Introduction
Skeletal dysplasias or osteochondrodysplasias comprise a large heterogeneous group
of genetic disorders affecting the development of bone and cartilage, with more than
450 recognized disorders.[1]
[2] Although they are individually rare conditions, together, they account for an average
incidence of 1 in 5000 births and a prevalence of approximately 2.3 to 7.6 per 10,000
births according to various studies.[1]
[2]
[3]
[4] A majority of these dysplasias lead to significant morbidity in the affected children,
while some of them are lethal in the perinatal period.[5] The diagnosis of this complex group of disorders requires the consolidation of clinical,
laboratory, and radiological data. However, most of these dysplasias are notorious
for significant clinical as well as imaging overlap, posing a diagnostic dilemma to
the radiologist. A skeletal survey is routinely performed in the evaluation of a suspected
case of skeletal dysplasia; hand radiographs form a part of the complete survey. Accurate
diagnosis is imperative because in addition to treating the child; it is crucial to
provide genetic counselling to predict the outcome of future pregnancies.[5]
[6]
Frontal radiographs of the hand and wrist are acquired in posteroanterior projection
with a film focal distance of 100 cm. While imaging the nondominant hand suffices
in bone age assessment, radiographs of both hands should be acquired when suspecting
a skeletal dysplasia. [Fig. 1A] demonstrates an optimally acquired normal hand radiograph.
Fig. 1 Descriptive terms in the interpretation of hand radiographs: (A) Normal, (B) arachnodactyly, (C) short fingers in brachydactyly, (D) clinodactyly, and (E) synpolydactyly.
Conditions Where Hand Radiograph Is Diagnostic
Desbuquois Dysplasia
Desbuquois dysplasia is an autosomal recessive chondrodysplasia characterized by mutations
in the CANT1 gene thereby leading to severe growth retardation, short extremities
and multiple dislocations.[9] Patients typically present within 6 years of age. Diagnostic findings on hand radiographs
include short metacarpals (brachymetacarpism), bifid distal phalanx of the thumb,
phalangeal dislocations, advanced carpal bone age, and delta phalanx, which refers
to a longitudinally oriented bracketed small epiphysis located on the lateral aspect
of the phalanx. It additionally lies parallel to the phalanx and thereby gives the
appearance of a delta ([Fig. 2]).[10] Other supporting features include flattened proximal femoral metaphysis with a medial
spike and exaggerated lesser tuberosity, thereby giving the “Swedish key” appearance,
flattened acetabular roof, proximal fibular overgrowth, coronal spinal clefts, enlarged
first metatarsals, and precocious tarsal bone age.[9]
[10]
Fig. 2 Desbuquois dysplasia. Posteroanterior projectional radiographs (A and B) of bilateral hands demonstrate short metacarpals with a longitudinally oriented
bracketed small “delta” epiphysis on the radial aspect of and paralleling the proximal phalanx of left middle
finger (arrow).
Progressive Pseudorheumatoid Arthropathy
Progressive pseudorheumatoid arthropathy (PPRA), also known as progressive pseudorheumatoid
dysplasia (PPRD), is a genetic skeletal dysplasia occurring due to a loss-of-function
mutation in WNT-1 inducible signaling protein 3 (WISP3) gene that encodes for type II collagen, hence leading to progressive deterioration
of articular cartilage.[11]
[12] Usual presentation is between 3 and 6 years of age with painless stiffness and restricted
movement in multiple joints, gait abnormalities, and bony enlargement of interphalangeal
joints in hands.[12] Features of juvenile idiopathic arthritis (JIA), namely articular pain and morning
stiffness, are typically absent in PPRD.[11]
[12] Radiographic findings characteristic of this entity include metaphyseal expansion
of proximal phalanges of hand and feet with associated flexion deformities or camptodactyly,
which are usually most marked at proximal interphalangeal joints ([Fig. 3]). Bone age is often delayed. Typical findings on lateral spine radiographs include
gouge-shaped anterosuperior vertebral endplate defects with mild platyspondyly and
kyphosis.[11]
[12] Epiphyseal and metaphyseal enlargement with associated irregularity and flexion
deformities in long bones are other supportive findings. Spine-related findings with
preserved density and absence of periarticular bone erosions help to distinguish this
entity from the more common JIA.[12]
Fig. 3 Progressive pseudorheumatoid arthropathy in a patient who initially presented with
a clinical suspicion of juvenile idiopathic arthritis. Posteroanterior hand radiographs
(A) demonstrate diffuse osteopenia and metaphyseal expansion involving the phalanges,
which is the most marked at distal ends of the proximal phalanges (arrows). Periarticular
erosions are distinctly absent. Lateral spine radiograph (B) shows mild platyspondyly (asterisks) with the characteristic “gouge-shaped” scooping
erosions involving the anterosuperior ends of vertebral bodies (arrows, B).
