Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 71 ppt

25 Congenital Scoliosis Francis H. Shen, Vincent Arlet Core Messages ✔ Most cases of congenital scoliosis are sporadic and therefore are non-hereditary ✔ Up to 60 % of patients with congenital scoliosis may have malformations of other organ sys- tems, particularly the genitourinary, cardiovas- cular, and nervous systems ✔ The classification system is based on either fail- ure of formation, failure of segmentation, or mixed (failure of both formation and segmenta- tion) ✔ Curve progression in congenital scoliosis is based on both the type and location of verte- bral anomaly ✔ MRI searching for associated neurologic malfor- mations is mandatory ✔ The treatment of congenital scoliosis is primar- ily surgical ✔ The goal of prophylactic surgery is to prevent curve progression or attempt a slow progres- sive correction over time through fusions in situ and/or hemiepiphysiodeses ✔ The principle of corrective surgery focuses on attempting to correct the spinal deformity at the time of spinal fusion through either osteo- tomies or spinal resections ✔ Neurologic monitoring is essential during cor- rection of congenital curves Epidemiology Most cases of congenital scoliosis are sporadic and therefore non-hereditary Thepresenceofacoronal plane curvature secondary to an anomalous congenital vertebral defect that is present at birth is known as congenital scoliosis. This can be distinguished from infantile idiopathic scoliosis by the presence of a structural ver- tebral abnormality. If the vertebral anomaly results in a sagittal plane deformity it will result in congenital k yphosis or lordosis. Frequently, the resulting deformity is a combination of both planes, with congenital kyphoscoliosis being more common than congenital lordoscoliosis. The true incidence of congenital scoliosis is unknown. Among the large studies reported there do not appear to be any signifi- cant ethnic or geographic differences, although there is a greater female to male ratio (1.4–2.5 to 1). Most cases of congenital scoliosis are non-hereditary and pose little risk to subsequent siblings or offspring [3, 45, 47]. In a review of 1250 congeni- tal deformities at a single institution, Winter found that approximately 1% of patients with congenital spinal deformities had a known relative with the problem [43]. In fact, the majority of identical twin studies have shown the congenital defect to exist in one of the siblings, but not in the other [15, 29, 40]. Rare reports of both twins having congenital spinal anomalies do exist [1]. Cases with a syndromic asso- ciation (Jarcho-Levine, spondylothoracic dysplasia, spondylocostal dysplasia) can have a hereditary component, and are typically associated with multiple levels of bilateral failuresof segmentation, multiple fused ribs, and missing segments [11, 27, 30]. In these cases, where multiple complex anomalies exist, the related risk is up to 10% for similar lesions in siblings or subsequent generations [22]. The incidence of associated malformation has been reported to be as high as 25% for urologic condi- tions [25], 10% for cardiac conditions [4], and 28–40% for neuroaxis anomalies [4,8,33,34,46]. Spinal Deformities and Malformations Section 693 ab c d e Case Introduction Technique for surgical excision of a hemivertebra through a posterior only approach. A 7-month-old girl was diagnosed with a congenital hemivertebra. An MRI was obtained revealing a tethered cord which was subsequently released. She was otherwise healthy and the remaining work-up did not reveal any other associated genitourinary, cardiac, or neurologic malforma- tions. Radiographs ( a) demonstrate a fully segmented hemivertebra located at the lumbosacral junc- tion. Due to the magnitude of the curve, location of the anomaly resulting in an oblique take-off of the spine, and associated pelvic obliquity. The patient developed a substantial clinical deformity ( b) with coronal imbalance. These cases are perhaps the best indica- tion for early surgical intervention. As a result, at 7 years of age the patient underwent an excision of thehemivertebrathroughaposte- rior approach only ( Fig. 4). Intra- operative images ( c) and postoperative radiographs (d) confirm the position of the instrumentation and correction of the deformity. Clinically, the patient has immediate improvement in her coronal balance ( e). Pathogenesis Upto60%ofpatients may have malformations of other organ systems The etiology in sporadic cases is believed to be related to an insult to the fetus during the 4th–6th week of gestation during spine embryological development [24]. It is also during this gestational period that other organ systems are devel- oping in the fetus. As a result, up to 60% of children with congenital scoliosis have malformations in other organ systems, particularly the genitourinary, car- diovascular, and nervous systems [4]. Therefore, a careful search for associated anomalies should be conducted in these patients. 