Morphological structure of the vertebra and predisposition to fatigue spondylolysis in the human population - geometric morphometrics studies on skeletal material - MINIATURA 8 (2024/08/X/NZ8/00212) dataset

Abstract

Fatigue spondylolysis is commonly interpreted in bioarchaeology as a direct skeletal marker of increased axial loading, particularly in pre-industrial populations engaged in strenuous manual labour. However, clinical studies in contemporary populations suggest that vertebral morphology may also play an important role in fracture susceptibility. The present project examined whether anatomical predisposition contributed to fatigue spondylolysis in historical human populations from the Brześć Kujawski microregion (Kuyavia, central Poland), dating from the early Middle Ages to the mid-nineteenth century. Fifth lumbar vertebrae (L5) representing individuals with and without spondylolytic fractures were selected from osteological collections housed at the University of Lodz. Following cleaning and, where necessary, recomposition, the vertebrae were scanned using structured-light 3D surface scanning. Their morphology was analysed using landmark-based geometric morphometrics, including fixed landmarks and sliding semilandmarks, and the resulting data were statistically evaluated in MorphoJ, R software environment and Statistica. The analyses revealed statistically significant differences in L5 anatomy between spondylolytic and non-pathological vertebrae. Fractured vertebrae displayed morphological features suggestive of functional predisposition to injury. In addition, previously undescribed differences in fluctuating asymmetry were identified between the two groups, indicating that developmental instability may also have contributed to fracture susceptibility. These findings suggest that fatigue spondylolysis in pre-industrial populations should not be regarded solely as a simple indicator of increased spinal loading. Instead, its occurrence appears to reflect an interaction between mechanical stress as well as individual anatomical and developmental predispositions. The study demonstrates the utility of geometric morphometrics for investigating vertebral variation in archaeological populations and provides a more nuanced framework for interpreting spondylolysis in bioarchaeological research.