Kyphosis

William C. Warner Jr

Jeffrey R. Sawyer

Kyphosis is a curvature of the spine in the sagittal plane in which the convexity of the curve is directed posteriorly. Lordosis is a curvature of the spine in the sagittal plane in which the convexity of the curve is directed anteriorly. The thoracic spine and the sacrum normally are kyphotic, and the cervical spine and the lumbar spine normally are lordotic (1). Although several authors have tried to define normal kyphosis of the thoracic spine and normal lordosis of the lumbar spine, these studies have shown much variability in what is considered normal (2, 3, 4, 5, 6, 7 and 8). The ranges of normal kyphosis and lordosis change with increasing age and vary according to the gender and the area of the spine involved (2, 3, 4 and 5). The degree of kyphosis or lordosis that is considered normal or abnormal depends on the location of the curvature and the age of the patient. For example, 30 degrees of kyphosis is normal in the thoracic spine but abnormal at the thoracolumbar junction.

The normal range of thoracic kyphosis is considered to be 19 to 45 degrees and that of lumbar lordosis, 30 to 60 degrees (9). Measurements of kyphosis and lordosis are made from standard scoliosis radiographs with the patient standing with his or her knees locked, feet shoulder width apart, elbows bent, and knuckles in the supraclavicular fossa bilaterally. This will place the patient’s arms at approximately a 45-degree angle from the vertical axis of the body (10). Thoracic kyphosis is measured on a lateral radiograph as the angle between the superior end plate of T2 and the inferior end plate of T12. Proximal thoracic kyphosis is measured from the superior end plate of T2 to the inferior end plate of T5. Middle and lower thoracic kyphosis is measured from the superior end plate of T5 to the inferior end plate of T12. The apex of normal thoracic kyphosis is the T6-T7 disc space (11, 12). The thoracolumbar junction should have no kyphosis or lordosis (11). Lumbar lordosis begins at L1-L2 and increases gradually until the L3-L4 disc space. There is a reciprocal relationship between the orientation of the sacrum, sacral slope, and the pelvic incidence and the characteristics of lumbar lordosis and location of the apex of lumbar lordosis (Fig. 19-1) (13, 14, 15 and 16). A sacral slope of <35 degrees and a low pelvic incidence are associated with a relatively flat, short lumbar lordosis. A sacral slope of more than 45 degrees and a high pelvic incidence are associated with a long, curved lumbar lordosis (14).

Initially, during fetal and intrauterine development, the entire spine is kyphotic. During the neonatal period, the thoracic, lumbar, and sacral portions of the spine remain in a kyphotic posture. Cervical lordosis begins to develop when a child starts holding his or her head up. When an upright posture is assumed, the primary and secondary curves begin to develop. The primary curves are thoracic and sacral kyphosis, and the secondary or compensatory curves in the sagittal plane are cervical and lumbar lordosis. These curves balance each other so that the head is centered over the pelvis (2, 17, 18).

The ranges of normal thoracic kyphosis and lumbar lordosis are dynamic, progressing gradually with growth (19). During the juvenile and adolescent growth periods, thoracic kyphosis and lumbar lordosis become more pronounced and take on a more adult appearance. Mac-Thiong et al. (13) showed that pelvic incidence and tilt increased with growth but sacral slope remained stable.

Differences also exist between male and female spines (6), and thoracic kyphosis and spine mobility are different in boys and girls: during the juvenile and adolescent periods (ages 8 to 16 years), girls have less thoracic kyphosis and thoracic spinal mobility than do boys of the same age (3, 12). Thoracic kyphosis also tends to progress with age: from 30 to 70 years of age, women have a progressive increase in kyphosis, from a mean of 25 degrees to a mean of 40 degrees (19). Men also show a definite progression with age, but at a lower rate.

FIGURE 19-1. Radiographic measurements of pelvic incidence (a), sacral slope (b), and pelvic tilt (c). SS, sacral slope; HRL, horizontal reference line; PI, pelvic incidence; PT, pelvic tilt; VRL, vertical reference line. (From MF, Kuklo TR, Blanke KM, et al. Radiographic measurement manual: Spinal Deformity Study Group (SDSG). Memphis, TN: Medtronic Sofamor Danek, Fall 2004.)

Normal sagittal balance is defined as a plumb line dropping from C7 and intersecting the posterosuperior corner of the S1 vertebral body (Fig. 19-2). Positive sagittal balance occurs when the plumb line falls in front of the sacrum, and negative sagittal balance occurs when the plumb line falls behind the sacrum (20).

Different forces are exerted on the spine, depending on the presence of kyphosis or lordosis. In the upright position, the spine is subjected to the forces of gravity, and several structures maintain its stability: the disc complex (nucleus pulposus and annulus), the ligaments (anterior longitudinal ligament, posterior longitudinal ligament, ligamentum flavum, apophyseal joint ligaments, and interspinous ligament), and the muscles (the long spinal muscles, the short intrinsic spinal muscles, and the abdominal muscles). Alteration in function resulting from paralysis, surgery, tumor, infection, or alteration in growth potentials can cause a progressive kyphotic deformity in a child (21). Both compressive and tensile forces are produced by the action of gravity on an upright spine (Fig. 19-3). In normal thoracic kyphosis, the compressive forces borne by the anterior elements are balanced by the tensile forces borne by the posterior elements. In a lordotic spine, the compressive forces are posterior and the tensile forces are anterior. These forces of compression and tension on the spinal physes can cause changes in normal growth, and a growth deformity can be added to a biomechanical deformity to cause a pathologic kyphosis (21, 22).

FIGURE 19-2. A plumb line is dropped from the middle of the C7 vertebral body to the posterosuperior corner of the S1 vertebral body. (From Bernhardt M. Normal spinal anatomy: normal sagittal plane alignment. In: Bridwell KH, DeWald RL, eds. The textbook of spinal surgery, 2nd ed. Philadelphia, PA: Lippincott-Raven, 1997:185.)

Voutsinas and MacEwen (23) suggested that relative differences in forces applied to the spine are reflected more accurately by the length and width of a kyphotic curve than by just the degree of the curve. For example, curves that are longer and wider (farther from the center of gravity) are more likely to cause deformity in an immature spine (Fig. 19-4). Winter
and Hall (24) classified disorders that result in kyphosis of the spine. Only the more common causes are presented in this chapter; the other causes are discussed elsewhere in this book (Table 19-1).

FIGURE 19-3. Forces that contribute to kyphotic deformity of the thoracic spine. The anterior vertebral bodies are in compression, and the posterior vertebral elements are in tension. (From White AA III, Panjabi MM. Practical biomechanics of scoliosis and kyphosis. In: White AA, Panjabi MM, eds. Clinical biomechanics of the spine. Philadelphia, PA: JB Lippincott, 1990:127.)

