Splinting for the carpometacarpal joint relieves experimental basal thumb pain and loss of pinch strength

Background Splinting is a quite common intervention for the first carpometacarpal (CMC) osteoarthritis, however, underlying mechanisms of biomechanical and analgesic effects has not been fully investigated. The aim of this study was to develop an experimental basal thumb pain model and to elucidate the effects of CMC splinting on the pain profile and motor function. Methods In 14 healthy subjects, experimental basal thumb pain was induced by hypertonic saline injection into the dorsal radial ligament located on base of the first metacarpal bone. Isotonic saline was injected contralaterally as a control. Two experimental sessions with or without CMC splinting were conducted. Before, during and after injections, tip pinch strength was measured and surface electromyography of the abductor pollicis brevis (APB), first dorsal interosseous (FDI) and extensor pollicis longus (EPL) during tip pinch were evaluated in each session. Results Hypertonic saline induced significantly greater pain compared with baseline and isotonic saline (p