Pressure pain threshold and temporal summation in patients after musculoskeletal trauma in the upper limb: a cross-sectional study

Objective: This cross-sectional study aimed to compare pressure pain threshold and temporal summation in patients following acute musculoskeletal trauma at different sites of the upper limb and to investigate the association of these variables with a neuropathic component of pain. Methods: Adults of both sexes with musculoskeletal trauma in the upper limb were included. Pain intensity, injury type and causes, and pain medication were collected. The pressure pain threshold assessment by a digital algometer in the upper trapezius and anterior tibial muscles, bilaterally, and Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) questionnaire were used. Results: A total of 82 patients were evaluated, 24 with proximal injuries (proximal and shaft humerus, clavicle, scapula), 25 with elbow and forearm injuries, and 33 with distal injuries (distal forearm, wrist and hand). Injuries causes were traffic (45%), work (30%), domestic (17%, including falls from height) and others (8%). The pressure pain threshold was (F=7.71; p<0.01) lower in the proximal compared to elbow (p = 0.04; effect size = -0.76) and distal injuries (p =<0.01, effect size = -1.11) for the upper trapezius ipsilaterally to the injury side. There was a negative and weak correlation between this pressure pain threshold and LANSS (p = 0.03; r = -0.22). Conclusion: Pressure pain threshold in the upper trapezius ipsilaterally to the affected side was lower in the proximal injuries compared to elbow, distal forearm, wrist and hand injuries. Decreased values of pressure pain threshold were associated to increased neuropathic component.