Calcaneal Spurs in Thai Skeletons: High Prevalence and Population-Specific Patterns for Forensic Identification

Background/Objectives: Calcaneal spurs are pathological bone formations at entheseal attachment sites with clinical implications but limited forensic anthropological applications. While entheseal changes have been proposed as age estimation markers in forensic contexts, empirical validation remains insufficient, particularly for Southeast Asian populations. This study evaluated calcaneal spur utility for forensic age estimation in Thai skeletal remains while establishing population-specific osteological reference data for forensic individuation. Materials and Methods: The 3516 dry calcanei from 1758 Northeastern Thai skeletons (1031 males, 727 females; age 22–106 years) were examined. Spurs were classified by anatomical location as dorsal (D-type), plantar (P-type), or combined plantar–dorsal (P–D type). The morphometric measurements were performed bilaterally. Age-associated patterns were analyzed across four age cohorts (≤40, 41–50, 51–60, ≥61 years), and Random Forest machine learning classification tested forensic age estimation capacity using 10-fold cross-validation. Results: Overall prevalence reached 67.63% with distinctive P–D type predominance. While age-stratified prevalence increased from 24.56% (≤40 years) to 74.77% (≥61 years), Random Forest modeling explicitly demonstrated overall classification accuracy of 62.5%. Compared between sexes, the maximum length of calcaneal spurs was significantly longer in males. Dimensional analyses revealed weak age correlations and substantial inter-individual morphological variation precluded reliable age prediction. Interestingly, the unique P–D type distribution pattern (77.5% among spur-bearing individuals) may serve as an auxiliary marker for Thai population affinity assessment in forensic contexts. Conclusions: This study established the first comprehensive Thai-specific osteological reference for calcaneal spurs, revealing distinctive plantar–dorsal type predominance valuable for forensic population affinity assessment and provided population-specific baseline data for forensic individuation.