Spondyloepiphyseal Dysplasia 

Updated: Nov 22, 2019
Author: Shital Parikh, MD; Chief Editor: Jeffrey D Thomson, MD 

Overview

Practice Essentials

Spondyloepiphyseal dysplasia (SED) is a descriptive term for a group of disorders with primary involvement of the vertebrae and epiphyseal centers resulting in a short-trunk disproportionate dwarfism. Spondylo- refers to the spine, epiphyseal refers to the growing ends of bones, and dysplasia refers to abnormal growth.

Two major types of SED are recognized: SED congenita and SED tarda. Spranger and Wiedemann first described SED congenita in 1966,[1]  and Spranger and Langer provided a further review of 29 patients in 1970.[2]  In 1969, Fraser noted the particular association of SED with myopia, retinal detachment, and deafness.[3]  In 1939, Jacobsen recognized SED tarda in a report of 20 patients.[4]

The American Academy of Pediatrics (AAP) and the Committee on Genetics have made recommendations to assist the pediatrician in caring for children with SED and their families. A clinical geneticist may be of help to provide counseling to the family. A geneticist may also be a valuable resource for the pediatrician seeking additional information or consultation.

Orthopedic and other surgical procedures are indicated in patients with SED. Although these can be performed safely in most patients, specific structural and physiologic abnormalities should be carefully considered, especially by the anesthesia team.

The Skeletal Dysplasia Management Consortium has developed best practice guidelines for diagnosis and management of type II collagen skeletal dysplasias (including SED).[5]

Pathophysiology

Dwarfing conditions are frequently referred to as short-limb or short-trunk types, according to whether the limbs or the trunk is more extensively involved. SED, metatropic dysplasia, and Kniest syndrome are considered short-trunk dwarfing conditions.

SED is a generalized dysplasia with primary involvement of the vertebrae and proximal epiphyseal centers. Other generalized dysplasias with significant vertebral involvement, such as spondylometaphyseal dysplasia or spondyloepimetaphyseal dysplasia, affect the metaphyseal region of the long bone or the metaphyseal and epiphyseal regions of the long bone, respectively.[6]

The clinical and radiographic differences among the various spondylodysplasias are frequently age-related. SED congenita is a nonlethal form of congenital dwarfism characterized by typical skeletal dysplasias, vertebral changes, and ocular manifestations. It can be diagnosed at birth. In contrast, SED tarda is milder than SED congenita and later in onset, and appearance may be normal at birth.

With the increasing molecular definition of several types of collagen and recognition of the concentration of certain types in cartilage tissue, many skeletal dysplasias came to be defined as collagen abnormalities. Studies have indicated abnormal synthesis of type II collagen in SED congenita.

Type II collagen is a primary matrix protein of physeal and epiphyseal cartilage. Because an abnormality in type II collagen should affect the molecules throughout the body, it remains unclear how the currently defined abnormality can translate into major structural abnormalities of the vertebrae and capital femoral epiphysis while leaving the distal femur, proximal tibia, and other regions structurally unaffected.

Other rare forms of SED have been described. SED Maroteaux type is a form with manifestations limited to the musculoskeletal system.[7] SED tarda Toledo type is a form of SED tarda with peripheral corneal opacities and a qualitative abnormality of urinary mucopolysaccharides, mainly chondroitin-6-sulfate. Wynne-Davies recognized a form of SED tarda associated with progressive arthropathy similar to juvenile rheumatoid arthritis.[8] Kohn recognized an autosomal recessive variant of SED tarda associated with mental retardation.[9]

Similarly, other forms of SED, such as SED with brachydactyly and SED tarda Namaqualand type (NSED), have been recognized and classified under the International Nomenclature and Classification of the Osteochondrodysplasias. Bailey suggested two groups in addition to SED congenita and SED tarda: pseudo-Morquio disease and pseudoachondroplasia SED.[10]

In this article, only the most common types of SED (ie, SED congenita and SED tarda) are discussed in detail.[11]

Etiology

Spondyloepiphyseal dysplasia congenita

Genetic

SED congenita is transmitted as an autosomal dominant trait. The gene for SED congenita has been mapped to the long arm of chromosome 12 (12q14.3). Gonadal mosaicism has been reported. Advanced paternal age is recognized as a risk factor.

