Congenital Spine Anomalies. Congenital Scoliosis. Klippel-Feil Syndrome. Cervical Ribs. Spina Bifida.

Introduction

Congenital spine anomalies arise from disturbances of embryological vertebral and spinal- cord development between approximately the third and tenth weeks of gestation. They encompass a wide spectrum: from minor variants without clinical consequence — accessory cervical ribs, transitional vertebrae — to severe deformities producing progressive scoliosis and neurological impairment, to the dysraphic states (myelomeningocele, meningocele, spina bifida occulta) that combine vertebral malformation with overt or covert neural tube defects. This chapter, synthesizing content from Rothman-Simeone The Spine, Tachdjian’s Pediatric Orthopaedics, Apley & Solomon’s, and Miller’s Review, addresses congenital vertebral anomalies producing scoliosis, congenital kyphosis, Klippel-Feil syndrome of cervical vertebral fusion, cervical ribs and their thoracic outlet implications, and the spectrum of dysraphic states.

Embryological Background

The vertebral column develops from the paraxial mesoderm, which forms paired somites in cranio-caudal sequence between weeks 3 and 5 of gestation. Each somite divides into a dermatome (skin), myotome (muscle), and sclerotome (vertebra). The sclerotome subsequently divides into a cranial and caudal half, and the vertebrae are formed by fusion of the caudal half of one somite with the cranial half of the next caudal somite — the process of resegmentation. This intricate sequence produces vertebrae and adjacent muscles in different segmental positions, with the spinal nerves emerging between vertebrae. The neural tube closes between days 22 and 28 of gestation; failure of closure produces the dysraphic disorders. Disturbances of sclerotome formation, division, or resegmentation produce the spectrum of failure of formation (hemivertebrae, wedge vertebrae) and failure of segmentation (block vertebrae, unilateral unsegmented bars) that underlie congenital scoliosis.

Congenital Scoliosis

Classification and Pathogenesis Congenital scoliosis is scoliosis arising from anomalous vertebral development, in contrast to idiopathic scoliosis (in which the vertebrae form normally but become deformed by an unknown developmental process). The defects are classified into three categories: failures of formation, failures of segmentation, and mixed defects. Failures of formation: A wedge vertebra is a partially formed vertebra with only one ossification center developed, producing a hemivertebra. The hemivertebra is the commonest cause of congenital scoliosis and is classified by its relationship to adjacent vertebrae: a fully segmented hemivertebra has open disc spaces above and below and produces the greatest progressive deformity; a semi-segmented hemivertebra is fused above or below and produces less progression; an incarcerated hemivertebra is fused

above and below within an otherwise intact vertebral column and produces minimal progression; a non-segmented hemivertebra (the “block hemivertebra”) rarely produces progressive deformity. Failures of segmentation: A block vertebra is the failure of separation of two adjacent vertebrae, with bilateral fusion of the disc and bony elements. An unilateral unsegmented bar is the failure of separation on one side of two or more adjacent vertebrae — and is the single most progressive anomaly because the unaffected side continues to grow while the affected side does not, producing rapid progressive scoliosis. Mixed defects: Combinations of failure of formation and failure of segmentation — particularly an unilateral unsegmented bar combined with a contralateral hemivertebra — produce the most rapidly progressive deformities and the greatest urgency for early surgical intervention. Natural History The natural history depends on the specific anomaly. The risk of progressive scoliosis is greatest with unilateral unsegmented bars (especially combined with contralateral hemivertebrae, with predicted progression of 5-10° per year), moderate with isolated hemivertebrae (depending on segmentation status), and minimal with block vertebrae or unsegmented blocks. The progression is greatest during periods of rapid skeletal growth — infancy (0-3 years), juvenile years (4-9), and adolescent growth spurt (10-15). The mid- childhood years between rapid-growth periods are relatively quiescent. Associated Anomalies Congenital scoliosis is associated with a substantial rate of additional anomalies that must be sought systematically: spinal cord anomalies (tethered cord, diastematomyelia, syringomyelia, intraspinal lipoma) in approximately 20-40%, renal anomalies in approximately 25-35% (because the kidney shares vertebral mesodermal origin), cardiac anomalies in approximately 10-15%, and other systemic anomalies including limb anomalies, anal atresia, and others. The acronym VACTERL (vertebral, anal, cardiac, tracheoesophageal, renal, limb) describes the most consequential of these associations. Every child with a congenital vertebral anomaly therefore requires investigation of all of these systems: total-spine MRI for the spinal cord, renal ultrasound for the kidneys, cardiac echocardiogram, and examination for limb and anorectal anomalies. Imaging Plain radiographs (AP and lateral views of the spine) demonstrate the vertebral anomalies; specific views such as bend films or three-dimensional CT may be required for complex anomalies. MRI of the entire spine is essential to identify spinal cord anomalies that may dictate management. CT with three-dimensional reconstruction is increasingly used for preoperative planning of complex surgery.

