Cervical Spondylosis

Definition

Cervical spondylosis describes the age-related degenerative cascade affecting the cervical spine, involving intervertebral discs, vertebral bodies (osteophytes), facet joints, and ligaments. It represents a spectrum from asymptomatic radiographic findings to debilitating myelopathy.

Epidemiology

• Prevalence: Increases linearly with age. 25% at age 40, over 85% at age 60.
• Risk Factors:
  • Non-Modifiable: Age (primary), Genetics (family history of early degeneration).
  • Modifiable: Smoking (accelerates disc desiccation), Heavy labor (axial loading), Vibration exposure (jackhammering), Contact sports.
  • Trauma History: Previous whiplash or cervical injury often initiates the cascade early.
• Natural History: Generally benign. Most symptomatic cases resolve or stabilize. Myelopathy is the exception (stepwise deterioration).

Pathophysiology

The process begins with disc desiccation (loss of water content). This leads to:

1. Loss of disc height: Which reduces the tension on the annular fibers and ligaments.
2. Segmental Instability: The vertebral bodies move more than normal ("wobble").
3. Osteophyte Formation: The body responds to this instability by forming bony spurs (osteophytes) to increase surface area and restabilize the joint.
4. Uncinate Hypertrophy: The Uncovertebral joints carry more load as the disc collapses, leading to osteophytes that project into the foramen (Radiculopathy).
5. Facet Hypertrophy: Posterior joints degenerate, causing pain and encroaching on the canal.
6. Ligamentum Flavum Buckling: With loss of height, the ligamentum flavum becomes redundant and buckles inward, compressing the cord from behind (Myelopathy).

OPLL (Ossification of Posterior Longitudinal Ligament):

• A distinct but related pathology often co-existing, particularly in Asian populations (Japanese/Korean).
• Causes severe, hard compression of the anterior cord.
• Risk: Hard to remove anteriorly (dural tear risk is high as ossification can merge with dura).
• Presence of OPLL often dictates a posterior approach (Laminoplasty) or corpectomy to avoid dural tear.

The Degenerative Cascade (Kirkaldy-Willis)

Key Anatomy

Ligamentous Structures:

• Anterior Longitudinal Ligament (ALL): Strong broad band. Prevents hyperextension. Often site of large anterior osteophytes (DISH).
• Posterior Longitudinal Ligament (PLL): Narrower band behind bodies. Prevents hyperflexion. Can ossify (OPLL) causing stenosis.
• Ligamentum Flavum: Connects laminae. Elastic (yellow). Hypertrophy or buckling in extension causes posterior cord compression.

Neural Foramen Boundaries:

• Anterior: Uncovertebral joint, disc, vertebral body (posterior aspect).
• Posterior: Facet joint (Superior articular process of lower vertebra), ligamentum flavum.
• Superior/Inferior: Pedicles of the levels above and below.
• Contents: Exiting nerve root (Dorsal Root Ganglion is usually in the foramen), radicular artery, venous plexus.
• Pathology: Osteophytes from the uncinate process compress the nerve root from the Anterior direction. Facet hypertrophy compresses from Posterior.

Spinal Canal Dimensions:

• Normal: 17-18mm
• Relative Stenosis: less than 13mm (watch for symptoms)
• Absolute Stenosis: less than 10mm (high risk of cord injury)
• Cord Compression: less than 8mm effective diameter. The ratio of canal diameter to vertebral body diameter (Torg Ratio) less than 0.8 suggests stenosis, but has high false positive rate; absolute measurement on MRI is preferred.

Blood Supply of the Cord:

• Anterior Spinal Artery: Supplies anterior 2/3 of cord (motor tracks, spinothalamic). Prone to compression from anterior osteophytes or disc herniations.
• Posterior Spinal Arteries: Supply posterior columns (proprioception). Paired vessels.
• Watershed: The gray matter is highly vascular, but the watershed zone makes the anterior cord susceptible to ischemia from compression (osteophytes). This contributes to the pathophysiology of CSM (Cervical Spondylotic Myelopathy).
• Radicular Arteries: Enter via the foramen. The largest is the Artery of Adamkiewicz (usually T9-L1, but can be higher).

Vertebral Artery:

• Ascends in the transverse foramen from C6 to C1.
• Note: It usually skips C7 transverse foramen (enters at C6).
• Segments: V1 (Pre-foraminal), V2 (Foraminal C6-C2), V3 (Extradural/Atlas loop), V4 (Intradural).
• Vulnerable to injury during lateral dissection or screw insertion (lateral mass/pedicle).
• Dominance: Left is often larger than Right. Occlusion of a dominant artery can be fatal (Wallenberg syndrome/Stroke).

History

Differentiate the three main syndromes:

Differential Diagnosis

Double-crush phenomenon: concurrent proximal (cervical root) and distal (e.g. carpal tunnel) compression can produce symptoms greater than either lesion alone — always examine the whole limb.

