Leg bowing in pediatric population: A pictorial review
Poster No.: C-2338
Congress: ECR 2014
Type: Educational Exhibit
Authors: 1 1 1 2
M. Sah , S. Babu , S. A. R. Mustafa , G. Herdman , S. J. Morris ;
1
1 2
Cardiff/UK, Bridgend/UK
Keywords: Genetic defects, Dysplasias, Congenital, Intrauterine diagnosis,
Imaging sequences, Education, Ultrasound, Plain radiographic
studies, Pediatric, Musculoskeletal bone, Bones
DOI: 10.1594/ecr2014/C-2338
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Learning objectives
1. To illustrate the various causes of leg bowing in children.
2. Characteristic imaging appearances in a variety of causes of leg
bowing in paediatric population.
3. Differentiating imaging features for lower extremity bowing.
Images for this section:
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Fig. 9: Osteogenesis imperfecta type 3: The AP radiograph of the lower extremity of a
new-born shows marked deformity, multiple fractures and bowing of the long bones.
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Background
This article provides an overview of different causes of lower extremity bowing in children
and examples from our clinicoradiological practice.
The commonest cause of leg bowing in children is physiological. The pathological
causes include traumatic, infection (osteomyelitis, syphilis), metabolic diseases (rickets,
scurvy), connective tissue disorders (osteogenesis imperfecta), genetic disorders
(neurofibromatosis type 1, achondroplasia), Blount's disease and various developmental
and congenital causes.
We also describe the characteristic radiological findings of foetal limb bowing
(campomelic dysplasia, thanatophoric dysplasia).
We discuss briefly the merits of various imaging modalities and the salient imaging
features of different conditions.
Images for this section:
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Fig. 20: Neurofibromatosis type 1: The AP radiograph shows anterolateral bowing of the
tibia with thinning of the fibula. Pseudoarthrosis, fracture and cortical thickening at the
level of lower one third of the tibia are noted in both AP and lateral images.
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Findings and procedure details
The aetiology of lower extremity bowing in infants and children:
Varieties of conditions results in leg bowing in the paediatric population and vary
according to the patient's age. Trauma, neoplastic and infective (Osteomyelitis and
Syphilis) causes need to be considered in all age groups.
Furthermore, radiologists should always be alert of the possibility of non-accidental
trauma (NAI) as a differential diagnosis.
Physiological leg bowing:
Genu varum (angle out): The most common cause for lower extremity bowing is
physiological. The cause of this is due to the folded leg position in utero. The bowing of
leg is symmetrical and is not progressive. Usually by eighteen months to three years of
age, the alignment of leg corrects and straightens out [1].
Genu valgum (angle in): To a certain degree, majority of children become knocked kneed
between 3 to 5 years of age. This usually resolves by seven years. Knock knees are
usually associated with leg bowing (Fig. 1).
The causes of pathological bowing are detailed as below
(Entries are not exhaustive):
1. Trauma Torus/ Greenstick fracture ,Plastic
deformation, Malunion, NAI
2. Infective Osteomyelitis, Syphilis
3. Tumours Primary osseous tumours: Osteosarcoma,
Ewing's, haemangioma
Metastasis:lymphoma,neuroblastoma
Soft tissue tumours
4. Metabolic Rickets, Hypophosphatasia, Scurvy
5. Genetic/Hereditary Neurofibromatosis type 1, Achondroplasia,
Metaphyseal dysplasia, Thanatophoric
dysplasia, Campomelic dysplasia
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6. Congenital or Developmental bone Fibrous dysplasia (McCune Albright
disorders syndrome),Skeletal dysplasia, Fibular
hemimelia
7. Neuromuscular/ connective tissue Osteogenesis imperfecta, Cerebral
disorders palsy, Ehlers-Danlos syndrome, Marfan's
syndrome
8. Inflammatory Infantile cortical hyperostosis or Caffey's
disease
9. Miscellaneous Blount's disease, Lead intoxication,
Fluoride intoxication
Red Flag signs indicating specialist referral [2, 3]:
1. Limping or unwell (tachycardia, fever, malaise) child with functional disability of more
than 4 weeks, complaining of night pain or early morning stiffness.
2. History of weight loss, bruising, constant pain unrelated to movement should alert the
possibility of malignancy.
3. Persistence of bow legs in children older than three years and significant knock knees
beyond age seven.
4. Unilateral or an excessive asymmetrical deformity
5. Progressive deformity.
6. Bowing as a result of trauma or associated skeletal deformities.
7. In a case of genu valgum if the intermalleolar separation is more than 8 cm. During
supine position this is the distance between malleoli with knees together.