694 Section Spinal Deformities and Malformations Classification Congenital spinal anomalies can be classified as failure of formation, failure of segmentation or mixed The congenital anomalies are classified as either failure of formation, failure of segmentation, or mixed (failure of both formation and segmentation) [27, 44]. Examplesoffailureofformationarehemivertebraandwedgevertebra,while unilateral unsegmented bars and block vertebra are examples of failure of seg- mentation ( Fig. 1). A wedge vertebra represents a partial failure of formation on one side of the vertebra. A complete unilateral failure of vertebral formation is known as a hemi- vertebra, and depending on the presence, or absence, of the disc space(s) is fur- ther described as: fully segmented partially segmented, or non-segmented Fully segmented hemivertebrae have a normal disc space both superior and infe- rior to the vertebral anomaly, while a partially segmented hemivertebra has only one normal disc space and is fused to the adjoining vertebra on the remaining side. A non-segmented hemivertebra has no intervening disc space at all and is fused to both the superior and inferior vertebrae. Furthermore, depending on its relationship to the spine, a hemivertebra can be further described as: incarcerated or non-incarcerted Wedge vertebra and hemi- vertebra are examples of failure of formation An incarcerated hemivertebra appears to be “tucked into” the spine with its pedi- cle falling in-line with the adjacent pedicles, while a non-incarcerated hemiverte- a Figure 1. Classification of congenital scoliosis Congenital anomalies of the spine can be classified either as failure of formation or failure of segmentation. a Hemiverte- bra and wedge vertebra are two common examples of failure of formation. Notice that hemivertebra can be further sub- classified as fully segmented, semi- (or partially) segmented, non-segmented, incarcerated and non-incarcerated. Congenital Scoliosis Chapter 25 695 b Figure 1. (Cont.) b Block vertebra is an example of a bilateral failure of segmentation while unilateral bars are examples of unilateral failure of segmentation. A unilateral bar with a contralateral hemivertebra has the worst prognosis for progression and is an example of a mixed anomaly (both failure of formation and failure of segmentation). bra protrudes out of the spine with its pedicle lying outside the line of the adja- cent pedicles [26]. In general, a non-incarcerated vertebra has a worse prognosis for progression when compared to an incarcerated vertebra. Unilateral unsegmented bars and block vertebra are examples of failure of segmentation A unilateral unsegmented bar is a vertebral bar fusing the discs and facets on one side of the vertebral column, while a block vertebra is the result of bilateral failure of segmentation with complete fusion of the disc between the involved vertebrae. In some cases, fused ribs may also be present, typically on the same side as the unsegmented bar. Mixed anomalies are combinations of both failure of formation and failure of segmentation and can occur in any combination. Clinical Presentation History Congenital spinal anomaly may be found incidentally Patients with congenital scoliosis can present at any time. Often the diagnosis of the spinal deformity is made in utero at the time of the prenatal ultrasound [5]. Although in most cases the exact anomaly cannot be diagnosed at that time, it is essential that the ultrasonographer also look for other associated conditions such as spina bifida, and cardiovascular, urogenital or other syn- dromic malformations. Prenatal counseling and awareness of the overall prog- Congenital scoliosis is often associated with other non-spinal anomalies nosis of these kinds of deformities is essential to provide appropriate informa- tion to the parents. The congenital curve may also be discovered incidentally on routine radiographs performed for any other reason, such as a chest X-ray for respiratory problems or congenital heart disease, or abdominal films for belly pain. The importance of these images should not be overlooked, because later they can provide essential information in assessing progression of the deformity. 696 Section Spinal Deformities and Malformations ab c d Figure 2. Physical findings suggestive of congenital spinal anomaly A careful physical examination of the whole body is mandatory. Findings may be as obvious as a gross coronal imbalance; however, often the signs are more subtle. Evidence of a spinal asymmetry, b a hairy patch, c calf or d foot asymme- try is suggestive of an underlying congenital malformation. Otherwise, the child will be referred for the evaluation of a spinal deformity that was picked up by the family, school nurse, or their physician. Findings that should raise the suspicion of an underlying congenital malformation are: ahairypatch midline skin hemangioma a sacral dimple afootmalformation leg asymmetry urinary symptoms an unusual or rigid curve ( Fig. 2) Skin stigmata or musculo- skeletal anomalies may indicate congenital anomaly In extreme cases, congenital scoliosis is only discovered at the time of the surgical procedure (of what was thought to be an idiopathic scoliosis), as it may not have