Physical Examination

Provocative Tests:

• Spurling Test: Extension + Lateral Rotation + Axial Load. Positive = Radicular pain. High specificity (93%).
• Shoulder Abduction Test (Bakody): Relief of arm pain with hand on head = C5/C6 radiculopathy (relieves tension).
• Lhermitte's Sign: Shock sensation down spine on flexion = Myelopathy/Cord compression.
• Finger Escape Sign: Unable to hold fingers extended and adducted (Myelopathy, C8/T1 weakness).
• Grip and Release Test: Normal is 20 times in 10 seconds. Slower in myelopathy.
• Inverted Radial Reflex: Tapping supinator causes finger flexion instead of wrist/supinator reflex. Indicates C5/6 cord compression.
• Valsalva Maneuver: Increases intrathecal pressure, aggravating radiculopathy.

Neurological Assessment:

• C5: Deltoid (Motor), Lateral Arm (Sensory), Biceps (Reflex).
• C6: Wrist Ext (Motor), Thumb index (Sensory), Brachioradialis (Reflex).
• C7: Triceps (Motor), Middle finger (Sensory), Triceps (Reflex).
• C8: Finger Flex (Motor), Little finger (Sensory).
• T1: Interossei (Motor), Medial forearm (Sensory).

Imaging Algorithm

Multimodal Imaging Examples

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Dysphagia:

• Most common complaint (up to 70% transient).
• Prevention: Minimize retractor pressure, intermittent relaxation of retractors, use endotracheal tube cuff deflation during retraction.
• Management: Reassurance (most resolve), Speech pathology review, Nasogastric tube if severe aspiration risk, Steroids (dexamethasone) intra-op may help edema. chronic dysphagia is rare.

Adjacent Segment Disease (ASD):

• Rate: ~2.9% per year (clinical), up to 92% radiographic at long term.
• Cause: Increased existing stress at levels above/below fusion.
• Management: Conservative initially, extension of fusion if symptomatic.

C5 Palsy:

• Incidence: 5% in posterior decompression (Laminoplasty/Laminectomy), less common in ACDF.
• Pathophysiology: Posterior drift of the cord tethers the C5 root (which has a shorter, more direct course) causing traction injury. Also reperfusion injury.
• Prognosis: Good. Most resolve spontaneously over 6-12 months.

Other Major Risks:

• Recurrent Laryngeal Nerve (RLN) Palsy: Hoarseness. 1-2%. More common on Right side (nerve is variable). ENT scope if persistent.
• Esophageal Injury: Rare but catastrophic. Can lead to mediastinitis. Immediate repair vs flap. Early recognition is key.
• Vertebral Artery Injury: Rare. Can occur during drilling or screw insertion. Tamponade vs sacrifice (if contralateral patent).
• Horner's Syndrome: Sympathetic chain injury (ptosis, miosis, anhidrosis).
• Dural Tear: Risk of CSF leak. Repair primarily or use patch/sealant. Bed rest/Drain.

Global Epidemiology

Degenerative cervical myelopathy (DCM) is the most common cause of non-traumatic spinal cord dysfunction in adults worldwide, a point emphasised by both the AOSpine/CSRS clinical practice guideline (Fehlings et al, 2017) and the AOSpine North America cohort. Radiographic spondylosis rises steeply with age and is near-universal in older adults, yet only a minority become symptomatic. Ossification of the posterior longitudinal ligament (OPLL) is a major contributor to cervical stenosis in East Asian populations (notably Japan and Korea) and shifts surgical decision-making toward posterior or corpectomy strategies.

Side-by-Side Guidance

Registry & Practice Variation

Spine procedures are tracked in national datasets such as the British Spine Registry and various European spine registries, which consistently show that ACDF and posterior decompression are the dominant constructs, with cervical disc arthroplasty used selectively for single-level disease in younger patients. Practice varies internationally: a higher prevalence of OPLL drives greater use of laminoplasty in Japan and Korea, whereas anterior approaches predominate for focal one- to two-level pathology elsewhere. Across systems, progressive myelopathy is prioritised for earlier surgery over isolated axial pain.

Medication & Rehabilitation Notes

Neuropathic agents (gabapentin, pregabalin) are used for radicular pain but show modest benefit and carry sedation and misuse risk; access is restricted under several national subsidy schemes (for example, authority requirements under the Australian PBS). Opioids are discouraged for chronic non-cancer neck pain in favour of multidisciplinary, exercise-based rehabilitation. High-velocity cervical manipulation should be avoided where myelopathy or instability is suspected.

Return to Driving

Patients should not drive in a rigid collar and should resume driving only when able to comfortably rotate the head to check blind spots and perform an emergency stop — typically a few weeks postoperatively, guided by local licensing authority advice (for example, Austroads in Australia or DVLA in the UK).