Anterolisthesis of C4 on C5: understanding the condition

Anterolisthesis of the fourth cervical vertebra on the fifth represents a significant spinal pathology that affects the delicate biomechanical balance of the cervical spine. This condition, characterised by the forward displacement of C4 relative to C5, presents unique clinical challenges due to the critical anatomical structures within this region. The C4-C5 segment bears considerable responsibility for cervical spine mobility whilst simultaneously protecting vital neurological structures, making any instability at this level potentially consequential.

Understanding this condition requires a comprehensive grasp of cervical spine biomechanics, pathophysiological processes, and the intricate relationship between structural integrity and neurological function. The complexity of C4-C5 anterolisthesis extends beyond simple vertebral displacement, encompassing a cascade of degenerative changes that can profoundly impact quality of life. Healthcare professionals must recognise the subtle early manifestations and understand the progression patterns to provide optimal patient care.

Anatomical structure and biomechanics of C4-C5 vertebral segment

The C4-C5 vertebral segment represents a transitional zone within the cervical spine, exhibiting unique anatomical characteristics that distinguish it from both upper cervical segments and the cervicothoracic junction. This level demonstrates the typical subaxial cervical vertebral morphology, with rectangular vertebral bodies, bifid spinous processes, and distinctive uncovertebral joints that contribute to the segment’s biomechanical behaviour.

Cervical spine architecture and facet joint configuration at C4-C5 level

The facet joints at the C4-C5 level maintain an orientation of approximately 45 degrees to the horizontal plane, facilitating the complex multiplanar motion characteristic of the cervical spine. These synovial joints possess thin joint capsules that allow considerable mobility but provide relatively limited inherent stability compared to thoracolumbar segments. The facet joint orientation at this level permits significant flexion-extension motion whilst constraining lateral bending and axial rotation to a lesser degree.

The vertebral bodies at C4 and C5 exhibit the typical cervical lordotic curvature, with C4 being slightly smaller than C5. The superior endplate of C5 demonstrates a subtle concavity that accepts the convex inferior endplate of C4, creating the interbody articulation. This configuration, combined with the uncinate processes, forms the uncovertebral joints of Luschka, which provide additional stability and guide motion patterns whilst potentially contributing to degenerative changes over time.

Intervertebral disc characteristics and load distribution mechanisms

The C4-C5 intervertebral disc represents one of the more substantial discs in the cervical spine, reflecting the increased load-bearing requirements at this level. The disc height typically measures 4-5 millimetres in healthy individuals, with the nucleus pulposus positioned slightly posteriorly compared to lumbar discs. This posterior positioning influences the disc’s response to loading patterns and its susceptibility to posterior migration during degenerative processes.

Load distribution through the C4-C5 segment demonstrates complex patterns influenced by head position and cervical spine posture. During neutral positioning, approximately 36% of axial loads transmit through the intervertebral disc, whilst the remaining load distributes through the facet joints and supporting ligamentous structures. Forward head posture, increasingly common in modern society, significantly alters these load distribution patterns, potentially accelerating degenerative changes at the C4-C5 level.

Ligamentous support systems: anterior longitudinal and posterior longitudinal ligaments

The ligamentous architecture surrounding the C4-C5 segment provides crucial stability whilst permitting physiological motion. The anterior longitudinal ligament at this level demonstrates robust attachment to the vertebral bodies and intervertebral disc, providing resistance to excessive extension movements. This ligament becomes particularly important in preventing anterolisthesis, as its integrity directly influences anterior translation stability.

The posterior longitudinal ligament, whilst thinner than its anterior counterpart, plays a vital role in constraining flexion movements and preventing posterior disc migration. At the C4-C5 level, this ligament exhibits a characteristic narrowing as it approaches the intervertebral disc space, creating potential weak points that may contribute to disc herniation patterns. The ligamentum flavum, capsular ligaments, and interspinous ligaments complete the ligamentous complex, each contributing specific biomechanical properties to segmental stability.

Neurological structures: spinal cord and C5 nerve root anatomy

The spinal cord at the C4-C5 level maintains its oval configuration with dimensions typically measuring 10-12 millimetres in the anteroposterior direction and 13-14 millimetres transversely. At this level, the cord contains crucial neural pathways including descending motor tracts and ascending sensory pathways that serve the upper and lower extremities. The cervical enlargement begins around C4, reflecting the increased neural tissue associated with upper extremity innervation.

