Distribution of strength potential of the thumb muscles and their relationship to trapeziometacarpal osteoarthritis: An exploratory cadaveric study.

Abstract

The ten muscles of the thumb allow for a variety of movement combinations yielding similar functional outcomes yet using different load transmission with different biomechanical stresses resulting in heterogenous trapeziometacarpal wear patterns. Our exploratory study investigates the correlation between the severity and location of trapeziometacarpal joint osteoarthritis and estimated individual thumb muscles maximal force. Normalized muscle mass to body mass and physiological cross-sectional area ratio were calculated following systematic muscular dissection of 19 cadaveric hands, 60 % males, average age 79.2, SD = 7.1. Correlations were analyzed with 3 different measures of articular degenerations. Moderate negative correlation was found between Eaton-Glickel osteoarthritis grade and normalized muscle mass of opponens pollicis (rₛ = -0.59, p < .01) and abductor pollicis longus (rₛ = -0.60, p < .01). Moderate negative correlation was also found between trapeziometacarpal index and normalized opponens pollicis and abductor pollicis longus muscle mass (rₛ = -0.63, p < .01) and (rₛ = -0.51, p < .05), respectively. No correlation was identified between physiological cross-sectional area ratios and the above degeneration metrics. Our current findings identified moderate negative correlations between the normalized mass to body mass of abductor pollicis longus and opponens pollicis for both Eaton-Glickel osteoarthritis grade and trapeziometacarpal index, which would support the current hand therapy exercise recommendations for the arthritic trapeziometacarpal population. Caution must be taken in the interpretation of correlations with articular zones degradation as our analytical power was reduced by the complete eburnation of few articular surfaces.