Occupational manual activity is reflected on the patterns among hand entheses

In anthropological sciences, entheses are widely utilized as occupational stress markers. However, the reaction of entheseal surfaces to mechanical loading is not well understood. Furthermore, previous studies on entheses relied on the individuals' occupation-at-death. Past research by one of us has identified two patterns among hand entheses, proposing that they reflect two synergistic muscle groups. Here, we investigate the association between these patterns and habitual manual activity using an extensively documented skeletal sample and a three-dimensional system of quantification.

The hand bones utilized belong to 45 individuals from mid-19th century Basel. These were male adults (18 to 48 years old) who were not directly related, showed no manual pathological conditions, and whose occupational activities during their lifetime were clearly documented and could be evaluated according to historical sources. The patterns of entheses were explored using principal component analysis on both raw and size-adjusted variables. The influence of age-at-death, body mass, and bone length was assessed through correlation tests.

The analysis showed that the previously proposed patterns of entheses are present in our sample. Individuals with the same or comparable occupations presented similar entheseal patterns. These results were not considerably affected by entheseal overall size, age-at-death, body mass, or bone length.

Individuals involved in intense manual labor during their lifetime presented a distinctive pattern of hand entheses, consistent with the application of high grip force. By contrast, individuals with less strenuous and/or highly mechanized occupations showed an entheseal pattern related to the thumb intrinsic muscles.