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What is Coxa Vara?

Coxa vara is a disorder of the hip seen in children.  

To better understand this condition, lets first review the anatomy of our hip.

The hip is a “ball-and-socket” joint where your thigh bone (the femur) joins with the pelvis (the acetabulum).  The femur is the “ball” while the pelvis is the “socket”.  The femur (thigh bone) is made up of a femoral head (which is the ball portion of the hip), a femoral neck (which connects the head to the shaft), and the femoral shaft (which is the bone you feel holding your thigh).  

Coxa vara is the flattening of the femoral neck, and this changes the angle of the hip joint (called a neck-shaft angle).  

Kids are born with a large neck shaft angle (about 150) and over time it decreases to about 120-130 in adults.  Coxa vara is a neck-shaft angle <100 degrees. 

The condition can be caused by many things and is grouped in to categories based on the cause. 

There is Developmental Coxa Vara means a child was born with this abnormal hip shape.  It is very uncommon and is usually associated with a dysfunctional growth plate (aka the capital femoral physis).

Coxa Vara  is more commonly caused by a weakening of the bone that acts as buttress for the hip and maintains the normal femoral neck angle.  This portion of bone is called the medial femoral column.  This weakening is caused by  poor blood supply to the region (aka avascular necrosis, as seen in Perthes, see talk) (or in SCFE, see talk) or when bone is replaced by softer fibrous tissue (like in fibrous dysplasia, see talk).  In these cases the weight of a kids body causes the neck to flatten (aka a varus position "vera"). 

There are also various forms of skeletal dysplasia (malformation of the bone) which cause coxa vara such as Rickets (vitamin d deficiency), fibrous dysplasia, and Paget's disease.

Diagnosing Coxa Vara:

Kids will present with a painless limp.  The limp is referred to as a Trendelenburg gait, which refers to abnormal hip abductor muscle function (when the hip angle changes, these muscles lose their normal tension and thus cannot function normally).  There is also a loss of hip motion (specifically regarding internal rotation and abduction).  

X-rays of the hips and pelvis can provide the diagnosis as well as guide treatment based on its severity.  Doctors measure the angle of the femoral neck (relative to the femoral shaft) and they measure the angle between Hilgenreiner's line and the proximal femoral growth plate (called Hilgenreiner's physeal angle). 

Treating Coxa Vara:

Treatment is based on the cause and severity of Coxa Vara.  

Mild and moderate deformity is classified as a Hilgenreiner's physeal angle less than 45 degrees, or between 45-60 degrees without any recent changes.  In these cases the child is monitored with x-rays every few months for signs of worsening but surgery is not required to change the shape of the bone.  Physical therapy is recommended to improve the flexibility and strength in the affected leg.  Many traumatic cases will improve as the child grows, however dysplastic and developmental cases rarely improve.

Severe deformity is defined as a Hilgenreiner's physeal angle over 60 degrees, or between 45-60 degrees with signs of progression (as seen on serial x-rays or based on worsening symptoms).  These severe cases require surgery for treatment because there is an increasing risk that the abnormal shape of the hip will put too much stress on the femoral neck and cause it to break (meaning it will cause a hip fracture).  Hip fractures can be very problematic in a younger population (see talk) and thus its better to address the issue before an injury occurs.  

The surgical procedure is called a Varus Derotational Osteotmy (slang "VDRO"), and it realigns the hip into a better (more physiologic) angle.  It is a significant procedure, but the outcomes are better than treating a broken hip in a young kid, and it can improve function of the affected leg.   




1) Beals RK. Coxa vara in childhood: evaluation and management.  JAAOS 1998; 6: 93-99. full article.

2) Weinstein JN, Kuo KN, Millar EA. Congenital coxa vara. A retrospective review. J Ped Ortho 1984; 4: 70-7. full article

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