POSTURAL KYPHOSIS

Postural kyphosis is a flexible deformity of the spine and is common in juvenile and adolescent patients. Usually, the parents are more concerned about the postural roundback deformity than the adolescent is, and these parental concerns typically are what bring the patient to the physician’s office. The physician’s role in this situation is to rule out more serious causes of kyphosis. Postural kyphosis should be differentiated from pathologic types of kyphosis, such as Scheuermann disease, and from congenital kyphosis. When observed from the side, patients with postural roundback have a gentle rounding of the back while bending forward (Fig. 19-5). Patients with Scheuermann disease and congenital kyphosis have a sharp angular kyphosis or gibbus on forward bending when observed from the side. Radiographs usually are necessary to rule out pathologic types of kyphosis. Patients with postural kyphosis do not have radiographic vertebral-body changes, and the deformity is completely correctable by changes in position or posture. This deformity is common in patients who are taller than their peers and in young adolescent girls undergoing early breast development who tend to stoop because they are selfconscious about their bodies (25).

No active medical treatment is necessary. Bracing is not indicated. Exercises have been suggested and may help maintain better posture, but adherence to such a therapy program is difficult for juveniles and young adolescents. This problem is best treated by educating the patient and, more important, the parents and by observation (26).

FIGURE 19-4. The two spinal curvatures represented by these drawings are different in magnitude; however, using cobb’s method to measure the deformities, the degrees of curvature are identical. The differences in the curves are more accurately reflected when the length of the curves (L) and their respective widths (W and W¹) are taken into consideration. (From Voutsinas SA, MacEwen GD. Sagittal profiles of the spine. Clin Orthop 1986;210:235.)

TABLE 19-1 Disorders Affecting the Spine and Resulting in Kyphosis

I. Postural disorders
II. Scheuermann kyphosis
III. Congenital disorders
	a. Defect of formation
	b. Defect of segmentation
IV. Paralytic disorders
	a. Poliomyelitis
	b. Anterior horn cell disease
V. Myelomeningocele
VI. Posttraumatic
	a. Acute
	b. Chronic
	c. With/without cord damage
VII. Inflammatory
	a. Tuberculosis
	b. Other infection
VIII. Postsurgical
	a. Postlaminectomy
	b. Postbody (tumor) excision
IX. Inadequate fusion
	a. Too short
	b. Pseudoarthrosis
X. Postirradiation
	a. Neuroblastoma
	b. Wilms tumor
XI. Metabolic
	a. Osteoporosis
		1. Senile
		2. Juvenile
	b. Osteogenesis imperfecta
XII. Developmental
	a. Achondroplasia
	b. Mucopolysaccharidosis
	c. Other
XIII. Collagen disease (e.g., Marie-Strumpell)
XIV. Tumor
	a. Benign
	b. Malignant
XV. Neurofibromatosis
From Winter RB, Hall JE. Kyphosis in childhood and adolescence. Spine 1978;3:285.

CONGENITAL KYPHOSIS

Congenital kyphosis is an uncommon deformity, but, despite its rare occurrence, neurologic deficits resulting from this deformity are frequent.

Congenital kyphosis occurs because of abnormal development of the vertebrae, including a failure of developing segments of the spine to form or to separate properly (27). The spine may be either stable or unstable, or it may become unstable with growth (28). Spinal deformity in congenital kyphosis usually progresses with growth, and the amount of progression is directly proportional to the number of vertebrae involved, the type of involvement, and the amount of remaining normal growth in the affected vertebrae (28, 29).

TABLE 19-2 Winter’s Classification of Congenital Deformity

Type	Description
I	Failure of formation of all or part of the vertebral body
II	Failure of segmentation of one or multiple vertebral levels
III	Mixed form, with elements of both failure of formation and failure of segmentation

Van Schrick in 1932 (30) and Lombard and LeGenissel in 1938 (31) initially described two basic types of congenital kyphosis: a failure of formation of part or all of the vertebral body and a failure of segmentation of part or all of the vertebral body. Winter et al. (27, 32) developed the most useful classification of congenital kyphosis, which divides the deformity into three types (Table 19-2). Type I is failure of formation of all or part of the vertebral body (Fig. 19-6A); type II is failure of segmentation of one or multiple vertebral levels (Fig. 19-6B); and type III is a mixed form, with elements of both failure of formation and failure of segmentation.

McMaster and Singh (33) further subdivided this classification into types of vertebral-body deformity. Defects of vertebral-body segmentation consist of a partial (anterior unsegmented bar) or a complete (block vertebrae) failure of segmentation. Defects of vertebral-body formation are divided into four types: (a) posterolateral quadrant vertebrae, (b) butterfly
vertebrae, (c) posterior hemivertebrae, and (d) wedged vertebrae (Fig. 19-7). Dubousset (34) and Zeller et al. (35) added a rotary dislocation of the spine, and Shapiro and Herring (36) further divided type III displacement into types A (sagittal plane only) and B (rotary, transverse, and sagittal planes). Any classification can be subdivided further into deformities with or without neurologic compromise; this is useful for making treatment decisions because each type of congenital kyphosis has a distinct natural history and risk of progression.

FIGURE 19-5. A: Lateral view of normal spinal contour on forward bending. B: Lateral view of a patient with Scheuermann disease on forward bending. Note the break in the normal contour and sharp angular nature of the spine.

FIGURE 19-6. A: Congenital kyphosis caused by failure of formation of the vertebral body (type I). B: Congenital kyphosis caused by failure of segmentation (type II). (Courtesy of Robert Winter, MD, Minneapolis.)

Most of the vertebral malformations that cause spinal deformity occur between the 19th and the 30th days of fetal development (28, 32, 37). The somatic mesoderm, which is devoted to the formation of the vertebral column and the rib cage, undergoes segmentation into 38 to 44 pairs of discrete, bilateral somites. The formation of a vertebra depends on contributions of cells from two separate and successive pairs of sclerotomes. This condensation of the paired sclerotomes occurs at approximately 5 weeks of gestation. If one side of the pair of sclerotomes fails to develop, a hemivertebra is formed, resulting in congenital scoliosis (38, 39).

Tsou (40) concluded that congenital kyphosis and congenital scoliosis occur during different periods of spinal development. He divided the development of the spine into an embryonic period (the first 56 days) and a fetal period (from day 57 to birth). During the embryonic period, failure of segmentation and aplasia of part of the vertebrae, resulting in hemivertebra formation, cause scoliosis, while congenital kyphosis occurs in the fetal period, during the cartilaginous phase of development (40). Failure of formation occurs in this phase when the cartilaginous centrum of the vertebral body forms a functionally inadequate growth cartilage.

Failure of formation varies from complete aplasia (which involves the pars and the facet joints and makes the spine unstable) to involvement of only the anterior one-third to one-half of the vertebral body. This abnormal development is
thought to be the result of inadequate vascularization of the vertebral body during the fetal period, leading to hypoplasia or aplasia of the anterior vertebral body. If one side of the vertebra is involved more than the other side, scoliosis also may occur (Fig. 19-8). Unlike hemivertebral anomalies that occur in the embryonic period because of maldevelopment of corresponding pairs of somites causing congenital scoliosis, posterior arch anomalies usually are absent in pure congenital kyphosis.

FIGURE 19-7. Drawings showing the different types of vertebral anomalies that produce congenital kyphosis or kyphoscoliosis. (From McMaster MJ, Singh H. Natural history of congenital kyphosis and kyphoscoliosis. J Bone Joint Surg 1999;81A:1367-1383.)

