Orthopaedic Surgery - Cervical Spine Anatomy and Examination

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Basics

The cervical spine consists of seven cervical vertebrae, C1 through C7, which support the head, protect the spinal cord, permit a wide range of motion, and provide passage for important neurovascular structures.

For practical purposes, the cervical spine can be divided into the upper cervical spine, consisting of C1 and C2, and the lower cervical spine, consisting of C3 through C7.

The upper and lower regions differ substantially in both morphology and function.

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Osteology

Typical cervical vertebrae contain a vertebral body, paired pedicles, paired laminae, transverse processes, articular structures, and a spinous process.

The bony architecture surrounds and protects the cervical spinal cord while contributing to stability and motion.

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Transverse Foramina

All cervical vertebrae contain transverse foramina within their transverse processes.

The vertebral arteries usually pass through the transverse foramina from C6 to C1, rather than through C7.

Protection of these vessels is one of the important functions of intact cervical vertebral anatomy.

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Upper Cervical Spine

The atlas (C1) and axis (C2) are considered atypical cervical vertebrae because their anatomy differs considerably from that of C3–C7.

Their specialized architecture allows extensive movement between the skull and upper cervical spine.

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Atlas

The atlas has no true vertebral body and no conventional spinous process.

It consists largely of anterior and posterior arches connected by lateral masses.

C1 articulates superiorly with the occipital condyles and inferiorly with the axis.

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Atlantoaxial Joint

The articulation between C1 and C2 forms the atlantoaxial joint.

Approximately 50% of cervical rotation occurs at this level.

The unique articulation between the atlas and odontoid process permits substantial axial rotation of the head.

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Axis

The axis (C2) contains a vertebral body and the characteristic odontoid process, or dens, which projects superiorly and acts as a pivot for rotation of C1.

The dens is clinically important because odontoid fractures are common upper cervical injuries.

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Odontoid Blood Supply

The odontoid process contains a relative vascular watershed region between its apex and base.

This limited blood supply can influence healing of certain odontoid fractures and contributes to the risk of nonunion in selected fracture patterns.

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Atlanto-Occipital Joint

A substantial proportion of upper cervical flexion and extension occurs at the atlanto-occipital articulation between the occiput and C1.

This joint is particularly important for nodding movements of the head.

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Cervical Lordosis

The normal sagittal alignment of the cervical spine is lordotic.

Loss or reversal of cervical lordosis may be associated with muscle spasm, degeneration, deformity, or traumatic injury, although alignment must always be interpreted in clinical context.

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Protective Function

Normal cervical vertebral anatomy protects both the spinal cord and vertebral arteries.

Trauma, instability, stenosis, or deformity can therefore have serious neurologic or vascular consequences.

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Neuroanatomy

There are eight cervical nerve roots despite only seven cervical vertebrae.

The cervical nerve roots generally exit above their correspondingly numbered vertebrae.

For example, the C5 nerve root exits between C4 and C5.

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C8 Nerve Root

The C8 nerve root exits between C7 and T1.

Below this level, thoracic and lumbar nerve roots exit below the correspondingly numbered vertebra.

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Orientation of Cervical Nerve Roots

Cervical nerve roots travel in a relatively horizontal direction as they leave the spinal canal.

Because of this arrangement, both central/paracentral and foraminal disc pathology may affect the same exiting cervical nerve root depending on the level and location of compression.

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Cervical Spine Examination

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Inspection

The examination should begin with visual inspection.

Adequate exposure is important so that the neck, shoulders, upper thorax, and surrounding soft tissues can be assessed systematically.

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Alignment

The examiner should assess gross cervical alignment and head position.

Abnormal posture, torticollis, deformity, or asymmetry may indicate muscle spasm, structural deformity, or neurologic disease.

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Skin and Soft Tissues

The skin should be inspected for wounds, scars, bruising, swelling, masses, or other soft-tissue abnormalities.

Muscle asymmetry, atrophy, or hypertrophy should also be noted.

