Coxa Vara

Definition

 

Deformity of proximal femur with neck-shaft angle <125°

 

Characterised by

- coxa vara

- decreased femoral anteversion

- limp / trendelenberg

- stress fractures

- early OA

 

Classification   

 

"ACDDC"

 

Acquired

 

2° to underlying disorder

- rickets

- renal osteodystrophy

- hyperparathyroidism

- Perthes disease

- infection

- trauma with early closure physis

- tumour

- SUFE

 

Congenital Coxa Vara

 

Dysplasia

- MED

- SED

- Achondroplasia

- Cleidocranial dysostosis

- Fibrous Dysplasia

 

Developmental / Infantile

- progressive disorder that develops in early childhood

- due to limb bud abnormality

- not congenital really infantile as appears after birth

- includes PFFD & congenitally short femur

 

Cretinism  (hypothyroid)

 

Developmental Coxa Vara

 

Epidemiology

- rare

- sex & side incidence equal

- bilateral in 1/3

- increased familial incidence - AD

 

Aetiology

 

Unknown / Multifactorial

 

Theories:

1. Metabolic abnormality - deficiency in proximal femur ossification

2. Excessive intrauterine pressure - causes depression in femoral neck

3. Non-specific mechanical abnormality - occurs during development

4. Vascular insult - arrest in neck development

5. Localized dysplasia - faulty maturation of cartilage & bone in femoral neck

 

Histology

 

Abnormality in medial proximal physis & adjacent neck

- cartilage

- 2° metaphyseal bone

 

Abnormality characterised by

- increased width of physis

- loss of progress of columns

- nests of cartilage in metaphysis

- porotic metaphyseal bone

 

NHx

 

Mild

- epiphyseal angle < 45°

- corrects spontaneously

 

Severe

- epiphyseal angle > 60°

- neck - shaft angle < 110o

 

Bilateral severe coxa vara with OA

 

Issues 

 

1.  Limp / trendelenberg

 

2. Stress fracture of femoral neck

 

3.  Early degenerative changes 

- untreated get severe early OA & often require THR early

 

Symptoms

 

Present at walking age with abnormal gait

- painless limp

 

Signs

 

Patient is short with hyperlordosis of spine & waddling gait

- limb-length discrepancy

- trendelenburg sign

- mimic DDH 

 

Gait

- short-leg

- trendelenburg sag 

- abductor lurch

- if bilateral - waddling gait

 

Decreased ROM 

- especially abduction & IR

 

Radiology

 

Inverted Y

- inferior sclerotic metaphyseal triangle

- pathognomonic of developmental

 

Varus femoral neck

- neck-shaft angle < 125° (normal is 150° in infant)

- difficult to define with severe disease

 

Hilgenreiner's Epiphyseal angle 

- angle between Hilgenreiner's & Physeal line

- normal < 25°

- < 45° should resolve

- 45-60° - watch

- > 60° will progress

 

Also

- decreased femoral anteversion / retroversion

- coxa breva

 

Management

 

Goals

 

Correction of varus angle

Conversion of femoral neck forces from shear to compression

Correction of LLD

Establish correct abductor tension

 

Management based on Epiphyseal Angle

 

<45°    - no treatment

45-60° - observe

>60°    - valgus osteotomy

 

Operative Indications

 

1.  Epiphyseal Angle > 60° 

2.  Epiphyseal Angle 45-60° with limp & progression of varus

 

 

Aims

 

Valgus derotation subtrochanteric osteotomy

- need to overcorrect to 150˚

- epiphyseal angle < 40o

- correct to anteversion 10o

 

Technique

 

Lateral approach

- K wire in central head

- mark distal and proximal with drill hole for rotation

- open periosteum and protect with homans

- sub-trochanteric osteotomy with saw

- application of 150o Synthes offset locking plate

- need also IR of about 20° at time of osteotomy

 

May require

- adductor tenotomy

- femoral shortening

- GT transfer

 

Plaster spica for 6 weeks post-op

 

If bilateral do about 6 months apart

 

Complications

 

1.  Loss of correction 

- related to undercorrection

 

2.  Premature physeal closure 

- related to increased pressure

- seen in 90% cases

 

3.  Greater trochanter overgrowth 

- associated with premature physeal closure

 

4.  Acetabular dysplasia 

- associated with premature physeal closure and undercorrection