8. Intercondylar distance > 6 cm in a case of genu varum. Clinically this is the distance
between knees with the malleoli touching.
Bowing of legs in the setting of trauma:
The epiphyseal growth plates are responsible for the longitudinal growth of a bone. Injury
to it may result into asymmetrical growth and bowing.
Torus or buckle fracture (caused by compressive force), greenstick fracture (force applied
to the side) and plastic deformation are the common form of injuries.
Targeted X-rays in at least two planes are necessary for the diagnosis. Majority of these
fractures are successfully treated in a cast (Fig. 2).
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Infection and lower extremity bowing:
Osteomyelitis: Possibility of infection arises in the presence of one or more of the clinical
or laboratory signs; e.g. if the child is unwell, tachycardic, swelling and tenderness over
the affected area with raised inflammatory markers. In paediatric population tibia is the
second most commonly affected bone (24%) after femur (27%) [4]. If not adequately
treated acute osteomyelitis may develop into chronic osteomyelitis and permanent
deformity of extremity [5].
Radiographs have a limited role in demonstrating early changes. However, after four
to six weeks these may show ill-defined lucencies with associated periosteal reaction.
MRI is the investigation of choice in demonstrating early altered bone marrow signal and
inflammatory changes in the soft tissue. It can also define the extent of the disease. Bone
scans may be the second-line investigation.
Syphilis: This is a rare cause for limb bowing in children. Long bones are commonly
affected in congenital or tertiary syphilis. Recurrent ulceration in limbs with anterior
bowing and classic thickening of tibia (sabre tibia) are usually present [6]. MRI is
extremely helpful in showing osseous involvement.
Tumours causing leg bowing in children:
Depending on the location of the tumours in long bones these may cause bowing of the
limbs.
The commonest paediatric primary osseous tumours are osteosarcoma andEwing's
sarcoma. The child most commonly presents with painful limb prior to development of
soft tissue swelling and mass lesion [7]. Pathological fractures are present in nearly 15%
of cases [8].
Conventional radiographs may show an aggressive looking lesion eroding through the
cortex and extending into the soft tissue, significant periosteal reaction with associated
soft tissue swelling (Fig. 3). MRI defines extent of local disease and also for assessing
bone and surrounding soft tissues changes. CT is commonly used for staging purpose
in malignant bone tumours while valuable in showing periosteal reaction inEwing's
sarcoma [8]. Osteosarcomas affect metaphysis whileEwing's sarcoma usually occurs in
the diaphysis.
Metabolic disorders affecting architecture of the long bones:
Rickets: Abnormal vitamin D metabolism results in deficient bone mineralization. The
affected children may presents with hypocalcaemia seizures, delayed gross motor
development or tetany [9]. The classic radiographic features are osteopenic bones,
thinning of long bones cortices, cupping and fraying of the metaphysis, widened
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growth plate with frayed physeal borders and enlarged epiphysis (Fig. 4). Associated
insufficiency fractures/looser zones may also be seen.
Hypophosphataemic rickets: This condition is a dominant X-linked disorder secondary
to phosphate-wasting. Anterolateral bowing of the femur with coxa and tibia vara is the
commonest deformity (Fig. 5). Windswept lower limb deformity which is angular valgus
deformity in one knee joint with varus deformity in the other knee is also a common finding
[10].
Scurvy: The underlying cause of this disease is vitamin C deficiency. Children are usually
very lethargic, complaining of bone pain and they are more prone to bleeding tendencies.
The important radiographic features include: generalised osteopenia, periosteal reaction
as a result of sub periosteal haemorrhage, metaphyseal spurs and cupping, dense zone
of provisional calcification (Frankel's line) and bowing of long bones (Fig 6). A round,
radiopaque shadow may also be seen surrounding the epiphyseal centre of ossification
which is a typical finding called Wimberger's sign.
Connective tissue disorders:
Osteogenesis Imperfecta (OI): OI is an inherited connective tissue disorder. The
common finding is generalised osteoporosis and is more prone to multiple fractures
resulting in callus formation and pseudoarthrosis. There are several types of OI. Type
1 is the most common and mildest form (Fig. 7). The lower limb imaging findings are
osteopenia, bowing of long bones and diaphyseal fractures. Type 2 is a perinatal lethal
form (Fig. 8). The condition is characterized by increased bone fragility, low bone density
and susceptibility to bone fractures. Children with type 2 OI may present with multiple
rib and long bone fractures. Marked deformities of the long bones, skull, scapulae and
pelvic bones are also seen.
