Background & Aims
Musculoskeletal shoulder pain has been burdening healthcare systems since it affects about 67% of the general population and is the 3rd most prevalent reason for seeking treatment (1,2). Contemporary pain science has been advocating that people with musculoskeletal pain may present with different pain modulation phenotypes mediated by dynamic modulation processes (3,4). Although impairments in central pain modulation often co-occur, the magnitude of the facilitatory or inhibitory pain responses can vary among people with chronic pain and may influence clinical picture and prognosis (4). In shoulder pain, a significant proportion of people with impairment in one of the central pain mechanisms has been described (5,6); however, the existence of pain modulation phenotypes has not been explored yet. To improve the understanding of shoulder pain, this study explored the existence of subgroups based on different pain modulatory phenotypes and their differences in clinical outcomes.
Financial Support:
FAPESP processo 09386-0
CAPES 001
Methods
Individuals between 18 and 60 years old, with shoulder pain for at least 4 weeks and intensity ? 3/10 in the anterior, posterior, or lateral region of the shoulder during active arm elevation were included. Pressure pain threshold (PPT) at the painful acromion was used for Temporal Summation of Pain (TSP) and Conditioned Pain Modulation (CPM). For TSP, PPT was applied once and, 1 minute later, 10 times with a 1-second interval. TSP was the difference between pain intensity reported by the individual at the tenth and the first stimuli (7). CPM was assessed by the Cold Pressor Test, in which the individual immersed the contralateral hand in a 4 ? 1oC water bath for 2 minutes and the PPT was measured at the hand withdraw. CPM was calculated as a percentage change in the PPT at the withdraw from the baseline (8). TSP ? 2 points was considered facilitated, and CPM ? 10.6% was considered impaired (5,9). Independent t-test and d-Cohen were used to verify differences between groups.
Results
Fifty-three individuals (32 ? 14.5 years old, 30 women) with 24.0 ? 46.1 months of shoulder pain were included. Four groups with distinct pain modulatory characteristics were formed. Group 1 (n = 11, 20.7%, shoulder pain intensity = 5.3 ± 2.1) had facilitated TSP and impaired CPM (TSP = 3.5 ± 1.9 points, CPM = -6.3 ± 9.9%). Group 2 (n = 23, 43.4%, shoulder pain intensity = 4.6 ± 2.0) had facilitated TSP and normal CPM (TSP = 4.1 ± 1.8, CPM = 37.3 ± 21.6%). Group 3 (n = 17, 32.1%, shoulder pain intensity = 4.1 ± 2.6) had normal TSP and normal CPM (TSP = 0.2 ± 1.2, CPM = 55.0 ± 35.8%). Group 4 (n = 2, 3.8%, shoulder pain intensity = 5.5 ± 0.3) had normal TSP and impaired CPM (TSP = 1.0 ± 0.0, CPM = -60.1 ± 56.3%,). Shoulder pain intensity and duration were not different between groups 1 and 3 (p = 0.32 and p = 0.06, respectively); however, shoulder pain intensity was clinically higher in group 1 (1.2/10) with moderate effect size (d = 0.52).
Conclusions
Based on the pain modulatory phenotypes, four distinct subgroups of people with musculoskeletal shoulder pain exist. One third of people with shoulder (32.1%) did not present signs of altered central pain processing. Facilitated TSP and normal CPM is the most prevalent (43.4%) pain modulatory phenotype. A significant proportion of people with shoulder pain (67.9%) show either impaired CPM or facilitated TSP, suggesting that an important subgroup of patients may be susceptible to central sensitization. Most people with shoulder pain are susceptible of having a facilitated nociceptive pain profile (facilitated TSP, 64.1%) rather than impaired antinociceptive profile (impaired CPM, 24.5%). Pain duration seems not be related with shoulder pain processing, but proper CPM functioning may play a role in clinical shoulder pain intensity. These exploratory results may have implications for future research on clinical assessment, prognosis, and treatment of shoulder pain.
References
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Presenting Author
Melina Haik
Poster Authors
Melina Nevoeiro Haik
PhD
UFSCar
Lead Author
Thainá Padovani dos Santos
Department of Physical Therapy. Federal University of São Carlos
Lead Author
Gabriel Gaspar Ribeiro
Department of Physical Therapy. Federal University of São Carlos
Lead Author
Lucas Araújo de Almeida
Department of Physical Therapy. University of Florida
Lead Author
Henrik Bjarke Vaegter
University of Southern Denmark and University Hospital Odense, Denmark
Lead Author
Topics
- Models: Musculoskeletal