The C5 nerve root emerges from the spinal canal through the C4-C5 foramen, making it particularly vulnerable to compromise in cases of anterolisthesis. This nerve root contributes to the formation of the brachial plexus and specifically innervates the deltoid, biceps, and several other muscles crucial for shoulder and elbow function. Understanding the anatomical course and vulnerability of the C5 nerve root proves essential for recognising clinical presentations of C4-C5 anterolisthesis.

Pathophysiology and classification systems of C4-C5 anterolisthesis

The pathophysiological development of C4-C5 anterolisthesis involves a complex interplay of biomechanical factors, degenerative processes, and structural failure patterns. Unlike lumbar spondylolisthesis, cervical anterolisthesis typically results from degenerative changes rather than congenital abnormalities or acute trauma. The process often begins with disc degeneration, which alters the normal load distribution patterns and places increased stress on the facet joints and supporting ligamentous structures.

Meyerding grading scale application for cervical anterolisthesis assessment

The Meyerding classification system, traditionally applied to lumbar spondylolisthesis, requires modification for cervical spine application due to the different anatomical proportions and clinical significance of displacement at cervical levels. Grade I anterolisthesis, representing less than 25% anterior displacement of C4 on C5, may produce significant neurological symptoms due to the smaller dimensions of the cervical spinal canal compared to lumbar levels.

Grade II displacement (25-50%) at the C4-C5 level often correlates with more severe clinical presentations, including cervical myelopathy signs and progressive neurological deterioration. Grade III and IV displacements remain rare at cervical levels, as the inherent stability provided by the facet joint orientation and ligamentous structures typically prevents such severe displacement without associated fracture or significant trauma. The clinical significance of each grade requires careful correlation with imaging findings and neurological examination results.

Degenerative cascade theory and Kirkaldy-Willis model in cervical spine

The Kirkaldy-Willis degenerative cascade model, whilst originally described for lumbar spine pathology, demonstrates relevance to cervical spine degeneration with certain modifications. The initial dysfunction phase involves repetitive microtrauma and altered biomechanics that begin the degenerative process. At the C4-C5 level, this often manifests as early disc degeneration with loss of proteoglycan content and subsequent height loss.

The instability phase follows, characterised by progressive ligamentous laxity and facet joint degeneration that permits abnormal motion patterns. During this phase, anterolisthesis may develop as the normal constraints to anterior translation become compromised. The final stabilisation phase involves osteophyte formation and ankylosis that may paradoxically reduce symptoms whilst limiting motion. Understanding this progression helps predict clinical course and guide treatment decisions for patients with C4-C5 anterolisthesis.

Biomechanical failure patterns: facet joint degeneration and capsular laxity

Facet joint degeneration at the C4-C5 level follows predictable patterns that contribute to anterolisthesis development. Initial cartilage fibrillation progresses to subchondral sclerosis and osteophyte formation, altering the joint’s biomechanical properties. The thin facet joint capsules become increasingly lax through repetitive loading, reducing their ability to constrain abnormal motion.

Capsular laxity permits excessive anterior translation during flexion movements, whilst concurrent disc degeneration reduces the restraining force normally provided by an intact disc-ligament complex. This biomechanical failure pattern creates a self-perpetuating cycle where increased abnormal motion accelerates further degeneration. The facet joints at C4-C5 may demonstrate asymmetric degeneration, leading to coupled motions that complicate the clinical picture and influence treatment planning.

White and panjabi stability criteria for cervical spine instability

The White and Panjabi stability criteria provide objective measures for assessing cervical spine instability, though their application to C4-C5 anterolisthesis requires careful interpretation. These criteria include anterior translation greater than 3.5 millimetres on flexion-extension radiographs, angular displacement exceeding 11 degrees between adjacent segments, and various combinations of radiographic parameters that suggest instability.

However, you must consider that the original criteria were developed using static radiographs and may not capture the dynamic instability patterns present in many patients with symptomatic C4-C5 anterolisthesis. Modern understanding emphasises the importance of functional imaging and clinical correlation rather than relying solely on radiographic measurements. The criteria serve as useful guidelines but must be integrated with clinical findings and dynamic studies for comprehensive assessment.

Aetiological factors and risk stratification for C4-C5 anterolisthesis

The development of C4-C5 anterolisthesis involves multiple aetiological factors that interact in complex ways to produce the clinical condition. Age-related degenerative changes represent the predominant causative factor, with the incidence increasing significantly after the fifth decade of life. The C4-C5 segment experiences considerable mechanical stress throughout daily activities, making it particularly susceptible to degenerative changes compared to other cervical levels.