Most cases result from random new mutations. Average-sized siblings have no increased risk of producing a child with SED congenita. When both parents are affected, 50% of offspring are heterozygous and affected; 25% are homozygous, which is ordinarily fatal in the first few months of life; and 25% are unaffected. When one parent is affected, the chance of transmitting this gene to each child is 50%.[12, 13, 14, 15, 16, 17]

Molecular

SED congenita is caused by mutations in COL2A1 (type II collagen alpha 1 chain) on chromosome 12.[18, 19, 20]  These result in abnormal type II collagen. Type II collagen is the major collagen of nucleus pulposus (spine), cartilage, and vitreous (eye).

Other skeletal dysplasias affected by collagen II include achondrogenesis type II, hypochondrogenesis, Kniest dysplasia, Stickler dysplasia, autosomal forms of SED tarda, and spondylometaepiphyseal (Strudwick) dysplasia.

Spondyloepiphyseal dysplasia tarda

Genetic

SED tarda is genetically distinct from SED congenita. Although it may be transmitted as an X-linked recessive, autosomal recessive, or autosomal dominant trait, the X-linked recessive type is most common.

The X-linked form has been mapped to the Xp22 region. Only males are affected, and mothers are carriers. Carrier females have a 25% risk of having an affected son, a 25% risk of having an unaffected son, a 25% risk of having a carrier daughter, and a 25% risk of having a noncarrier daughter. None of the sons of an affected male are affected; all daughters of an affected male are carriers. A case has been reported in which a girl with Turner syndrome had a diagnosis of SED tarda.[21]

Molecular

The X-linked form of SED tarda is caused by mutation in SEDL (the SED late gene). SEDL has been identified on band Xp22. It encodes a protein of 140 amino acids with a role in vesicular transport.[22]

More than 20 novel mutations affecting SEDL have been recognized; the most common type of SEDL-gene disruption was deletion, representing 40% of the types of identified mutations.

Epidemiology

International statistics

SED congenita is a rare genetic disorder. The prevalence is approximately 3.4 per million population.[8] The incidence rate is approximately 1 per 100,000 live births.

Age-related demographics

SED congenita can be diagnosed at birth.

In SED tarda, appearance may be normal at birth, but the condition becomes apparent later in life. Typically, the condition is clinically manifested around puberty. However, radiographic abnormalities may appear earlier.

Sex-related demographics

SED congenita is autosomal dominant; hence, males and females are affected in equal numbers. Occasional cases of autosomal recessive forms have been identified.

SED tarda is X-linked recessive; hence, only males are affected. However, certain autosomal forms have been recognized, so females are occasionally affected.

Race-related demographics

Most of the studies on SED involve patients from North America, Europe, and South Africa. Isolated cases have been reported from Asia and other Arab countries. Though patterns of inheritance have been identified, most cases result from sporadic mutation. No racial predilection exists.

Prognosis

SED is nonlethal, and life expectancy is not reduced. However, morbidity is increased, and regular monitoring and follow-up care should be encouraged. Morbidity associated with SED may include the following conditions:

Patients with SED live as long as people without SED. They can have families and are able to contribute to society. They should be encouraged to live a productive and active life.

Patient Education

A clinical geneticist may be of help to provide counseling to the family. The proper establishment of the mode of inheritance aids in genetic counseling.

Patients with neck instability should be advised regarding activity restrictions (see Activity).

Dwarfism resource sites include LPA Online and Dwarfism.org. These comprehensive sites provide information on various organizations, specialized equipment, and tips on activities of daily living.

 

Presentation

History

Spondyloepiphyseal dysplasia congenita

Wynne-Davies and Hall identified two clinical groups of spondyloepiphyseal dysplasia (SED) congenita, differentiated by the magnitude of skeletal involvement and severity of coxa vara of the hip.[24] This distinction can be made in patients aged 3-4 years. Patients with mild coxa vara fall just below the third percentile of height. Those with severe coxa vara have adult height of 90-120 cm. The hands and feet are normal in length, in striking contrast to the proximal (rhizomelia) and middle segments (mesomelia) of the limbs, which are extremely short.

