Functional Anatomy of the Cervical Spine
Introduction[edit | edit source]
The cervical spine supports and promotes movement of the head and neck. [1] [2]The cervical spine is subjected to extrinsic factors such as repetitive movements, whole body vibrations and static load.[3]
Key Terms[edit | edit source]
Axes: lines around which an object rotates. The rotation axis is a line that passes through the centre of mass. There are three axes of rotation: sagittal passing from posterior to anterior, frontal passing from left to right, and vertical passing from inferior to superior. The rotation axes of the foot joints are perpendicular to the cardinal planes. Therefore, motion at these joints results in rotations within three planes. Example: supination involves inversion, internal rotation, and plantarflexion.
Bursae: reduce friction between the moving parts of the body joints. A bursa is a fluid-filled sac. There are four types of bursae: adventitious, subcutaneous, synovial, and sub-muscular.
Capsule: one of the characteristics of the synovial joints. It is a fibrous connective tissue which forms a band that seals the joint space, provides passive and active stability and may even form articular surfaces for the joint. The capsular pattern is "the proportional motion restriction in range of motion during passive exercises due to tightness of the joint capsule."
Closed pack position: the position with the most congruency of the joint surfaces. In this position, joint stability increases. For example, the closed pack position for the interphalangeal joints is a full extension.
Degrees of freedom: the direction of joint movement or rotation; there is a maximum of six degrees of freedom, including three translations and three rotations.
Ligament: fibrous connective tissue that holds the bones together.
Open (loose) pack position: position with the least joint congruency where joint stability is reduced.
Planes of movement: describe how the body moves. Up and down movements (flexion/extension) occur in the sagittal plane. Sideway movements (abduction/adduction) occur in the frontal plane. The transverse plane movements are rotational (internal and external rotation).
Cervical Spine Structure[edit | edit source]
Cervical vertebrae[edit | edit source]
There are seven lumbar vertebrae, which are known as C1-C7. Considering the small weight-bearing load of the cervical spine, large vertebral bodies are not required. In this section of the spine, vertebral size is not as important as flexibility and range of motion. Increased movement correlates to a heightened injury potential of the spinal cord and its associated neurovascular structures.[2]
- Vertebral body
- Triangular vertebral foramen
- Bifid spinous process – spinous process splits into two distally
- Transverse foramina – holes in the transverse processes.
- space for vertebral artery, vein and sympathetic nerves[4]
** The C7 vertebrae has a singular and larger spinous process which is similar to those in the thoracic vertebrae.[2]
Atlas and Axis[edit | edit source]
The atlas and axis vary in their features from other cervical vertebrae.[4]
he atlanto-axial joints are formed by the articulation between the atlas and the axis:
- Lateral atlanto-axial joints (x2) – formed by the articulation between the inferior facets of the lateral masses of C1 and the superior facets of C2. These are plane type synovial joints.
- Medial atlanto-axial joint – formed by the articulation of the dens of C2 with the articular facet of C1. This is a pivot type synovial joint.
The atlanto-occipital joints consist of an articulation between the spine and the cranium. They occur between then superior facets of the lateral masses of the atlas and the occipital condyles at the base of the cranium. These are condyloid type synovial joints, and permit flexion at the head i.e. nodding. NEED REFERENCE
Atlas- need reference[edit | edit source]
The atlas is the first cervical vertebra and articulates with the occiput of the head and the axis (C2). It has no spinous process or vertebral body.
