Definition
Coxa vara, coxa adducta, coxa flexa,
Alteration of the angle made by the axis of the femoral neck to the
axis of the femoral shaft so that the angle is less than 135°; the
neck becomes more horizontal. |
Radiographic Appearance
Radiographically, an angle of less than 120 degrees is
seen between the femoral shaft and neck. As the angle approaches 90
degrees or less, the epiphyseal cartilage plate assumes an
increasingly vertical position. Associated with this change is the
relative elevation of the greater trochanter, which often appears
enlarged and beaked. In almost all patients there are irregularities
and fragmentation of the metaphyseal-epiphyseal junction, and in
many widening of the epiphyseal cartilage plate is seen. Oftentimes,
a triangular bone fragment may be present at either the superior or
inferior margin at the junction of the neck and epiphyseal
cartilage. This may result in the so-called "Y" or inverted "Y"
appearance.
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Pathology
Idiopathic coxa vara is a deformity of the femoral neck
characterized by a decrease in the normal angle formed by the neck
and the shaft of the femur as a result of caudal bowing in the
region of the neck. Normally, at birth the angle of inclination of
the femoral neck is 1500. This angle decreases to 120 - 130 0 in the
adult. In idiopathic coxa vara, this angle is decreased below the
normal 1200.
Although the cause of this entity is often unknown, the lesion has
been grouped into two general categories by some schools. First,
there are those cases which are deemed to be congenital in nature.
They may be associated with other anomalies such as hip dislocation,
faulty development of the femur or such syndromes as
craniocleidodysostosis. These congenital cases, because of their
associations with other anomalies, are usually recognized at birth.
The other group, known as the developmental cases, are acquired
lesions associated with a broad range of injury to or weakening of
the promixal femur. These include associations with such processes
as rickets, osteomalacia, osetogenesis imperfecta, infection, and
slipped capital femoral epiphysis. Others speculate that those cases
without an obvious cause may be due to unrecognized metaphyseal
chondrodysplasia. The developmental type lesions tend to present
after infancy or in early childhood. Coxa vara presenting after age
4 is always developmental.
Clinically, the abnormality often presents with delay or difficulty
in walking. Pain is usually not a feature until walking and weight
bearing have produced secondary changes. The enitity shows equal
frequency in girls and boys. It is unilateral in 60-75% cases. Those
cases of bilateral involvement are often associated with generalized
weakening of the bones such as seen in rickets, osteomalacia,
osteogenesis imperfecta, or other skeletal dysplasias.
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Treatment:
Evaluation of Hilgenreiner's epiphyseal < (angle between
Hilgenreiner's line & line thru
proximal femoral physis) is key to treatment;
- normally this angle is 25 deg or less;
- angle < 45 deg will spontaneously correct, where as angle of > 60
deg (&
neck shaft angle of < 110 deg) will usually require surgery;
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Image 1
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Useful Link
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