Introduction: The contributions of the ligaments of the craniocervical junction to overall stability and the effects of the occipitoatlantal (OA) joint capsules on pathological translation are unknown. Determining which stabilizing ligaments at the craniocervical junction are most important in restraining pathological translation could assist in understanding subluxation cases.
Methods: Seven cadaveric specimens were tested with a six degrees of freedom spine simulator under the conditions: intact; clivus/alar removal (CR), transverse ligament destruction (TL), and OA capsule sectioning (OAS). Flexion-extension (FE), lateral bending (LB), axial rotation (AR) was applied (2.5N-m) to a C0-C2 segment while anterior-posterior (AP), and cranial-caudal (CC) translations were recorded. Average motions were normalized to intact (Intact = 100%) for each joint.
Results: At C0-C1 joint, there were significant (p<0.05) increases from intact in FE: TL (154%), and OAS (174%); and in AR: TL (178%) and OAS (224%). AP translation, during LB, increased significantly following TL (248% intact). CC translation, during FE, increased significantly following TL (188%) and OAS (361%).
At C1-C2 joint, there were significant increases from intact in FE: TL (172%) and AAS (160%); in LB: TL (286%) and AAS (332%); in AR there were no statistical differences. AP translation increased significantly following CR (280%). CC translation also increased significantly following CR (205%) and TL (298%), during LB.
Overall the craniocervical junction had significant increases compared to intact in FE: TL (161%), OAS (163%), and AAS (165%); in LB: TL (202%), OAS (224%), and AAS (241%).
There were not any significant increases at C0-C1 during LB, or C1-C2 and C0-C2 during AR.
Conclusions: The transverse and alar ligaments appear to be the main stabilizers of the craniocervical junction. The vertical structures attaching on the clivus and OA joint capsules appear to function as secondary stabilizers. Models of craniocervical trauma should section all three restraining structures for future studies.
Patient Care: Craniocervical dislocations are difficult to identify, and many of the patients suffer neurological effects or even death. To understand cases of subluxation at these joints a repeadtable accurate cadaver model could be used to determine proper surgical techinques. This study may also assist in allowing other researchers to use this injury model to further understand injuries at the joint capsules and ligaments of teh craniocervical junction.
Learning Objectives: The craniocervical junction is unique in comparison to any other area of the spine. It is stabilized by the cruciate ligament, alar ligaments, and tectorial membrane. The relative contributions of each ligament to overall stability and the effects of the occipito-atlantal joint capsule and atlanto-axial joint capsules are unknown. Traumatic occipitocervical dislocations, which may cause destruction of stabilizing ligaments, are often associated with increased rotational instability and pathological cranial-caudal and anterior-posterior translations. To our knowledge injury models have not encompassed translation and rotation measurements.The goal of this biomechanical study is to identify the key contributions of each major ligament and joint capsule by incremental dissection.