- lateral masses connected by arches
- anterior
- articulates with dens of axis
- secured by transverse ligament of atlas
- posterior
- groove for C1 spinal nerve and vertebral artery
- anterior
- facets
- superior articular facet
- articulates with occipital condyles
- inferior articular facet
- articulates with C2
- superior articular facet
Axis- need reference[edit | edit source]
- C2 has an odontoid process (dens)
- extends superiorly from the anterior portion of the vertebra
- articulates with the anterior arch of the atlas creating atlanto-axial joint
- facilitates rotation of the head independently from torso
Intervertebral Disc (IVD)[edit | edit source]
In general, intervertebral discs involve 25% of the height of the entire spine. In the cervical region, the discs compromise 40% of the height. This increased height compared to vertebral body height gives the advantage of greater range of motion potential. [5]Disks are thicker anteriorly than posteriorly to enable the lordotic curvature of the cervical spine. The nucleus pulposus of cervical discs dries out by the age of 30 to a firm, fibrocartilaginous plate.[6]
- Coronal plane
- concave superior surface
- convex inferior surface to conform to adjacent vertebral bodies
- movement limited by uncinate process
- anteroposterior translation does occur
** Due to location of uncinate process, posterolateral disk herniations are less frequent
- Cartilaginous endplate
- composed of hyaline cartilage
- located adjacent to the subchondral bone.
- serves as a barrier to nucleus pulposus pressure on the vertebral body
- limiting protrusion.
- The ALL and the posterior longitudinal ligament (PLL) are confluent with the outer fibers of the annulus[7]
Joints | Disc Joint | Facet Joint or Zygapophyseal joints | Uncovertebral |
---|---|---|---|
location/articulations | between vertebral bodies | formed by articulations of superior and inferior articular processes from adjacent vertebrae |
|
functions |
|
|
small synovial articulationsto form anterior wall of foramen |
Orientation |
|
Lumbar Lordosis[edit | edit source]
Lordosis = the natural curve for the lumbar spine. This curve defines lumbar spine alignment in the saggital plane. However, the pelvis is "the cornerstone of spinal sagittal alignment". The curve of the sacrum determines the lumbar curve.
The sagittal alignment of the lumbar spine offers two main benefits during locomotion:
- Allows the body's centre of mass to be positioned above the hip, knee, and ankle joints
- Minimises the muscular force used for postural control
Assessment of lumbar spine alignment must include an analysis of the alignment of the lower limbs. For instance, measuring the degree of knee flexion and pelvic shift might help clinicians identify compensatory mechanisms resulting from the sagittal plane malalignment.
Bones, Articulations and Kinematics of the Lumbar Spine[edit | edit source]
Bones and Articulations[edit | edit source]
The lumbar spine has two types of joints located between each lumbar vertebra:
- intervertebral disc joint
- zygapophyseal joint or facet joint
Bones | Articulations | Characteristics | Key palpation points |
---|---|---|---|
Vertebral body | Intervertebral disc joint | This joint is formed between the inferior surface of one vertebral body and the superior surface of the vertebral body that lies below (for example, the inferior surface of L1 and the superior surface of L2). An intervertebral disc separates the vertebral bodies. | To find each segment of the lumbar spine, position the patient prone. The location of the spinous processes will determine the location of each segment. You can palpate the spinous processes in the centre of the patient's back.
Start with finding T12 by palpating the patient's lowest rib and following your finger along the border of the rib towards the centre of the spine. The T12 spinous process is in line with the 12th rib (which inserts into T12 spinal segment). Below T12, you can palpate L1 and continue along the spinous process of L2, L3, and L4. If you start your palpation from the distal end of the lumbar spine, you must consider the following: the spinous process of L4 "is usually determined by the position of the highest point on both sides of PSIS", but the accuracy of palpation is only 36%. |
Articular processes | Zygapophyseal joint (Facet joint) | Formed between the articular processes of each lumbar vertebra.
Located on the left and right sides of the spine. They link one vertical segment to the other. For example, the facet joint between L3 and L4 will connect L3 to L4. The superior articular surface is vertical and concave, and the inferior is vertically convex. Their primary role includes the stabilisation of the spinal motion segment. They also contribute to axial compressive load transmission. |
The facet joint CANNOT be directly palpated due to overlying soft tissue. When you move your fingers two to three centimetres in the lateral direction from the spinous process, you will be on the muscles overlying the facet joint. |
Kinematics[edit | edit source]
The lumbar spine is considered a three-joint complex or an articular triad. The zygapophyseal (facet) joints and intervertebral disc joint are part of a "spinal motion segment". The various parts of the spinal motion segment work together to allow spinal motion and to protect the spine from excessive movements.
