Abstract：
Genetic diseases with craniofacial malformations can be associated with anomalies of the craniocervical joint (CCJ). The functions of the CCJ are thus impaired, as mobility may be either limited by abnormal bone fusion causing headaches, or exaggerated in the case of hypermobility, which may cause irreparable damage to the spinal cord. Restoring the balance between mobility and stability requires surgical correction in children. The anatomy and biomechanics of the CCJ are quite unique, yet have been overlooked in the past decades. Pediatric evidence is so scarce, that investigating the adult CCJ is our best shot to disentangle the form-function relationships of this anatomical region. The motivation of the present study was to understand the morphological and functional basis of motion in the CCJ, in the hope to find morphological features accessible from medical imaging able to predict mobility. To do so, we have quantified the in-vitro kinematics of the CCJ in nine cadaveric asymptomatic adults, and estimated a wide range of mobility variables covering the complexity of spinal motion. We compared these variables with the shape of the occipital, the atlas and the axis, obtained using a dense geometric morphometric approach. Morphological joint congruence was also quantified. Our results suggest a strong relationship between bone shape and motion, with the overall geometry predicting best the primary movements, and the joint facets predicting best the secondary movements. We propose a functional hypothesis stating that the musculoligamental system determines movements of great amplitude, while the shape and congruence of joint facets determine the secondary and coupled movements, especially by varying the geometry of bone stops and the way ligaments are tensioned. We believe this work will provide valuable insights in understanding the biomechanics of the CCJ. Furthermore, it should help surgeons treating CCJ anomalies by enabling them to translate objectives of functional and clinical outcome into clear objectives of morphological outcome.
摘要：
患有颅面畸形的遗传性疾病可能与颅颈关节（CCJ）异常有关。因此，CCJ的功能受到损害，因为活动可能受到异常骨融合导致头痛的限制，或者在过度行动的情况下被夸大了，这可能会对脊髓造成不可挽回的损害。恢复机动性和稳定性之间的平衡需要对儿童进行手术矫正。CCJ的解剖学和生物力学非常独特，然而在过去的几十年里却被忽视了。儿科证据太稀少了,调查成年CCJ是我们解开该解剖区域的形态与功能关系的最佳选择。本研究的动机是了解CCJ中运动的形态和功能基础，希望从医学成像中找到能够预测移动性的形态学特征。要做到这一点，我们已经量化了9名无症状成人中CCJ的体外运动学，并估计了涵盖脊柱运动复杂性的各种移动性变量。我们将这些变量与枕骨的形状进行了比较，地图集和轴，使用密集的几何形态计量法获得。还量化了形态关节一致性。我们的结果表明骨骼形状和运动之间有很强的关系，整体几何形状最好地预测主要运动，关节面最好地预测二次运动。我们提出了一个功能假设，指出肌肉零散系统决定了大幅度的运动，而关节小平面的形状和一致性决定了二次运动和耦合运动，特别是通过改变骨挡块的几何形状和韧带的张紧方式。我们相信这项工作将为理解CCJ的生物力学提供有价值的见解。此外，它应帮助外科医生治疗CCJ异常,使他们能够将功能和临床结局的目标转化为明确的形态学结局目标.
