Distal radius fractures are common, particularly in post-menopausal women. Several factors have been identified such as osteopenia and an increased risk of falling. We hypothesised that increased soft tissue padding from muscle and fat in the volar hand may confer an element of protection against fractures more in men than women and more in younger than older patients. The aim of the study was to assess for thenar and hypothenar thickness and assess whether it varies between sexes and changes with age. We retrospectively evaluated hand MRI scans performed for non-acute conditions in adults without previous injury or surgery. Using the Patient Archiving and Communication System (PACS) we measured the distance (mm) from the volar surface of the trapezium to the skin, the hook of the hamate to skin and the pisiform to skin as measures of thenar and hypothenar thickness. We also recorded the sex and age of the subjects. Soft tissue thickness was corrected for hand size by dividing by capitate length which we measured; we have already established this as a surrogate measure of hand size. The scans of 51 men (mean age 35, range 19–66) years and 27 women (mean age 49, range 19–79) years were reviewed. Men had significantly thicker soft tissues compared to women over both the thenar and hypothenar eminences (p=0.0001). Soft tissue thickness did not change significantly with age (p> 0.05). The study confirms a significant difference in volar hand soft tissue thickness between men and women accounting for differences in hand size. Our previous research has shown how we fall onto our outstretched hands in the upper limb falling reflex and we have shown that padding the thenar and hypothenar eminences reduces force transmission to the forearm bones. In theory thicker thenar and hypothenar musculature would help protect against distal radius fractures following a fall on an outstretched hand. The thinner musculature on women may further predispose them to an increased risk of distal radius fractures. Further research is needed to assess for any loss of volar hand soft tissue thickness beyond age 75 years.