The spinal motion segment has the following characteristics:
- The intervertebral disc joint transmits mostly vertical compressive loads
- The facet joints guide and stabilise the motion segment
- In an erect standing position and erect sitting posture, spine load is also transmitted through the facet joints
Joint | Type of joint | Plane of movement | Motion | Kinematics | Closed pack position | Open pack position |
---|---|---|---|---|---|---|
Intervertebral disc joint | Cartilaginous joint, symphysis | A single joint: structurally fused but allows very limited, multidirectional movements
All lumbar intervertebral disc joints and zygapophyseal joints combined together: Saggital Frontal Transverse |
Single joint: Translating, tilting, rocking and compressing movements.
All lumbar intervertebral disc joints and zygapophyseal joints combined together: Flexion/extension Lateral flexion Rotation |
All lumbar intervertebral disc joints and zygapophyseal joints combined together:
Flexion 60 degrees Extension 25 degrees Lateral flexion 20-30 degrees Rotation 1-5 degrees |
Full extension | Halfway between flexion and extension |
Zygapophyseal joint (facet joint) | Synovial plane joint | Facilitate a multiplanar and multidirectional movement of the spine.
Enable lumbar spine extension, lateral flexion, and rotation in the saggital, transverse and frontal planes. |
Flexion/extension
Lateral flexion Rotation |
All lumbar intervertebral disc joints and zygapophyseal joints combined together:
Flexion:60 degrees Extension 25 degrees Lateral flexion 20-30 degrees Rotation 1-5 degrees |
Full extension | Halfway between flexion and extension |
Cervical Spine Ligaments[edit | edit source]
Unique to Cervical Spine
- Nuchal ligament – a continuation of the supraspinous ligament. It attaches to the tips of the spinous processes from C1-C7, and provides the proximal attachment for the rhomboids and trapezius.
- Transverse ligament of the atlas – connects the lateral masses of the atlas, and in doing so anchors the dens in place.
(Note: Some texts consider the interspinous ligament to be part of the nuchal ligament).[4]
Key ligaments | Origin | Insertion | Action/role | Key palpation points |
---|---|---|---|---|
Anterior longitudinal ligament | The anterior portion of the vertebral body at the base of the skull | The anterior portion of the vertebral body at the sacrum | Limits extension of the vertebral column.
Reinforces the intervertebral disc. |
|
Posterior longitudinal ligament | The body of C2 | Posterior surface of the sacrum | Limits flexion of the vertebral column.
Reinforces the intervertebral disc. |
|
Ligamentum flavum:
A series of short ligaments that connect the laminae of each vertebra. There are two ligamenta flava at each vertebra. Each ligament is divided into: The medial portion: passes to the back of the next lower lamina and across the gap between the adjacent vertebrae, fusing with the interspinous ligament The lateral portion: passes in front of the facet joint, attaches to the anterior aspect of the inferior and superior articular processes and forms the anterior capsule. The most lateral fibres extend beyond the superior articular process to the pedicle below. |
The lower half of the anterior surface of the lamina above | The posterior surface and upper margin of the lamina below | Their high elastin content prevents the ligament from buckling into the spinal canal.
Assists with lumbar spine flexion and extension. Compresses the intervertebral discs. |
|
Intertransverse ligaments | Transverse processes of the vertebra above | Transverse processes of the vertebra below | Contributes to the stability of the lumbar spine.
Limits lateral flexion. |
To palpate the transverse process, position the patient in sitting. The transverse processes of the lumbar spine are most likely located directly in line with the spinous process of the corresponding vertebra. Start by palpating the spinous process of the L1 vertebra and move directly lateral to find the transverse process of L1. |
Supraspinous ligament | Tip of spinous processes of the vertebra above from the seventh cervical vertebra to the third or fourth lumbar vertebra | Tip of spinous processes of the vertebra below | Prevents the separation of the spinous processes during forward flexion, thus limiting lumbar spine flexion | You can palpate the spinous processes in the centre of the patient's back.