Treatment The treatment principles are: serial observation of deformities at low risk of progression; surgical intervention before significant deformity develops in those at high risk of progression. Bracing has only a limited role in congenital scoliosis because the deformity is structural rather than ligamentous; some compensatory curves above or below the structural area may respond to bracing. Hemivertebra excision is the procedure of choice for the isolated progressive hemivertebra producing scoliosis. The procedure is typically performed in early childhood (1-5 years) via a posterior approach, with excision of the hemivertebra and adjacent disc spaces and posterior instrumented fusion to close the resulting wedge. The procedure achieves immediate correction of the deformity at one or two levels with limited overall fusion length. Convex hemiepiphysiodesis is a procedure used in young children with progressive curves not amenable to hemivertebra excision. The convex side of the curve is fused at the apex, while the concave side is allowed to continue growing; the differential growth gradually corrects the curve. The procedure is less effective than hemivertebra excision and is less commonly used in modern practice. Posterior in-situ fusion of progressive curves is the historical treatment and remains a reasonable option for moderate progressive curves where excision is not feasible. The fusion arrests progression but does not correct existing deformity. Growth-friendly techniques (growing rods, vertical expandable prosthetic titanium rib — VEPTR, MAGEC magnetic growing rods) are increasingly used for early-onset congenital scoliosis to allow continued spinal growth while controlling the deformity. The procedures require serial lengthenings over several years. Definitive correction and fusion with modern segmental instrumentation, sometimes combined with three-column osteotomies (pedicle subtraction osteotomy, vertebral column resection), is the standard for late-presenting or established severe deformities in older children and adolescents. The procedures are extensive and carry substantial morbidity, but produce powerful correction of fixed deformities.

Congenital Kyphosis

Congenital kyphosis is a sagittal-plane deformity produced by anomalous vertebral development. The classification, parallel to that of congenital scoliosis, recognizes failures of formation (anterior or anterolateral hemivertebrae producing anterior wedging) and failures of segmentation (anterior or anterolateral unsegmented bars producing anterior tethering). Type I — failure of formation — typically produces the most rapidly progressive deformity, particularly when the anterior vertebral body is absent. Progression is often >10° per year, and the high risk of paraplegia from progressive kyphosis with cord compression makes early surgical intervention essential.

Type II — failure of segmentation — produces a slower, more predictable progression. Type III — mixed defects — varies according to the specific anomaly. Treatment principles emphasize early surgical correction of progressive Type I deformities, often with anterior plus posterior fusion to provide the necessary anterior support. The risks of paraplegia from progressive kyphosis are sufficient that surgical intervention is recommended even in the very young child with rapidly progressive disease.

Klippel-Feil Syndrome

Definition and Epidemiology Klippel-Feil syndrome, described by Maurice Klippel and André Feil in 1912, is the congenital fusion of two or more cervical vertebrae. The classical clinical triad — short neck, low posterior hairline, and limited cervical motion — is present in only a minority of cases; many patients have isolated fusion of two vertebrae without the obvious clinical phenotype. Incidence is approximately 1 in 40,000-50,000 live births, with female predominance.