FIGURE 19-8. The five most common patterns of congenital vertebral hypoplasia and aplasia are illustrated in lateral and transverse views. Types B and E tend to produce pure congenital kyphosis. (From Tsou PM. Embryology of congenital kyphosis. Clin Orthop 1977;128:18.)

Failure of segmentation has been described as an osseous metaplasia of the annulus fibrosus (40, 41) that acts as a tether against normal growth and causing spinal deformity. The height of the vertebral bodies is relatively normal, but the depth of the ossification of the annulus fibrosus varies. Ossification may be delayed, with a period of normal growth followed by spontaneous ossification. Kyphosis caused by a “segmentation defect” is believed to represent a developmental defect of the perivertebral structures (the annulus fibrosis, the ring apophysis, and the anterior longitudinal ligament) rather than a true intervertebral bar (42).

The natural history of congenital kyphosis is well known and based on the type of kyphosis: failure of formation (type I), failure of segmentation (type II), or mixed anomalies (type III). Congenital kyphosis tends to be progressive, with the greatest rate of progression occurring during the time of most rapid growth of the spine (birth to 3 years of age) and during the adolescent growth spurt. Winter et al. (32) found that failure of formation (type I deformity) produces a much more severe kyphosis, with a rate of progression that averages 7 degrees per year, whereas type II deformities progress an average of 5 degrees per year. McMaster and Singh found the most rapid progression in type III kyphosis, followed by type I, because of involvement of posterolateral quadrant vertebrae. In their study, a type III kyphosis progressed at a rate of 5 degrees per year before 10 years of age and 8 degrees per year thereafter until the end of growth. Type I (failure of formation) kyphosis progressed 2.5 degrees per year before 10 years of age and 5 degrees per year thereafter (33). Type I and III deformities are associated with a much higher incidence of neurologic involvement and paraplegia than are type II deformities. Neurologic problems occur more frequently in patients with type I and III deformities because they tend to have an acute angular kyphosis over a short segment, which places the spinal cord at higher risk for compression at the level of acute angulation. Type II deformities (failure of segmentation) rarely result in neurologic problems because involvement of several segments produces a more gradual kyphosis, and vertebral-body height usually is maintained with little or no vertebral-body wedging. The most frequent location of congenital kyphosis is T10-L1 (32).

Patients with congenital kyphosis may have other anomalies. Intraspinal abnormalities have been reported to occur in 5% to 37% of patients with congenital kyphosis and congenital scoliosis (43, 44, 45 and 46). A study by Bradford et al. (47) indicated that this incidence may be even greater. They found that six of eight patients with congenital kyphosis had spinal cord abnormalities visible on magnetic resonance imaging (MRI). Although the proposed time of development of the deformity may be different from that of congenital scoliosis, other nonskeletal anomalies such as cardiac, pulmonary, renal, and auditory disorders or Klippel-Feil syndrome (48, 49) can be associated with congenital kyphosis. McMaster et al. (50) found an adverse effect on lung development and function caused by an increasing constriction of the rib cage and impairment of diaphragmatic movement. The more cranial the level of the congenital kyphosis, especially above T10, the more significant the effect on respiratory impairment.

Patient Presentation.

The diagnosis of a congenital spine problem usually is made by a pediatrician before the patient is seen by an orthopaedist. The deformity may be detected before birth on prenatal ultrasonography (51) or noted as a clinical deformity in a newborn. If the deformity is mild, congenital kyphosis can be overlooked until a rapid growth spurt makes the condition more obvious. Some mild deformities are found by chance on radiographs that are obtained for other reasons. Clinical deformities seen in a newborn tend to have a worse prognosis than those discovered as incidental findings on plain radiographs. Physical examination usually reveals a kyphotic deformity at the thoracolumbar junction or in the lower thoracic spine. An attempt should be made to determine the rigidity of the deformity
by flexion and extension of the spine. A detailed neurologic examination should be done, looking for any subtle signs of neurologic compromise. Associated musculoskeletal and nonmusculoskeletal anomalies should be sought on physical examination.

High-quality, detailed anteroposterior and lateral radiographs provide most information in the evaluation of congenital kyphosis (Fig. 19-9). Failure of segmentation and the true extent of failure of formation may be difficult to detect on early films because of incomplete ossification. Flexion and extension lateral radiographs are helpful in determining the rigidity of the kyphosis and possible instability of the spine. Computerized tomography (CT) with three-dimensional reconstructions can identify the amount of vertebral-body involvement and can determine whether more kyphosis or scoliosis might be expected (Fig. 19-10). CT scans can identify only the nature of the bony deformity and the size of the cartilage anlage. They do not show the amount of growth potential in the cartilage anlage, and therefore only an estimate of possible progression can be made. MRI should be obtained in most cases because of the significant incidence of intraspinal abnormalities. In addition, the location of the spinal cord and any areas of spinal cord compression caused by the kyphosis can be seen on MRI. The cartilage anlage will be well defined by MRI in patients with failure of formation (Fig. 19-11); however, as with CT scans and plain radiographs, MRI cannot reveal how much growth potential is present in the cartilage anlage and can only help estimate the probability of a progressive deformity.

FIGURE 19-9. A 2-year-old child with type I congenital kyphosis measuring 40 degrees. Radiograph demonstrates failure of formation of the anterior portion of the first lumbar vertebra.

Congenital kyphosis, as well as associated renal problems, can be seen on routine prenatal ultrasonography as early as 19 weeks of gestation (51). Myelograms have been used for documenting spinal cord compression but have been mostly replaced by MRI. If myelography is used, images should be taken with the patient prone and supine. Myelograms obtained in only the prone position may miss information about spinal cord compression because of pooling of dye around the apex of the deformity. Myelography can be used in conjunction with CT scanning to add to the diagnostic information obtained.

Treatment.

Because the natural history of this condition usually is one of continued progression with an increased risk of neurologic compromise, surgery usually is the preferred method of treatment (27). If the deformity is mild or if the diagnosis is uncertain, close observation may be a treatment option. However, observation of a congenital kyphotic deformity must be used with caution, and the physician must not be lulled into a false sense of security if the deformity progresses only 3 to 5 degrees over a 6-month period. If the deformity is observed over 2 to 3 years, it will have progressed 18 to 30 degrees and cannot thereafter be easily corrected. Bracing has no role in the treatment of congenital kyphosis, unless compensatory curves are being treated above or below the congenital kyphosis (27, 48, 52). Bracing a rigid structural deformity, such as congenital kyphosis, neither corrects the deformity nor stops the progression of kyphosis. To document that there has been a significant change in kyphosis, radiographs should be taken by a standardized method, and the same end vertebral bodies should be measured. This will ensure that any change that has occurred since the previous radiograph is accurately measured.

Surgery is the recommended treatment for congenital kyphosis. The type of surgery depends on the type and size of the deformity, the age of the patient, and the presence of neurologic deficits. Procedures can include posterior fusion, anterior fusion, both anterior and posterior fusions, and anterior osteotomy with posterior fusion. Fusion can be done with or without instrumentation.

Treatment of Type I Deformities.

The treatment of type I deformities depends on the stage of the disease: early with mild deformity, late with moderate or severe deformity, and late with severe deformity and spinal cord compression.

