Objectives: Knee osteoarthritis (KOA) can be associated with local and central sensitization. As an indicator of the central gain, facilitated temporal summation of pain (TSP) has been found in KOA patients. This facilitation is predictive of the development of chronic postoperative pain after total knee arthroplasty (TKA). Other studies have suggested hypoesthesia/hypoalgesia to thermal stimuli as a feature in KOA. This study investigated associations between preoperative TSP, thermal sensitivity and radiological severity for the development of chronic postoperative pain after TKA.
Methods: Radiological KOA (Kellgren & Lawrence, KL), TSP, and thermal stimuli were collected preoperatively. Clinical knee pain intensity (VAS 0-10) was assessed before and 12 months following TKA. Subjects were categorized into a chronic postoperative pain group if they experienced less than 30% pain reduction of the initial pain after 12 months.
Results: 19% of the subjects were categorized as chronic pain subjects and presented facilitated preoperative TSP (P<0.05) and a trend towards increased heat pain threshold (P=0.077) compared with subjects with normal recovery. Pearson correlations found that preoperative TSP (R=0.193, P=0.013), KL (R=-0.168, P=0.027), warm detection threshold (R=0.195, P=0.012), and heat pain threshold (R=0.196, P=0.012) were associated with pain intensity 12 months after TKA where TSP was identified as an independent factor.
Discussion: This study showed that preoperatively facilitated TSP in KOA patients was predictive of the development of chronic postoperative pain following TKA. Furthermore, this study is the first to find an association between preoperative hypoalgesia to heat and the development of chronic postoperative pain following TKA.
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