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

Dysplasias: abnormalities of bone ± cartilage growth

Osteodystrophies: abnormalities of bone ± cartilage texture

• Conditions referenced elsewhere

Group 25 (dysplasia with increased bone density)

– Osteogenesis imperfecta (Section 5 Chapter 7, Osteogenesis imperfecta)

Group 31 (disorganized development of cartilagenous and fibrous skeletal components)

– Multiple cartilaginous exostoses (diaphyseal aclasis) (Section 5 Chapter 5, Osteochondroma)

– Enchondromatoses (± haemangiomas) (Section 5 Chapter 5, Benign bone tumours: (En)chondroma)

– Fibrous dysplasia (Section 5 Chapter 5, Fibrous dysplasia)

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