Cervical myelopathy may result from atlantoaxial instability. Symptoms include delayed motor development, decreased endurance, progressive weakness, hypotonia, sleep apnea, and alterations in respiration. Respiratory insufficiency may develop secondary to thoracic dysplasia. Sensations tend to be maintained for a considerable period.

Neurologic findings are often greater on one side than the other because the cervical cord often is displaced to one side. Some children may have a triad of findings including odontoid hypoplasia, atlantoaxial instability, and spinal cord compression; symptoms often begin when they are aged 5-10 years. Gait problems are often attributed to the hip and knee deformities, and the diagnosis of the cervical deformities may be delayed. Cervical kyphosis may be present in some patients.

Spinal deformities, such as thoracolumbar scoliosis, kyphosis, and kyphoscoliosis, are common in these patients. These deformities occur much earlier, progress more quickly, and are more rigid than those in idiopathic conditions. Spinal cord compression and spastic paraparesis can occur, primarily with kyphosis or kyphoscoliosis.

Patients with hip deformities (coxa vara, avascular necrosis (AVN)-like changes in the capital femoral epiphysis) may present with hip pain or decreased walking tolerance. They are prone to premature osteoarthritis. Some patients may have valgus deformities of the knee in addition to coxa vara of the hip. These patients frequently have knee pain and increased laxity of the medial collateral ligament. Some patients have clubfeet.[25, 26]

Spondyloepiphyseal dysplasia tarda

Children with SED tarda appear normal at birth and develop clinical manifestations of trunk or hip when older than 4 years. Some patients experience mild growth retardation in childhood. Mild disproportionate trunk shortening occurs, but many patients achieve an adult height of more than 153 cm. Thus, true dwarfism may not be present.

Atlantoaxial instability may be present, and patients may present with neurologic deficits or symptoms. Scoliosis or thoracic kyphosis with exaggerated lumbar lordosis may develop. Patients may present with back pain or stiffness.[27]

Patients may present with hip pain and stiffness in the first or second decade of life. Progressive symptomatic osteoarthritis of the hips and knees may be seen. Angular deformities of the lower extremities are mild.

Physical Examination

Spondyloepiphyseal dysplasia congenita

The diagnosis can be made at birth. Newborn infants are short, with disproportionate involvement of the trunk. In certain cases, patients who are assessed in the neonatal period and in their first year of life may not demonstrate short stature according to clinical height measurements and growth charts, though the diagnosis may be evident by clinical features and radiographic abnormalities.

Generally, in patients with SED congenita, the outstretched fingers reach the knee region instead of midthigh because of the short trunk, even in the neonate. The head-to-pubis (upper segment) measurements are reduced to approximately 75% of normal value, whereas the pubis-to-heel (lower segment) measurements are reduced to approximately 60-80% of normal value.[8, 24]

Adult height ranges from 90 to 167.5 cm. Height charts have been developed for SED congenita. The hands and feet are normal in length, in striking contrast to proximal and middle segments of the limbs, which are extremely short.

Motor development may be delayed. Intelligence is usually unaffected.

Head circumference is normal, but the face is flat, with wide-set eyes. Cleft palate is common. The neck is short, and a pectus carinatum deformity may be present in combination with a barrel-shaped chest.

Os odontoideum or odontoid hypoplasia may lead to atlantoaxial instability. Throughout growth and development, the neurologic status must be assessed in these patients to detect any deficits.[28]  The signs suggestive of spinal cord compression include pyramidal tract signs—namely, spasticity, hyperreflexia, Babinski sign, and clonus. Motor weakness may be present; however, sensory examination findings are usually normal. Gait may be abnormal and should be evaluated.

Increased incidence of lumbar lordosis and associated hip flexion contractures are observed even in the newborn period. The abdomen is protuberant. Thoracic scoliosis or kyphosis may become evident in adolescence. Single- and double-curve patterns have been noted. Thoracic kyphosis may be severe, measuring up to 130°. Kyphosis or kyphoscoliosis can be rigid and severe.