Start with finding T12 by palpating the patient's lowest rib and following your finger along the border of the rib towards the centre of the spine.T12 spinous process is in line with the 12th rib that inserts into the spinal segment. Below T12, you can palpate L1 and continue along the spinous process of L2, L3, and L4. |
Interspinous ligament | Spinous processes of the vertebra above between the ligamenta flava anteriorly and the supraspinous ligament posteriorly | Spinous processes of the vertebra below between the ligamenta flava anteriorly and the supraspinous ligament posteriorly | Limits forward flexion of the vertebral column. | |
** special to C-Spine
Nuchal ligament |
tips of the spinous process from C1-C7 | proximal attachment for rhomboids and trapezius | ||
** special to C-spine
Transverse ligament |
connects lateral masses of atlas | anchors dens in place |
Muscles of the Lumbar Spine and Abdominal Wall[edit | edit source]
The muscles of the back can be grouped according to their function and location.
When grouped according to function, the muscles of the lumbar spine can be organised as follows:
- Flexors: psoas major, psoas minor, internal oblique, external oblique, and rectus abdominis
- Extensors: quadratus lumborum, interspinales lumborum, multifidus, and the erector spinae (iliocostalis, longissimus)
- Lateral flexors: intertransversarii lumborum, psoas major, quadratus lumborum, erector spinae, internal and external obliques
- Rotators: multifidus, internal and external obliques
When grouped according to location, the muscles of the lumbar spine can be divided as follows:
- The intrinsic (deep) group:
- Superficial layer: erector spinae muscles
- Middle (deep) layer: multifidus
- Deepest layer: interspinales lumborum and intertransversarii lumborum
- The abdominal wall group: transverse abdominis, the internal oblique, rectus abdominis, and the external oblique
- The hip group: psoas major, psoas minor, quadratus lumborum
The following tables group muscles according to their function. Please note, that when a muscle has multiple functions, it is included in all relevant tables. These tables only list muscle actions associated with the lumbar spine and abdominal wall. If a muscle acts on other joints, these actions are discussed on the relevant page. For example, psoas major is also a major hip flexor - this role is detailed on the Functional Anatomy of the Hip page.
Lumbar Spine Flexors[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Psoas major | Vertebral bodies of T12-L4
Intervertebral discs between T12-L4 Transverse processes of L1-L5 vertebrae |
Lesser trochanter of femur | Anterior rami of spinal nerves L1-L3 | Contribute to lumbar spine flexion when acting bilaterally and when the insertion point is fixed. |
Psoas minor | Vertebral bodies of T12 to L1 | Iliopubic eminence | Anterior ramus of spinal nerve L1 | Weak trunk flexor. This muscle is absent in 40% of people. |
Internal obliques | Thoracolumbar fascia
Iliac crest Inguinal ligament |
Lower four ribs
Linea alba Pubic crest |
Lower intercostal nerves Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve | Bilateral action: lumbar flexion
Assist in raising intra-abdominal pressure |
External obliques | Ribs five to twelve | Linea alba
Pubic tubercle Iliac crest |
Intercostal nerves T7- T11 and the T12 subcostal nerve | Bilateral action: lumbar flexion |
Rectus abdominis | Pubis, pubic symphysis | Xiphoid process of the sternum
Fifth to seventh costal cartilage |
Thoracoabdominal nerves | Lumbar spine flexion
Assists in raising intra-abdominal pressure |
Lumbar Spine Extensors[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Quadratus lumborum | Iliac crest
Iliolumbar ligament |
The inferior border of the 12th rib
Transverse processes of L1-L4 vertebrae |
Subcostal nerve
Anterior rami of spinal nerves L1-L4 |
Bilateral action: trunk extension |
