The impaired attenuation of pain by the application of a noxious conditioning stimulus at a segmentally distinct site, known as conditioned pain modulation (CPM), has been implicated in clinical pain states. Chronic lateral epicondylalgia (LE), which is characterized by lower pressure pain thresholds (PPTs) at sites remote to the affected elbow and spinal cord hyperexcitability, is a clinical pain state that might plausibly involve less efficacious CPM. This study aimed to determine whether LE exhibits a less efficacious CPM compared with that in pain-free controls.
Results: Twenty participants with LE, aged 50.7 years (SD=7.05) and who had their condition for 10.2 months (range: 2 to 80 mo), were matched by age and sex to 22 pain-free participants. All participants indicated their PPT over the lateral epicondyle(s) before and during a conditioning noxious heat stimulus that was applied over the calf. A CPM score was calculated as the difference between the PPT before and during the heat pain-conditioning stimulus expressed as a percentage of PPT before the heat pain-conditioning stimulus. The condition (LE vs. control) by side (affected vs. unaffected) analysis of variance revealed a significant condition effect (P=0.001), but not side effect (P=0.192) or side-by-condition interaction effect (P=0.951). Follow-up tests for the effect of condition revealed a mean deficit in CPM of −24.5% (95% confidence interval, −38.0 to −11.0) in LE compared with that in pain-free participants.
The results that suggest an impaired ability to modulate pain might be associated with the previously observed spinal cord hyperexcitability and the mechanical hyperalgesia that characterizes LE.
*Centre of Clinical Research Excellence in Spine, Division of Physiotherapy, School of Health and Rehabilitation Sciences, the University of Queensland, St Lucia
‡Centre for National Research on Disability and Rehabilitation (CONROD), NHMRC Centre of Research Excellence in Road Traffic Injury, Menzies Health Institute Queensland, Griffith University, Parklands Drive, QLD, Australia
†Department of Physiotherapy, Singapore General Hospital, Singapore, Singapore
This work was carried out at the Centre of Clinical Research Excellence in Spine, School of Health and Rehabilitation Sciences and Physiotherapy, University of Queensland, St Lucia, QLD, Australia.
E.C.W.L. received a fellowship from The Australian Government’s Department of Education and Training (Endeavor Research Fellowship). M.S. received a fellowship from the National Health and Medical Research Council of Australia.The remaining author declares no conflict of interest.
Reprints: Bill Vicenzino, BPhty, Grad Dip Sports Phty, MSc, PhD, Centre of Clinical Research Excellence in Spine, Division of Physiotherapy, School of Health and Rehabilitation Sciences, University of Queensland, St Lucia, QLD 4067, Australia (e-mail: email@example.com).
Received June 30, 2016
Received in revised form December 4, 2016
Accepted December 21, 2016