Classification Three Feil types are recognized: Type I, massive fusion of cervical vertebrae often with thoracic involvement; Type II, fusion of one or two cervical vertebrae (the commonest type); Type III, Type I or II features combined with lower thoracic or lumbar fusion. A more clinically relevant Samartzis classification (2006) groups patients by the pattern of cervical fusion: Type I, single congenitally fused cervical segment; Type II, multiple non-contiguous congenitally fused segments; Type III, multiple contiguous congenitally fused segments.

Associated Anomalies Klippel-Feil syndrome is strongly associated with multiple systemic anomalies that must be sought systematically: scoliosis (in approximately 50%), Sprengel deformity (elevated, hypoplastic scapula due to failed descent during development, in approximately 30%), renal anomalies (in approximately 35%, with absent kidney being the most common single anomaly), cardiac anomalies (particularly ventricular septal defect), hearing impairment (approximately 30% — conductive, sensorineural, or mixed), and Duane retraction syndrome (in approximately 4%). The combination of Klippel-Feil and Sprengel deformity, sometimes combined with renal anomalies, constitutes the more complete clinical syndrome. Clinical Features and Management The cervical fusion itself is rarely symptomatic in childhood. The principal clinical concerns are: (1) progressive degenerative changes in the unfused segments adjacent to the fused segments, occurring decades earlier than in the normal cervical spine because of the increased motion demands; (2) C2-C3 fusion with adjacent occipito-C1 instability, which can produce catastrophic neurological injury after relatively minor trauma; (3) associated

scoliosis requiring management; and (4) the management of associated systemic anomalies. The clinical implications for the orthopedic surgeon are: avoidance of high-impact activities that risk cervical injury (high-risk patients — particularly those with C2-C3 fusion combined with occipito-C1 abnormality — should be counseled to avoid contact sports and high-speed activities); careful preoperative airway assessment in patients requiring general anesthesia (intubation may be difficult or impossible without fiberoptic guidance because of the restricted cervical motion); imaging of the entire spine for associated congenital anomalies; and renal and cardiac evaluation. Surgical management is reserved for symptomatic adjacent-segment degeneration or instability and follows the principles of cervical spine surgery in general.

Sprengel Deformity

Sprengel deformity, often associated with Klippel-Feil syndrome, is the congenital failure of normal descent of the scapula from the cervical region to its definitive thoracic position. The scapula is elevated, small, often rotated medially, and may be connected to the cervical vertebrae by a fibrous, cartilaginous, or osseous bar — the omovertebral bone. Presentation is with an elevated shoulder, neck asymmetry, and limited shoulder abduction. Imaging — particularly CT — defines the position of the scapula and the presence of an omovertebral bone. Treatment of severe symptomatic Sprengel deformity is surgical, with options including the Woodward procedure (release of the scapular medial- border muscles and downward translation of the scapula with reattachment of muscles), the Green procedure (similar with scapular morcellation), and the Mears procedure with resection of the superomedial corner of the scapula. The procedures should generally be performed before age 8 because of the high risk of brachial plexus injury with attempted late correction.

Cervical Ribs and Thoracic Outlet Syndrome

Cervical Ribs A cervical rib is a supernumerary rib arising from the seventh cervical vertebra. The condition occurs in approximately 0.5-1.0% of the population and is bilateral in approximately 50%. The cervical rib varies from a small bony stump to a complete rib that articulates with the first thoracic rib. Most cervical ribs are asymptomatic and are discovered incidentally; the clinical importance lies in the small minority that produce thoracic outlet syndrome. Thoracic Outlet Syndrome (TOS) Thoracic outlet syndrome is the constellation of neurological, vascular, or combined symptoms produced by compression of the brachial plexus, subclavian artery, or subclavian vein as they pass through the thoracic outlet between the cervical spine and the upper rib cage. Three principal subtypes are recognized.