Brachytelephalangic Chondrodysplasia Punctata
Chondrodysplasia punctata (CDP) refers to a heterogeneous group of epiphyseal dysplasias
characterized by defective endochondral ossification and subsequent deposition of
multiple calcific foci.[13]
[14] Mutation in arylsulfatase gene has been identified in about 30% cases with plausible
causal association with vitamin K deficiency.[13] Patients with brachytelephalangic CDP present with facial dysmorphism in the form
of mid facial hypoplasia, flat nose, hypertelorism along with short digits.[13]
[14 ]Punctate calcifications and stippling in the vertebrae and in the epiphysis of the
long bones are commonly observed, as in all CDPs.[14] Imaging findings peculiar to this entity include calcific stippling in the craniocervical
region, tarsal and carpal bones and vertebra with hypoplasia of phalanges, metacarpal
and metatarsal bones, and triangle-shaped hypoplastic distal phalanges being most
characteristic ([Fig. 4]).[13]
[14] Craniocervical junction (CVJ) stenosis with subsequent spinal compromise is common;
imaging of CVJ with computed tomography (CT) and magnetic resonance imaging (MRI)
should, therefore, be offered in the neonatal period for early detection and stabilization.[14]
Fig. 4 Brachytelephalangic chondrodysplasia punctata in a 7 months' male infant patient.
Posteroanterior hand radiographs (A and B) showing punctate stippling of carpal and metacarpal bones with hypoplastic phalanges,
especially the distal phalanges that appear triangle-shaped (arrow).
Angel Shaped Phalango-Epiphyseal Dysplasia
This rare genetic condition is characterized by disordered phalangeal development
and ossification with an autosomal dominant pattern of inheritance.[15] Age of presentation is variable; clinical features include extensive hyperextensibility
of the fingers, swan neck deformity hypodontia, and precocious osteoarthritis of the
hips.[15]
[16] Hand radiographs demonstrate brachydactyly, delayed and incomplete ossification
of phalanges with pseudoepiphysis formation.[16] These abnormalities are most pronounced in the middle phalanges, thereby resulting
in the characteristic “angel shaped” phalanges, which is a result of defective epi-meta-diaphyseal
development. Resultant diaphyseal cuffing (representing the “wings” of an angel),
surrounding the metadiaphyseal region (body) with a cone-shaped epiphysis (“skirt”)
and pseudoepiphysis (“head”) produces this appearance.[15] ([Fig. 5]) Carpal age is often delayed. Pelvic radiographs show delayed femoral head ossification,
which evolve into small, fragmented epiphysis (similar to Perthes) with subsequent
degeneration of the hip joint. Evaluation of other long bones shows a generalized
delay of ossification of epiphyses and apophyses with Scheuermann like irregularities
in spine.[15]
Fig. 5 Angel shaped phalango-epiphyseal dysplasia. Hand radiograph (A) demonstrating brachytelephalangy (solid arrows). Magnified image (B) of the distal phalanges show variable morphology of the distal phalanges. The left
fourth distal phalanx shows an “angel like” appearance. The arrowheads depict the
hands, and the arrows, the skirt.
Albright's Hereditary Osteodystrophy
Pseudohypoparathyroidism type Ia (OMIM entry # 103580), also known as Albright's Hereditary Osteodystrophy (AHO), is an inherited
metabolic disorder occurring due to maternal allelic loss of function mutation in
the Gs-alpha isoform of the GNAS gene that ultimately leads to multihormonal end organ resistance.[17]
[18] Common clinical features include short stature, obesity, round facies, and brachydactyly.
