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Congenital Skeletal Anomalies


Developmental Skeletal Anomalies

Osteochondrodysplasias

  • These are classified into 33 groups (1–33) ▸ abnormalities are intrinsic to bone and cartilage and will continue to evolve throughout life

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      Dysplasias: abnormalities of bone ± cartilage growth

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      Osteodystrophies: abnormalities of bone ± cartilage texture

  • Conditions referenced elsewhere

Dysotoses (Localized Disorders With Predominant Cranial and Facial Involvement)

  • These are classified into 3 groups (A–C)

  • They are due to altered blastogenesis occurring during the 1 st 6 weeks of life ▸ previously normal bones will remain so (unlike an osteochondrodysplasia) ▸ more than 1 bone may be involved

Osteo-onychodysostosis (nail-patella syndrome, Fong syndrome)

Clinical presentation

Autosomal dominant ▸ multiple skeletal abnormalities (dysplastic knees and elbows) ▸ dysplastic fingernails ▸ clinodactyly (curving of the 5 th finger towards the 4 th finger) ▸ renal disease

Radiological features

Posterior iliac horns ▸ absent or hypoplastic patellae ▸ hypoplastic lateral femoral condyles ▸ genu valgum ▸ hypoplastic capitellum ▸ radial head dislocation ▸ short 5 th metacarpals

Apert's syndrome

Clinical presentation

Sporadic (autosomal dominant in some families) ▸ abnormalities are present from birth ▸ malformations of the skull, face, hands and feet ▸ proptosis ▸ high arched or cleft palate ▸ bifid uvula

Radiological features

Progressive carpal and tarsal fusions ▸ progressive ankylosis of the phalangeal joints ▸ dislocated radial heads ▸ progressive fusion within the cervical spine (commonly C5/C6) ▸ progressive fusion of the large joints ▸ hypoplasia of the glenoid fossae

  • Craniosynostosis: premature fusion of the skull sutures and facial bones

  • ‘Mitten’ or ‘sock’ deformities: these are due to syndactyly (fused digits) of the hands and feet

Mandibulofacial dysostosis (Treacher Collins syndrome)

Clinical presentation

Autosomal dominant ▸ ear deformities ▸ deafness ▸ downslanting eyes ▸ lateral coloboma of the lower eyelid ▸ hypoplastic malar bone ▸ cleft palate

Radiological features

Symmetrical stenosis or atresia of the external auditory meati ▸ maxillary hypoplasia ▸ mandibular hypoplasia ▸ hypoplastic paranasal sinuses

Chromosomal Disorders

Trisomy 21 (Down's syndrome)

Clinical presentation

Craniofacial abnormalities (e.g. brachycephaly, microcephaly, hypertelorism and relatively small facial bones)

Radiological features

The iliac wings are flared with relatively horizontal acetabulae ▸ frequently there are 11 pairs of gracile ribs ▸ there are often two ossification centres within the manubrium sterni (normally only one) ▸ atlantoaxial subluxation and instability with hypoplasia of the odontoid process (which is frequently a cause of myelopathy) ▸ generalized joint laxity ▸ relatively tall vertebral bodies ▸ short hands with clinodactyly of the little finger due to a hypoplastic middle phalanx

  • Associations: congenital heart lesions (e.g. endocardial cushion defects and intra- and extracardiac shunts) ▸ duodenal atresia and stenosis ▸ Hirschsprung's disease ▸ anorectal anomalies

45XO (Turner's syndrome)

Clinical presentation

Short stature ▸ cubitus valgus ▸ webbed neck ▸ widely spaced nipples ▸ lymphoedema

  • Patients have a classical form of ovarian dysgenesis (with streak ovaries and a small uterus) ▸ a 25% incidence of associated ovarian tumours such as a dysgerminoma (occurring up to the age of 20 years)

Radiological features

A short 4 th metacarpal ▸ flattening of the medial tibial condyle with a transitory exostosis ▸ beaked vertebral bodies ▸ osteoporosis ▸ scoliosis ▸ coarctation of the aorta ▸ increased occurrence of urinary tract anomalies (e.g. a horseshoe kidney) ▸ delayed skeletal maturation

