China
Africa
Explore chapters and articles related to this topic
The Anatomy of Joints Related to Function
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
The occipital condyles are convex in both transverse and anteroposterior planes; the radii and centers of curvature are similar enough in these planes to allow a small degree of axial rotation to occur here, as well as the more familiar movements of flexion-extension and (smaller) lateral flexion (136–139). The radius of curvature is sufficiently large topush the axis of flexion and extension into the posterior cranial fossa (136,138), so that the presence of medial and lateral “collateral” ligaments, attached close to the axis of motion and remaining taut throughout the range of flexion-extension, is not possible. Thus the capsules of the atlantooccipital joints must be relatively lax for significant motion to occur here, and the stabilizing ligaments for the midrange of atlantooccipital motion must be concentrated more anteriorly. These comprise, inter alia, an extension of the anterior longitudinal ligament, the weak apical ligament of the dens, the vertical components of the cruciform ligament, and an extension of the posterior longitudinal ligament (the membrana tectoria). These all predominantly limit extension (133,138).
Neuroanatomy overview
Published in Michael Y. Wang, Andrea L. Strayer, Odette A. Harris, Cathy M. Rosenberg, Praveen V. Mummaneni, Handbook of Neurosurgery, Neurology, and Spinal Medicine for Nurses and Advanced Practice Health Professionals, 2017
Carolina Sandoval-Garcia, Daniel K. Resnick
The craniocervical region has an additional set of ligaments worth mentioning separately. Given the importance of maintaining stability while allowing for full mobility of the head in relationship to the rest of the body, one of the key ligaments in the occipitocervical junction is the cruciate ligament. The superior and inferior limbs that form this complex offer no significant support, but in turn, the transverse ligament is the strongest found in the cervical spine and maintains the odontoid process anteriorly against the dorsal surface of the anterior arch of C1 while separating it from the spinal cord. The alar ligaments start on the lateral aspects of the odontoid process and attach to the base of the skull and the apical ligament, also known as suspensory or middle odontoid, attaches the tip of the odontoid process to the basion. Dorsally, the posterior atlantooccipital membrane is a thin ligament spanning from foramen magnum to atlas. It is continuous with the posterior atlantoaxial membrane, which in turn becomes ligamentum flavum inferiorly (Tubbs et al., 2011). The ligamentous structures of the craniocervical junction are illustrated in Figure 7.4.
The neck
Published in Ashley W. Blom, David Warwick, Michael R. Whitehouse, Apley and Solomon’s System of Orthopaedics and Trauma, 2017
The atlantoaxial unit contributes to the majority of the neck rotation movement and is the most mobile segment of the spine, although it is structurally weak. Simultaneously, it has specific stabilizing structures that prevent excessive motion and disarrangement. The articulation between the atlas and axis comprises one midline atlanto-odontoid joint and two lateral atlantoaxial facet joints. The articular capsules of the lateral facets provide stability and are reinforced by important ligaments, such as the alar ligaments and the transverse atlantal ligament, which is the thickest and the primary stabilizer of the atlas against anterior subluxation. The transverse ligament allows rotation, while the alar ligaments prevent excessive rotation. The apical ligament has an accessory or vestigial role.
Integrity of the tectorial membrane is a favorable prognostic factor in atlanto-occipital dislocation
Published in British Journal of Neurosurgery, 2020
Gil Kimchi, Gahl Greenberg, Vincent C. Traynelis, Christopher D. Witiw, Nachshon Knoller, Ran Harel
The underlying instability in AOD is often attributed to rupture of the tectorial membrane and alar ligaments.2 The craniocervical junction is supported anteriorly by a ligamentous complex that comprises two distinct groups;12 the first includes the atlanto-condylar articulation, the cruciate ligament and the anterior atlanto-occipital ligament. This group provides stability chiefly to the atlanto-cranial and the atlanto-dental complexes. The second group of ligaments provides stability to the cranium-odontoid complex. It consists of the tectorial membrane, the apical ligament and the alar ligaments. Of special importance within that group is the tectorial membrane; this strong collagenous continuum of the posterior longitudinal ligament lies posteriorly to the transverse ligament and connects the dorsum of the dens to the clivus. Its primary role is to resist hyperextension, although it may also serve to limit hyperflexion as well.13 The prominent role of the tectorial membrane in craniocervical stabilization is well elucidated in a cadaver study,14 in which the authors removed the alar and transverse ligaments and applied various manipulations on the CCJ. They revealed that the tectorial membrane acts as the ‘second line of defense’ by preventing the odontoid process from translating posteriorly and consequently compressing the spinal canal.