Biomechanical features of the craniovertebral region

The first two cervical vertebrae (Atlas and Axis), together with the occipital bone of the skull, form 3 head joints: the paired atlanto-occipital joint, the paired lateral atlanto-axial joint and the median atlanto-axial joint of Cruveilhier. In medicine, this region is called the “craniovertebral junction” (from Latin Cranium – skull, from Latin Vertebrae – vertebrae).

In addition to the occipital bone of the skull and the first two cervical vertebrae, the craniovertebral region also includes the medulla oblongata and the cerebellum.

The atlanto-occipital joint is a paired articulation located between the occipital bone of the skull and the first cervical vertebra, the Atlas. The joint is formed by the two condyles of the occipital bone of the skull and the two superior articular surfaces of the atlas. Both pairs of articulating surfaces are enclosed in joint capsules.

The following movements are possible in the atlanto-occipital joint:

In pathology, there is a moderate or complete restriction of joint mobility. The patient may have limitation when trying to bend / straighten the head; cannot touch the collarbone with the chin; feels a blocking of the backward extension movement of the head and tension / pain in the thoracic region. When pathology is present, there is often crunching of the articulating surfaces of the joints, shooting pains and an aching pain in the neck that turns sharp at maximum flexion / extension of the head forward / backward.

In pathology, there is unilateral partial restriction or complete blocking of joint mobility. The patient may feel that the head tilts worse to one side than to the other. The same movements in different directions may be performed with varying degrees of difficulty, accompanied by painful sensations and shooting pains. With blockage, the articulating surfaces of the joints are subjected to excessive friction, as a result of which crunching and clicking may be heard.

Total range of motion in pathology: down to 0° (0-5° in each direction).

In pathology, there is unilateral partial restriction or complete blocking of joint mobility. During combined movements, the crunching of the articulating surfaces of the joints, which occurs as a result of the intense compressive force of the muscles, may be especially pronounced or not audible at all (complete block). The patient may feel that the head turns worse to one side than to the other. The same movements in different directions may be performed with varying degrees of difficulty, accompanied by painful sensations and shooting pains.

The second cervical vertebra, the Axis, differs from all other vertebrae in its unusual shape, namely the presence of the odontoid process, around which the first cervical vertebra, the Atlas, rotates, and the skull along with it.

The lateral atlanto-axial joint provides significant rotation of the head left and right. The normal range of rotational movement is up to 33° to each side out of the 90° of total rotation of the entire cervical spine. In case of joint hypermobility, rotation can reach 40°.

In patients with C1-C2 segment dysfunction who suffer from headaches, rotation may be significantly reduced due to inferior oblique muscle syndrome and, in rare cases, completely blocked. When there are displacements in the vertebrae, a peculiar prolonged rustling of the articular surfaces rubbing against each other may be heard, which the patient usually picks up in silence.

For this purpose, Body Balance Clinic has developed an individual method for testing the biomechanics of the head joints, which in terms of its accuracy is much more precise than the flexion-rotation test used in kinesiology.

When performing the test, the patient sometimes cannot turn the head at all because of blockage of the head joints.

As you already know, the joints should provide head rotation totalling up to 35-42° to each side. With blockage of these joints, the body compensates for the imbalance by distributing the muscle load onto the trapezius muscles. As a result, a patient with blocked head joints may experience sharp pain even with moderate squeezing of the trapezius muscles, which is not observed if the head joints work correctly.

Body Balance Clinic distinguishes 2 types of head joints dysfunction:

Body Balance Clinic’s internal statistics, compiled by analyzing a large number of patients’ CT scans, show that ~ 30% of patients belong to type 1 and ~ 70% of patients to the second type. The second type includes patients who have a rotational or lateral displacement of more than 3° of at least one of the vertebrae and in whom biomechanical tests also reveal blockage of the mobility of the head joints.

Images of serious displacements: 

A muscle can be in 4 different states: normal, contracture, flaccidity and local myofascial hypertonus (a fibrous and painful muscle induration in which the muscle shortens somewhat, which is an indicator of muscle tone).

In head joints dysfunction, the patient’s occipital muscles are almost always in a state of contracture or local myofascial hypertonus (rarely). Body Balance Clinic distinguishes 4 degrees of muscle contracture:

The long-term persistence of muscle spasms leads to the development of local painful indurations in the muscles (areas of fibrosis), which over time increases their stiffness and the stage of their condition.

The craniovertebral junction is an important strategic zone that largely determines a person’s health. That is why for many years it has been in the focus of attention of neurologists, vertebrologists, specialists in manual therapy and osteopathy, including cranial osteopathy. Body Balance Clinic strives to structure the available knowledge and publishes some scientific discoveries made by professors of medicine so that the reader can once again be convinced of the importance of the problem and the need for a professional approach to it:

? The craniovertebral junction plays a key role in the redistribution of body weight and in the formation of the supporting function of the lower limbs (Ivanichev G.A., 2008).

?Dysfunction of the craniovertebral junction and the functional block Cr-CI contribute to impaired mobility of the sacrum between the iliac bones, decreased tone of the iliopsoas muscles and the development of twisted pelvis syndrome (Zozulya I.S., Bredikhin A.V., 2011; Chikurov Yu.V., 2004).

?According to G. Goodheart (1968), decreased tone of the iliopsoas muscles is associated with the presence of a Cr-C1 block. Functional blockade of the craniovertebral region is, as a rule, accompanied by secondary blockades of the sacroiliac joint (Ivanichev G.A., 2008).

?The dura mater of the spinal cord is firmly attached to the foramen magnum, the atlas and the axis, so any impairment of mobility in this zone affects the craniosacral mechanism (Orel A.M., 2009).

? Kinetic dysfunctions at this level change the patterns of the sphenobasilar synchondrosis (SBS), which leads to a change in the primary respiratory mechanism (Novoseltsev S.V., 2009).

? In craniovertebral dysfunction, dizziness, more often non-systemic, decreased hearing and hearing loss may be observed. One of the main syndromes is loss of balance with a sudden change in head position, especially when moving from a lying to a standing position (resembles vestibular ataxia) (Ivanichev G.A., 2008).

? Craniovertebral dysfunction may be accompanied by cervicogenic headache, which occurs against the background of impaired spinal biomechanics and myofascial dysfunction with the formation of local muscle spasm and trigger points. Cervicogenic headache can develop through three mechanisms: vascular (vasomotor, ischemic and venous), neuralgic and muscle tension (Morozova O.P., Yaroshevsky A.A., Zdybsky V.I., 2009).

? Reflex spasm when the inferior oblique muscle of the head is stretched, combined with hyperflexion, provokes subluxation of the atlanto-axial joint. In this case, the greater occipital nerve and the occipital artery, which approaches the CI-CII intervertebral joint on the side opposite to the head rotation, may be compressed between the layers of the muscle’s fascia (Bogorodinsky D.K., Skoromets A.A., 2008).

? Impaired craniovertebral biomechanics leads to spasm of the muscles of the head and cervical spine and of the extravertebral muscles, contractures of these muscles, the appearance of latent trigger points in them (muscular, fascial, musculoligamentous, ligamentous-osseous) and regional muscle imbalance. Functional muscular, fascial, musculoligamentous and dural craniovertebral blocks C0-CI, CI-CII develop (Ivanichev G.A., 2008), and irritative-reflex syndromes arise: As a result, the following clinical syndromes form: cervicocranialgia, cervicalgia, cervicobrachialgia, cervicopectalgia (Zharkov P.L., 1994).