• CV refers to the proximal femoral varus deformity when the neck shaft angle (NSA <110°). Incidence is 1 in 1000 live births.
• CV includes a wide spectrum of types, pathologies, aetiologies and natural history.
• Confusion and controversy exist in the literature as to terminology and classification of this disorder.
• CV is commonly grouped as:

1. Congenital CV; caused by a primary cartilaginous defect in the femoral neck and it is usually part of congenital short femur, proximal femoral focal deficiency (PFFD), and congenital bowed femur. It presents at birth but manifests clinically during early childhood and commonly follows a clinical course that is progressive with growth.
2. Developmental CV (formerly infantile or cervical coxa vara): presents in early childhood with classical radiographic changes (Fairbank’s triangle; inferior and posterior bony metaphyseal fragment) and no other skeletal manifestations. Incidence ~1 in 250 000
3. Acquired CA:  refers to bone bending caused by either weakness (SUFE, rickets, fibrous dysplasia, Osteomalacia, Osteoporosis, Paget disease, or Infection) or fractures.

Various types of CV. Image 1 showed congenital CV with IM rod following short femur lengthening. Image 2 showed developmental CV while 3 showed acquired CV: 3.1 part of OA, 3.2 iatrogenic following femoral osteotomy for DDH and 3.3 secondary to fibrous dysplasia.

• Developmental CV usually presents with a painless limp with LLD which is gradually getting worse. There may be a family history and it can be bilateral (30-50% are bilateral).
• Presentation of other types of CV usually relates to the underlying pathology.
• Examination usually reveals prominent and elevated greater trochanters, positive Trendelenburg test and LLD.

• Neck shaft angle (NSA),
• Hilgenreiner epiphyseal angle (HEA): the angle between Hilgenreiner line and the line through the epiphyseal plate (normally ≤ 20°)
• Articulotrochanteric distance (ATD). A decreased ATD indicates that the location of the pathology in the physeal or inter-trochanteric area while normal ATD indicates it is in the subtrochanteric region.

Plain radiographs of developmental CV showing NSA, HEA and ADT.

This is usually directed to the cause although anatomical correction may be required as well.

Weinstein (1) reviewed 42 patients with coxa vara and introduced the HEA to aid in deciding candidacy for surgery. Average normal value is 20°. HEA of less than 45°; usually improves without intervention.

HEA of more than 60°; usually worsens if left untreated and it is an indication for surgery. HEA of 45-60°; require observation. If progressed, surgical intervention is indicated.

The surgical treatment involves corrective osteotomy to achieve the following goals:

1. NSA ≥ 140°and HEA to less than 35-40°
2. Correction of femoral version to normal values ( usually there is a retroversion)
3. Ossification and healing of the defective inferomedial femoral neck fragment
4. Restoring ATD and abductor mechanism length-tension relationship
5. Adductors tenotomy to remove  deforming force

• There are two distinct forms: proximal focal femoral deficiency (PFFD) and congenital short femur (CSF).
• PFFD describes a deformity in which there is discontinuity (with loss of various length of the femur) between the femoral neck and shaft.
• CCSF describes short but full femur with no bony loss or discontinuity. In most cases.
• The cause of the femoral deficiency is unknown; however, it can be part of genetically transmitted syndromes.
• Three classifications are in use:

1. Aitken’s
2. Gillespie and Torode
3. Paley

Gillespie and Torode recognised 3 types:

Group A: Femur is short by about 20% but child can weight bear on the affected leg.

Group B: The femur is short by 40% (the foot of the affected level is at level between the knee and mid-tibia compared with the normal side).

Group C: The thigh is short and bulbous and the leg is externally rotated with the foot at or near the level of the other knee.

Paley’s classification:

Type I: Intact femur with mobile hip and knee:

   a) Normal ossification proximal femur

   b) Delayed ossification proximal femur

Type II: Mobile pseudarthrosis (hip not fully formed, a false joint) with mobile knee

   a) Femoral head mobile in acetabulum

   b) Femoral head absent or stiff in acetabulum

Type III: Diaphyseal deficiency of femur (femur does not reach the acetabulum)

   a) Knee motion > 45 degrees

   b) Knee motion < 45 degrees

Type I is further sub-classified into:

0)     No factors to correct before lengthening

1)     One factor to correct before lengthening

2)     Two factors to correct before lengthening

3)     Three factors to correct before lengthening

4)    etc.

Examples of factors requiring correction prior to lengthening of femur are NSA < 90°, delayed ossification proximal femur, central edge angle (CEA) < 20°, subluxing patella and/or dislocating knee.

Treatment must be tailored to individual patients based on LLD, hip and knee stability, femoral rotation, proximal musculature, foot condition, availability of the expertise and patient and family motivation. The two broad options are reconstructive surgery or amputation and prosthetic replacement.

Plain radiographs showing various severity of CFD, type A (top left), Type C (top right) and type B and C in bottom image.