Occupational factors play a substantial role in disease development, with individuals engaged in repetitive cervical flexion activities demonstrating higher incidence rates. Computer-based work, which promotes sustained forward head postures, creates chronic loading patterns that accelerate disc degeneration and facet joint arthritis. Studies suggest that workers maintaining forward head postures for more than six hours daily exhibit a three-fold increased risk of developing symptomatic cervical spondylolisthesis.

Genetic predisposition influences collagen metabolism and disc composition, affecting individual susceptibility to degenerative changes. Certain genetic polymorphisms associated with collagen IX and aggrecan genes may predispose individuals to accelerated disc degeneration. Additionally, congenital variations in cervical spine anatomy, such as narrow spinal canals or atypical facet joint orientations, may increase vulnerability to symptomatic anterolisthesis even with minor degrees of displacement.

Trauma, whilst less commonly causative of degenerative anterolisthesis, can accelerate the degenerative cascade through disruption of normal biomechanical relationships. Previous cervical spine injuries, including whiplash-associated disorders, may initiate inflammatory processes that contribute to long-term structural changes. The role of previous surgical interventions at adjacent levels must also be considered, as altered biomechanics following cervical fusion can increase stress at the C4-C5 level, potentially promoting anterolisthesis development.

Clinical presentation and neurological manifestations

The clinical presentation of C4-C5 anterolisthesis demonstrates considerable variability, ranging from asymptomatic structural abnormalities discovered incidentally to severe neurological compromise requiring urgent intervention. Early manifestations often include mechanical neck pain that worsens with specific movements or sustained postures. Patients frequently describe stiffness and reduced range of motion, particularly affecting cervical extension and lateral rotation movements.

Cervical radiculopathy patterns: C5 nerve root distribution symptoms

C5 radiculopathy resulting from C4-C5 anterolisthesis produces a characteristic pattern of symptoms that affects shoulder and upper arm function. Patients typically experience pain radiating from the neck into the shoulder region, often described as deep, aching discomfort that may extend to the lateral aspect of the upper arm. The pain pattern follows the C5 dermatome distribution, though overlap with adjacent nerve roots can complicate clinical localisation.

Motor weakness involving C5 innervated muscles becomes apparent through careful examination, with deltoid and biceps weakness being most commonly identified. Patients may report difficulty with overhead activities and reduced strength when lifting objects away from their body. The weakness pattern helps distinguish C5 radiculopathy from other cervical nerve root pathologies and guides appropriate imaging studies to confirm the diagnosis.

Sensory changes in C5 radiculopathy typically involve the lateral shoulder and upper arm region, though sensory symptoms may be less prominent than motor and pain manifestations. Paraesthesias and numbness in the lateral deltoid distribution provide additional diagnostic clues when present. The combination of motor, sensory, and pain symptoms creates the complete clinical picture that suggests C5 nerve root compromise secondary to C4-C5 anterolisthesis.

Cervical myelopathy signs: hoffmann’s reflex and inverted radial reflex

Cervical myelopathy represents the most serious potential consequence of C4-C5 anterolisthesis, occurring when spinal cord compression develops secondary to vertebral displacement and associated degenerative changes. Early myelopathy may present subtly, with patients experiencing clumsiness of hand movements, difficulty with fine motor tasks, and gait disturbances that may be attributed to other causes.

Hoffmann’s reflex, elicited by flicking the terminal phalanx of the middle finger, provides a sensitive indicator of cervical myelopathy when present bilaterally. The reflex indicates upper motor neuron dysfunction and suggests significant spinal cord compromise requiring urgent evaluation. However, you should interpret positive Hoffmann’s reflexes carefully, as they may occasionally occur in asymptomatic individuals or those with other neurological conditions.

The inverted radial reflex represents another pathognomonic sign of cervical myelopathy, particularly at the C5-C6 level, though it may also indicate compromise at C4-C5 with cord compression. This reflex involves finger flexion instead of the normal biceps contraction when testing the brachioradialis reflex. The presence of inverted reflexes strongly suggests cervical myelopathy and warrants immediate imaging studies to assess for spinal cord compression.

Mechanical neck pain characteristics and referred pain patterns

Mechanical neck pain associated with C4-C5 anterolisthesis exhibits specific characteristics that help distinguish it from other cervical pathologies. The pain typically worsens with cervical extension movements and improves with flexion positioning. Patients often report increased discomfort when looking upward or maintaining extended neck positions for prolonged periods.

