coxa vara

definition

·      deformity of proximal femur characterised by decreasing neck-shaft angle

classification
Congenital

·      present at birth

·      due to limb bud abnormality

·      includes

·      PFFD

·      congenitally short or bowed femur

Dysplasias

·      multiple epiphyseal dysplasia

·      achondroplasia

·      cleidocranial dysostosis

Cretinism

Acquired

·      secondary to underlying disorder

·      rickets

·      renal osteodystrophy

·      hyperparathyroidism

·      Perthes disease

·      infection

·      trauma with premature closure of physis

·      tumour

·      SUFE

Developmental

·      progressive disorder that develops in early childhood

Developmental coxa vara

epidemiology

·      rare

·      sex and side incidence equal

·      bilateral in 1/3

·      increased familial incidence

·      may be autosomal dominant inheritance

aetiology

·      unknown

·      theories

1.   metabolic abormality

·      deficiency in proximal femoral ossification

2.   excessive intrauterine pressure

·      causes depression in femoral neck

3.   nonspecific mechanical abnormality

·      occur during devlopment

4.   vascular insult

·      arrest in femoral neck development

5.   devlopmental error

·      faulty maturation of cartilage and bone in femoral neck

pathogenesis
Histology

·      abnormality in medial proximal physis and adjacent neck in

·      cartilage

·      secondary metaphyseal bone

·      abnormality is

·      increased width of physis

·      loss of progression of columns

·      nests of cartilage in metaphysis

·      porotic metaphyseal bone

Natural history

·      if mild (epiphyseal angle < 45o)

·      corrects spontaneously

·      if severe (epiphyseal angle > 60o)

·      progressive varus deformity

·      stress fracture of femoral neck

·      nonunion of stress fracture

·      early degenerative changes

clinical
Presentation

·      usually present between age 1 and 5

·      present with painless limp

Findings

·      limb-length discrepancy

·      positive Trendelenburg sign

·      gait is

·      short-leg

·      Trendelenburg sag or lurch

·      if bilateral

·      waddling gait

·      increased lumbar lordosis

·      decreased ROM

·      esp. abduction and IR

radiology

·      varus femoral neck

·      neck-shaft angle < 125o

·      difficult to define with severe changes

·      vertical physis

·      measured by epiphyseal angle

·      angle between Hilgenreiner’s line and physeal line

·      usually < 25o

·      inverted Y radiolucency in inferior femoral neck

·      with interposed triangular metaphyseal fragment

·      pathognomonic

·      may be

·      decreased femoral anteversion

·      coxa breva

·      mild acetabular dysplasia

·      early degenerative changes

treatment
Goals

·      correction of varus angle

·      conversion of femoral neck forces from shear to compression

·      correction of limb length inequality

·      re-establishment of correct tension in abductor

Nonoperative

·      spica cast immobilisation unsuccessful in preventing progression

Indications

·      epiphyseal angle < 45o

Operative

·      in form of proximal femoral osteotomy

Indications

·      epiphyseal angle > 60o  OR

·      epiphyseal angle 45-60o with limp and progression of varus

Timing

·      when indications become manifest

Technique

·      valgus derotation subtrochanteric osteotomy

·      fixation with plate

·      may require

·      adductor tenotomy

·      shortening of femur

Results

·      80% good or excellent results