Some patients have mental retardation with defective olfaction. Enamel hypoplasia
and blunt root development are frequent dental defects.[19] Laboratory findings include hypocalcemia and hyperphosphatemia, which resemble parathyroid
hormone deficiency.[19] Typical manifestations in hand radiographs include brachydactyly with brachymetacarpia
and brachytelephalangy, which are most pronounced at III, IV, and V metacarpals and
I distal phalanx and have been reported in approximately 70% of patients ([Fig. 6]).[18] Delayed bone age, osteopenia, and subcutaneous ossifications are other typical features.[18]
[19]
Fig. 6 Albright's hereditary osteodystrophy. Posteroanterior hand radiograph showing brachymetacarpia
most marked at left third and bilateral fourth, and fifth metacarpals (arrows). Brachytelephalangy,
especially in bilateral first and second digits, is also appreciated (arrowheads).
The child had heterotopic nontraumatic ossifications over the face.
Robinow Syndrome
Robinow syndrome is a heterogeneous disorder characterized by mesomelic or acromesomelic
shortening of limbs, facial spinal, and genital anomalies.[20] Two major forms based on inheritance are recognized, namely the severe autosomal
recessive and mild autosomal dominant varieties.
Clinically, there is short stature, midfacial hypoplasia with hypertelorism, short
upturned nose with flat nasal bridge, tented upper lip and low set ears, and an occasional
midline capillary hemangioma[20]
[21]. Generally, the mesomelic shortening of the forearm is more striking than the shortening
in the leg.
Radiographs demonstrate brachydactyly with shortening of the distal phalanx, fusion
of the phalanges, and fusion of the carpal bones. A diagnostic feature is the splitting
or clefting of one or more distal phalanges, especially that of the thumb ([Fig. 7]).[20]
[21] The radial head is dislocated (especially in recessive form) with Madelung deformity
due to hypoplastic distal ulna.[21] The latter finding is, however, nonspecific and has other more common causes like
exostosis and Leri–Weill dyschondrosteosis. Spinal radiographs show kyphoscoliosis
with segmentation anomalies and hemivertebrae.[20] Genital abnormalities include micropenis, cryptorchidism, reduced clitoral size,
and hypoplastic labia minora. The dominant variety presents with normal stature and
mild mesomelic shortening with normal upper lip and few spinal abnormalities. Radial
head dislocation is absent in this entity.[20]
[21]
Fig. 7 Robinow syndrome. Radiograph of the left hand demonstrating brachydactyly with shortened
distal phalanges and a longitudinal split in the distal phalanx of the thumb (arrow),
which is a diagnostic for this entity.
Hereditary Multiple Exostoses
Exostosis or osteochondromas are benign bone tumors of cartilaginous origin arising
from the growth plate. Multiple exostoses occur as an autosomal dominant inherited
condition, known as diaphyseal achalasia or hereditary multiple exostoses (HME).[22] Positive EXT gene germline mutations on chromosomes 8, 11, and 19 have been linked to this condition.[23] Frequent sites of involvement include the distal femur, proximal tibia, wrist and
hands, humerus, ankle, pelvis, and ribs. Osteochondromas in HME are more likely to
be sessile than pedunculated.[22] On radiographs, they are seen as bony outgrowths demonstrating medullary continuity
with the parent bone and are directed away from the growth plate direction. The cartilaginous
cap is difficult to identify on radiographs unless mineralized.[22]
[23] These may cause a “bayonet hand” or pseudo-Madelung deformity in the upper limbs
due to foreshortening of the ulna in relation to the radius, which has been reported
in about one-third of patients ([Fig. 8])[23]. Common complications include fractures, vascular compromise, impingement on nerves
and tendons, overlying bursitis, and malignant transformation, which have been reported
in up to 3 to 25% of patients.[22]
[24] Suspicious features include growth after skeletal maturity, pain after physeal closure,
new onset cortical destruction, soft tissue, and a thickened cartilage cap more than
1.5 cm.[22]
[23]
Fig. 8 Hereditary multiple exostosis. Posteroanterior hand radiographs (A) showing a sessile bony outgrowth in distal metaphysis of right ulna (arrow) suggestive
of an osteochondroma. Mild bowing of the radius is also seen. Radiographs of left
upper limb (B) showing multiple similar sessile and pedunculated outgrowths (arrows) in the long
bones.