Referred pain patterns may extend beyond the typical C5 distribution, involving the occipital region, interscapular area, and occasionally the anterior chest wall. These atypical pain patterns can confuse the clinical picture and lead to misdiagnosis if not properly recognised. The referred pain results from convergence patterns within the cervical spinal segments and shared innervation of various anatomical structures.

Morning stiffness represents another characteristic feature, with patients reporting significant neck stiffness upon awakening that gradually improves throughout the day. This pattern reflects the inflammatory component of the degenerative process and the effects of prolonged static positioning during sleep. Activity modification and appropriate ergonomic adjustments often provide significant symptom relief for patients with mechanical neck pain secondary to C4-C5 anterolisthesis.

Spurling’s test and cervical compression manoeuvres diagnostic utility

Spurling’s test represents a fundamental examination technique for evaluating suspected cervical radiculopathy in patients with C4-C5 anterolisthesis. The test involves extending the neck, laterally flexing toward the symptomatic side, and applying axial compression to reproduce radicular symptoms. A positive test strongly suggests nerve root compression and helps localise the pathology to the appropriate cervical level.

The sensitivity and specificity of Spurling’s test for cervical radiculopathy range from 50-95% and 85-100% respectively

, depending on the specific technique employed and the experience of the examining clinician. The test’s diagnostic value increases when combined with other clinical findings and imaging studies to provide comprehensive assessment of nerve root compromise.

Cervical compression manoeuvres extend beyond the traditional Spurling’s test to include various modifications that may enhance diagnostic accuracy. The shoulder abduction test involves having the patient place their hand on top of their head, which may relieve radicular symptoms by reducing tension on the affected nerve root. Relief of symptoms with this manoeuvre supports the diagnosis of cervical radiculopathy and suggests that nerve root compression is the primary source of symptoms.

Additional provocative tests include the cervical distraction test, where manual traction is applied to the head and neck whilst monitoring symptom response. Improvement with distraction suggests mechanical compression of neural structures that may benefit from conservative treatments involving cervical traction. These examination techniques, when used in combination, provide valuable clinical information that guides diagnostic imaging decisions and treatment planning for patients with suspected C4-C5 anterolisthesis.

Advanced imaging protocols and radiological assessment techniques

Radiological assessment of C4-C5 anterolisthesis requires a systematic approach utilising multiple imaging modalities to fully characterise the pathology and guide treatment decisions. Plain radiographs serve as the initial imaging study, providing essential information about vertebral alignment, disc space height, and overall cervical spine curvature. Lateral cervical spine radiographs in neutral positioning allow measurement of anterior displacement using established criteria, typically requiring displacement greater than 2-3 millimetres to be considered significant.

Flexion-extension radiographs represent a crucial component of the imaging evaluation, revealing dynamic instability patterns that may not be apparent on static films. These studies demonstrate the degree of abnormal motion occurring at the C4-C5 segment during physiological movements. Dynamic imaging may reveal anterolisthesis that increases substantially during flexion, indicating significant ligamentous incompetence and segmental instability requiring more aggressive treatment approaches.

Magnetic resonance imaging provides superior soft tissue contrast and detailed visualisation of neural structures, making it indispensable for evaluating patients with neurological symptoms. MRI demonstrates disc degeneration patterns, ligamentous injury, spinal cord morphology, and nerve root compression with exceptional clarity. T2-weighted sagittal images reveal disc hydration status and posterior disc bulging, whilst T1-weighted images provide excellent anatomical detail of vertebral body alignment and marrow signal characteristics.

Advanced MRI techniques, including diffusion tensor imaging and functional MRI, offer emerging possibilities for assessing spinal cord integrity and function in patients with cervical myelopathy. These techniques may detect subtle spinal cord changes before they become apparent on conventional imaging, potentially allowing earlier intervention in selected cases. However, their clinical utility remains under investigation, and conventional MRI sequences continue to provide the primary diagnostic information for most patients.

Computed tomography scanning excels at demonstrating bony anatomy and may reveal subtle fractures or congenital abnormalities not visible on plain radiographs. CT imaging proves particularly valuable when evaluating patients with trauma-related anterolisthesis or when assessing bone quality prior to surgical intervention. Three-dimensional CT reconstruction provides excellent visualisation of complex anatomical relationships and assists in surgical planning when intervention becomes necessary.

