Microtrauma at the humeral medial epicondyle: Quantifying lacunar lesions to reconstruct activity patterns in past populations.

OBJECTIVE Lacunar lesions at the anterior medial collateral ligament (MCL) bundle attachment on the humeral medial epicondyle may represent partial avulsion fractures. This study developed and validated a quantitative approach to assess their morphology.

MATERIALS Two Neolithic samples were studied: Parisian Basin (France, N = 45) and Meuse Valley (Belgium, N = 25).

METHODS Lesions were extracted using a 3D protocol with ambient occlusion and curvature filters, then screened and analyzed using size, shape and surface metrics. Reproducibility was assessed using Lin's concordance correlation coefficient.

RESULTS The protocol was successfully validated with excellent intra-observer agreement. Lesions occurred exclusively on right humeri at the anterior MCL bundle footprint, while showing uniform shape but variable size, flattening and surface characteristics.

CONCLUSIONS The protocol provides an objective, reproducible method for lesion characterization and, when applied, revealed cortical-confined depths and surface areas smaller than the anterior MCL bundle footprint, suggesting specific fiber involvement. Right-side bias indicates a potential link with handedness, while morphological patterns align with clinical descriptions of proximal MCL partial avulsion fractures common in youth throwing athletes.

SIGNIFICANCE Findings support an activity-related etiology and demonstrate potential for reconstructing past behaviors from skeletal remains while complementing clinical studies on long-term injury outcomes.

LIMITATIONS Limitations include small sample size, reliance on absolute measurements, dependence on imaging resolution, and lack of direct clinical validation.

SUGGESTIONS FOR FURTHER RESEARCH Studies should apply this protocol to larger, diverse samples, confirm the clinical association, and adapt it to additional imaging modalities for broader archaeological and clinical applications.