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Chapter Summary
• Context: Cervical spine deformities (CSD) encompass a heterogeneous spectrum of sagittal and coronal multiplanar malalignments capable of impairing head posture, horizontal gaze, neurological function, and basic activities of daily living including ambulation, swallowing, respiration, and hygiene. They arise from iatrogenic post-surgical instability, degenerative spondylosis, trauma, congenital anomalies, tumors, infections, or inflammatory conditions (ankylosing spondylitis), and frequently represent compensatory adjustments to thoracolumbar deformities. The cervical region presents distinct biomechanical vulnerabilities due to its high mobility, transitional cervicothoracic junction, intimacy with the spinal cord and vertebral arteries, and constant demand to maintain the head balanced over the pelvis. Consequently, cervical deformity cannot be interpreted by local Cobb angle alone: etiology, curve flexibility, spinopelvic balance, primary versus secondary drivers, neurological status, and functional disability must be analyzed to guide observation, conservative therapy, or reconstructive surgery.
• Chapter Objective: To present the anatomical, biomechanical, clinical, and radiographic foundations of cervical spine deformities. The reader will master etiology identification, interpret key cervical and global alignment parameters (T1 slope, cervical lordosis, cSVA, CBVA), differentiate flexible from rigid deformities, apply classificatory systems, select appropriate imaging (including CTA for vertebral artery course), and master anterior, posterior, or combined surgical approaches, cervical osteotomies, and complication prevention.
• The cervical spine within global spinopelvic alignmentThe primary biomechanical function of the cervical spine is supporting the head and maintaining horizontal gaze with minimal muscular expenditure. When cervical lordosis is lost, muscular fatigue and pain escalate. Cervical alignment operates reciprocally with thoracic kyphosis, lumbar lordosis, and pelvic tilt. The chapter utilizes parameters including T1 slope, cervical lordosis (C2-C7), cervical sagittal vertical axis (cSVA), and the chin-brow vertical angle (CBVA) to evaluate alignment. Deformity may be primary cervical pathology or a secondary compensation for distal thoracic or lumbar flatback.
• Etiology dictates mechanism and surgical strategyPost-laminectomy iatrogenic kyphosis is highlighted as a major cause, resulting from posterior tension band disruption. Degenerative disease, ossification of the posterior longitudinal ligament (OPLL), trauma, congenital hemivertebrae, and inflammatory spondyloarthropathies also cause severe deformities. Figure 41.1 demonstrates a rigid chin-on-chest deformity in ankylosing spondylitis. Figures 41.5 to 41.7 illustrate coronal etiologies including Grisel syndrome, congenital torticollis, and cervical hemivertebrae.
• Spinal cord and vertebral artery anatomy condition surgical safetyProgressive cervical kyphosis causes myelopathy not only through direct anterior bony compression, but also via increased longitudinal spinal cord tension—the 'stretching myelopathy' concept (Figure 41.3). The course of the vertebral artery is equally critical; anatomical variations, tortuosity, or intraosseous loops directly impact the safety of pedicle screw placement and osteotomies. Figure 41.2 shows a vertebral artery anomaly identified by CT angiography, underscoring vascular mapping in complex reconstructions.
• Classifying morphology, driver location, and flexibilityThe chapter reviews classification frameworks that categorize deformities by apex location (cervical vs cervicothoracic), coronal component, and rigidity (Table 41.1). Standing full-spine radiographs assess global reciprocal alignment; dynamic flexion-extension views test flexibility; CT details osseous bridges and pedicle channels; MRI evaluates cord compression and signal change; and CT angiography visualizes vertebral arteries.
• Proportional reconstructive surgeryMild or flexible deformities can be managed conservatively or with anterior-only procedures (ACDF/corpectomy). Rigid deformities require osteotomies scaled to the deformity apex and rigidity: posterior facet releases, anterior uncinate osteotomies, or three-column pedicle subtraction osteotomy (PSO) / vertebral column resection (VCR) at C7 or T1. Figures 41.8 to 41.10 illustrate post-laminectomy reconstructions and three-column osteotomies. The central rule is performing the least invasive procedure capable of restoring horizontal gaze, neural decompression, and biomechanical stability.
• Clinical Application: In clinical practice, cervical deformity evaluation must begin with the patient in a functional standing position, evaluating horizontal gaze, swallowing, respiration, and myelopathy (gait, hand dexterity, hyperreflexia). Imaging must encompass the entire spine; a cervical kyphosis is frequently a compensatory response to thoracic hyperkyphosis or lumbar flatback. Correcting the neck without addressing lumbar flatback leads to construct failure and catastrophic junctional breakdown. T1 slope, cSVA, and CBVA define whether the deformity is primary cervical or reciprocal. Dynamic radiographs determine flexibility: flexible curves can be corrected via anterior discectomies/corpectomies with posterior fixation, whereas rigid ankylosed curves require formal osteotomies (PCO, anterior osteotomies, or C7/T1 PSO). CT angiography is mandatory before high-grade osteotomies or instrumentation near anomalous vertebral arteries. The ultimate goal is restoring horizontal gaze (CBVA between -10° and +10°) and neurological decompression while preventing distal junctional kyphosis.