Coxa vara of varying severity is almost universal. A waddling gait may be apparent. Coxa vara may be associated with progressive dislocation if ligamentous laxity is present. The delayed ossification of the capital femoral epiphysis predisposes the hip to deformation with flattening, lateral extrusion, hinge abduction, and premature osteoarthritis. Often, a valgus alignment of the knees may develop, associated with overgrowth of the medial femoral condyle. Genu varum may also occur, albeit rarely. Clubfeet may be present in some patients.

Associated ocular anomalies include myopia with retinal detachment (>50%) and cataracts.[29]  Other ocular manifestations include buphthalmos, secondary glaucoma, and strabismus; however, the corneas are clear.

Other associated conditions include deafness and abdominal or inguinal hernia. A rare form of SED congenita is associated with nephrotic syndrome.

Spondyloepiphyseal dysplasia tarda

In SED tarda, appearance is normal at birth. True dwarfism may not be present. Patients exhibit normal achievement of motor and cognitive milestones. Mild disproportionate trunk shortening occurs. In some patients, the condition remains unrecognized until the adolescent years, when hip pain or scoliosis develops. The diagnosis is suggested in males with disproportionately short stature in adolescence or adulthood and with a relatively short trunk and barrel-shaped chest. Upper-to-lower body segment ratio is usually about 0.8. Arm span typically exceeds height by 10-20 cm.

Atlantoaxial instability may occur secondary to odontoid hypoplasia or os odontoideum. The upper cervical spine should be assessed and a neurologic examination should be performed.[30]  Scoliosis or kyphosis with an exaggerated lumbar lordosis may be present. The curves are similar to those observed in patients with adolescent idiopathic scoliosis. These curves may progress and become severe enough to require treatment.

Epiphyseal involvement in patients with SED tarda is primarily in the shoulders, hips, and knees. Involvement is symmetrical bilaterally. Changes in the hip may mimic bilateral Legg-Calve-Perthes disease. Varying degrees of coxa magna, flattening, extrusion, and subluxation may be present. Osteoarthritis of the hip is a common sequela.

Nephrotic syndrome has been reported in association with SED tarda.[31]

Complications

Common conditions associated with SED include the following:

  • Neck instability
  • Spinal deformities such as scoliosis, kyphosis, or lordosis
  • Ocular abnormalities such as myopia or retinal detachment
  • Hearing deficits
  • Hip deformities, including coxa vara and capital femoral epiphyseal involvement
  • Equinovarus foot
  • Degenerative joint disease of the hips, knees, or shoulders

Patients with musculoskeletal dysplasias, such as SED, who undergo total joint arthroplasty may be at increased risk for surgical-site infection and perioperative hemorrhage, possibly because of the anatomic complexity encountered.[32]

 

DDx

Diagnostic Considerations

Other problems to be considered include the following:

  • Morquio disease (see Table 1 below)
  • Chondrodysplasia punctata
  • Pseudoachondroplasia (short-limb dwarfism, hands and feet affected)
  • Perthes disease (asymmetrical stages, evidence of healing)
  • Kniest disease (characteristic facies, absent platyspondyly)
  • Metatrophic dwarfism (paper-thin vertebrae, dumbbell-shaped metaphyseal flaring, battleaxe-like pelvic configuration)

Table 1. Differential Diagnoses of Spondyloepiphyseal Dysplasia Congenita vs Morquio Disease (Open Table in a new window)

Characteristic

SED Congenita

Morquio Disease

Inheritance

Autosomal dominant

Autosomal recessive

Molecule affected

Collagen type II

Mucopolysaccharides

Clinical manifestation

Birth

End of first year

Flared ilia

Absent

Present

Os pubis ossification

Absent

Present

Acetabular angle

Small

Wide

Femoral neck

Varus

Valgus

Hands and feet affected

Minimal

Severe

Eye changes

Myopia, retinal tears

Corneal clouding

Keratosulfaturia

Absent

Present

Differential Diagnoses

 

Workup

Laboratory Studies

Fine metachromatic inclusions have been described in peripheral lymphocytes. The urinary excretion of acid mucopolysaccharides, including keratosulfate, is normal in patients with spondyloepiphyseal dysplasia (SED), in contrast to that in patients with Morquio disease.

