Bilateral Pressure Pain Hypersensitivity over the Hand as Potential Sign of Sensitization Mechanisms in Individuals with Thumb Carpometacarpal Osteoarthritis

Objective: To investigate whether bilateral deep tissue pressure hyperalgesia exists in individuals with unilateral thumb carpometacarpal osteoarthritis (CMC OA). Methods: A total of 32 patients with CMC OA (29 females and 3 males, aged 69-90 years old) and 32 healthy matched controls (29 females and 3 males, aged 70-90 years) were recruited. Pressure pain thresholds (PPTs) were bilaterally assessed over the first CMC joint, the hamate bone and the lateral epicondyle in a blinded design. Mixed models analyses of variance were conducted to determine the differences in pressure pain sensitivity between groups and sides. Results: The results showed that PPTs were significantly decreased over the first CMC joint (F=6.551, P=0.012) and the hamate bone (F=9.783, P=0.002) but not over the lateral epicondyle (F=2.712, P=0.102) in patients with thumb CMC OA as compared with healthy controls; patients with unilateral thumb CMC OA exhibited bilateral pressure pain hyperalgesia in both hands compared with healthy people. PPTs were not significantly associated to the intensity of pain (all, P>0.05). Discussion: This study revealed bilateral localized pressure pain hypersensitivity over the hand in individuals with unilateral thumb CMC OA, suggesting spinal cord sensitization mechanisms in this population. Future studies should analyze the presence of widespread pressure pain sensitivity in patients with thumb CMC OA to further determine the presence of central sensitization mechanisms.