Multiplanar CT reconstruction allows detailed assessment of facet joint orientation and degenerative changes that contribute to segmental instability. The ability to visualise bone anatomy from multiple perspectives enhances understanding of the pathological process and helps identify concurrent pathologies such as uncovertebral joint arthritis or neural foraminal stenosis. CT myelography remains useful in selected cases where MRI is contraindicated or provides insufficient detail of neural compression patterns.

Evidence-based treatment algorithms and surgical intervention strategies

Treatment of C4-C5 anterolisthesis follows evidence-based algorithms that consider symptom severity, neurological involvement, degree of instability, and patient-specific factors. Conservative management remains the first-line treatment for most patients, particularly those with mild displacement and minimal neurological symptoms. The conservative approach typically involves activity modification, anti-inflammatory medications, physical therapy, and careful monitoring for symptom progression or development of neurological complications.

Pharmacological management begins with non-steroidal anti-inflammatory drugs to address the inflammatory component of the degenerative process and provide pain relief. Muscle relaxants may prove beneficial for patients experiencing significant cervical muscle spasm, whilst neuropathic pain medications such as gabapentin or pregabalin can help manage radicular symptoms when present. Corticosteroid injections, either epidural or facet joint injections, may provide temporary symptom relief and help identify pain generators for targeted treatment approaches.

Physical therapy protocols for C4-C5 anterolisthesis focus on strengthening the deep cervical flexors, improving posture, and maintaining cervical spine mobility within safe ranges. Cervical stabilisation exercises help develop muscular support for the compromised segment, potentially reducing symptoms and preventing progression. Manual therapy techniques, including gentle mobilisation and soft tissue treatments, may provide additional symptomatic relief when applied by experienced practitioners.

Cervical traction represents a controversial treatment modality with mixed evidence regarding its effectiveness. Some patients experience significant symptom relief with intermittent cervical traction, whilst others may experience symptom exacerbation. The decision to utilise traction requires careful patient selection and close monitoring of response, with discontinuation recommended if symptoms worsen. Modern traction protocols typically employ lighter forces and shorter duration treatments compared to historical approaches.

Surgical intervention becomes necessary when conservative treatments fail to control symptoms or when progressive neurological deterioration occurs. The primary surgical goals include decompression of neural structures, restoration of spinal alignment, and achievement of segmental stability through fusion techniques. Anterior cervical discectomy and fusion represents the most commonly performed procedure for C4-C5 anterolisthesis, providing direct access to compressed neural structures whilst allowing restoration of disc height and lordotic alignment.

The anterior approach offers several advantages, including excellent visualisation of the disc space, ability to remove degenerative disc material completely, and restoration of neuroforaminal dimensions through appropriate graft placement. Interbody fusion using structural bone graft or modern cage devices provides immediate stability whilst promoting long-term fusion. The addition of anterior plating systems enhances construct stability and may improve fusion rates, though their necessity in single-level procedures remains debated.

Posterior cervical fusion techniques may be considered when significant facet joint pathology exists or when anterior approaches are contraindicated. Posterior fusion provides excellent biomechanical stability but requires more extensive soft tissue dissection and may result in greater postoperative pain. Modern posterior techniques utilise lateral mass or pedicle screw fixation systems that provide superior biomechanical properties compared to traditional wiring techniques.

Combined anterior-posterior approaches may be necessary in cases of severe instability or when single-approach procedures fail to achieve adequate stability. These circumferential fusion procedures provide maximum biomechanical stability but involve increased surgical morbidity and longer recovery periods. Patient selection for combined approaches requires careful consideration of symptom severity, degree of instability, and overall medical condition to ensure favourable risk-benefit ratios.

Surgical outcomes for C4-C5 anterolisthesis generally demonstrate favourable results when appropriate patient selection criteria are applied. Fusion rates exceed 90% with modern techniques, whilst neurological improvement occurs in the majority of patients with preoperative deficits. However, adjacent segment degeneration represents a long-term concern, with studies suggesting acceleration of degenerative changes at levels adjacent to fusion constructs. Motion-preserving technologies, including artificial disc replacement, offer theoretical advantages but require long-term studies to establish their role in treating anterolisthesis.

Postoperative care involves gradual mobilisation with appropriate cervical orthoses to protect the fusion construct during early healing phases. Physical therapy typically begins several weeks after surgery, focusing initially on range of motion exercises before progressing to strengthening activities. Long-term follow-up remains essential to monitor fusion progress, assess for complications, and detect adjacent segment pathology that may develop over time. Patient education regarding activity restrictions and signs of potential complications ensures optimal outcomes and early recognition of problems requiring intervention.