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Anterior Bony Palpation

Palpation of the anterior neck should identify tenderness, crepitus, masses, asymmetry, or malalignment.

Several palpable landmarks can help estimate cervical spinal levels.

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Hyoid Bone

The hyoid bone approximately corresponds to the level of the C3 vertebral body.

It can serve as a useful surface landmark during examination.

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Thyroid Cartilage

The superior portion of the thyroid cartilage approximately corresponds to the C4 vertebral body.

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Cricoid Cartilage

The cricoid cartilage is located approximately at the C6 vertebral level.

It may be easier to palpate during swallowing because movement of the laryngeal structures makes the anatomy more distinct.

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Carotid Tubercle

The anterior tubercle of the C6 transverse process is known as the carotid tubercle.

The right and left carotid tubercles should not be compressed simultaneously because doing so could reduce blood flow through both carotid arteries.

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Tracheal Examination

The trachea should be palpated to confirm that it remains in the midline.

Deviation may indicate a mass, swelling, mediastinal process, or other abnormality.

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Posterior Bony Palpation

Posterior examination begins at the occiput and proceeds inferiorly along the cervical spinous processes.

Tenderness, step-off, displacement, or asymmetry should be noted.

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Inion

The inion is the most prominent palpable point of the lower occiput.

It serves as an important posterior surface landmark.

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Spinous Processes

The spinous processes should generally form a straight midline sequence.

C7 and T1 are usually the most prominent and easiest to palpate.

Deviation from normal alignment can suggest rotational injury, including unilateral facet dislocation.

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Bifid Spinous Processes

The spinous processes of approximately C3–C5 may be bifid.

This is a normal anatomical variation and should not be mistaken for pathology.

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Facet Joints

The cervical facet joints lie approximately 2.5 cm lateral to the spinous processes.

Degenerative disease frequently affects the lower cervical facets, particularly around C5–C6.

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Anterior Soft-Tissue Palpation

Anterior soft-tissue examination should include the sternocleidomastoid muscles, parotid glands, cervical lymph nodes, thyroid gland, carotid pulses, and supraclavicular fossae.

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Thyroid Examination

The thyroid gland should normally feel relatively smooth and symmetric.

Enlargement, nodularity, or asymmetry should be documented.

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Supraclavicular Fossa

The supraclavicular area should be palpated for abnormal masses or bony prominences.

A prominent structure may represent a cervical rib.

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Posterior Soft-Tissue Palpation

Posterior soft-tissue examination includes the trapezius muscles, greater occipital nerves, and ligamentum nuchae.

The trapezius should be assessed for tenderness, muscle asymmetry, or abnormal masses.

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Lymph Nodes

Palpable lymph nodes in the posterior neck should be considered abnormal if enlarged or otherwise clinically suspicious.

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Greater Occipital Nerves

The greater occipital nerves can become tender or prominent after trauma, including whiplash-type injuries.

Irritation may contribute to occipital pain or headache.

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Ligamentum Nuchae

The ligamentum nuchae extends from the inion to the C7 spinous process.

It can be palpated in the posterior midline.

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Neurologic Examination

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General Principles

Neurologic evaluation of the cervical spine includes sensory, motor, and reflex testing.

Findings should be carefully documented to identify nerve-root compression, spinal cord dysfunction, or peripheral neuropathy.

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Sensory Examination

Patients should be asked to identify altered sensation as specifically as possible.

The most commonly assessed sensory modalities are light touch and pinprick.

Comparison between sides is useful.

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Upper Cervical Dermatomes

Sensation from C2 through C4 generally progresses from the posterior scalp and neck toward the anterior neck and shoulder region.

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C5 Dermatome

The C5 dermatome is represented mainly over the lateral shoulder and upper arm.

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C6 Dermatome

The C6 dermatome extends along the lateral forearm toward the radial side of the hand, particularly the thumb and adjacent radial digits.