Ollier's Disease
Ollier's disease denotes the presence of multiple enchondromas, which are benign cartilaginous
tumors. Coexistence of these tumors with osteochondromas is called metachondromatosis.[24]
[25] Short bones of the hand are the most commonly predisposed site of involvement. Radiographs
demonstrate multiple radiolucent lesions with narrow transition zone, sclerotic margins,
and characteristic “rings and arcs, popcorn” varieties of chondroid calcification
([Fig. 9]).[25] Rates of malignant degeneration to chondrosarcoma reach up to 50% in this condition,
according to a recent study and MRI may be used as a screening method detecting malignant
transformation in both HME and Ollier's disease.[24]
Fig. 9 Ollier's disease. Anteroposterior radiograph of the left forearm and wrist demonstrating
few expansile lytic lesions with flocculent “popcorn” calcifications in the distal
metadiaphyseal region of ulna (arrow) and fifth metacarpal suggestive of enchondromas.
Associated bowing of the radius is also present.
Mucopolysaccharidosis
Mucopolysaccharidosis (MPS) is a group of disorders characterized by deficiency of
enzymes responsible for the degradation of glycosaminoglycans (GAG). As a result,
there is progressive multisystemic accumulation of GAGs. A gamut of skeletal abnormalities
is seen in MPS, collectively termed as dysostosis multiplex. Hand radiographs in MPS
show a claw hand deformity resulting from accumulation of GAGs in soft tissues. Short
and thick metacarpals with proximal pointing are seen, with bullet-shaped phalanges.
Carpal bones are hypoplastic, with dysplastic epi-metaphysis of the radius and ulna,
resulting in a V-shaped deformity, which causes alteration in the carpal angle ([Fig. 10]).[26]
Fig. 10 Mucopolysaccharidosis I. Radiograph of hand (A) demonstrating short and thick metacarpals, with proximal pointing (white arrow).
Also note the bullet-shaped appearance of the phalanges (arrowheads) and dysplastic
radial, ulnar epiphysis (asterisk). Lateral radiograph of the spine (B) showing anterior beaking (arrow) with a thoracolumbar kyphus. Radiograph of the
pelvis (C) showing rounded iliac blades (arrow), inferior tapering of iliac wings, and an underdeveloped
acetabulum (asterisk, C). Lateral radiograph of the skull (D) showing a J-shaped sella (arrow).
Mucolipidosis
Mucolipidosis (ML) is autosomal recessive lysosomal storage disorder that results
in development of abnormal cell architecture and inclusion of intracytoplasmic bodies
within the mesenchymal cells, particularly fibroblasts. Resultant overflow of lysosomal
enzymes is seen into the serum/CSF/urine. Hand radiographs in ML demonstrate changes
of dysostosis multiplex similar to MPS with proximal pointing of the metacarpals,
diaphyseal thickening (undertubulation), and bullet shaped phalanges ([Fig. 11]). Madelung deformity due to abnormal epi-metaphyseal development of the distal radius
and ulna may also be seen. Since proximal pointing of metacarpals is also shared MPS,
it is imperative to differentiate between the two entities; periosteal thickening
or cloaking at distal ulna and radius is an important feature observed in ML and is
absent in MPS ([Fig. 11]).[27]
Fig. 11 Mucolipidosis. Posteroanterior radiograph of the left hand (A) showing significant absence of the normal diaphyseal constriction (undertubulation—white
arrows, A) in hand bones along with proximal pointing of the metacarpals (black arrow). The
metaphysis of the radius and ulna is abnormal with shortening of the ulna and periosteal
cloaking of ulna (arrowhead). Frontal and lateral radiographs of the spine (B and C) demonstrating anterior beaking within the vertebral bodies (arrows, b).