been visible on the radiographs due to the rotation of the vertebrae. Physical Findings Theevaluationofthepatientfollowsthesamerulesasforanyspinaldeformity examination. An assessment is made of: balance of the trunk (plumb line dropped from C7 and the skull) balance of the shoulders Congenital Scoliosis Chapter 25 697 rigidity of the curve the rib hump associated malformations The physical examination should include: whole spine skin a complete musculoskeletal status a thorough neurologic examination The evaluation must follow the same rules as for any spinal deformity examination The clinical assessment should also search for: craniofacial malformations Klippel-Feil web neck cardiac malformation urinary malformations Serial clinical photographs are helpful for monitoring progression Clinical digitalized photographs should be obtained because they best reflect the patient’s clinical presentation. It is important to note that sometimes, although the Cobb angle does not change, the clinical deformity may worsen and may be picked up as an increased shoulder imbalance, trunk shift or a worsening of the compensatory curve requiring early surgical intervention. Diagnostic Work-up The high frequency of associated malformations necessitates a thorough diag- nostic work-up of the patient and it is mandatory to not only concentrate on the spinal deformity. Imaging Studies Standard Radiographs Standard radiographs are still the method of choice for an initial screening and assessment. The appropriate initial work-up of patients with congenital scoliosis should include: whole spine radiographs functional views cervical spine radiographs spot views of the malformation chest radiographs Whole spine posteroanterior (PA)and lateral radiographs are essential to assess the deformity comprehensively. The best X-rays are usually ones taken at birth, and one should track them down if they are available. After 1 year of age, radiographs should be taken as upright standing films, with the legs in extension and the pelvis level, to compensate for any leg length discrepancy. The Cobb angle should be mea- sured from endplate to endplate or, if not feasible, one should use the pedicle lines. It is essential that the same landmarks be used during subsequent follow-up mea- surements. Several Cobb angles may have to be calculated and recorded, including the Cobb angle measuring the congenital deformity and one of the overall curve. The same landmarks should be used during each follow-up radiographic measurement Functional views (flexion/extension, side bending, or traction views) can be used to provide information about instability, flexibility, and rigidity of the deformity. It is accepted that in congenital scoliosis a worsening of the Cobb angle of at least 10° is sufficiently significant to be termed as progression [23]. 698 Section Spinal Deformities and Malformations The diagnosis of progression is based on serial clinical and radiographic exami- nations (every 6–9 months from birth to 5 years of age, every year from 5 to 10, Always compare the mea- surements with the first assessment and every 6 months from puberty to the end of skeletal maturity). Serial radio- graphs should always be compared with the initial radiographs, and measure- ments should include: Cobb angle of the whole curve Cobb angle of the deformity Cobb angle of any compensatory curves assessment of vertebral rotation rib vertebral angle (ribs becoming more vertical) Additional cervical spine X-rays are indicated to rule out a Klippel-Feil syn- drome or a cervical hemivertebra. The association between congenital scoliosis and Klippel-Feil syndrome has been well described and may present with the classic clinical triad of short neck and low posterior hairline, with a limited neck range of motion. These malformations are often not very well visualized in whole spine radiographs, and spot views of the malformation and flexion-extension lat- eral radiographs may also be necessary. Recently, studies have noted that the increased anterior atlantoaxial interval (ADI) frequently seen in these patients may not necessarily be related to clinical symptoms and that the presence of occi- pitalization and decreased posterior ADI may provide additional information for Search for rib synostosesidentifying patients at risk for developing subsequent neurologic sequelae [34, 36]. In addition, chest cage X-rays will be required in the case of a thoracic curve to look for rib synostoses, which may behave as a bar if they areclose to the spine. Magnetic Resonance Imaging When a further assessment is needed or in the process of surgical planning, MRI can provide valuable anatomic detail. MRI with cartilage sequences provides the best quality pictures of the cartilage endplates, possibly giving the best informa- tion on growth potential and contact with the intramedullary elements. In addi- tion to better defining the congenital anomaly, MRI has become the modality of choice for the diagnosis of commonly associated intramedullary disorders such as syrinx, tethered cord, or Chiari malformations ( Fig. 3a–c). Obtaining an MRI scan to