Pain hypersensivity and myofascial trigger point of the first dorsal interossem muscle in patients with rhizarthrosis

Background and aims: As for the clear functional role of the first dorsal interosseous muscle (FDI) in thumb motion, considering the presence of myofascial trigger point (MTrP) in patients with rhizoarthrosis could be a relevant factor for musculoskeletal pain management. The aim of this study was to investigate the presence of FDI MTrP in patients with rhizoarthrosis. Methods: 67 patients with rhizoarthrosis of the dominant hand were consecutively recruited. Pressure pain thresholds (PPTs) were assessed bilaterally over the first carpometacarpal joint and in the C5-C6 zygapophyseal joint. Intensity of pain (Visual analogue scale, VAS), Quick Disability of the Arm, Shoulder and Hand (Quick-DASH scale), pinch strength test (dynamometer) were also measured bilaterally. The muscle was examined by an assessor blinded to establish the clinical conditions of the FDI following the international consensus on diagnostic criteria of MTrP. Results: In patients with rhizoarthtrosis, prevalence of latent MTrP was higher when compared with nondominant hand (72.0% vs 47%); No significant difference between right and left was found on the average level of PPT over the FDI muscle (P< 0.05) and no significant difference during pinch strength test was detected (P< 0.05). Conclusions: A higher presence of latent MTrP in the dominant hand of patients with rhizarthtrosis was found. Previous study revealed bilateral widespread pressure pain hypersensitivity in patients with rhizartrosis and also exhibited a bilateral strength reduction. Future research should be conducted in order to establish if MTrP treatments improve hypersensivity in this population.