Diastrophic Dysplasia
Diastrophic dysplasia is a rare autosomal recessive skeletal dysplasia that manifests
as shortened limbs, spinal abnormalities, joint abnormalities, and “Hitchhiker thumb.”[28] Clinically, patients have proximal abducted thumbs and great toe, joint contractures,
short limbs, cleft palate, normal intellect, cervical kyphosis, and club feet. Radiographs
demonstrate characteristic abducted, hypermobile, proximally placed thumb (hitchhiker's
thumb), marked shortening of the first metacarpal with irregular lengthened other
metacarpals, ankylosis of proximal interphalangeal joints, and bizarre ossification
of the hand bones ([Fig. 12]).[28] Epiphyseal and metaphyseal irregularity in distal femur and tibia with V-shaped
or chevron deformities are other features ([Fig. 12]). The vertebral bodies also appear irregular.[28]
Fig. 12 Diastrophic dysplasia. Clinical images (A and B) showing limb shortening with abducted thumb (A) and great toes (B) representing the characteristic Hitchhiker deformity. Hand radiograph (C) demonstrating markedly shortened first metacarpal bilaterally (arrows, C). Other metacarpals appear shortened and irregular (asterisks) with bizarrely ossified
carpal bones (short arrows). The distal radial epiphyses are widened, irregular, and
“V” shaped. Knee radiograph (D) showing epimetaphyseal enlargement and irregularity in distal femur and proximal
tibia that appear chevron shaped (arrows, D).
Larsen Syndrome
Larsen syndrome is an autosomal dominant osteochondrodysplasia occurring due to mutation
in the FNLB gene.[29] Clinical features include recurrent large joint dislocations, cylindrical fingers
with broad fingertips (spatulate), and facial dysmorphism (midface hypoplasia, depressed
nasal bridge and cleft palate). Radiological examinations show multiple joint dislocations
along with vertebral anomalies. Hand radiographs demonstrate supernumerary carpal
and tarsal bones, with small distal phalanges (particularly of the thumb) ([Fig. 13]). Differentiation from desbuquois dysplasia is made on the basis of its autosomal
recessive inheritance, presence of accessory ossification centers of metacarpals and
phalanges, advanced carpal ossification, and hand deformities that are seen in DBDS.[30]
Fig. 13 Larsen syndrome. Hand radiograph (A) showing supernumerary carpal bones (solid arrows) with shortening of the metacarpals
(arrowheads). Also note significant shortening of the phalanges of the thumb (asterisk)
and accessory ossification centers for the proximal phalanges (arrows). Frontal and
lateral radiographs of the left knee (B and C) showing dislocation of the knee joint with medial and anterior displacement of the
femoral condyle over the tibia (arrows).
Rubenstein-Taybi Syndrome
Rubinstein-Taybi syndrome (also known as broad thumb syndrome) is a rare genetic disorder
characterized by facial dysmorphism, intellectual disability and broad, angulated
thumbs and great toes. Facial dysmorphism is in the form of an antimongoloid slant,
beaked nose, and a high arched palate. Diagnosis is often evident clinically with
an additive role of radiographs in supporting the diagnosis. Radiographs of the hand
demonstrate a broad thumb which is angulated radially, with a delta (triangular) appearance
of the 1st proximal phalanx.[31] In addition, terminal broadening of the distal phalanges has been reported, along
with clinodactyly of the fifth digit.[32]
Conditions Where Hand Radiograph Are Suggested
These conditions have been summarized in [Table 3].
