Wing hinge

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Membrana tectoria, transverse and ligamenta alaria
Atlas-Dreher joint from above with the wing ligaments, the ligamenta alaria

The alar ligaments (syn .: alar ligaments , alar ligaments ; ligamenta alaria ; singular ligamentum alare , English check ligament of the odontoid ) are short, extremely tough, fibrous fibers ( ligaments ) in the area of ​​the head joints .

The ligamenta alaria run from the dorsolateral surface of the tip of the dens axis to the ventromedial edge of the condyles ( condyli occipitales ) of the occipital bone (os occipitale) at the edge of the occipital opening . Their caudal fibers insert into the massa lateralis of the atlas . The right and left bands form an angle of approximately 170 ° with one another.

The ligamenta alaria (often abbreviated as Ligg.alaria) primarily have a braking and holding function. In the neutral-zero position, some parts of the fiber are taut, others are relaxed. They prevent the head from shifting sideways when rotating in relation to the two head joints. They also limit flexion and axial rotation of the skull in relation to the cervical spine . They ensure that the second cervical vertebra - and the first cervical vertebra connected to it - are kept centered in relation to the base of the skull. Their anatomical situation prevents translation and subluxation of the vertebrae, particularly when the head is tilted sideways (lateral flexion) and rotated .

Injuries to the ligamenta alaria

Injuries to the alar ligaments occur in connection with injuries to the cervical spine. An exemplary injury is the fracture of the occipital condyles type III according to Anderson and Montesanto in the sense of a bony ligament tear in one of the ligaments. alaria due to forced lateral flexion or rotation of the head. The type I dens fracture according to Anderson and D'Alonzo can also be seen as a torn ligament of the ligament. alaria to be understood. Further injuries are the atlanto-occipital dissociation, the atlanto-axial rotational instability (AARI). The suspected diagnosis can be made in the context of a computed tomography based on indirect signs (fragment display in the case of a bony ligament tear, lateral deviation of the dens axis in the case of a unilateral rupture). The diagnosis is usually confirmed with an MRI.

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  • Bohndorf: Radiological diagnosis of bones and joints. 3rd, completely revised and exp. Edition. Georg Thieme Verlag, 2014, ISBN 978-3-13-110983-5 .
  • Bühren, Josten: Surgery of the injured spine. Springer-Verlag, Berlin / Heidelberg 2013, ISBN 978-3-642-02207-4 .
  • K. Thomann, C. Schomerus, T. Sebesteny, M. Rauschmann: Isolated injury to the ligamenta alaria. Magnetic resonance imaging diagnostics and operative therapy. In: Orthopedist. 39, Mar 2010, pp. 285-298. PMID 20177876