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C7 Dermatome

The C7 dermatome is commonly tested at the middle finger.

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C8 Dermatome

The C8 dermatome involves the ulnar side of the hand, particularly the ring and little fingers.

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T1 Dermatome

The T1 dermatome lies primarily along the medial forearm.

Dermatomal patterns overlap, so sensory findings should always be interpreted together with motor and reflex abnormalities.

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Motor Examination

Motor testing should evaluate major muscle groups corresponding to cervical nerve roots.

Strength should be graded consistently to allow changes over time to be recognized.

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Muscle Strength Grading

Grade 0: No visible or palpable muscle contraction.

Grade I: Muscle contraction is visible or palpable, but no joint movement occurs.

Grade II: Full range of motion is possible with gravity eliminated.

Grade III: Full range of motion is possible against gravity.

Grade IV: Full range of motion is possible against gravity and some resistance.

Grade V: Normal strength against full resistance.

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C3–C5 Motor Function

The levator scapulae can be assessed with resisted scapular elevation and receives contributions predominantly from C3 and C4, with possible C5 involvement.

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C5 Motor Function

The deltoid is tested with shoulder abduction and primarily reflects C5 motor function.

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C6 Motor Function

C6 function can be evaluated with elbow flexion through the biceps and wrist extension.

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C7 Motor Function

C7 is assessed through triceps-mediated elbow extension, wrist flexion, and finger extension.

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C8 Motor Function

C8 contributes substantially to finger flexion and thumb adduction.

Testing grip and intrinsic hand function can therefore help assess lower cervical nerve-root function.

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Deep Tendon Reflexes

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Reflex Examination

Deep tendon reflex testing helps distinguish nerve-root compression from spinal cord disease.

Diminished reflexes may indicate radiculopathy, whereas hyperreflexia can suggest an upper motor neuron lesion such as cervical myelopathy.

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Biceps Reflex

The biceps reflex primarily evaluates the C5 nerve root, with some contribution from C6.

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Brachioradialis Reflex

The brachioradialis reflex primarily evaluates C6.

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Triceps Reflex

The triceps reflex primarily evaluates C7.

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Range of Motion

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General Principles

Active cervical range of motion should be assessed in flexion, extension, rotation, and lateral bending.

Pain, limitation, asymmetry, and reproduction of radicular symptoms should be noted.

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Flexion and Extension

A large proportion of flexion-extension occurs in the upper cervical spine, while the remainder is distributed across the subaxial cervical levels.

The C5–C6 segment often demonstrates particularly substantial motion.

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Muscles Used in Flexion and Extension

Cervical flexion assesses muscles including the sternocleidomastoid and deeper cervical flexors.

Extension involves the paraspinal extensors and trapezius.

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Rotation

Approximately half of cervical rotation occurs at C1–C2, with the remainder distributed through the lower cervical spine.

The patient should normally be able to rotate the chin approximately 60–80° to either side.

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Rotational Muscles

The sternocleidomastoid is an important cervical rotator, although normal rotation is produced by coordinated activity of several muscle groups.

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Lateral Bending

Lateral bending is distributed throughout the cervical spine and usually occurs in combination with some rotation.

The patient is asked to bring the ear toward the ipsilateral shoulder without elevating the shoulder.

Normal lateral bending is approximately 45°.

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Muscles Used in Lateral Bending

The scalene muscles contribute substantially to cervical lateral flexion.

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Provocative Tests

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Modified Spurling Maneuver

The modified Spurling test evaluates cervical nerve-root irritation.

The neck is extended and rotated toward the symptomatic side, followed by gentle axial loading.

A positive test reproduces radicular pain or paresthesias in the ipsilateral upper extremity.

The test is relatively specific for cervical radiculopathy but has limited sensitivity.

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Shoulder Abduction Test

The patient actively or passively raises the symptomatic arm over the head.

Relief of radicular symptoms with ipsilateral shoulder abduction constitutes a positive test and may suggest cervical nerve-root compression.