Early Treatment of Mild Deformities.

For type I deformities, the best treatment is early posterior fusion. If the deformity is <50 or 55 degrees and the patient is younger than 5 years of age, posterior fusion alone, extending from one level above the kyphotic deformity to one level below, is recommended (27, 32, 48, 53). This may allow for some improvement in the kyphotic deformity because of continued growth anteriorly from the anterior end plates of the vertebrae one level above and one level below the congenital kyphotic vertebrae that are included in the posterior fusion. McMaster and Singh (54) reported 15 degrees of correction in nine of 11 patients treated with this technique. Kim et al. (55) reported that after posterior fusion alone correction of kyphosis occurred with growth only in patients younger than 3 years of age and with type II and III deformities. Anterior and posterior spinal fusions at least one level above and one level below the congenital kyphosis are indicated in curves of more than 60 degrees (55). Anterior and posterior fusions predictably halt the progression of the kyphotic deformity but, because of ablation of the anterior physes (35, 53, 55), do not allow for the possibility of some correction of the deformity with growth.

FIGURE 19-10. Congenital kyphosis. A,B: Anteroposterior and lateral radiographs. Note inadequate detail of kyphosis on lateral radiograph of spine. C-E: CT three-dimensional reconstruction views that clearly demonstrate the bony anatomy of congenital kyphosis.

FIGURE 19-10. (Continued)

Late Treatment of Moderate to Severe Deformities.

In older patients with type I kyphotic deformities, posterior arthrodesis alone may be successful if the kyphosis is <50 to 55 degrees (32, 56). If the deformity is more than 55 degrees (which usually is the case in deformities detected late), anterior and posterior fusion produces more reliable results (32, 56). Anterior arthrodesis alone will not correct the deformity. Any correction of the deformity requires anterior strut grafting with temporary distraction and posterior fusion, with or without posterior compression instrumentation. The posterior instrumentation may allow for some correction of the kyphosis but should be regarded more as an internal stabilizer than as a correction device (27). Instrumentation has been reported to decrease the pseudoarthrosis rate (55). Correction by instrumentation should be used with caution in rigid, angular curves because of the high incidence of neurologic complications. If anterior strut grafting is done, the strut graft should be placed anteriorly under compression. If no correction is attempted and the goal of surgery is just to stop progression of the kyphosis, a simple anterior interbody fusion combined with a posterior fusion can be used. Smith et al. (57) described simultaneous anterior and posterior approaches through a costotransversectomy that allowed resection of the posterior hemivertebra and correction of the kyphosis with posterior compression instrumentation. Correction of the kyphosis could be obtained safely once the posterior hemivertebra was removed and the thecal sac could be observed during corrections. The use of skeletal traction (halo-pelvic, halo-femoral, or halo-gravity) to correct the deformity is tempting, but is not recommended because of the risk of paraplegia (58). In a patient with a rigid gibbus deformity, traction pulls the spinal cord against the apex of the rigid kyphosis and can lead to neurologic compromise (Fig. 19-12).

FIGURE 19-11. MRI of type I congenital kyphosis. Failure of formation of the anterior vertebral body is demonstrated, but the growth potential of the involved vertebra cannot be determined. Note the pressure on the dural sac.

FIGURE 19-12. The effect of traction on a rigid congenital kyphosis. A: The apical area does not change with traction, but the adjacent spine is lengthened. B: As the spine lengthens, so does the spinal cord, producing increased tension in the cord and aggravating existing neurologic deficits. (From Lonstein JE, Winter RB, Moe JH, et al. Neurologic deficit secondary to spinal deformity. Spine 1980;5:331.)

ANTERIOR STRUT GRAFT FOR KYPHOSIS.

Strut grafts are most often used for patients with severe kyphotic deformities with or without associated scoliosis. Strut grafts can also be used in cases of tumor resections and/or vertebral-body collapse secondary to infections and/or trauma. Anterior strut grafting with a free graft is generally used for a kyphosis without neurologic deficits in order to prevent further progression of the deformity (Figs. 19-13, 19-14, 19-15, 19-16 and 19-17). It can be used either by an in situ fusion technique or fusion with minimal intraoperative correction. If intraoperative correction is anticipated, the kyphosis must be mobile at its apex. There must be no fusions posteriorly or, if there are, these must be released prior to any attempt at correction. Distraction of a rigid kyphosis carries a high risk of neurologic injury for the patient and therefore should never be attempted. The struts can be from the fibula or rib, or both. Vascularized or free vascularized grafts may also be used for these procedures. Nonvascularized fibular grafts are the most commonly used structural grafts for kyphotic deformities, as they provide the greatest structural support. The fibula is ideal because one can obtain a large length (up to 26 cm) in mature patients. The disadvantage, however, of using free fibula is that the graft may take a long time to incorporate (up to 2 years). These free fibular grafts are at their weakest point 6 months postoperatively (creeping substitution) and hence subject to fracture, particularly when the graft is placed more than 4 cm anterior to the apex of the kyphosis.

Although rib can be used, it is structurally a very weak graft. Rib is most often used to supplement a fibular autograft (58).

The strut graft generally extends from one end vertebra of the kyphosis to the other. It should lie as far anteriorly and as close to the midline as possible to allow for maximum structural support. Strut grafting has the advantage of being able to stabilize the kyphotic deformity by placing a compression arthrodesis in the line of axial stress of the spine. A vascularized rib graft is a useful alternative when rapid incorporation (6 to 8 weeks) is desired and ligation of segmental vessels is contraindicated. This may be used in kyphosis with preexisting neurologic lesions and especially in cases where fusion in situ is indicated to prevent further curve progression. Vascularized grafts are not subjected to creeping substitution. When a vascularized rib graft is planned, it is obtained by swinging a portion of the rib down with a vascular pedicle to provide an anterior strut for a kyphotic deformity. The rib selected is chosen to best fit with the level to be bridged. For kyphosis with an apex between T2 and T5, a rib two or three segments below the apex of the kyphosis is the ideal rib to use. If the apex of the kyphosis is at T6 or below, a rib two or three segments proximal to the kyphosis apex is the one to be selected. The rib is rotated on a muscle pedicle flap. This technique requires meticulous dissection with preservation of the vasculature. Firm incorporation is achieved within 6 to 8 weeks; hence, this technique is ideally suited for fusion in situ as the grafts have a low mechanical load capacity.

Strut grafting is contraindicated when a second procedure is planned that may produce enough correction to dislodge the anterior strut graft. If this is anticipated, the strut grafting should be done after the corrective posterior procedure is completed. Other contraindications include conditions where the bone is so soft that the strut graft may penetrate the posterior cortex and cause spinal cord injury.