The severe form is type 3 and the features are short stature, spinal deformities, limb
bowing and multiple fractures (Fig. 9, 10) [11]. These severe forms have anterolateral
bowing of proximal femur (shepherds' crook deformity), multiple wormian bones and blue
sclera.
Developmental bone disorders affecting lower extremity:
Fibrous dysplasia: This causes expansion of the bones due to replacement of medullary
cavity with fibrous tissue. Two forms are known, they are monostotic and polyostotic
(Fig. 11). Polyostotic fibrous dysplasia occurs in McCune- Albright syndrome (Fig.12, 13).
The radiographic manifestations are well defined, expansile, mixed sclerotic or lucent
bone lesions. There is characteristic ground glass opacity. The lower extremity findings
of severe polyostoic form are shepherd's crook deformity of femur neck (coxa vara),
protrusio acetabuli and severe bowing of long bones [12].
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Leg bowing in genetic disorders:
Neurofibromatosis Type 1 (Von Recklinghausen disease): This is an autosomal
dominant disorder, however; 50% of cases may arise as spontaneous mutations.
Children usually present in infancy with unilateral anterolateral bowing of the lower
leg but a child may be born with fracture or pseudoarthrosis [13, 14] (Fig. 14). Tibia
is the commonest bone affected in the long bones. It can result in non union with
the development of a pseudoartherosis. On conventional radiographs usually the tibial
bowing appears typically near the junction of the middle and distal thirds of the tibia. Often
the distal fragment is pointed with cupped proximal end [14]. Other feature may include
a thin or absent fibula. MRI is very useful for preoperative planning [14].
Thanatophoric Dysplasia: The commonest congenital lethal skeletal dysplasia. It
occurs sporadically with an unknown aetiology. Ultrasound is capable of diagnosing the
condition second trimester onwards [15] (Fig. 15). Suspicious features include a dwarf
foetus with shortened femur and bowing of limbs (Fig.16). Other findings include narrow
conical thorax, short neck, protuberant abdomen and clover-leaf deformity of the skull.
Intrauterine death is very common.
Achondroplasia: There is abnormal enchondral bone formation with typical proximal
limb shortening. The iliac wings are squared with narrow sciatic notches. Flat acetabular
roofs are present. There are shortened and thickened long bones with metaphyseal
flaring. The distal femur has abnormal shape of growth plate. The ankle varus deformity
can result in relative shortening of tibia in comparison to fibula [16] (Fig. 17).
Campomelic dysplasia: Rare genetic disorder with mutation of chromosome 17. The
radiographic findings are dysplastic pelvic bones, bowing of femur and tibia. Other
skeletal manifestations are hypoplastic scapula and spinal anomalies. The limb bowing is
diagnosed with antenatal ultrasound. More than 95% are lethal in neonatal period, death
due for respiratory failure [17]. Ischio- pubic- patella syndrome is a characteristic imaging
finding of this condition [18].
Metaphyseal dysplasia (Pyle's disease): Rare genetic disorder with autosomal
recessive inheritance. The radiographic findings are metaphyseal widening and cortical
thinning of long bones resulting in Erlenmeyer flask deformity of the distal femur and
proximal tibia [19] (Fig.18). Other findings are mild hyperostotic cranium.
Inflammatory conditions resulting in leg bowing:
Caffey's disease (Infantile cortical hyperostosis): The affected infant usually presents
with proliferative bone changes, soft tissue swelling and irritability. Plain films help in
confirmation of the presence of skeletal manifestations and soft tissue swelling. The
condition is usually unilateral which typically only affects the diaphysis of the long
bones. A thickened, laminated sub periosteal new bone formation occurs with cortical
hyperostosis.
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Miscellaneous:
Blount's disease: Aetiology is unknown. This occurs in young children and adolescents
and presents as growth disturbance of the medial tibial growth plate resulting in
angulation of the bone. Commonly bilateral and is asymmetric. There are three types:
infantile, juvenile and adolescent forms. Findings include tibia varus deformity with
fragmented medial tibial epiphyses and beaking of the proximal tibial metaphyses
(Fig.19). The metaphyseal- diaphysis angle is > 11 degrees (the angle is formed between
the lines drawn perpendicular to long axis of tibia and through the tibial metaphyseal
beak [20].
Images for this section:
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Fig. 1: Physiological leg bowing: AP image of knees of a young patient showing slight
bowing of distal femurs.
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Fig. 2: The AP radiograph shows bowing deformity of the distal shaft of femur as a result
of an old fracture.
