Statistical Shape Modeling of the Clavicle: Morphological Variation, Sex Differences, and Surgical Implications

Clavicle fracture fixation is frequently complicated by implant mismatch and mechanical failure due to the complex and highly variable S-shaped anatomy of the clavicle. Conventional morphometric classification systems rely on subjective assessments of curvature and fail to capture the continuous spectrum of clavicular shape variation, limiting their utility for personalized implant design and preoperative planning. Furthermore, large-scale statistical shape modeling studies focusing on Asian populations remain scarce. Therefore, this study aimed to characterize clavicular morphology in an Asian cohort using statistical shape modeling (SSM), investigate sex- and side-related differences, and evaluate the validity of traditional morphological classification systems.

A retrospective study analyzed 288 clavicles reconstructed from CT scans of 144 adults (94 females, 50 males). Three-dimensional models were segmented in 3D Slicer, aligned, and processed using the Scalismo platform. Principal component analysis (PCA) was performed to establish the SSM and extract modes of variation (MoV). Morphometric parameters were calculated automatically. Independent t-tests assessed sex and side differences, and clustering analysis was conducted to compare data-driven groupings with traditional three-type classifications.

The first six MoV explained 82.38% of total variance. PC01 (50.84%) reflected clavicular length and midshaft width; PC02-PC06 represented curvature and rotational variations. Significant sex differences were observed in PC01, PC02, and PC06 (p < 0.05), whereas no side differences were detected. Agglomerative clustering identified two morphological groups with poor concordance with traditional three-type classifications (Adjusted Rand Index≈0), indicating a continuous rather than discrete distribution of clavicular shapes.

Clavicular morphology exhibits sex-dependent but not side-dependent variability. Traditional categorical classifications inadequately capture anatomical diversity. Large-scale SSM provides objective morphometric evidence to guide personalized preoperative planning and improve implant design in clavicle fracture fixation.