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Cervical Distraction Test

The examiner applies gentle longitudinal traction to the head, typically with the neck in slight flexion or neutral alignment.

Improvement in radicular symptoms during distraction supports the possibility of cervical nerve-root compression.

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Lhermitte Sign

The Lhermitte maneuver is performed by flexing the cervical spine anteriorly.

An electric or shooting sensation traveling down the arms, trunk, or legs suggests irritation or dysfunction of the cervical spinal cord.

It may occur with cervical cord compression as well as other disorders affecting the dorsal columns.

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Hoffmann Sign

To test the Hoffmann reflex, the patient’s hand is supported and relaxed.

The examiner grasps the middle finger and sharply flicks the distal phalanx or nail.

A positive response consists of reflex flexion or adduction of the thumb and index finger.

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Significance of Hoffmann Sign

A positive Hoffmann sign can suggest upper motor neuron or corticospinal tract dysfunction, including cervical myelopathy.

It should not be interpreted in isolation and must be correlated with the remainder of the neurologic examination.

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Romberg Test

The Romberg test evaluates balance and proprioception.

The patient stands with the arms extended and eyes initially open, then closed.

Loss of balance when the eyes are closed suggests impaired proprioceptive function.

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Dynamic Balance Assessment

Observation of abnormal arm drift, progressive elevation of the arms, or instability during static or dynamic balance testing may provide additional evidence of neurologic dysfunction.

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Gait Assessment

Gait examination is an essential part of cervical neurologic evaluation.

It can provide information regarding balance, coordination, lower-extremity function, posture, spasticity, and possible spinal cord dysfunction.

Patients with cervical myelopathy may exhibit a stiff, broad-based, unsteady, or spastic gait.

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Imaging

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Plain Radiographs

Standard cervical spine radiography commonly includes anteroposterior and lateral views.

When possible, imaging is obtained with the patient upright so that physiologic alignment can be assessed.

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Trauma Radiographs

In trauma patients, an initial cross-table lateral radiograph may be used when appropriate, but the entire cervical spine must be adequately visualized for the image to be diagnostically useful.

Modern trauma evaluation frequently relies heavily on CT when significant cervical injury is suspected.

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Oblique Views

Oblique radiographs can help assess the neural foramina, facet alignment, subluxation, and facet dislocation.

They are particularly helpful in selected cases when foraminal anatomy requires further evaluation.

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Open-Mouth Odontoid View

The open-mouth view is used to assess the odontoid process, atlantoaxial joints, and alignment of the lateral masses of C1 relative to C2.

Asymmetry may indicate fracture, displacement, or rotational injury.

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Pediatric Radiographs

In young children, normal ossification centers and developmental variants may resemble fractures.

Knowledge of age-related cervical spine anatomy is therefore essential to avoid misinterpreting normal findings as traumatic injury.

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MRI

MRI is the preferred modality for evaluating soft-tissue structures of the cervical spine.

It provides detailed visualization of the intervertebral discs, spinal cord, nerve roots, ligaments, joint capsules, and other neural and soft-tissue structures.

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Clinical Role of MRI

MRI findings should be correlated with the patient’s symptoms and physical examination because asymptomatic degenerative abnormalities are common.

It is particularly valuable when evaluating disc herniation, spinal stenosis, ligamentous injury, spinal cord compression, and myelopathy.

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CT

CT provides excellent definition of cervical osseous anatomy.

It can rapidly and accurately identify fractures, facet injuries, displacement, and complex bony abnormalities.

For suspected cervical spine trauma, CT is particularly useful for fracture characterization and surgical planning.

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Integration of Examination and Imaging

Cervical spine assessment requires correlation of history, physical examination, neurologic findings, provocative testing, and imaging.

No single examination maneuver or imaging abnormality should be interpreted in isolation.

A systematic approach is particularly important when distinguishing cervical radiculopathy, myelopathy, structural injury, and peripheral nerve disease.