Neurogenic TOS (the commonest, accounting for >90% of TOS cases) involves compression of the lower trunk of the brachial plexus (C8 and T1 fibers) against a cervical rib, an anomalous fibrous band, or the scalene muscles. Presentation is with pain and paresthesia in the medial aspect of the arm and the ulnar nerve distribution of the hand, weakness of the intrinsic hand muscles, and occasionally atrophy. The classical clinical sign is the wasting of the thenar eminence with preservation of the hypothenar musculature in advanced disease, a pattern reflecting predominant compression of the C8-T1 motor fibers. Diagnostic provocative maneuvers include the Roos test (the patient holds the arms in the “stick-up” position with elbows flexed for 3 minutes, with reproduction of symptoms indicating positive test) and the Adson maneuver (loss of radial pulse on inspiration with the head turned to the affected side); these tests have substantial false-positive rates in normal subjects. Nerve conduction studies, MRI, and CT angiography refine the diagnosis. Vascular TOS involves compression of the subclavian artery (arterial TOS, often producing a post-stenotic aneurysm with distal embolization) or vein (venous TOS, producing the Paget-Schroetter syndrome of effort-induced subclavian vein thrombosis in young athletic patients). Vascular TOS is uncommon but consequential. Treatment of TOS is initially conservative for the great majority of cases: physiotherapy directed at posture correction, scalene stretching and strengthening of the lower trapezius and serratus anterior, ergonomic modifications, and weight loss. Surgical decompression is reserved for refractory cases or for vascular TOS with established arterial or venous compromise. Surgical options include cervical rib resection (transaxillary approach is classical; supraclavicular approach gives better access to the brachial plexus), first rib resection, scalenectomy, and combinations of these. The outcomes are variable, with the best results in true neurogenic TOS with objective findings (motor weakness, EMG abnormalities); the patient with subjective sensory symptoms only often has disappointing surgical results.

Spina Bifida and the Dysraphic States

Definitions and Classification The dysraphic states are a spectrum of congenital malformations of the spinal cord, vertebral column, and overlying tissues, resulting from failure of normal closure of the neural tube. The principal entities are: Spina bifida occulta: A bony defect in the posterior vertebral arch (typically L5 or S1) without external evidence of neurological involvement. Often asymptomatic and discovered incidentally on radiograph. May be associated with overlying skin findings — hair patch, dimple, hemangioma, lipoma — that signal underlying spinal cord tethering and warrant MRI investigation. Meningocele: A herniation of the meninges through the bony defect, containing cerebrospinal fluid but not neural elements. Typically presents with a sac protruding through the back; neurological function is usually preserved.

Myelomeningocele: A herniation of the meninges and neural elements (spinal cord, nerve roots) through the bony defect, with severe neurological consequences. The neural placode lies open on the surface of the back in the newborn period. Tethered cord syndrome: Abnormally low position and fixation of the conus medullaris, often associated with a thickened or fatty filum terminale, intradural lipoma, dermal sinus tract, or split-cord malformation. The mechanical tension on the conus produces progressive neurological deterioration. Diastematomyelia (split-cord malformation): Splitting of the spinal cord into two hemicords, often divided by a bony or fibrocartilaginous bar. Myelocystocele, myeloschisis, and other rare variants complete the spectrum. Myelomeningocele Myelomeningocele is the most consequential of the dysraphic states from an orthopedic standpoint. The condition arises from failure of neural tube closure at approximately day 28 of gestation; multiple causes are implicated, with folate deficiency being the most- modified by preventive measures. The prevalence has fallen dramatically with widespread folate supplementation, but the condition remains an important cause of childhood disability. The clinical level of the neurological deficit corresponds approximately to the anatomical level of the lesion: thoracic, high lumbar (L1-L2), middle lumbar (L3-L4), low lumbar (L5), and sacral lesions produce different patterns of motor and sensory loss. Patients with thoracic and high lumbar lesions typically do not achieve community ambulation; those with middle and low lumbar lesions can ambulate with various orthoses; those with sacral lesions usually achieve community ambulation but often with characteristic foot deformities. The orthopedic manifestations of myelomeningocele include: (1) hip deformities — hip dislocation in approximately 50% of midlumbar lesions, due to muscle imbalance between flexors-adductors (innervated, spastic) and extensors-abductors (denervated); (2) knee deformities — typically flexion contractures or quadriceps weakness depending on level; (3) foot deformities — clubfoot, calcaneus, equinus, valgus, vertical talus, all with variable severity; (4) scoliosis — paralytic, neuromuscular, often progressive into adulthood; (5) hydrocephalus and Arnold-Chiari II malformation — the latter being almost universal in myelomeningocele and producing cerebellar tonsillar herniation; (6) tethered cord — symptomatic in many patients in late childhood and adolescence, requiring untethering surgery; (7) latex allergy — substantially elevated rate in patients with myelomeningocele, requiring latex-free environments in all medical and surgical care; (8) neurogenic bladder and bowel — requiring lifelong management; (9) pressure sores — from insensate skin, particularly over bony prominences; (10) shortened life expectancy and complex medical comorbidity. Orthopedic management is highly individualized, focuses on functional goals (sitting balance, transfers, ambulation, prevention of pressure sores), and must be coordinated