Table 3
Conditions where the hand radiograph is suggestive of an underlying skeletal dysplasia
|
Condition
|
Findings on hand X-ray
|
Other findings on skeletal survey
|
|
Achondroplasia
|
Trident hand
|
Trident pelvis, progressive narrowing of lumbar interpedicular distance, rhizomelic
long bone shortening, “tombstone” pelvis
|
|
Osteogenesis imperfecta
|
Thin osteopenic metacarpals and phalanges
|
Multiple vertebral platyspondyly, thin long bones with bowing and fractures/ deformity,
multiple Wormian bones
|
|
Osteopetrosis
|
Sclerotic bones with “bone within bone” appearance
|
Generalized osteosclerosis, “sandwich” vertebrae, similar long bone appearance
|
|
Pyknodysostosis
|
Sclerotic bones, acro-osteolysis of distal phalanges
|
Obtuse mandibular angle, multiple Wormian bones, open sutures, “spool shaped” vertebral
bodies
|
|
Hajdu-Cheney syndrome
|
Band acro-osteolysis of distal phalanx
|
Bulging of the squamous occipital bone, Wormian bones, platybasia, aplasia of the
frontal sinuses
|
|
Metaphyseal chondrodysplasia
|
Irregularity and sclerosis of metaphyses of wrist joint and short long bones of the
hand
|
Similar appearance of other metaphyses
|
|
Spondylometaphyseal dysplasia
|
Irregularity and sclerosis of metaphyses of wrist joint
Metaphyseal “corner fracture” in a variant
|
Similar appearance of other metaphyses
Variable vertebral changes
|
|
Ellis-van Creveld syndrome
|
Postaxial polydactyly, carpal coalition (capitate and hamate), and fusion of the metacarpals
|
Outward curve of humeri, delayed ossification of the lateral tibial condyle and proximal
tibial exostosis, trident pelvis
|
|
Acromicric dysplasia
|
Delayed bone age with shortening of the metacarpals and phalanges, internal notching
of the second and external notching of the fifth metacarpals
|
Similar changes in the feet
|
|
Acromesomelic dysplasia
|
Short and broad hand bones with cone shaped epiphysis
|
Supra-acetabular notch, shortening of the dorsal margins of the vertebrae with a ventral
protrusion
|
|
Multiple epiphyseal dysplasia
|
Small irregular sclerotic carpal bones and epiphyses
|
Similar epiphyseal changes around other joints of the body, double-layered patella
(in autosomal recessive variant)
|
|
Thanatophoric ([Fig. 23])
|
Trident hand
|
Trident pelvis, platyspondyly, “telephone handle” femora
|
|
Pseudoachondroplasia ([Fig. 24])
|
Delayed bone age, small irregular epiphyses, wide flared metaphyses, cone shaped metaphyses,
small metacarpals
|
Central “tongue-like” protrusion of anterior vertebral bodies
Delayed ossification of femoral head and y cartilage
|
|
Cleidocranial dysostosis ([Fig. 25])
|
Accessory epiphysis at the base of second metacarpal
|
Pseudo pubic diastasis
Absent/hypoplastic clavicles
|
Achondroplasia
Achondroplasia is the most common nonlethal skeletal dysplasia, resulting from a mutation
in the gene affecting fibroblast growth factor receptor 3 and presenting with rhizomelic
dwarfism. The abnormalities on hand radiographs include short and thick tubular bones,
with widening of the space between the 2nd and 3rd digits, resulting in a trident
hand deformity. Decreased distance between the epi and metaphysis of the bone is seen,
with the limbs of the metaphysis encompassing the epiphysis resulting in a “V”/chevron
deformity and apparent widening of the joint spaces ([Fig. 14]).[33]
Fig. 14 Achondroplasia. Hand radiographs (A) demonstrating short and tubular hand bones with widened space between the second
and third digits (asterisks), known as the trident hand deformity. Radiograph of the
pelvis and bilateral lower limbs (B) showing squared iliac blades with trident acetabuli (black arrows) along with rhizomelic
shortening of bilateral femori. The distal femoral epiphyses are small with the flared
metaphyses forming a “V” or a chevron deformity (arrowheads) at bilateral knee joints.
Osteogenesis Imperfecta
Osteogenesis imperfecta (OI), also known as “brittle bone disease,” is an osteopenic
skeletal dysplasia occurring due to mutations in the genes responsible for polypeptide
arrangement in collagen, resulting in altered biomechanical properties in the involved
tissues. This is responsible for the radiographic features, which include osteopenia,
multiple fractures, and progressive skeletal deformities. Several types of OI have
been described, with varying severity and radiographic findings. Hand radiographs
in OI show significant osteopenia with cortical thinning, along with thinned out metacarpals
([Fig. 15]).[34] Deformities secondary to prior fractures may also be seen.[35]
Fig. 15 Osteogenesis imperfecta. Hand radiograph (A) showing osteopenia with slender and thinned out metacarpals with associated cortical
thinning (white arrows). Radiographs of the dorsolumbar spine (B and C) showing significant osteopenia with biconcave collapse of the vertebral bodies and
resultant scoliotic deformity. Lateral radiograph of the skull (D) showing multiple Wormian bones (arrows).