  • Madelung deformity: a reduced angle between the distal radial and ulnar metaphyses

Neurocutaneous Syndromes

Neurofibromatosis

Clinical presentation

Autosomal dominant ▸ multiple neurofibromas and schwannomas ▸ axillary freckling, café au lait spots and molluscum fibrosum

  • Up to 85% of patients with neurofibromatosis manifest a musculoskeletal abnormality

Radiological features

See table

Radiographic musculoskeletal features of neurofibromatosis
Soft tissues

  • Focal gigantism (soft tissue overgrowth or plexiform neurofibroma)

  • Neurofibrosarcomas

Skull

  • Macrocrania

  • Aplasia/hypoplasia of the sphenoid wings (‘bare’ orbit)

  • Hypoplasia of the posterosuperior orbital wall (pulsatile exophthalmos)

  • Mesodermal dysplasia (calvarial defects)

  • Neuromas ± fibromas (with enlarged cranial foramina)

Spine

  • Angular kyphoscoliosis

  • Posterior scalloping of the vertebral bodies (dural ectasia)

  • Dumb-bell neurofibromas/lateral meningoceles

Ribs

  • ‘Ribbon’ ribs (mesodermal dysplasia)

  • Rib notching

Tubular bones

  • Pseudoarthroses of the tibia, fibula, or clavicle

  • Anteromedial tibial bowing

  • Fibrous cortical defects (multiple and large)

  • Intraosseous cysts

(A) Apert's syndrome. Radiograph of the hand. ‘Mitten’ polysyndactyly of soft tissues and bones. (B) Apert's syndrome. Lateral radiograph of the cervical spine. Progressive fusion of the cervical spine is a recognized feature of this condition. ©35

Nail-patella syndrome. (A) Radiograph of the pelvis showing hypoplastic pelvic wings (more pronounced on the right side) and a small iliac horn on the right ilium. (B) Lateral knee radiograph. Note absence of the patella bone. ©35

Turner's syndrome. (A) Typical shortening of fourth metacarpals. (B) The medial tibial plateau is depressed and the adjacent femoral condyle enlarged. †

Type 1 neurofibromatosis with a short angular thoracolumbar curve as seen on an anteroposterior radiograph (A) and coronal T2-weighted MR image (B). There is scalloping of the posterior vertebral body wall and enlargement of the exit foramen. The MR image demonstrates dural ectasia with a widened spinal canal. (C) A cystic lesion (arrow) in the tibia at the prefracture stage. The distal fibula is dysplastic and bowed. ©35 , ©34

Selected Osteochondrodysplasias

Achondroplasia (Group 1)

Definition

  • This results from defective endochondral bone formation

  • Limb shortening: rhizomelic (proximal) ▸ mesomelic (medial) ▸ acromelic (distal)

Clinical Presentation

  • Autosomal dominant ▸ short limbs and trunk ▸ narrowed thorax with respiratory distress in infancy ▸ bowed legs ▸ lumbar lordosis ▸ prominent forehead with a depressed nasal bridge ▸ hydrocephalus, brainstem and spinal cord compression (dilatation of lateral cerebral ventricles)

Radiological Features

  • A decreasing interpedicular distance within the lumbar spine (travelling caudally) ▸ short vertebral pedicles ▸ posterior vertebral body scalloping ▸ flat acetabular roofs ▸ short ribs and short wide tubular bones ▸ a large skull vault and a small foramen magnum ▸ relative overgrowth of fibula

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      ‘Bullet-shaped’ vertebral bodies: with an antero-inferior anterior beak

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      ‘Tombstone’ appearance: squared small iliac wings with a small sciatic notch

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      ‘Champagne glass’ pelvis: the pelvic inlet resembles a champagne glass

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      ‘Chevron’ deformity: V-shaped growth plate notches

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      ‘Trident hand’: the fingers are all the same length and diverge into 2 pairs

Pearls

Achondrogenesis

This is a fatal autosomal recessive dwarfism where the abnormalities are similar to those seen in achondroplasia (but are much more severe)

