Chaochao Zhou1, Runsheng Guo2, Cong Wang3, Tsung-Yuan Tsai3, Yan Yu4, Wei Wang5, Guoan Li6, Thomas Cha1. 1. Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, Newton, MA, USA; Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. 2. Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, Newton, MA, USA; Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Department of Orthopaedics, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China. 3. School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China. 4. Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, China. 5. Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, Newton, MA, USA; Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; School of Biological Science and Medical Engineering, Beihang University, Beijing, China. 6. Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, Newton, MA, USA. Electronic address: gli1@partners.org.
Abstract
BACKGROUND: Frequently, treatment decisions for craniocervical injuries and instability are based on imaging findings, but in vivo ligament kinematics were poorly understood. This study was to determine in vivo deformation patterns of primary ligaments in the craniocervical junction (i.e., C0-2), including the cruciform ligament, alar ligaments, and accessory ligaments, during dynamic head axial rotation. METHODS: The skulls and cervical spines of eight asymptomatic female subjects were dynamically imaged using a biplane fluoroscopic imaging system, when they performed left and right head axial rotations. Using a 3D-to-2D registration technique, the in vivo positions and orientations of cervical segments were determined. An optimization algorithm was implemented to determine ligament wrapping paths, and the resulting ligament deformations were represented by percent elongations. Using paired t-tests, ligament deformations in the end-range position were compared to those in the neutral position. FINDINGS: No significant differences were observed in segmental motions during left and right head rotations (p > 0.05). In general, slight deformations occurred in each component of the cruciform ligament. For the alar ligaments, the ipsilateral ligament was lengthened from -0.7 ± 13.8% to 16.6 ± 15.7% (p < 0.001*). For the accessory ligaments, the contralateral ligament was lengthened from -2.9 ± 7.5% to 10.1 ± 6.2% (p < 0.001*). INTERPRETATION: This study reveals that there are distinct deformation patterns in craniocervical junction ligaments during dynamic axial head rotation. These ligament deformation data can enhance our understanding of the synergic function of craniocervical junction ligaments, and guide the treatment of craniocervical instability.
BACKGROUND: Frequently, treatment decisions for craniocervical injuries and instability are based on imaging findings, but in vivo ligament kinematics were poorly understood. This study was to determine in vivo deformation patterns of primary ligaments in the craniocervical junction (i.e., C0-2), including the cruciform ligament, alar ligaments, and accessory ligaments, during dynamic head axial rotation. METHODS: The skulls and cervical spines of eight asymptomatic female subjects were dynamically imaged using a biplane fluoroscopic imaging system, when they performed left and right head axial rotations. Using a 3D-to-2D registration technique, the in vivo positions and orientations of cervical segments were determined. An optimization algorithm was implemented to determine ligament wrapping paths, and the resulting ligament deformations were represented by percent elongations. Using paired t-tests, ligament deformations in the end-range position were compared to those in the neutral position. FINDINGS: No significant differences were observed in segmental motions during left and right head rotations (p > 0.05). In general, slight deformations occurred in each component of the cruciform ligament. For the alar ligaments, the ipsilateral ligament was lengthened from -0.7 ± 13.8% to 16.6 ± 15.7% (p < 0.001*). For the accessory ligaments, the contralateral ligament was lengthened from -2.9 ± 7.5% to 10.1 ± 6.2% (p < 0.001*). INTERPRETATION: This study reveals that there are distinct deformation patterns in craniocervical junction ligaments during dynamic axial head rotation. These ligament deformation data can enhance our understanding of the synergic function of craniocervical junction ligaments, and guide the treatment of craniocervical instability.
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