anatomy Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

, the transverse ligament of the atlas is a broad, tough

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

which arches across the ring of the atlas (first cervical vertebra) posterior to the dens to keep the dens (odontoid process) in contact with the atlas. It forms the transverse component of the cruciform ligament of atlas.

Structure

The length of the ligament is variable; its mean length is 2 cm. The ligament broadens and thickens

Gray's anatomy ''Gray's Anatomy'' is a reference book of human anatomy written by Henry Gray, illustrated by Henry Vandyke Carter and first published in London in 1858. It has had multiple revised editions, and the current edition, the 42nd (October 2020 ...

, 1918 medially. The anterior medial aspect of the ligament is lined by a thin layer of articular cartilage. The neck of the odontoid process is constricted where it is embraced posteriorly by the transverse ligament so it retains the dens in position even after all other ligaments have been sectioned.

Attachments

The ligament attaches on either side onto a small yet prominent tubercle upon the medial aspect of either lateral mass of atlas.

Cruciate ligament

A strong median band (''crus superius'') extends superiorly from the superior margin of the ligament to attach onto the

basilar part of occipital bone The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline. In the young skull, this area is rough and uneven, and is joined ...

(between the attachments of the apical ligament of dens, and

tectorial membrane The tectoria membrane (TM) is one of two acellular membranes in the cochlea of the inner ear, the other being the basilar membrane (BM). "Tectorial" in anatomy means forming a cover. The TM is located above the spiral limbus and the spiral org ...

). A weaker and somewhat inconsistent median band (''crus inferius'') extends inferiorly from the ligament to attach onto the posterior aspect of the body of

axis An axis (: axes) may refer to: Mathematics *A specific line (often a directed line) that plays an important role in some contexts. In particular: ** Coordinate axis of a coordinate system *** ''x''-axis, ''y''-axis, ''z''-axis, common names ...

. The ligament and the two median bands together constitute the cruciate ligament of atlas.

Relations

The transverse ligament divides the

vertebral foramen In a typical vertebra, the vertebral foramen is the foramen (opening) of a vertebra bounded ventrally/anteriorly by the body of the vertebra, and the dorsally/posteriorly by the vertebral arch. In the articulated spine, the successive vertebral ...

of the axis into an anterior portion (constituting one third of its lumen) which contains the dens, and a posterior portion (constituting two thirds of the foramen's lumen) which contains the spinal cord and its coverings as well as the two accessory nerves (CN XI).

Clinical significance

Excessive laxity of the posterior transverse ligament can lead to atlantoaxial instability, a common complication in patients with Down Syndrome and

Ehlers–Danlos syndrome Ehlers–Danlos syndromes (EDS) is a group of 14 genetic connective-tissue disorders. Symptoms often include loose joints, joint pain, stretchy velvety skin, and abnormal scar formation. These may be noticed at birth or in early childhood. Co ...

. Laxity has also been hypothesized as the cause of degenerative hypertrophy and mechanical atlantoaxial stress. Degenerative processes can give rise to transverse ligament cysts, resulting in progressive cervical myelopathy. The treatment of choice for transverse ligament cysts with progressive neurological decline is surgical resection and cervical fusion. Conservative treatment with external neck immobilization is less commonly reported , but may be very useful in select cases where immediate surgical intervention is not indicated.

References