Anterior Strut Graft for Kyphosis (Figs. 19-13, 19-14, 19-15, 19-16 and 19-17)

FIGURE 19-13. Anterior Strut Graft for Kyphosis. A standard thoracotomy or thoracoabdominal approach is used over the rib to be excised. The rib to be excised is at the upper end vertebra of the kyphotic deformity. Another way to select the appropriate rib is to identify the apex of the kyphosis and draw a line to the midaxillary line. This line will intersect the appropriate rib to be removed. The resected rib is excised subperiosteally and cut off at the costal transverse joint. Appropriate retractors are placed. The parietal pleura is incised and opened from the most proximal disc space to be exposed and then opened distally to the distal end vertebra. The segmental vessels are isolated in the midline and tied with interrupted 2-0 silk sutures. The vessels and the parietal pleura are bluntly dissected off the entire spine, exposing the entire spine throughout the length of the intended fusion. As the next step, we prefer to expose the spine subperiosteally by the development of a periosteal flap beginning at the rib head of the most proximal vertebra to be incorporated in the fusion and ending at the rib head (or transverse process in the lumbar spine) of the most distal included vertebra. This subperiosteal flap is developed as far to the opposite side of the spine as possible; this is especially important if a scoliotic deformity is present. In scoliosis, deformity exposure must include the concavity of the curve. This periosteal flap is protective of the soft tissues on the opposite side; it also provides an excellent bed for bony fusion. Some surgeons may prefer extraperiosteal dissection.

FIGURE 19-14. All exposed intervertebral discs are then removed back to the posterior longitudinal ligament with rongeurs and curettes of varying sizes and shapes. In congenital deformities, large amounts of cartilaginous material may be present in the apex of the kyphosis or the apex of the kyphoscoliosis. All this cartilaginous material and the vertebral end plates should be removed completely, as far back as the posterior longitudinal ligament, leaving this ligament intact.

FIGURE 19-15. The fibular graft is harvested in the standard fashion. The fibular strut should lie as far anteriorly and as close to the midline as possible. A suture or a ruler can be used to measure the length of the most anterior strut. It is important not to overly shorten this strut prior to actual insertion. The anchoring holes for the fibular strut may be made in one of several ways. A burr can be used to develop anchoring holes in the anterior cortices of the vertebral body, or a trough can be prepared with curettes and gouges in the inferior aspect of the end vertebral body above and the superior aspect of the end vertebral body below. In this technique, a small notch is made in the cortex with a rongeur to allow the graft to be keyed into place during manual curve correction. For in situ fusion, mild correction will be obtained by use of manual compression over the apex of the kyphotic deformity. Manual pressure is applied over the apex of the kyphosis and the appropriate length graft keyed into position in one end vertebra and then the other. The end of the fibula may require some tapering, which is best done with a burr prior to insertion into the vertebral body. When the external pressure is relieved, the graft should be secure. If more than one structural graft is to be used, those closest to the apex must be inserted prior to insertion of the primary (most anterior) graft. Rib may be used for these secondary grafts and then morselized rib or iliac crest, or both, are packed into the intervening spaces.

FIGURE 19-16. A-C: Although the procedure is not often done today, if correction is to be attempted anteriorly, one of several types of distractors must be placed in the furthest anterior position and gradually elongated. The distractor should be gradually spread over time with careful monitoring of spinal cord function by electrophysiologic (motor and sensory) monitoring. Once maximal distraction is obtained, grafts are inserted in a manner similar to the aforementioned technique.

FIGURE 19-17. With the vascularized rib technique, the skin incision is made approximately at the level of the rib selected for the fusion. The intercostal musculature cranial to the rib is divided with the rib exposed subperiosteally at the costochondral margin and resected. The intercostal musculature is cut about 0.5 cm caudal to the selected rib leaving the neurovascular bundle intact. The appropriate length of rib is determined. The rib is subperiosteally exposed at the level of sectioning and the neurovascular bundle carefully ligated and sectioned. The intercostal musculature is then divided and the interspace opened further to allow exposure of the surgical area. The neurovascular bundle is then followed from the point of rib resection to the intervertebral foramen. The periosteum is freed on both ends of the ribs by approximately 1 cm to allow for insertion into the ends of the kyphotic segment. The fusion area can either be exposed as discussed above through subperiosteal dissection, or the graft can be keyed into position at the end vertebra as illustrated, without extensive subperiosteal dissection. I prefer to expose the bed for vascularized rib in the same fashion as for a free fibular graft.

Technique.

The patient is placed in a standard lateral decubitus position. If the kyphotic deformity is associated with scoliosis, the kyphosis is approached from the convex side of the curvature. If, however, it is a pure kyphotic deformity, then in the thoracic region, a right-sided thoracotomy is preferred, whereas if the kyphosis apex is at the thoracolumbar junction, then a left-sided thoracotomy is preferred.

Late Treatment of Severe Deformities with Cord Compression.

It is difficult to attempt late treatment of a severe congenital kyphotic deformity that is accompanied by spinal cord compression. If congenital kyphosis causes spinal cord compression, anterior decompression is indicated. The compression is created by bone or disc material pressing into the front of the spinal cord, and this can be decompressed only by an anterior procedure; laminectomy has no role in the treatment of this condition (24). If associated with scoliosis, the anterior approach for decompression may be on the concavity of the scoliosis to allow the spinal cord to move both forward and into the midline after decompression. After adequate decompression has been achieved, the vertebrae involved are fused with an anterior strut graft. This is followed by a posterior fusion, with or without posterior stabilizing instrumentation. Postoperative support with a cast, brace, or halo cast may be required.

Treatment of Type II Deformities.

Treatment of type II deformities can be divided into early treatment of mild deformities and late treatment of severe deformities as outlined by
Mayfield et al. (59). If a type II kyphosis is mild and detected early, posterior fusion with compression instrumentation can be done. The kyphosis should be <50 degrees for a posterior fusion alone to have a good chance of success. The posterior fusion should include all the involved vertebrae, plus one vertebra above and one vertebra below the congenital kyphosis.

Compression instrumentation can be used more safely in type II deformities, because the kyphosis is more rounded and affects several segments, instead of being sharply angular as in type I deformities. If the deformity is severe and detected late, correction can be obtained only with anterior osteotomies and fusion, followed by posterior fusion and compression instrumentation (59).

Complications of Treatment.

Some of the more frequent complications of treatment of congenital kyphosis are pseudarthrosis, progression of kyphosis, and paralysis. Pseudarthrosis and progression of the kyphotic deformity can be minimized by using anterior and posterior fusions for deformities of more than 50 degrees. The posterior fusion should extend from one level above to one level below the involved vertebrae. This may allow for some correction with growth.

Paralysis is perhaps the most feared complication of spinal surgery. The risk of this complication can be lessened by not attempting to maximally correct the deformity with instrumentation. Instrumentation should be used only for stabilization of rigid deformities unless simultaneous anterior vertebralbody resection and posterior fusion and instrumentation are done through a costotransversectomy approach as described by Smith et al. (57). The use of halo traction in rigid congenital kyphotic deformities has been associated with an increased risk of neurologic compromise (58). Another long-term problem, occurring in approximately 38% of patients with kyphosis, is low back pain caused by increased lumbar lordosis, which is needed to compensate for the kyphotic deformity (60).