Radiography

Spondyloepiphyseal dysplasia congenita

According to Spranger and Langer,[2]  a complete skeletal survey is warranted in the initial assessment. This includes the following[33] :

  • Anteroposterior (AP) and lateral skull, cervical skull with AP, open mouth, and lateral views in flexion, neutral, and extension
  • Posteroanterior (PA) views of the wrist and hand
  • AP and lateral projections of the elbows, hips, and knees
  • AP and lateral views of the thoracolumbar vertebrae
  • AP film of the lumbar and sacral regions

A generalized delay occurs in the development of ossification centers. The epiphyseal centers of the distal femur and proximal tibia, os pubis, calcaneus, and talus, which are usually present at birth, are absent in these patients. The femoral heads may not be apparent on radiographs until patients are aged 5 years. When the epiphyses do appear, they are flattened and irregular in shape (see the image below).

Spondyloepiphyseal dysplasia. Radiograph of the pe Spondyloepiphyseal dysplasia. Radiograph of the pelvis depicting delayed ossification of capital femoral epiphyses, metaphyseal flaring, horizontal acetabular roofs, triangular fragment on the inferior aspect of the broad femoral neck, and coxa vara.

Varying degrees of platyspondyly are present, with posterior wedging of vertebral bodies giving rise to oval, trapezoid, or pear-shaped vertebrae (see the image below). The ossification of the bodies may be incompletely fused, as depicted in frontal projection. In adolescents and young adults, end-plate irregularities and narrowed intervertebral disk spaces become obvious with increased AP diameter of the vertebral bodies. Lumbar lordosis is usually exaggerated. Progressive kyphoscoliosis may develop in late childhood. The most marked abnormality is usually at the thoracolumbar junction, where gross ventral hypoplasia may be present.

Spondyloepiphyseal dysplasia. Radiograph of the sp Spondyloepiphyseal dysplasia. Radiograph of the spine depicting increased anteroposterior diameter, platyspondyly, posterior wedging of the vertebrae, and increased lumbar lordosis.

Skull examination may reveal a steep anterior base, with an increased angle between the floor of the anterior fossa and clivus (up to 165°, compared with 110-145° in healthy individuals). Odontoid hypoplasia or os odontoideum leading to atlantoaxial instability is common (see the first image below). Flexion-extension lateral cervical radiographs may reveal anterior, posterior, or AP instability. The thorax is broad and bell-shaped (see the second image below), and the ribs may flare at the anterior ends. Costovertebral angles are increased, and intercostal spaces are narrow.

Spondyloepiphyseal dysplasia. Radiograph of the up Spondyloepiphyseal dysplasia. Radiograph of the upper cervical vertebrae depicting ununited odontoid process.
Spondyloepiphyseal dysplasia. Radiograph of the ch Spondyloepiphyseal dysplasia. Radiograph of the chest, depicting bell-shaped chest and decreased height of the trunk due to platyspondyly.

The iliac crests are short and small, with horizontal acetabular roofs and delayed ossification of the pubis. The iliac bones are small in their cephalocaudad dimension, with lack of normal flaring of the iliac wings. The Y cartilage is wide. The acetabular fossae are deep and appear empty as a consequence of the severely retarded ossification of femoral heads. Coxa vara of varying severity is almost always present (see the image below)

Spondyloepiphyseal dysplasia. Radiograph of the pe Spondyloepiphyseal dysplasia. Radiograph of the pelvis depicting delayed ossification of capital femoral epiphyses, metaphyseal flaring, horizontal acetabular roofs, triangular fragment on the inferior aspect of the broad femoral neck, and coxa vara.

In patients with severe coxa vara, progressive varus deformity may occur, leading to discontinuity of the femoral neck and proximal migration of the greater trochanter. The femoral shafts ride high under the iliac wings, and pseudoarticulation of the greater trochanters with the lateral margins of iliac crest is suggested.