search for associated neurologic malformations is mandatory Thepatientwithatethered cord may be asymptomatic or present with a range of neurologic symptoms ranging from increased spasticity or gait disturbances, to progressive loss of motor or bowel and bladder function. MRI findings may include the presence of a low lying conus or thickened filum terminale. If present, surgical untethering is typically warranted to avoid incurring further neurologic deficits. Another association frequently identified on MRI includes the Chiari malformation. Although the clinical presentation in these patients is extremely variable, the common MRI finding is characterized by caudal displacement of the cerebellar vermis, tonsils, and cervicomedullary junction into the spinal canal ( Fig. 3c). Computed Tomography CT can help define the congenital anomaly better Tomographs are classic for showing a bony bar, but have lost their role in the diagnostic assessment with the advent of thin-slice high resolution computed tomography (CT). CT with thin slices and with reconstruction is useful in very complex deformities and to facilitate surgical planning. Congenital Scoliosis Chapter 25 699 abc Figure 3. MRI identifies common associated intramedullary disorders Spinal cord anomalies can occur in up to 40% of patients with congenital spinal scoliosis. Common associated findings include a syrinx, b tethered cord with low lying conus, or c Chiari malformation. Specific Investigations Renal and bladder ultrasound imaging is recommended for all patients on their initial presentation and further genitourinary imaging is obtained as indicated. A cardiac assessment is also required by the cardiologist, as congenital scoliosis has a 12% incidence of associated cardiac malformation. Echocardiography is therefore often indicated to rule out an underlying cardiac problem. Non-operative Treatment Bracing usually is ineffective in congenital scoliosis Non-operative treatment of congenital scoliosis will consist in either observation of the curve or bracing. Observation should be applied only for non-progressive balanced curves. In most instances bracing is ineffective in congenital scoliosis. It may be indicated for long flexible curves, controlling compensatory lumbar curves, helping to rebalance the spine, orpostoperative use until the fusion is solid. A prerequisite for counseling patients on the choice of treatment is a thorough knowledge of the natural history particularly when surgery is considered. In con- genital scoliosis, natural history is predominately influenced by the risk of curve progression. Natural History and Progression Curve progression in congenital scoliosis is related to the type and location Because of the wide range of deformities that can occur in congenital scoliosis, predicting the risk of curve progression can be difficult. As a general rule, the rate of progression is directly related to: the potential for asymmetric growth, and therefore related to the presence or absence of an intervening disc(s) the location of the vertebral anomaly ( Case Introduction) 700 Section Spinal Deformities and Malformations Therefore, it follows that a fully segmented vertebra, with the presence of two disc spaces (and therefore two sites of growth potential), has a greater risk for curve progression than a non-segmented hemivertebra that is completely fused to the two adjoining vertebrae and has no available disc spaces. Similarly, block vertebrae have no growth potential and therefore remain stable. Table 1 provides guidelines for the risks of progression for each type of anomaly and average degree of progression per year. Table 1. Risk of progression for common vertebral anomalies Greatest risk of progression unilateral unsegmented bar with contralateral hemivertebra (5 –10 degrees/year) unilateral unsegmented bar (3–9 degrees/year) two unilateral fully segmented hemivertebrae (2 –5 degrees/year) one fully segmented hemivertebra (1 –3 degrees/year) wedge vertebra (minimal to no growth potential) block vertebra (stable) Lowest risk of progression While these examples are fairly straightforward, the anatomy in many mixed anomalies can be unclear, with a prognosis that is unknown. In these instances, the patient must be followed closely for evidence of curve progression. In gen- eral, the overall average progression per patient is 5 degrees per year [44]. Early surgical intervention may be required to address curves that result in significant shoulder, pelvic, or trunk imbalance Location of the congenital anomaly can affect both curve progression and overall appearance of the patient. Upper thoracic curves tend to progress less than thoracolumbar and lumbar curves. However, although these upper thoracic curves seldom reach 30°, they can cause significant shoulder imbalance that may require early surgical intervention. Similarly, low lumbar curves can induce an oblique take-off from the spine resulting in pelvic obliquity and truncal imbal- ance. Mid-thoracic curves, with the apex centered at T5–T7, can induce a pro- gressive compensatory low thoracic or lumbar curve that may need