PROGRESSIVE ANTERIOR VERTEBRAL FUSION

Progressive anterior vertebral fusion (PAVF) is rare and is an uncommon cause of kyphosis in pediatric patients; however, if discovered late it may be confused with type II congenital kyphosis. Knutsson (61), in 1949, was the first to describe PAVF in the English-language literature, and fewer than 100 cases have since been reported (62, 63, 64, 65, 66, 67 and 68). Because the largest reported series (26 patients) was from the University Hospital of Copenhagen (68), some have named this the Copenhagen syndrome. This condition is distinguishable from type II congenital kyphosis because the disc spaces and vertebral bodies are normal at birth and later become affected with an anterior fusion. Although the etiology is unknown, PAVF is probably a distinct clinical condition; however, it may represent a delayed type II congenital kyphosis.

Dubousset (34) suggested that certain forms of type II congenital kyphosis (failure of segmentation) may be inherited. The patients have a failure of segmentation, with delayed fusion of the anterior vertebral elements, which is not visible on radiographs until 8 or 10 years of age. He described one family in which three individuals had delayed ossification and congenital kyphosis, and another family in which the grandmother, mother, and two sisters had the deformity. Kharrat and Dubousset (62) also found this condition to be familial in 6 of 15 patients, and Van Buskirk et al. (63) reported associated anomalies in 7 of 15 patients, including heart defects, tibial agenesis, foot deformities, Klippel-Feil syndrome, Ito syndrome, pulmonary artery stenosis, and hemisacralization of L5.

Neurologic deficits are usually not seen in patients with PAVF, but Smith (63) reported one case of spinal cord compression resulting from an acutely angled kyphosis. Van Buskirk et al. (63) and Dubousset (28, 34) described five stages of PAVF: stage 1 is disc space narrowing, which occurs to a greater extent anteriorly than posteriorly; stage 2 is increased sclerosis of the vertebral end plates of the anterior and middle columns; stage 3 is fragmentation of the anterior vertebral end plates; stage 4 is fusion of the anterior and sometimes the middle columns; and stage 5 is development of a kyphotic deformity. Hughes and Saifuddin (67) described the MRI appearance of PAVF in three patients: early anterior disc narrowing (Fig. 19-18A), significant end-plate edema and fatty marrow changes (Fig. 19-18B), and finally multilevel anterior fusion and disc obliteration (Fig. 19-18C-E)

Kyphosis is the last stage in PAVF and is caused by the anterior disc space fusing while part of the posterior disc space remains open, allowing for continued growth in the posterior disc space and the posterior column. Bollini et al. (65) found that patients with thoracic PAVF had a relatively good prognosis, whereas those with lumbar involvement had a poor prognosis. Involvement of the thoracic spine is better tolerated by patients than is involvement of the lumbar area because of the normal kyphotic posture of the thoracic spine. Therefore, nonoperative treatment is recommended for most thoracic PAVF deformities. For PAVF in the lumbar spine, a posterior spinal fusion is indicated in stages 1, 2, and 3. In stages 4 and 5, the kyphotic deformity has already occurred in a normally lordotic lumbar spine. Posterior fusion will only stop progression of kyphotic deformity. If normal sagittal alignment is to be obtained, an anterior osteotomy followed by posterior fusion and instrumentation is recommended (61, 62, 63, 64, 65, 66, 67 and 68).

INFANTILE LUMBAR HYPOPLASIA

Campos et al. (69) reported thoracolumbar kyphosis secondary to lumbar hypoplasia in seven normal infants; the thoracolumbar kyphosis resolved spontaneously with growth. Patients presented with a clinically apparent kyphotic deformity in the first year of life. Radiographically, the patients had a relatively sharply angled kyphosis, with the apex at the affected vertebra (Fig. 19-19A). The affected vertebra had a wedge shape with an anterosuperior indentation, giving it a “beaked” appearance (Fig. 19-19B,C). Only one vertebra was involved in all seven infants, either at L1 or L2. The average initial kyphosis was 34 degrees. The kyphosis spontaneously improved after walking age and had corrected to normal by 6 years of age (Fig. 19-19D,E). Campos et al. recommended an initial period of observation for most patients with this type of congenital kyphosis to get a better assessment of the anomaly as ossification progresses and avoid overtreatment of lumbar hypoplasia that spontaneously improves with growth.

FIGURE 19-18. Progressive anterior vertebral fusion. A: Lateral radiograph of the thoracolumbar spine at age 12 months. Note narrowing at the T11/T12 and L2/L3 disc spaces anteriorly (arrows). B: MR imaging at age 12 months with sagittal STIR sequences through the thoracolumbar spine demonstrates early loss of anterior disc height at the T11/T12 and L2/L3 levels (black arrows). The horizontal high-signal intensity STIR abnormality (white arrowhead) at multiple end-plate levels is likely to represent normal physeal appearance at this age. C: Lateral radiograph (with gridlines for alignment) at age 12 years shows anterior fusion at multiple levels. D: MR image at age 12 years. Sagittal T2 FE sequences through the lumbar spine. Note solid fusion at the L2/L3 level (long white arrow), discovertebral anterior corner SI changes at the L3/L4 level (short white arrow), and fusion with the posterior elements. E: MR sagittal scanning through the thoracolumbar levels with T2 FSE sequences demonstrates T10/T11 and T11/T12 fusion and multilevel anterior disc space obliteration. (From Hughes RJ, Saifuddin A. Progressive non-infectious anterior vertebral fusion (Copenhagen syndrome) in three children: features on radiographs and MR imaging. Skeletal Radiol 1906;35:397-401.)

FIGURE 19-19. Spontaneous resolution of lumbar hypoplasia. Radiographs at 13 months of age (A), 1 year and 11 months of age (B), and 4 years and 6 months of age (C). Radiograph (D) and computed tomographic three-dimensional reconstruction (E) show “beaked” L2 vertebra. (From Campos MA, Fernandes P, Dolan LA, et al. Infantile thoracolumbar kyphosis secondary to lumbar hypoplasia. J Bone Joint Surg Am 1908; 90:1726-1729.)

SEGMENTAL SPINAL DYSGENESIS

Segmental spinal dysgenesis is a congenital anomaly of the lumbar or thoracolumbar spine, consisting of focal agenesis or dysgenesis of the spine, and resulting in severe spinal stenosis and instability (70). A progressive kyphosis occurs at the site of segmental spinal dysgenesis. This condition often is confused with other spinal anomalies such as type I congenital kyphosis, sacral agenesis, lumbosacral agenesis, and lumbar agenesis. Faciszewski et al. (71) gave detailed radiographic and clinical definitions of this condition. Segmental spinal dysgenesis is characterized by severe focal stenosis of the spinal canal at the involved segment and is associated with significant narrowing of the thecal sac and absence of adjacent nerve roots. At the involved level, a ring of bone encircles the posteriorly positioned spinal canal, causing stenosis. The spinal canal is hourglass-shaped with no neurocentral junctions. There is limited potential for enlargement with growth because of the absence of neurocentral junctions, where growth occurs (Fig. 19-19). No pedicles or spinous or transverse processes are present at this level. Anterior to the bony ring is a fat-filled space. The distal bony anatomy and the spinal canal are usually normal, although spina bifida has been noted in a few cases (72). Neurologic function can range from normal to complete paraplegia. Associated anomalies are common, and there is a high incidence of neurogenic bladder (Fig. 19-20).