The delayed ossification of the femoral head predisposes the hip to deformation with flattening, lateral extrusion, hinge abduction, and premature osteoarthritis. Ossification of the femoral head and neck proceeds slowly, frequently from multiple foci. The metaphyseal line of ossification frequently has a mottled appearance, and the femoral heads appear mottled and granular.

The ossification centers of the distal femur and proximal tibia are delayed, leading to flattening and irregularity. Genu valgum is usually present, with overgrowth of the medial femoral condyle. Mild flaring of the metaphyses of long tubular bones may be present, along with irregular ossification from alterations in endochondral bone formation. Full-length radiographs of the lower extremity may be indicated to depict the overall alignment before surgical procedures of the hip or knee.

The long tubular bones are relatively short and broad. Some metaphyseal flaring is present, especially in the region of the distal femur and proximal and distal humerus. The short tubular bones of the hands and feet are minimally broadened and shortened. Ossification of carpal and tarsal centers is usually delayed or disorganized, with occasional extra epiphyses. Wynne-Davies reported on the appearance of an epiphysis at the base of the second metacarpal, first seen in the patient at age 1-2 years.

Spondyloepiphyseal dysplasia tarda

Changes may not be apparent in radiographic images in children younger than 4-6 years.

Changes suggestive of atlantoaxial instability, platyspondyly, kyphoscoliosis, and epiphyseal involvement are similar to those seen in patients with SED congenita. However, the thoracic spine is typically involved to a greater extent in SED tarda. In the X-linked recessive type of SED tarda, a mound of bone is typically present in the central and posterior portions of the superior and inferior end plates. These changes are seen on lateral radiographs and are not features of the autosomal dominant or recessive types of SED tarda.

Epiphyseal involvement in SED tarda is primarily in the shoulders (see the image below), hips, and knees symmetrically. For the weightbearing joints of the lower extremities, delayed ossification predisposes the joint to deformation and premature osteoarthritis. Changes in the hip may mimic bilateral Legg-Calve-Perthes disease.

Spondyloepiphyseal dysplasia. Radiograph of should Spondyloepiphyseal dysplasia. Radiograph of shoulder, depicting severe epiphyseal involvement of proximal humerus, leading to premature osteoarthritis.

Varying degrees of coxa magna, flattening, extrusion, and subluxation are present.

Magnetic Resonance Imaging

Cervical myelopathy may result from C1-2 instability. Magnetic resonance imaging (MRI) can be used to delineate cord compression. MRI may be obtained before surgical intervention in patients with severe spinal deformities.

MRI may be used to evaluate the condition of the epiphyseal centers before reconstructive procedures.

Hip Arthrography

Hip arthrography may be indicated to document congruity of the femoral head or hinge abduction. Severe varus deformity of the cartilaginous femoral neck is usually present and can be depicted on arthrography.

Computed Tomography

Computed tomography (CT) may be used to assess the configuration of bones and joints prior to surgical intervention. Three-dimensional reconstructed images may facilitate surgical planning in severe cases.

Other Tests

Although the gene for SED congenita has been located, its location is variable. Antenatal gene testing is available. Antenatal testing for SED tarda may be offered on the basis of molecular diagnosis.

Histologic Findings

Yang et al described the pathologic findings in patients with SED.[34] Abnormalities of the proliferative zone have been identified, with microcystic areas surrounded by a ring of cells. The chondrocytes of the resting zone appear vacuolated, containing periodic acid–Schiff (PAS)-positive cytoplasmic inclusions. Ultrastructural examination revealed these inclusions to be accumulations of fine granular material in dilated cisterns of rough endoplasmic reticulum. However, heterogeneity is present, and these findings are not consistent.