to be included in the fusion if they become bigger and structural. In these instances it may be important to consider early surgical intervention before these changes occur [3]. Operative Treatment General Principles The treatment of congenital scoliosis is primarily surgical The treatment of congenital scoliosis is primarily surgical [14, 46]. The goal is to achieve a solid fusion and prevent further progression, and if possible decrease the deformity to achieve as straight a spine as possible at the end of growth. How- ever, the curves are often rigid and correction difficult to achieve; therefore the best approach is early recognition and careful monitoring [22]. In this manner, early “prophylactic” surgery is possible by anticipating and halting progression before significant deformity occurs [3]. It is even possible in some cases to achieve partial correction over time. However, in many cases some degree of immediate correction is desired. In these cases, the surgical procedures are designed to correct the curve through the use of spinal instrumentation, osteoto- mies, and spinal column and vertebral resections. Congenital Scoliosis Chapter 25 701 Surgical Techniques “Prophylactic” Surgical Procedures These procedures are predominantly referred to as “in situ fusions and hemiepi- physiodesis.” The general principle is to balance the growth by slowing or stop- ping the convex side growth while allowing the remaining concave growth poten- tial to catch up. In situ fusion can be done with a single posterior fusion with or without instrumentation, or with an anterior fusion, or as an anterior-posterior fusion. These operations can be performed if the three-dimensional aspects of the defor- mity have been fully understood. However, the compensatory curve above or below the fused segment may still progress after such procedures. Some correc- tion of the so-called fusions can be achieved if one uses a corrective cast postop- eratively. Asymmetric growth is balanced by arresting growth on the convex side Hemiepiphysiodesis tends to achieve progressive correction over time, taking advantage of the intact growth plates on the concave side of the deformity ( Case Study 1 ). In most cases it requires an anterior and posterior approach to the spine. Anteriorly, one-third of the disc space and corresponding endplates on the convexity of the curve are removed and fused. The hemiepiphysiodesis can be performed through a mini-thoracotomy, thoracoscopically, or even transpedicu- larly [17, 31]. Posteriorly only the convex side is approached and fused. The patient is then immobilized in a cast in the position of maximum correction to take advantage of the flexibility of the curve. The results are, however, somewhat unpredictable [13, 18, 42], and these procedures are typically limited to young The outcome of hemiepiphysiodesis is not easily predictable patients (under 5 years of age) and to curves of less than 50°. They should not be carried out if there is a kyphosis component to the deformity. A very careful fol- low-up is necessary, as progression of the deformity can still occur during the adolescent growth spurt. Corrective Surgery Procedures Posterior Curve Corrections Neurologic monitoring is essential during correc- tion of congenital curves Posterior spine fusion without instrumentation and correction with a cast is an option in young children, but the lack of anterior fusion exposes the spine to the crankshaft phenomenon if the anterior growth plates overcome the posterior fusion. Posterior spine fusion with instrumentation is indicated in older patients, where there is no risk of crankshafting [46]. Anterior and posterior spine fusion with discectomies and instrumentation can achieve a significant correction in the mobile segments of the spine. The danger with all corrective procedures is overcorrection and distraction of the curve with subsequent neurologic compli- cations.Insuchcasesthedistractionshouldnotbedonefirst.Thecompression rod should be inserted first and then only minimal distraction applied on the concave rod. The use of spinal cord monitoring and/or a wake-up test after cor- rection is mandatory. Neurologic monitoring can never be emphasized enough during such corrections ( Case Study 2). Anterior stabilization of the spine with a strut graft done through a convex, or for biomechanical reasons from a concave, approach should be considered if there is a significant kyphotic component to the deformity. 702 Section Spinal Deformities and Malformations . classified as either failure of formation, failure of segmentation, or mixed (failure of both formation and segmentation) [27, 44]. Examplesoffailureofformationarehemivertebraandwedgevertebra,while unilateral. and block vertebra are examples of failure of seg- mentation ( Fig. 1). A wedge vertebra represents a partial failure of formation on one side of the vertebra. A complete unilateral failure of. for progression and is an example of a mixed anomaly (both failure of formation and failure of segmentation). bra protrudes out of the spine with its pedicle lying outside the line of the adja- cent