Equine tibia model measurements in mode 2.

The objective of this study was to provide an overarching description of the inter-subject variability of the equine femur and tibia morphology using statistical shape modeling. Fifteen femora and fourteen tibiae were used for building the femur and tibia statistical shape models, respectively. Geometric variations in each mode were explained by biometrics measured on ±3 standard deviation instances generated by the shape models. Approximately 95% of shape variations within the population were described by 6 and 3 modes in the femur and tibia shape models, respectively. In the femur shape model, the first mode of variation was scaling, followed by notable variation in the femoral mechanical-anatomical angle and femoral neck angle in mode 2. Orientation of the femoral trochlear tubercle and femoral version angle were described in mode 3 and mode 4, respectively. In the tibia shape model, the main mode of variation was also scaling. In mode 2 and mode 3, the angles of the coronal tibial plateau and the medial and lateral caudal tibial slope were described, showing the lateral caudal tibial slope angle being significantly larger than the medial. The presented femur and tibia shape models with quantified biometrics, such as femoral version angle and posterior tibial slope, could serve as a baseline for future investigations on correlation between the equine stifle morphology and joint disorders due to altered biomechanics, as well as facilitate the development of novel surgical treatment and implant design. By generating instances matching patient-specific femorotibial joint anatomy with radiographs, the shape model could assist virtual surgical planning and provide clinicians with opportunities to practice on 3D printed models.

本研究旨在借助统计形状建模（statistical shape modeling），系统阐明马股骨与胫骨形态的个体间差异。本研究分别纳入15根股骨与14根胫骨，用于构建股骨统计形状模型与胫骨统计形状模型。通过形状模型生成的±3倍标准差样本所测得的生物测量学指标，可阐释各形态模式下的几何变异。在群体层面，股骨形状模型与胫骨形状模型分别通过6种与3种形态模式，即可覆盖约95%的群体形态变异。在股骨形状模型中，第1种变异模式为整体缩放，第2种变异模式则主要体现为股骨机械-解剖角（femoral mechanical-anatomical angle）与股骨颈角（femoral neck angle）的显著变化。第3种与第4种变异模式分别对应股骨滑车结节（femoral trochlear tubercle）的位置，以及股骨扭转角（femoral version angle）的变化。在胫骨形状模型中，主要变异模式同样为整体缩放。第2种与第3种变异模式分别对应胫骨平台冠状面角度（coronal tibial plateau），以及胫骨内、外侧后髁倾斜角（medial and lateral caudal tibial slope），结果显示外侧后髁倾斜角显著大于内侧。本研究构建的股骨与胫骨形状模型，辅以股骨扭转角、胫骨后倾斜角（posterior tibial slope）等量化生物测量学指标，可作为未来研究的基准框架：用于探究马膝关节（equine stifle）形态与生物力学改变引发的关节疾病之间的关联，同时也可助力新型外科治疗方案与植入物设计的开发。通过结合X光影像生成匹配患者个体股胫关节（femorotibial joint）解剖结构的样本，该形状模型可辅助虚拟外科手术规划，并为临床医师提供3D打印模型实操练习的机会。