Osteopetrosis
Osteopetrosis (also known as marble bone disease) is a sclerosing bone dysplasia,
characterized by a failure of osteoclast development or maturation, resulting in impaired
resorption of the primary spongiosa and hence dense bones (however more prone to fractures
due to reduced bone mass). Multiple subtypes have been described, based on the age
of presentation and severity. The autosomal recessive form has been described with
multiple fractures in utero and generalized osteosclerosis with narrowing of the skull
base foramina. The autosomal dominant form presents in childhood and adolescents with
increased bone density, characteristic “sandwich vertebrae,” and narrowing of the
normal medullary cavity of long bones.[36] Hand radiographs demonstrate generalized osteosclerosis with obliteration of the
medullary cavity. In addition, the primitive (endobones) may be seen replacing the
medullary cavity, resulting in a “bone within bone” appearance ([Fig. 16]). The distal radius and ulna may show alternating dense transverse bands.[37]
Fig. 16 Osteopetrosis. Hand radiographs (A) showing loss of the medullary cavity within the bones with well-defined “endobones”
replacing the same (arrows). Radiographs of the dorsolumbar spine (B) and (C) showing generalized increased bone density with maintained vertebral height (white
arrows, C). There is mild bulbous prominence of the posterior ends of the ribs suggestive of
extramedullary hematopoiesis (black arrows, B).
Pyknodysostosis
Also known as Maroteaux-Lamy dysplasia, pyknodysostosis is another sclerosing bone
dysplasia that results from impaired osteoclast function. Clinical presentation is
in the form of short stature and hypoplasia of the midface. Hand radiographs demonstrate
generalized increase in bone density with a preserved medullary cavity. In addition,
there is resorption of the terminal phalangeal tips (acro-osteolysis) ([Fig. 17]).[37] Preservation of the medullary cavity, presence of acro-osteolysis, and widely open
anterior fontanelle along with an obtuse mandibular angle help to differentiate pyknodysostosis
from osteopetrosis on radiographs.
Fig. 17 Pyknodysostosis. Radiograph of the right hand in a 7-year-old girl (A) showing generalized increase in bone density with preservation of the medullary
cavity (arrows). Resorption of the tuft of the second terminal phalanx is seen (arrowheads),
suggestive of acro-osteolysis. Lateral radiograph of the skull (B) showing an obtuse mandibular angle (arrowhead) along with an open posterior fontanelle
(arrow).
Hajdu-Cheney Syndrome
Hajdu-Cheney syndrome is a rare autosomal dominant disorder of the connective tissue
that occurs as a result of mutation in the NOTCH2 gene responsible for regulation
of skeletal development and bone remodeling. Hajdu-Cheney syndrome presents clinically
with short stature, progressive shortening of fingers and toes, and a flat facial
profile with coarse hair. Predominant radiological findings include abnormalities
of the cranial vault (bulging of the squamous occipital bone, Wormian bones, platybasia,
aplasia of the frontal sinuses) along with band acro-osteolysis in the hands and feet.[38] Band acro-osteolysis appears as a linear band of lucency just distal to the proximal
end of the terminal phalanx, and is characteristic of this condition.[39]
Metaphyseal Chondrodysplasia
Metaphyseal chondrodysplasia (MCD) is a group of disorders, with dysplastic development
of the metaphysis of long bones. Depending on the predominant various types of bone
involvement, they are classified into different subtypes. Of them, Jansen type MCD
is the one that commonly affects the short long bones of the hand and the wrist joint
([Fig. 18]).[40]
Fig. 18 Metaphyseal chondrodysplasia (Jansen type). Hand radiograph showing significant metaphyseal
irregularity with associated sclerosis involving the distal metaphysis of the bilateral
radii and ulna. Metaphyses of the rest of hand bones are normal.
Spondylometaphyseal Dysplasias
Spondylometaphyseal dysplasias are a group of disorders wherein the spine is also
affected in addition to the long bone metaphysis. Various subtypes are described.