Interspinales lumborum | Superior aspects of spinous processes of L2-L5 | Inferior aspects of spinous processes of L1-L4 | Posterior rami of spinal nerves | Stabilise the lumbar spine Extend the lumbar spine |
Multifidus | Sacrum
Posterior superior iliac spine The mammillary processes of the lumbar vertebrae Transverse processes of T1-3 Articular processes of C4-C7 |
Spinous processes of the vertebrae above their origin | Medial branches of the posterior rami of the spinal nerves in the corresponding lumbar region | Extends the lumbar spine
Provides core stability |
Erector spinae: Iliocostalis lumborum (ICL) Longissimus thoracis (LT) | ICL: Iliac crest
LT : Lumbar intermuscular aponeurosis, medial part of sacropelvic surface of ilium, posterior sacroiliac ligament |
ICL: L1-L4 lumbar transverse processes, angle of 4-12 ribs and thoracolumbar fascia
LT: Accessory and transverse processes of vertebrae L1-L5 |
Dorsal rami of spinal nerves | Bilateral action: lumbar spine extension |
Lumbar Spine Lateral Flexors[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Intertransversarii lumborum (ITL):
Lateral (ITLL) Medial (ITLM) |
ITLL: Transverse and accessory processes of L1-L4
ITLM: Accessory processes of L1-L4 |
ITLL: Transverse process of the following vertebra
ITLM: Mammillary processes of the following vertebra |
Anterior rami of spinal nerves | Assists in lateral flexion
Stabilises the lumbar spine |
Psoas major | Vertebral bodies of T12-L4
Intervertebral discs between T12-L4 Transverse processes of L1-L5 vertebrae |
Lesser trochanter of femur | Anterior rami of spinal nerves L1-L3 | Lateral flexion of the trunk |
Quadratus lumborum | Iliac crest
Iliolumbar ligament |
The inferior border of the 12th rib
Transverse processes of L1-L4 vertebrae |
Subcostal nerve
Anterior rami of spinal nerves L1-L4 |
Unilateral action: ipsilateral lumbar spine lateral flexion |
Erector spinae:
Iliocostalis (IC) Longissimus (L) |
ICL: Iliac crest
LT : Lumbar intermuscular aponeurosis, medial part of sacropelvic surface of ilium, posterior sacroiliac ligament |
ICL: L1-L4 lumbar transverse processes, angle of 4-12 ribs and thoracolumbar fascia
LT: Accessory and transverse processes of vertebrae L1-L5 |
Dorsal rami of spinal nerves | Unilateral action: ipsilateral side flexion and rotation of the vertebral column |
Internal oblique | Thoracolumbar fascia
Iliac crest Inguinal ligament |
Lower four ribs
Linea alba Pubic crest |
Lower intercostal nerves
Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve. |
Unilateral action: lumbar spine lateral flexion and/or rotation to the ipsilateral side
Assists in raising intra-abdominal pressure |
External oblique | Ribs five to twelve | Linea alba
Pubic tubercle Iliac crest |
Intercostal nerves T7- T11 and the T12 subcostal nerve | Unilateral action: lumbar spine lateral flexion to the ipsilateral side and rotation to the contralateral side |
Lumbar Spine Rotators[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Multifidus | Sacrum
Posterior superior iliac spine The mammillary processes of the lumbar vertebrae |
Spinous processes of the vertebrae above their origin | Medial branches of posterior rami of spinal nerves in the corresponding lumbar region. | Rotates the lumbar spine away from the side of the body on which they are located
Provides core stability |
Internal oblique (IO) | Thoracolumbar fascia
Iliac crest Inguinal ligament |
Lower four ribs
Linea alba Pubic crest |
Lower intercostal nerves
Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve. |
Rotation to the same side
Works together with opposite EO to rotate the spine - e.g. right external oblique works with left internal oblique to rotate the spine. |
External oblique (EO) | Ribs five to twelve | Linea alba Pubic tubercle
Iliac crest |
Intercostal nerves T7- T11 and the T12 subcostal nerve | Rotation to the opposite side