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Fig. 3: Tumour: A large soft tissue haemangioma in a neonate, causing bowing of the
tibia.
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Fig. 4: Rickets: The lateral radiograph of knee shows metaphyseal flaring, cupping and
modelling deformity of the lower femur. The growth plate is also widened
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Fig. 5: Hypophosphotaemic rickets: The image demonstrates metaphyseal cupping of
the femur and tibia. Slight bowing of the tibia is also noted.
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Fig. 6: Scurvy: AP radiograph of knee of a 24 months old child showing epiphyseal
widening and bowing of the distal femur and proximal tibia. Spurring of the proximal tibial
metaphysis is also seen. There is lucency in the distal femur due to bone infarct.
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Fig. 7: Osteogenesis imperfecta type 1: The AP radiograph showing generalised
osteopenia, spiral fracture of the distal tibia and proximal fibula and bowing of tibia.
Fig. 8: Osteogenesis imperfecta Type 2: Babygram of 21 weeks old showing severe
shortening and multiple fractures of long bones.
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Fig. 9: Osteogenesis imperfecta type 3: The AP radiograph of the lower extremity of a
new-born shows marked deformity, multiple fractures and bowing of the long bones.
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Fig. 10: Osteogenesis imperfecta type 3: Bone scan shows abnormal tracer uptake of
the right femur and tibia due to multiple fractures. Marked bowing of the right tibia and
fibula are also seen.
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Fig. 11: Monostotic fibrous dysplasia: The lateral radiograph shows a mixed density
lesion in the middle third of the tibia. Subtle anterior tibial bowing, endosteal scalloping
and a transverse pathological fracture are also noted.
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Fig. 12: AP plain film: A case of McCune-Albright syndrome with polyostotic fibrous
dysplasia. The blue arrow demonstrates the shepherd's crook deformity of the right
proximal femur. Ground glass changes of the proximal femur with medullary expansion
are seen.
Fig. 13: AP radiograph of the pelvis: Surgical correction of coxa vara in a case of
polyostotic fibrous dysplasia. Marked bowing of the right femur is noted.
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Fig. 14: Neurofibromatosis type 1: This lateral radiograph of an adolescent male
demonstrates marked anterior bowing of the distal tibia. Significant pseudoarthrosis of
the distal tibia and surrounding bony remodelling are also noted. Fracture of the distal
fibula is seen which is encroaching the posterior aspect of the distal tibia.
Fig. 15: Thanatophoric Dysplasia. Ultrasound of 35 weeks old shows bowing of the femur.
The length measures 25.3 mm.
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Fig. 16: Thanatophoric dysplasia: Babygram of 20 weeks old showing short and broad
iliac bones. The long bones are very short with flared and cupped metaphysis. Mild
bowing of femora are also noted. Short and bullet shaped phalanges are seen.
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Fig. 17: Achondroplasia: The image showing extensive bony deformity, degenerative
changes, valgus deformity and bowing of both tibias.
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Fig. 18: Metaphyseal dysplasia: The AP radiograph of the right leg showing proximal
metaphyseal widening of the tibia with lateral bowing. Blue arrow shows widened distal
femur. Classic Erlenmeyer flask deformity is seen.
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Fig. 19: Blount's disease: The AP film of a young adolescent shows beaking of the
proximal medial metaphases and bowing of the distal femur.
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Conclusion
Recognition of important pathologic conditions is important for differentiating those that
will resolve spontaneously from those entities requiring surgical input or other treatment.
Personal information
M.Sah, B.Sc.(Hons.), M.B.B.S (Hons.), DRCOG
Department of Radiology, Cardiff and Vale University Health Board, University Hospital
of Wales, Cardiff, Wales, United Kingdom.
mmahaseth@yahoo.com
S.Babu, M.B.B.S, DCH, FRCR
Department of Radiology, Cardiff and Vale University Health Board, University Hospital
of Wales, Cardiff, Wales, United Kingdom.
sivadevi_dr@yahoo.co.uk
S.A.R. Mustafa, MBBS, MRCS
Department of Radiology,
University Hospital of Wales, Cardiff, Wales, United Kingdom.
smustafa@doctors.org.uk
Dr. G. Herdman, M.B.B.S, FRCR
Consultant MSK radiologist.
Princess of Wales Hospital, Bridgend, Wales, United Kingdom.
Dr. S.J. Morris, MBBS, DCH, MRCP, FRCR
Consultant radiologist.
Department of Radiology, Cardiff and Vale University Health Board, University Hospital
of Wales, Cardiff, Wales, United Kingdom.
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