The etiology of segmental spinal dysgenesis is unknown. The diagnosis can be made on the basis of plain radiographs, but MRI and CT scans and three-dimensional reconstructions are usually needed to fully show the extent of this condition. Tortori-Donati et al. found that the patient’s clinical status correlated with the amount of neural tissue seen on MRI at the level of the lesion (73). Progressive kyphosis occurs with this condition, and progressive neurologic deterioration was noted by Flynn et al. (74) and Faciszewski et al. (71). Early anterior and posterior fusions, with or without
decompression, are recommended. The use of spinal instrumentation is controversial because of the small size of the patient. Hughes et al. (72) recommended that treatment be directed toward the establishment and maintenance of spinal stability first and toward decompression of the cord secondarily. Bristol et al. recommended rigid spinal immobilization for 12 to 18 months to allow growth and development before spinal fusion (75).

FIGURE 19-20. Segmental spinal dysgenesis. Anteroposterior (A) and lateral (B) radiographs show narrowing of spinal canal and absence of L1 and part of L2 vertebral bodies.

SACRAL AGENESIS

Sacral agenesis consists of a complete or partial absence of the sacrum (76, 77, 78 and 79). Rarely is it associated with absence of the most caudal segment of the lumbar spine. The association with maternal diabetes has been well documented (76, 77, 78 and 79). Kyphosis may occur with this condition, although it usually is not progressive and does not require treatment (80, 81).

SCHEUERMANN DISEASE

Scheuermann disease is a common cause of structural kyphosis in the thoracic, thoracolumbar, and lumbar spine. Scheuermann originally described this rigid juvenile kyphosis in 1919; it is characterized by vertebral-body wedging that is believed to be caused by a growth disturbance of the vertebral end plates (82, 83) (Fig. 19-21).

Classification.

Scheuermann disease can be divided into two distinct groups: a typical form and an atypical form. These two types are determined by the location and natural history of the kyphosis, including symptoms occurring during adolescence and after growth is completed. Typical Scheuermann disease usually involves the thoracic spine, with a well-established natural history during adolescence and after skeletal maturity (84). In this classic form of Scheuermann kyphosis three or more consecutive vertebrae, each wedged 5 degrees or more (Sorensen criteria), produce a structural kyphosis. In contrast, atypical Scheuermann disease usually is located in the thoracolumbar junction or in the lumbar spine, and its natural history is well defined. The atypical type is characterized by vertebral end-plate changes, disc space narrowing, and anterior Schmorl nodes but does not necessarily fulfill Sorensen’s criteria of three consecutively wedged vertebrae of 5 degrees. Thoracic Scheuermann is the more common form, with the atypical form less frequently seen.

Epidemiology.

Typical Scheuermann disease consists of a rigid thoracic kyphosis in a juvenile or adolescent spine. The apex of kyphosis is located between T7 and T9 (11). The reported incidence of Scheuermann deformities in the general population ranges from 0.4% to 10% (85, 86, 87, 88 and 89). Reported male-to-female ratios vary in the literature. Scheuermann originally reported a male preponderance of 88% (82). Most reports in the literature note either a slight male preponderance or an equal male-to-female ratio (87, 88, 89, 90, 91 and 92). Bradford et al. (86) have been the only ones to report an increased incidence of Scheuermann disease in women.

FIGURE 19-21. Lateral radiograph of a patient with Scheuermann disease and an 81-degree kyphotic deformity. Note the narrowing of the intervertebral disc spaces and the irregularity of the vertebral end plates. There is an associated increase in lumbar lordosis below the kyphotic deformity.

The age at onset of Scheuermann kyphosis is during the prepubertal growth spurt, between 10 and 12 years of age. Sorensen (88) described a Scheuermann prodrome in patients who had a lax, asthenic posture from the age of approximately 4 to 8 years, and in whom, within a few years, a fixed kyphosis developed. The clinical detection of Scheuermann disease occurs at approximately 10 to 12 years of age. Wedging of apical vertebrae has not been reported before 10 years of age (93). Radiographic evidence of Scheuermann disease usually is not detectable in patients younger than 10 years of age because the ring apophysis is not yet ossified. Until the ring apophysis ossifies, vertebral-body wedging and irregularity of the end plate are difficult to measure on radiographs.

Etiology.

Many possible etiologies have been suggested for Scheuermann disease, but the true cause remains unknown. Genetic, vascular, hormonal, metabolic, and mechanical factors have been suggested as causes of Scheuermann kyphosis. Sorensen (88) noted a high familial predilection, and Halal et al. (94), in a study of five families, and McKenzie and
Sillence (95), in a study of 12 families, suggested that the disease may be inherited in an autosomal dominant fashion with a high degree of penetrance. Additional support for a genetic basis for this condition is provided by Carr et al. (96, 97) in a report of Scheuermann disease occurring in identical twins and by Damborg et al. (98), who found an almost 3% prevalence and 74% heritability in a large group of twins (over 35,000 individuals). Halal et al. (94), McKenzie and Sillence (95), and Carr et al. (97) reported possible autosomal dominant inheritance of Scheuermann kyphosis.

Scheuermann believed that the kyphosis was caused by a form of avascular necrosis of the ring apophysis, which led to a growth disturbance resulting in a progressive kyphosis with growth (82, 83). The problem with this theory is that the ring apophysis contributes little, if at all, to the longitudinal growth of the vertebrae (97, 99). Bick and Copel (99) demonstrated that the ring apophysis lies outside the true cartilaginous physis and contributes nothing to the longitudinal growth of the vertebral body. Therefore, a disturbance in the ring apophysis should not affect growth of the vertebrae or cause vertebral wedging.

Schmorl (100) described a herniation of disc material through the cartilaginous end plate, known as Schmorl nodes. He believed that the herniation of disc material occurred because of a weakened end plate. The disc herniation was thought to damage the anterior end plate, resulting in abnormal growth, which in turn caused the kyphosis. There is a definite increased incidence of Schmorl nodes in patients with Scheuermann kyphosis, but the problem with this theory is that Schmorl nodes are found outside the area of kyphosis and also are present in individuals who have asymptomatic, normal spines and do not have a kyphotic deformity.

Ferguson (101) suggested that persistence of an anterior vascular groove altered the anterior growth of the vertebral body, but Aufdermaur and Spycher (102, 103) and Ippolito and Ponseti (104) were unable to document growth disturbances around the anterior vascular groove and concluded that persistence of an anterior vascular groove is a sign of immaturity of the spine. Lambrinudi (105) postulated that Scheuermann disease resulted from upright posture and a tight anterior longitudinal ligament. The fact that no cases of Scheuermann disease have been found in quadruped animals lends support to this theory (106). This has led to the more popular belief that the anterior end-plate changes are caused by mechanical forces in response to Wolff’s law or the Hueter-Volkmann principle. Compression forces in the anterior physis cause a decrease in growth in the area of the kyphosis. Indirect support for this argument can be found in the changes in the wedging of the involved vertebral bodies and the reversal of these changes when bracing or casting is used in the immature spine. Scoles et al. (106) also supported this theory by demonstrating disorganized endochondral ossification in the involved vertebrae, similar to that seen in Blount disease. They concluded that the changes in endochondral ossification resulted from increased pressure on the vertebral physis.