Of them, Sutcliffe type/corner fracture type presents with metaphyseal corner fractures
around the wrist joints ([Fig. 19]). When suspected on hand radiograph; a spine radiographic finding of ovoid vertebrae;
and corner fractures around hip and knee joints confirm the radiological diagnosis
([Fig. 19]).[41]
Fig. 19 Spondylometaphyseal dysplasia (Sutcliffe type). Frontal radiograph of the left hand
(A) showing metaphyseal corner fractures involving the distal ulna (arrow). Frontal
radiograph of the right leg (B) showing metaphyseal corner fractures involving the medial end of the right proximal
and lateral end of the right distal tibia (white arrows). Radiographs of the dorsal
spine (C and D) showing ovoid shape of the vertebral bodies (black arrows).
Ellis-van Creveld Syndrome
Ellis-van Creveld syndrome (also known as chondroectodermal dysplasia) is a cause
of mesomelic shortening of bones, characterized by cardiac anomalies, genu valgum,
and dysplastic nails and teeth. Radiological findings include shortening of the forearm
and leg bones, delayed ossification of the lateral tibial condyle, and proximal tibial
exostosis along with a trident shaped acetabulum. Hand radiographs demonstrate postaxial
polydactyly, carpal coalition (capitate and hamate), and fusion of the metacarpals
([Fig. 20]).[42]
Fig. 20 Ellis-van Creveld syndrome. Radiograph of both hands (A and B) showing bilateral postaxial polydactyly with fusion of the metacarpals for the third,
fourth and fifth, sixth digits bilaterally (arrows, A and B). Radiograph of the chest (C) showing a narrow thoracic cage with outwardly curved bilateral humeri (arrows).
Bilateral lower limb radiograph (D) showing shortening of the leg bones, suggestive of mesomelic shortening with trident
pelvis (arrows).
Acromicric/Acromesomelic Dysplasia
Acromicric dysplasia is a rare bone dysplasia that presents with short stature, short
hands and feet, and facial dysmorphism (round facies, bulbous nose, prominent philtrum).
Classical radiographic abnormalities in the hand include delayed bone age with shortening
of the metacarpals and phalanges, internal notching of the second metacarpals, and
external notching of the fifth metacarpals. These notches tend to disappear in adulthood
([Fig. 21]).[43]
Fig. 21 Acromicric dysplasia. Hand radiograph (A) demonstrating brachymetacarpia (arrows) and brachydactyly with subluxation at third
proximal interphalangeal joints and internal notching of the 2nd metacarpal. Radiographs
of pelvis (B) showing internal notching of femoral head (arrow).
Acromesomelic dysplasias are characterized by severe short stature with shortening
of the middle and distal segments. Head is disproportionately large with flattening
of the midface. Radiographs demonstrate short and broad hand bones with cone-shaped
epiphyses and shortening of the forearm bones. Spine radiographs show shortening of
the dorsal margins of the vertebrae with a ventral protrusion.[44] A supra-acetabular notch on pelvis radiograph is also characteristic ([Fig. 22]).
Fig. 22 Acromesomelic dysplasia. Radiograph of the left hand (A) showing short and broad hand bones (white arrows) along with shortening of the forearm
bones (black arrows). Radiographs of pelvis and proximal femora (B and C) showing supra-acetabular notches (arrowheads), which are characteristic of this
condition.
Fig. 23 Thanatophoric dysplasia. Hand radiograph (A) of a newborn with thanatophoric dysplasia showing short hand bones with a separation
in between the middle and ring fingers (asterisk) suggestive of trident hand. Infantogram
(B) demonstrating hypoplastic iliac blades with trident acetabuli (arrows), rhizomelic
shortening in bilateral femoris that characteristically show telephone handle appearance
(black arrows).
Fig. 24 Pseudoachondroplasia. Hand radiograph (A) showing small irregular epiphyses with
flared metaphyses in the hand bones and small metacarpals (arrows, A), diffuse osteopenia,
and markedly delayed bone age. Frontal (B) and lateral (C) projections of spine radiographs
showing central “tongue-like” protrusion of anterior vertebral bodies (arrowheads,
C) with small irregular femoral heads (arrows, B).
Fig. 25 Cleidocranial dysplasia. Hand radiograph (A) showing an accessory epiphysis at the
base of the second metacarpal (black arrow). Chest radiograph (B) demonstrating hypoplastic
bilateral lateral clavicles, more pronounced on right (white arrows). Pelvic radiograph
(C) showing delayed ossification of pubic bones with resultant pseudo widening and
bilateral coxa vara (arrows).
