Coxa vara

Coxa vara is a deformity of the hip, whereby the angle between the ball and the shaft of the femur is reduced to less than 120 degrees. This results in the leg being shortened, and therefore a limp occurs. It is commonly caused by injury, such as a fracture. It can also occur when the bone tissue in the neck of the femur is softer than normal, meaning it bends under the weight of the body. This may either be congenital, also known as Mau-Nilsonne Syndrome, or the result of a bone disorder. The most common cause of coxa vara is either congenital or developmental. Other common causes include metabolic bone diseases (e.g. Paget's disease of bone), post Perthes deformity, osteomyelitis, and post traumatic (due to improper healing of a fracture between the greater and lesser trochanter). Shepherds Crook deformity is a severe form of coxa vara where the proximal femur is severely deformed with a reduction in the neck shaft angle beyond 90 degrees. It is most commonly a sequela of osteogenesis imperfecta, Pagets disease, osteomyelitis, tumour and tumour-like conditions (e.g. fibrous dysplasia).

Symptoms
The condition is asymptomatic if congenital or developmental. However in unilateral cases (eg. post traumatic), there may be shortening, leading to a short limb gait characterised by limp which is seen as a vertical dip on the affected side during the stance phase (as opposed to a lurch characterised in a Trendelenburg gait). In severe cases abduction maybe severely restricted, causing a waddling type gait. The biomechanics of the hip will be affected as the lever arm is lengthened causing more shear forces through the femoral neck predisposing it to stress fractures. This may also lead to progression of the deformity.

Diagnosis
The diagnosis is mainly radiological. Clinical signs include a widened bitrochanteric measurement. The patient may have a short limbed gait, or in severe cases a Trendelenburg gait (due to restriction of abduction). Trendelenburg's sign maybe positive.

Synonyms are Femoral Angle and Mikulicz's angle. When a patient is positioned for a radiographic image attempting to demonstrate Coxa Vara it is important that the technician insures that the patient medially rotates the foot 15° on the ipsilateral side (same side) being depicted in the film.

Treatment
Treatment depends on the cause of the condition. Most cases do not require any treatment. If treatment is required, it is usually a valgus osteotomy of the femur fixed by an angled blade plate device or even a dynamic hip screw.