  • Abnormalities include: severe short limb dwarfism ▸ unossified vertebral bodies ▸ a large head with normal or reduced ossification

  • Type I: severe

  • Type II: less severe ▸ it is caused by type II collagen abnormalities leading to abnormal bone and cartilage formation

Achondroplasia in a neonate. (A) Sloping metaphyses, oval transradiant proximal femora and a narrow thorax with short ribs. (B) Mild kyphosis, posterior scalloping of the vertebral bodies, ‘bullet-shaped’ vertebral bodies and short pedicles with associated spinal stenosis. (C) Small square iliac wings, horizontal acetabular roofs, short sacrosciatic notches, progressive caudal narrowing of the lumbar interpedicular distances and low-set sacrum. (D) Short skull base with prominent frontal bone and narrow cervical canal. *

Trident hand in achondroplasia. †

Hypochondroplasia (Group 1)

Definition

  • This is also known as ‘achondroplasia tarda’ with milder features than those seen with achondroplasia

Clinical Presentation

  • Autosomal dominant ▸ variable short stature and a prominent forehead

Radiological Features

  • No normal widening is demonstrated in the interpedicular distance within the lumbar spine (travelling caudally) ▸ short and relatively broad long bones ▸ elongation of the distal fibula and ulnar styloid process ▸ variable brachydactyly

Hypochondroplasia. A narrowed interpedicular distance at L5. †

Overgrowth of the distal fibula in hypochondroplasia. †

Thanatophoric Dysplasia (Group 1)

Clinical Presentation

  • Sporadic, autosomal dominant mutation ▸ this is the most common lethal neonatal skeletal dysplasia ▸ short markedly curved limbs ▸ respiratory distress due to a (small thoracic cage)

Radiological Features

  • Short ribs with wide costochondral junctions ▸ severe platyspondyly ▸ horizontal acetabular roofs with medial spikes ▸ small sacroiliac notches ▸ marked shortness and bowing of the long bones ▸ irregular metaphyses ▸ short broad tubular bones in the hands and feet ▸ small scapulae

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      ‘Telephone handle’ appearance of the long bones: this is due to metaphyseal flaring

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      ‘Cloverleaf skull’: this is due to lateral temporal bulging

  • Type 1: normal skull

  • Type 2: ‘clover leaf’ skull

Thanatophoric dwarfism. A cloverleaf skull is present. The scapulae are hypoplastic and the clavicles high. Platyspondyly is shown, resulting in H-shaped vertebral bodies. The bones are short and bowed. †

Asphyxiating Thoracic Dysplasia (Jeune's) (Group 9)

Clinical Presentation

  • Autosomal recessive (often lethal) ▸ respiratory problems with a long narrow thorax ▸ short hands and feet ▸ nephronophthisis in later-life survivors

Radiological Features

  • Small thorax with short ribs (horizontally orientated) ▸ widened costochondral junctions ▸ high clavicles ▸ short iliac bones ▸ horizontal acetabula with medial and lateral ‘spurs’ (‘trident’ appearance) ▸ ‘wineglass’ pelvis ▸ premature appearance of the proximal femoral ossification centres ▸ cone-shaped phalangeal epiphyses ▸ may have polydactyly (10%)

Asphyxiating thoracic dystrophy. (A) Narrow thorax and short ribs. (B) Horizontal acetabular roofs and pronounced medial spurs, less pronounced laterally (‘trident’ appearance). *

Metatropic Dysplasia (Group 8)

Definition

  • The development of dwarfism changes over time – the trunk gradually shortens relative to the limbs (due to the developing kyphoscoliosis) – hence the name 'metatropic'

Clinical Presentation

  • Variable inheritance (autosomal dominant or recessive) ▸ short limbs ▸ relatively narrow chest ▸ small appendage in the coccygeal region (tail) ▸ progressive kyphoscoliosis