 

Treatment

Medical Care

The American Academy of Pediatrics (AAP) and the Committee on Genetics have developed recommendations to assist the pediatrician in caring for children with spondyloepiphyseal dysplasia (SED) and their families. The Skeletal Dysplasia Management Consortium has developed best practice guidelines for diagnosis and management of type II collagen skeletal dysplasias (including SED).[5]

A clinical geneticist may be of help to provide counseling to the family. A geneticist may also be a valuable resource for the pediatrician seeking additional information or consultation. The proper establishment of the mode of inheritance not only aids in genetic counseling but also enables the orthopedist to distinguish achondroplastic dwarfism from other forms of dwarfism, many of which have an autosomal recessive inheritance.

The following services should be involved for the comprehensive care of the patients:

  • Ophthalmologist - Regular ophthalmologic examination is necessary in patients with SED congenita to identify pathologic retinal conditions, vitreoretinal degeneration, or severe myopia
  • Neurologist - Consultation is recommended for assessment of infantile hypotonia, generalized motor delay, or myelopathy
  • Pulmonologist - Pulmonary functions should be evaluated, and respiratory complications such as apnea, pneumonia, restrictive lung diseases, and cyanosis should be evaluated

Surgical Care

Orthopedic and other surgical procedures are indicated in patients with SED. Although these can be performed safely in most patients, specific structural and physiologic abnormalities should be carefully considered, especially by the anesthesia team.

Spondyloepiphyseal dysplasia congenita

Most of the orthopedic problems encountered in patients with SED congenita are related to atlantoaxial instability and spine, hip, and knee deformities.[35]

Posterior atlantoaxial fusion is indicated for patients with signs and symptoms of atlantoaxial instability measuring 8 mm or more or myelopathy. Fusion to the occiput may be required due to the small size of the posterior ring of the atlas or the presence of a large midline synchondrosis. Halo vest immobilization is necessary postoperatively in patients with odontoid hypoplasia and extension instability.

In skeletally immature patients with scoliosis measuring 40° or less, initial treatment should be use of a brace. Bracing is often ineffective by reason of the small trunk size, the rigidity of the curves, and the marked amount of trunk rotation. However, Milwaukee brace treatment may be useful in delaying the fusion until the patient is older.[36]

Patients with curves that progress despite brace treatment or that measure more than 50° should be considered candidates for a posterior spinal fusion. In patients aged 3-10 years, a distraction rod inserted without spinal fusion allows growth to continue for several years and minimizes the scoliosis. The spine is then fused at skeletal maturity.

The use of anterior (open or video-assisted thoracoscopic surgery [VATS]) and posterior approaches improves correction in these patients, in whom rigidity is more prominent and occurs at earlier ages than in patients with idiopathic SED. Instrumentation systems designed for smaller younger patients combined with the use of sensory and neuromuscular monitoring increase the safety of surgical intervention.

In adult patients, standard instrumentation may be used because the spinal canal is not narrowed by bone dysplasia. The lordosis in these patients is not sufficient to warrant primary surgery.

Although antilordotic bracing has been used, no indication of its effectiveness has been published. Much of the lumbar lordosis is secondary to hip flexion deformities and improves upon surgical correction of hip position. Milwaukee brace with kyphosis pads was successful in preventing progression of thoracic kyphosis in one study.[36]

When the deformity progresses in spite of nonsurgical management, surgical fusion is required to prevent spinal cord compression and spastic paraplegia. Anterior and posterior fusions are recommended for rigid curves and in younger patients.

In patients with coxa vara, if the femoral neck-shaft angle measures 100° or less, the Hilgenreiner-epiphyseal angle is greater than 60°, or an inverted triangular fragment is present, Bassett recommended a valgus intertrochanteric osteotomy to prevent progressive varus deformity or discontinuity of the femoral neck. The neck-shaft angle should be corrected to at least 140° at the time of surgery to prevent recurrent deformity. Simultaneous extension with the valgus osteotomy decreases the flexion deformity of the hip and may improve lumbar lordosis.

Bayhan et al assessed midterm (mean follow-up, 5 years) clinical, radiographic, and gait outcomes after valgus hip osteotomy in 26 patients (12 boys, 14 girls; 48 hips) with SED congenita and coxa vara.[37]  Preoperative pain was noted in 30 hips; at final follow-up, three hips were painful at the extreme range of motion (ROM). Passive ROM, radiographic neck shaft angle (NSA), and Hilgenreiner-trochanteric (H-T) angle improved postoperatively; NSA was maintained during follow-up, but the H-T angle deteriorated. Spinopelvic measurements changed significantly, and gait remained stable except for pelvic tilt, which reduced significantly after surgery.

