用于肩部生物力学CAD模型位置参数化的新方法论

《Surgeries》：New Methodology for the Shoulder Biomechanical CAD Model Position Parametrization

肩关节三维CAD模型标准化构建方法研究。基于Sternum作为固定参考点，通过参数化定位Clavicle、Scapula和Humerus的空间关系，结合Sawbones? CAD模型与SolidWorks软件实现标准化装配。解决了现有模型因解剖差异和影像采集位置导致参数不一致的问题，验证了模型在不同运动状态下的空间协同性，为有限元分析和生物力学研究提供可复现的基准模型。

　　
shoulder joint modeling has long been a challenging field due to its complex anatomical structure and dynamic biomechanical behavior. This study introduces a novel standardized methodology for constructing three-dimensional computer-aided design (CAD) models of the shoulder complex, addressing critical issues that hinder reproducibility in existing research. The key innovation lies in establishing a unified reference frame anchored to the sternum, which serves as the central fulcrum for all shoulder movements. This approach eliminates ambiguities arising from inconsistent initial positions in prior studies, particularly those derived from medical imaging scans that often capture the joint in non-neutral postures.

The shoulder complex is systematically decomposed into four primary bony components: sternum, clavicle, scapula, and humerus. Each component undergoes rigorous geometric parameterization using anatomical landmarks and standardized planes. For instance, the clavicle's orientation is determined by its 30° lateral rotation relative to the sagittal plane, while the scapula is positioned with a defined 60° medial-lateral angulation. The humerus's retroversion angle of 30° is precisely quantified through its anatomical axis and coronal plane relationships.

A critical advancement is the establishment of a hierarchical assembly sequence starting from the sternum as the fixed reference. The clavicle is then attached via its sternocostal joint, followed by the scapula connected through the acromioclavicular joint. Finally, the humerus is positioned relative to the glenoid cavity of the scapula. This sequence ensures spatial consistency across all components, with each assembly step validated through orthogonal views (anterior, lateral, superior) and three-dimensional isometric projections.

The methodology employs SolidWorks software for precise CAD modeling, utilizing predefined anatomical planes and axes. Key landmarks such as the trigonum spineae on the scapula and epicondyles on the humerus serve as reference points for defining coronal, sagittal, and transverse planes. Each bone's orientation is quantified through angular measurements relative to these planes, ensuring geometric consistency regardless of the original model source.

Validation includes comparing the standardized model with the Visible Human Project (VHP) cadaver data. The study reveals significant discrepancies in prior models, particularly in humeral positioning and scapulothoracic alignment. For example, VHP-derived models showed an average 65° medial-lateral rotation of the sternum, which this methodology standardizes to eliminate such variability. The standardized model demonstrates 92% reproducibility across different anatomical datasets, a marked improvement over previous 68% inter-study consistency reported by Garner and Pandy.

Practical applications extend to surgical planning and prosthetic design. The model supports dynamic simulations of shoulder movements, enabling analysis of joint kinematics during activities like abduction or internal rotation. Clinical relevance is evident in standardized preoperative planning, where the 90° abduction position can be precisely replicated using the defined angular parameters. prosthetic integration tests have shown a 40% reduction in misalignment errors when using this methodology compared to conventional models.

This work establishes a foundational framework for future biomechanical research. By mandating consistent anatomical references and parameterization protocols, it facilitates inter-study comparisons and accelerates model validation. The methodology's adaptability is demonstrated through successful reconstruction of the VHP model, which required only 15% manual adjustments compared to 70% needed for traditional models. This efficiency gain is particularly valuable in clinical applications where rapid model iteration is essential.

However, limitations include potential inaccuracies in soft tissue modeling and ligamentous representations. The study emphasizes the need for complementary validation through finite element analysis (FEA) and in vivo measurements. Future extensions could incorporate muscle-tendon units and neural pathways, but the current focus on bony geometry provides a necessary standardization layer.

The research underscores a paradigm shift from data-driven to parameter-driven modeling. By decoupling geometric configurations from specific imaging datasets, it enables scalable applications across diverse populations. This standardization is especially critical for developing universal reference frames in AI-driven orthopedic simulations and robotic surgical systems.

In conclusion, this methodology represents a significant step toward unifying shoulder modeling practices. By anchoring the assembly to the sternum's anatomical planes and enforcing strict angular relationships, it eliminates variability that has plagued comparative studies. The resulting CAD model not only enhances biomechanical analysis accuracy but also streamlines clinical applications ranging from prosthetic design to surgical training simulations. This standardized approach holds particular promise for collaborative research initiatives and clinical trials requiring consistent patient models.