable high risk patients to be targeted with pre-surgical interventions to improve their likelihood of a good outcome, or provide them with the opportunity to make an informed decision not to undergo major surgery which is unlikely to improve their pain.”
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Joanna Lyford, Senior medwireNews Reporter