Ascani et al. (107, 108) found that patients who have Scheuermann disease tend to be taller than normal for their chronologic and skeletal ages with bone age more advanced than their chronologic age. Because they found increased growth hormone levels in these patients, they suggested that the increased height and the advanced skeletal age could be caused by the increased growth hormone. The increased height and the more rapid growth may make the vertebral end plates more susceptible to increased pressure and result in the changes seen in Scheuermann disease. The increased growth hormone levels noted by Ascani et al. may also lead to a relative osteoporosis of the spine, which, in turn, may predispose the spine to the development of Scheuermann disease.

Bradford et al. (85, 109), Burner et al. (110), and Lopez et al. (111) reported in the 1980s that Scheuermann kyphosis may be caused by a form of juvenile osteoporosis. However, using quantitative CT scans, Gilsanz et al. (112) found no evidence of osteoporosis in patients with Scheuermann kyphosis compared with normal research subjects. The authors suggested that the technique used to determine osteoporosis might account for the differences between their report and those that show osteoporosis. In a study using single-photon absorptiometric analysis of cadaver vertebrae from patients with Scheuermann kyphosis, Scoles et al. (106) also found no evidence of osteoporosis.

What is shown by the histologic studies of Ascani et al. (107), Ippolito et al. (104, 113), and Scoles et al. (106) is that an alteration in endochondral ossification occurs. Whether this altered endochondral ossification is the cause or result of kyphosis is not known. Ippolito and Ponseti (104) found a decrease in the number of collagen fibers, which were thinner than normal, and an increase in proteoglycan content. Some areas of the altered end plate showed direct bone formation from cartilage instead of the normal physeal sequences of ossification. These studies help support the belief that Scheuermann kyphosis is an underlying growth problem of the anterior vertebral end plates.

Atypical Scheuermann kyphosis, or thoracolumbar and lumbar kyphosis, is believed to be caused by trauma to the immature spine, resulting in irregularities of the end plate (114).

Natural History.

Many early studies suggested an unfavorable natural history for Scheuermann disease and recommended early treatment to prevent severe deformity, pain, impaired social functioning, embarrassment about physical appearance, myelopathy, degeneration of the disc spaces, spondylolisthesis, and cardiopulmonary failure. Despite these reports, few longterm follow-up studies of Scheuermann disease were performed until that of Murray et al. (87). Findings by Travaglini and Conti (39, 115), Murray et al. (87), and Lowe (116) suggest that the natural history of the disease tends to be benign.

The kyphotic deformity progresses rapidly during the adolescent growth spurt. Bradford et al. (117) noted that, among the patients who required brace treatment, more than half had progression of their deformities during this growth spurt before brace treatment was begun. Little is known about progression of the kyphosis after growth is completed, and whether it is similar to that in scoliosis. It is not well documented whether the kyphosis will continue to progress beyond a certain degree during adulthood.

Travaglini and Conte (39) found that the kyphosis did progress during adulthood, but few patients developed severe deformities. What is known is that patients with Scheuermann kyphosis have more intense back pain, jobs that require relatively little physical activity, less range of motion of the trunk in extension, and different localization of back pain than the general population who do not have Scheuermann kyphosis (87). Even with these findings, when compared with normal individuals, patients with Scheuermann kyphosis have no significant differences in self-esteem, social limitations, or level of recreational activities. The number of days they miss from work because of back pain also is similar.

The data regarding the natural history of Scheuermann disease suggest that, although patients may have some functional limitations, their lives are not seriously restricted and they have few clinical or functional problems. Pulmonary function actually increases in these patients, probably because of the increased diameter of the chest cavity, until their kyphosis is more than 100 degrees. Patients with kyphosis of more than 100 degrees have restricted pulmonary function. Another finding in patients with Scheuermann kyphosis was that disc degeneration was five times more likely to be seen on MRI in patients with Scheuermann compared with controls (118). The clinical significance of this finding is not known (76).

Associated Conditions.

Mild-to-moderate scoliosis is present in about one-third of patients with Scheuermann disease (116), but the curves tend to be small, approximately 10 to 19 degrees. Scoliosis associated with Scheuermann disease usually has a benign natural history. The scoliotic curve rarely is progressive and usually does not require treatment. Deacon et al. (118, 119, 120) divided scoliotic curves in patients with Scheuermann disease into two types, based on the location of the curve and the rotation of the vertebrae into or away from the concavity of the scoliotic curve. In the first type of curves, the apices of scoliosis and kyphosis are the same and the curve is rotated toward the convexity. The rotation of the scoliotic curve is opposite to that normally seen in idiopathic scoliosis. Deacon et al. (101, 119) suggested that the difference in direction of rotation is caused by scoliosis occurring in a kyphotic spine, instead of the hypokyphotic or the lordotic spine that is common in idiopathic scoliosis. In the second type of curves, the apex of the scoliosis is above or below the apex of the kyphosis and the scoliotic curve is rotated into the concavity of the scoliosis, more like idiopathic scoliosis. This type of scoliosis seen with Scheuermann kyphosis is the more common, and it rarely progresses or requires treatment.

Lumbar spondylolysis is a frequently associated finding in Scheuermann kyphosis (Fig. 19-22). The suggested reason
for the increased incidence of spondylolysis is that increased stress is placed on the pars interarticularis because of the associated compensatory hyperlordosis of the lumbar spine in Scheuermann disease. This increased stress causes a fatigue fracture at the pars interarticularis, resulting in spondylolysis. Ogilvie and Sherman (121) found a 50% incidence of spondylolysis in the 18 patients they reviewed. Stoddard and Osborn reported a 54% incidence of spondylolysis in their patients with Scheuermann kyphosis (122).

FIGURE 19-22. A,B: Lateral radiographs demonstrating spondylolisthesis with kyphosis.

Other conditions reported in patients with Scheuermann disease include endocrine abnormalities (123), hypovitaminosis (124), inflammatory disorders (122, 123), and dural cysts (106, 125).

Clinical Presentation.

Clinical signs of Scheuermann disease occur around the time of puberty. The clinical feature that distinguishes postural kyphosis from Scheuermann kyphosis is rigidity. Often, mild Scheuermann disease is believed to be postural because the kyphosis may be more flexible in the early stages than in later stages. Usually, the patient seeks treatment because of a parent’s concern about poor posture. Sometimes the poor posture has been present for several months or longer, or the parents may have noticed a recent change during a growth spurt. Attributing kyphotic deformity in a child to poor posture often causes a delay in diagnosis and treatment.

Pain may be the predominant clinical complaint rather than deformity. The pain generally is located over the area of the kyphotic deformity, but also occurs in the lower lumbar spine if compensatory lumbar lordosis is severe. Back pain usually is aggravated by standing, sitting, or physical activity. The distribution and intensity of the pain vary according to the age of the patient, the stage of the disease, the site of the kyphosis, and the severity of the deformity. Pain usually subsides with the cessation of growth, although pain in the thoracic spine can sometimes continue even after the patient is skeletally mature (87, 126). More commonly, after growth is completed patients complain of low back pain caused by the compensatory or exaggerated lumbar lordosis.

Only gold members can continue reading. Log In or Register to continue