In patients with subluxation, hinge abduction, or osteoarthritis, reconstructive measures may be indicated. Open reduction with femoral and acetabular osteotomies may be performed to treat hip dislocation.

Hip arthroscopy has been used for the treatment of acute or semiacute changes in hip pain in patients with multiple epiphyseal dysplasia and SED.[38] A wide spectrum of intra-articular pathologies, such as labral tears, chondral flaps, and loose bodies, can be addressed through arthroscopy.

A varus supracondylar femoral osteotomy or a proximal tibial and fibular osteotomy can be considered for patients with symptomatic knees or severe valgus deformities. Proximal femoral valgus osteotomy for coxa vara further accentuates the distal femoral valgus. Medial hemiepiphyseal stapling of the distal femoral or the proximal tibial growth plate can be performed. Lateral patellar dislocation is relatively frequent, and treatment can be conservative or surgical, depending on the circumstances.[39]

Equinovarus deformities (clubfeet) may require surgical correction if they cannot be managed with physical therapy or serial casting.

Spondyloepiphyseal dysplasia tarda

Scoliosis in a patient with SED tarda should be managed in much the same fashion as idiopathic scoliosis in adolescents. Bracing should be considered for curves approaching 30° in skeletally immature patients. Posterior spinal fusion may be required for curves not controlled with bracing. Similarly, atlantoaxial instability may require posterior stabilization.

Osteoarthritis of the hip is a common sequela, and valgus or valgus-extension intertrochanteric osteotomy may improve hip congruity. Osteoarthritis in adulthood may be treated using total joint arthroplasty.[40] Custom components may be necessary due to the anatomy and length of the femur. Coxa magna may be evident, and acetabular augmentation may be useful if the acetabulum is insufficient to contain the enlarged femoral head.

As with SED congenita, a wide spectrum of intra-articular pathologies, such as labral tears, chondral flaps, and loose bodies, can be addressed through hip arthroscopy.[38]

Activity

Because of neck instability, persons with SED congenita should be advised to exercise caution and to avoid activities or sports that could result in trauma to the neck or head. Patients who have instability with an atlantodental interval (ADI) of 4 mm or more or symptomatic instability should not be allowed to participate in competitive sports.

Many low-impact activities are recommended for persons with SED, including bicycling, dancing, aerobics, rowing, spinning, swimming, walking, water jogging, and water aerobics.

Consultations

Before any surgical intervention, consideration should be given to various structural and physiologic abnormalities, especially by the anesthesia team. Odontoid hypoplasia, short and unstable neck, pectus carinatum, decreased pulmonary functions due to thoracic cage malformation, and rigid spinal deformities are some of the concerns that should be considered during preoperative evaluation. In addition, the following consultations are recommended:

  • Ophthalmologist - Regular ophthalmologic examination is necessary in patients with SED congenita to identify pathologic retinal conditions, vitreoretinal degeneration, or severe myopia
  • Neurologist - Consultation is recommended for assessment of infantile hypotonia, generalized motor delay, or myelopathy
  • Otolaryngologist - Consultation is recommended for assessment of sensorineural hearing loss, recurrent otitis media, and cleft palate
  • Geneticist - A clinical geneticist may be of help to provide counseling to the family and also may be a valuable resource for the pediatrician seeking additional information or consultation; proper establishment of the mode of inheritance not only aids in genetic counseling but also enables the orthopedist to distinguish achondroplastic dwarfism from other forms of dwarfism, many of which have an autosomal recessive inheritance
  • Pulmonologist - Pulmonary functions should be evaluated, and respiratory complications such as apnea, pneumonia, restrictive lung diseases, and cyanosis should be evaluated
  • Pediatrician - The AAP and the Committee on Genetics have issued recommendations to assist the pediatrician in caring for children with SED and their families