Asymmetric midshaft femur remodeling in an adult male with left sided hip joint ankylosis, Metal Period Nagsabaran, Philippines

Objective: This study investigated microstructural changes of the right and left midshaft femur in an archaeological individual afflicted with left-sided hip joint ankylosis to assess whether increased cortical porosity was present as a result of leg disuse.Materials: The individual is a middle-aged adult male excavated from the Metal Period (∼2000 BP) Nagsabaran, Luzon Island, Philippines.Methods: Following standard examination of femur gross anatomy and differential diagnosis of the hip joint fusion, ∼1 cm thick posterior midshaft femur samples were removed for microstructural examination. Using static histomorphometry, bone multi-cellular unit activity from Haversian canal (vascular pore) density, area, and circularity was reconstructed. Spatial positioning of Haversian canals was mapped using Geographic Information Systems software. Phosphate, carbonate, and carbonate:phosphate ratios were obtained using synchrotron-sourced Fourier transform infrared microspectroscopy.Results: The left femur had greater cortical pore density, with smaller and rounder vascular canals, in addition to lower matrix levels of phosphate and carbonate, when compared to the right femur.Conclusions: Our data indicate compromised bone tissue in the left femur, and conform to expected bone functional adaptation paradigms of remodeling responses to pathological and biomechanical changes.Significance: The preservation of this individual's hip abnormality created a unique opportunity to evaluate intra-skeletal bone health asymmetry, which may help other researchers evaluate the presence of limb disuse in archaeological samples.Limitations: A lack of lower limb data limits our interpretations to femur remodeling only.Suggestions for Further Research: Future research efforts should aim to examine the presence of remodeling changes in all bones of the lower limb.