C h a p t e r 4 3
Disorders of the Skeletal System: Trauma, Infections, Neoplasms, and Childhood Disorders
1101
bilateral. It has been classified into three types: infantile
(1 to 3 years of age), juvenile (4 to 10 years of age),
and adolescent (11 years or older). The juvenile and
adolescent forms are commonly combined as late-onset
tibia vara.
The infantile form of tibia vara, which is commonly
bilateral, is the most common. Untreated infantile
tibia vara is almost always progressive, with evidence
of outward angulation, flexion, internal rotation, and
abnormal lateral knee laxity. There is radiographic evi-
dence of progressive depression of the medial metaphy-
sis, the growth plate, and the epiphysis. Fusion of the
metaphysis to the epiphysis may occur in severe cases.
Night-brace treatment is used for mild early-onset dis-
ease. Valgum rotational osteotomy of the tibia is usually
indicated if angulation persists beyond 3 years of age.
Persistent tibia vara leads to early degenerative changes
of the knee.
Late-onset Blount disease is more common in obese
boys who are of normal or greater-than-normal height.
The condition may be bilateral or unilateral and char-
acterized by pain rather than deformity as the primary
initial complaint.
59
Radiography shows medial femoral
and tibial bowing. Bracing is not practical in obese ado-
lescents. Treatment includes osteotomy to realign the
limb or lateral growth plate closure to allow growth to
“catch up” medially.
Congenital Disorders
Congenital skeletal deformities can be caused by many
factors, including hereditary influences, external agents
that injure the fetus (e.g., radiation, alcohol, drugs,
viruses), and intrauterine environmental factors. They
range in severity from mild limb deformities, which
are relatively common, to major limb malformations,
which are relatively rare. The most common anomaly
of the toes or fingers is
polydactyly,
or the presence of
an extra digit on the hand or foot. There may also be a
simple webbing of the fingers or toes (syndactyly) or the
absence of a bone such as the phalanx, rib, or clavicle.
Joint contractures and dislocations produce more severe
deformity, as does the absence of entire bones, joints,
or limbs.
Osteogenesis Imperfecta
Osteogenesis imperfecta, or brittle bone disease, is a
hereditary disorder caused by deficiencies in the syn-
thesis of type I collagen.
18,19,60,61
Although it is usually
transmitted as an autosomal trait, a distinctive form
of the disorder with multiple lethal defects is thought
to be transmitted as an autosomal recessive trait.
19,61
In some cases, the disorder is caused by a spontaneous
mutation.
7 years
18 months
Infant
3 years
FIGURE 43-17.
Lower limb alignment
follows a predictable pattern. Infants
typically have a gentle varum bow
throughout the femur and tibia. By 18
to 24 months, the lower leg is nearly
straight, with a neutral mechanical
axis. Valgum gradually develops and is
most apparent between 3 and 4 years
of age. By 7 years of age, the lower
limb is in slight valgus and changes
very little thereafter. Varus should not
recur, nor should valgus increase.
(Adapted from Schoeneker PL, Rich
MM.The lower extremity. In: Morrissy
RT, Weinstein SL, eds. Lovell &Winter’s
Pediatric Orthopaedics. 6th ed.
Philadelphia, PA: Lippincott Williams &
Wilkins; 2006:1169.)
FIGURE 43-18.
Rotational deformity of the proximal tibia,
especially when unilateral, suggests tibia vara (Blount disease).
