Blount’s disease is a growth disorder of the tibia (shinbone) bone of the lower legs, causing them to bow outwards, resembling a bowleg. It’s named after the American pediatric orthopedic surgeon, Dr. Walter Putnam Blount (1900-1992) and is commonly seen in kids younger than 4 years and in adolescents. It’s also more common in children of African descent and associable with obesity and short stature.
The pathology of this condition results from excess pressure being applied on the growth plate at the head of the tibia, called the physis; this is made up of cartilage which is weaker than normal bones. The physis works as a growth plate, allowing the bone to lengthen and grow, but due to excessive weight pressure, it doesn’t grow normally. The outer portion of the tibia keeps growing, but the inner surface doesn’t, resulting in an uneven growth and a resultant bowing of the legs that doesn’t improve with time.
Unlike the normal bowlegs that some babies have which straighten out after they start walking, the cases with Blount’s disease only get worse with time, making early diagnosis important.
Symptoms – Aside from the most obvious sign of bowing of the legs below the knees, the legs may appear asymmetric, especially if one leg is more affected than the other. Though young kids might not complain of pain, most adolescents are already on pain-killers by the time they visit a doctor for help. If left untreated, Blount’s disease can also lead to arthritis of the knees and trouble in walking.
Aside from this, another major deformity might also develop known as ‘in-toeing’, wherein the tibia might also rotate inwards aside from bowing, such that the feet appear to be pointed inwards rather than facing forward.
Diagnosis – If there is bowing with pain and no history of injury or family history of bowlegs, an orthopedist might do an x-ray study to look for telltale bone growth patterns at the top of the tibia bone; it will also tell him about the progress of the disease.
Treatment depends on the age of the patient. Young patients might just need a supportive brace while older adolescents might need surgery, depending on the extent of the disease and how debilitating it is to the patient. Most adolescents experience pain in the hips, knees and ankles due to the abnormal weight distribution and are more prone to tripping over.
Non-surgical treatment involves the use of knee-ankle-foot orthoses, or braces, which is effective if the child is less than 3 years old.
Surgical treatment can be done in two major ways to straighten the tibia and stop further worsening and permanent damage to the growing areas of the bonehead.
Guided Growth – This type of surgery prevents growth on the healthy side of the physis to allow the abnormal side to ‘catch up’, thus straightening the leg.
Tibial Osteotomy – This involves cutting the tibia bone just below the knee, realigning it and holding it in place with internal or external plates and screws while it heals. ‘In-toeing’ can also be surgically corrected at this time, if present.
The patient may have to use crutches for a while along with physiotherapy. The good news however is that, there can be complete recovery in most cases. The take-away lesson here is to maintain a healthy weight and to protect the bones from excessive wear and tear.