Radiological Features

  • Short tubular bones with marked metaphyseal widening (‘dumb-bell’) ▸ platyspondyly ▸ relatively large intervertebral discs ▸ flat acetabular roofs ▸ short iliac bones ▸ short ribs with anterior widening ▸ hypoplastic odontoid process

Radiographs in a newborn with metatropic dysplasia. (A) Spine: dense vertebral bodies and short ribs with anterior splaying. (B) Thorax: long trunk and small chest. (C) Pelvis: short iliac wings, narrow sciatic notches, irregular acetabular roofs and halberd (hunting ax)-shaped with trumpet-shaped metaphyses. (D) Upper extremities: flared proximal humeral and distal radial and ulnar metaphyses ▸ shortened long bones. ©24

Metaphyseal Chondrodysplasia (Group 13)

Definition

  • Severe short-limbed dwarfism

  • Schmid type: more common ▸ mild ▸ predominantly involves the lower limbs

  • Jansen type: less common ▸ more severe ▸ symmetrical involvement of all tubular bones

Clinical Presentation

  • Autosomal dominant ▸ short limbs, short stature, presenting in early childhood ▸ genu varum (bow legs) ▸ waddling gait

Radiological Features

  • Metaphyseal flaring ▸ irregular widened growth plates (most marked at the hips) ▸ increased density and unevenness of the metaphyses (particularly the upper femora and around the knees) ▸ large femoral capital epiphyses ▸ coxa vara ▸ femoral bowing ▸ anterior cupping of the ribs ▸ normal spine

Metaphyseal chondrodysplasia (A) Jansen type. Femora are short with marked expansion, irregular ossification and some sclerosis of the metaphyses. Epiphyses are large and rounded. (B) Schmid type. There is bilateral coxa vara, the metaphyses are splayed and irregular and there is lateral bowing of the femora. *

Ellis–Van Creveld (Chondroectodermal Dysplasia) (Group 9)

Clinical Presentation

  • Autosomal recessive ▸ short stature ▸ short limbs (more marked distally) ▸ polydactyly ▸ hypoplasia of the nails and teeth ▸ ectodermal dysplasia with sparse hair ▸ congenital cardiac defects (e.g. ASD) ▸ fusion of upper lip and gum

Radiological Features

  • Short ribs in infancy ▸ short iliac wings ▸ ‘trident’ appearance – the pelvis becomes more normal in childhood ▸ premature ossification of the femoral capital epiphyses ▸ laterally sloping proximal tibial metaphysis ▸ exostosis of the medial upper tibial shaft ▸ carpal fusions ▸ cone-shaped epiphyses (middle phalanges) ▸ polydactyly of the hands and feet

Postaxial polydactyly in a patient with chondroectodermal dysplasia (Ellis-van Creveld syndrome). The plain radiographs show an extra digit on the ulnar side of the right hand. Note also bony fusion of the fifth metacarpal digit and the metacarpal of the extra digit (bony syndactyly). ©35

Ellis–van Creveld syndrome. Postaxial polydactyly, short middle and terminal phalanges, cupped metaphyses (the epiphyses will be cone-shaped when they ossify) and sloping of the proximal humeral metaphysis. **

Spondyloepiphyseal Dysplasia Congenita (Group 2)

Clinical Presentation

  • Autosomal dominant ▸ short stature ▸ cleft palate ▸ myopia ▸ maxillary hypoplasia ▸ thoracic kyphosis and lumbar lordosis ▸ barrel-shaped chest

Radiological Features

  • Ovoid, pear-shaped, irregular-sized vertebral bodies in infancy ▸ irregular platyspondyly in later life ▸ L5 smaller than L1 in infancy ▸ odontoid hypoplasia and cervical spine instability ▸ short long bones ▸ absent ossification of the epiphyses of the knees, talus and calcaneus at birth ▸ pubic and ischial hypoplasia ▸ severe coxa vara developing in early childhood ▸ horizontal acetabulum

Spondyloepiphyseal dysplasia congenita in a neonate. (A) Absent ossification of the pubic rami, short femoral necks and absent ossification of the epiphyses at the knees. (B) ‘Pear-shaped’ vertebral bodies with posterior constriction. *

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