Works together with opposite IO to rotate the spine - e.g. right external oblique works with left internal oblique to rotate the spine. |
Innervation of the Lumbar Spine and Abdominal Wall[edit | edit source]
Nerve | Origin | Branches | Motor fibres | Sensory fibres |
---|---|---|---|---|
Intercostal | Lumbar plexus | Muscular, collateral, lateral cutaneous, anterior cutaneous, and
communicating branches |
External obliques
Internal obliques |
Skin over the anterior abdomen |
Subcostal | Anterior ramus of the spinal nerve T12 | Muscular, cutaneous, communicating and collateral branches | Quadratus lumborum
External oblique |
The skin of the region under the umbilicus |
Iliohypogastric | Lumbar plexus | Lateral cutaneous branch
Anterior cutaneous branch |
Internal oblique | External abdominal oblique, transversus abdominis, internal abdominal oblique
The skin of the suprapubic region |
Ilioinguinal | Lumbar plexus | Anterior labial nerves
Anterior scrotal nerves |
Internal oblique | |
Dorsal (posterior) rami of spinal nerves | Spinal nerves | Medial
Intermediate Lateral |
Interspinales lumborum
Multifidus Erector spinae |
The skin of the back |
Ventral (anterior) rami of L1-L4 | Spinal nerves | Intertransversarii lumborum
Psoas major Psoas minor |
Ventrolateral body surface Structures in the body wall |
Vascular Supply of the Lumbar Spine and Abdominal Wall[edit | edit source]
Artery | Origin | Branches | Supply |
---|---|---|---|
Lumbar artery (LA):
Left (LLA) Right (RLA) |
Abdominal aorta | Medial
Middle Lateral |
Skin and muscles of the posterior abdominal wall
Joints of the lumbar spine The lumbar portion of the deep back muscles Lower two-thirds of the spinal cord |
Internal thoracic artery | Subclavian artery | Anterior collaterals
Posterior collaterals Terminal branches |
The superior aspect of the abdominal wall |
External iliac artery | Common iliac artery | Inferior epigastric,
Deep circumflex iliac arteries |
Lower abdominal wall |
Clinical Relevance[edit | edit source]
- Disc herniations are a common low back condition. They occur when the nucleus pulposus displaces from the intervertebral space. According to Yoon et al., when there is imaging confirmation of lumbar disc herniation that is "consistent with clinical findings, and failure to improve after six weeks of conservative care", surgical intervention may be required. You can read more about the management of disc herniation symptoms here.
- Spinal stenosis is a narrowing of the spinal canal. Spinal stenosis can be caused by a range of conditions, such as tumours or bone spurs. You can learn about low back pain assessment and prognosis by taking this course.
- Diastasis recti is a very common condition where the linea alba stretches and produces a gap between the two sides of the rectus abdominis muscle. Learn more about diastasis recti here.
References[edit | edit source]
- ↑ Frost BA, Camarero-Espinosa S, Foster EJ. Materials for the spine: anatomy, problems, and solutions. Materials. 2019 Jan;12(2):253
- ↑ 2.0 2.1 2.2 Kaiser JT, Lugo-Pico JG. Anatomy, Head and Neck, Cervical Vertebrae. 2019.
- ↑ Petersen JA, Brauer C, Thygesen LC, Flachs EM, Lund CB, Thomsen JF. Prospective, population-based study of occupational movements and postures of the neck as risk factors for cervical disc herniation. BMJ open. 2022 Feb 1;12(2):e053999.
- ↑ 4.0 4.1 4.2 Teach me anatomy The cervical Spine Available from:https://teachmeanatomy.info/neck/bones/cervical-spine/
- ↑ 5.0 5.1 Learn muscles . Cervical spine joints. Available from: https://learnmuscles.com/blog/2017/08/01/cervical-spinal-joints/ (last accessed 29.1.2020)
- ↑ Peng B, Bogduk N. Cervical discs as a source of neck pain. An analysis of the evidence. Pain Medicine. 2019 Mar 1;20(3):446-55.
- ↑ Musculoskeletal Cervical spine Available from:https://musculoskeletalkey.com/cervical-spine-anatomy/
- ↑ RSNA Joints of Luschka Available from: https://pubs.rsna.org/doi/10.1148/66.2.181 (last accessed 28.1.2020)