Coxa vara

Overview
A 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.

Pathophysiology
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, post traumatic (due to a malunion of a intertrochanteric fracture). 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 sequelae of osteogenesis imperfecta, Paget's disease, osteomyelitis, tumor and tumor-like conditions (e.g. fibrous dysplasia).

Symptoms
The condition is usually asymptomatic if congenital or developmental. However in unilateral cases (e.g. post traumatic), there maybe shortening, leading to a short limb gait characterized by limp which is seen as a vertical dip on the affected side during the stance phase (as opposed to a lurch characterized in a Trendelenburg gait). In severe cases abduction maybe severely restricted, causing a waddling type gait.

Usual symptoms include pain, stiffness, and difficulty in walking.

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.

Physical Examination
The patient may have a short limbed gait, or in severe cases a Trendelenburg gait (due to restriction of abduction). The Trendelenburg test maybe positive.

Imaging
The diagnosis is mainly radiological. Clinical signs include a widened bitrochanteric measurement.

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 DHS.