Morphometric features of the shoulder bone depending on sex, age and ethnicity

Abstract

The morphometry of the scapula has attracted increasing interest in anatomy, forensic anthropology and clinical practice due to its supporting role alongside well-established pelvic and cranial markers in sex and population assessment. Moreover, existing reference values are to date predominantly pelvis-based and population-specific, which limits their broader applicability and justifies the development of locally valid normative data for other shoulder-girdle bones. The scapula, being more sensitive to sex, age, body build and physiological loading than other bones of the shoulder girdle, remains relatively under-researched despite its importance in shoulder biomechanics and reconstructive surgery planning. The objective of the current study was to provide a review of the existing literature on scapular morphometry with respect to sex, age and ethnicity. Materials and methods: A narrative review of recent publications identified in PubMed and Google Scholar was performed using search terms related to scapular morphometry, sex and age estimation, ethnic variability, imaging-based measurements, assessment techniques and shoulder-girdle anatomy. The results of the literature review highlight that the scapula is a truly dynamic and age-dependent bone: its morphology, cortical–trabecular ratio and key parameters of the scapular spine and glenoid fossa are subject to systematic remodelling during adulthood, which influences the accuracy of sex and age estimation. Several geometric and linear approaches demonstrate pronounced sexual dimorphism in scapular size and 3D shape, with differences in overall profile, glenoid cavity size and acromial morphology that can be used for accurate sex estimation when population-specific discriminant functions are applied. Comparative studies across South African, Anatolian, Egyptian, Portuguese, Iranian and Turkish samples, as well as other ethnic groups, have shown significant inter-population differences in scapular and shoulder-girdle morphology, suggesting that standards developed in one group cannot simply be applied to another and that region-specific reference datasets are necessary, including in the two-dimensional (2D) domain, for both forensic and clinical purposes. Recent advances in three-dimensional (3D) CT-based morphometry and novel machine-learning methods have substantially increased the accuracy of scapular sex estimation and expanded its utility for preoperative planning, implant design and evaluation of degenerative joint changes. Furthermore, analyses of local anatomical variants (e.g. suprascapular notch types) and generational changes in scapular shape indicate the influence of lifestyle, occupational load and cohort effects, supporting the need for regular updating of normative databases. In conclusion, contemporary evidence indicates that scapular morphometric parameters are sex-, age- and ethnicity-dependent, and their effective application in forensic anthropological and orthopaedic practice requires the development of multi-tier, population- and age-specific norms with periodic reassessment.