with the broader multidisciplinary team. Surgical priorities include: closure of the neural defect in the first 24-72 hours of life (typically by neurosurgery, with later orthopedic involvement); management of hydrocephalus by ventriculoperitoneal shunt; orthopedic surgery for hip, knee, foot, and spine deformities staged according to functional priorities and the child’s growth.

Tethered Cord Tethered cord syndrome presents with progressive neurological deterioration in a child or adult with prior dysraphic findings or with subtle dorsal cutaneous findings (hairy patch, dimple, hemangioma). The clinical manifestations include progressive lower-extremity weakness, sensory changes, urinary or bowel dysfunction, and back or leg pain. MRI is diagnostic, showing the conus medullaris at a level below L1-L2 with associated findings of dermal sinus, lipoma, thickened filum, or other tethering structure. Treatment is surgical untethering, with detachment of the conus from the tethering structure. The outcomes are best when surgery is performed before significant neurological deterioration has occurred.

Other Notable Congenital Spine Anomalies

Atlanto-occipital Anomalies Atlanto-occipital assimilation (fusion of the atlas to the occiput), basilar invagination (upward displacement of the dens through the foramen magnum), and other craniovertebral junction anomalies may produce upper cervical instability and neurological compromise. The conditions are often associated with skeletal dysplasias (achondroplasia, Morquio syndrome, spondyloepiphyseal dysplasia) and require careful neurosurgical assessment.

Os Odontoideum Os odontoideum is a separated ossicle replacing the normal dens, with potential atlantoaxial instability. The condition may be congenital or post-traumatic (from a missed odontoid fracture in childhood). Symptomatic instability is treated by C1-C2 fusion.

Lumbosacral Transitional Vertebrae Sacralization of L5 (partial or complete) and lumbarization of S1 are common variants, mostly asymptomatic but occasionally associated with low back pain (the Bertolotti syndrome, in which an enlarged transverse process of L5 articulates with the sacrum to produce focal pain).

Summary and Take-Home Points

The congenital anomalies of the spine span a remarkable spectrum from minor radiographic variants to devastating myelomeningocele. Congenital scoliosis, classified as failures of formation (hemivertebrae), failures of segmentation (block vertebrae, unilateral unsegmented bars), or mixed defects, requires careful assessment of progression risk; unilateral unsegmented bars combined with contralateral hemivertebrae are the most progressive and warrant early surgical intervention. Associated anomalies — spinal cord,

renal, cardiac, and others — must be sought systematically (VACTERL screening). Klippel- Feil syndrome of cervical vertebral fusion produces the classical triad of short neck, low hairline, and limited motion, but the principal clinical concerns are adjacent-segment instability, scoliosis, Sprengel deformity, and renal and cardiac anomalies. Cervical ribs are common and usually asymptomatic but can produce thoracic outlet syndrome with characteristic neurological, vascular, or combined manifestations. The dysraphic states — spina bifida occulta, meningocele, myelomeningocele, and the tethered cord syndromes — produce a wide range of orthopedic, neurosurgical, and medical manifestations that require lifelong multidisciplinary management. Across all of these conditions, the principles of early recognition, systematic investigation for associated anomalies, staged surgical intervention according to functional priorities, and coordinated multidisciplinary care produce the best outcomes.