Blount’s Disease or Tibia Vara is a disorder of the growth of the tibia i.e. shin bone, which turns the lower leg inwards like bowleg.1
Blount’s disease most often affects the lower leg bone i.e. tibia which is also more commonly recognized as shin bone. This disease when occurs in infants usually affects bilaterally i.e. both the legs are affected. It affects the bones forcing them to form an angle in order to rotate the bones inwards. Blount’s disease when occurs in adolescents usually affects unilaterally i.e. only one leg is affected.
The structures present at the end point of the bones of a growing child are known as growth plates. The growth plate is located in between the metaphysis and the epiphysis of the bone. The growth plate is build up of a special kind of cartilage which forms the bone at the top of the end of the metaphysis and also lengthens the bone periodically.
Blount’s disease generally involves both metaphysis and epiphysis.2 The large part of the tibial bone shaft is metaphysis. In the initial phase, Blount’s disease affects the medial metaphysis by breaking it down and stopping the growth. Blount’s disease may affect the medial or inside edge of the bone. The metaphysis containing the growth plate consists of soft spongy bone in growing children that has not yet hardened.
In few cases abnormal growing of bone results in periodical worsening of bowing of the leg which is known as pathologic tibia varum or Blount’s disease.
Blount’s disease becomes visible between the age group of two and four years during which time the bowing worsens. Adolescents and teenagers may also develop it due to being overweight.
Types of Blount’s Disease or Tibia Vara
Blount’s Disease Is Classified Into Two Types
- Infantile Blount’s disease.
- Adolescent Blount’s disease.
Infantile Blount’s Disease: Infantile Blount’s disease usually affects toddlers younger than 4 years of age. About 70 percent of infantile cases are bilateral.
Adolescent Blount’s Disease: Teens and older children get affected with adolescent Blount’s disease.3 Adolescent Blount’s disease usually affects unilaterally or only one side.
Epidemiology of Blount’s Disease or Tibia Vara
Infantile Blount disease ratio is recorded as 0.007 or less than 1% in the population of young children in the United States. The adolescent Blount disease cases may reach 2.5% in United States. In some cases Blount disease may also increase due to affected family members. 70 percent of infantile cases are bilateral.
Causes and Risk Factors of Blount’s Disease or Tibia Vara
- Blount’s disease is usually caused in adolescents and young children. Although the exact cause is still not known, the suspected causes may include overweight on the growth plate due to which inner portion of the tibia or shin bone present under the knee stops developing normally.
- It gets worse gradually which may result in severe bowing of either or both legs.
- Blount’s disease more commonly affects African-American children. Early walking and obesity could also be responsible for Blount’s disease.
Signs and Symptoms of Blount’s Disease or Tibia Vara
- Either or both of the lower legs turn inward.
- The affect of angle or bowing is visible under the knee.
- Quick worsening of the symptoms.
Treatment for Blount’s Disease or Tibia Vara
- Bracing: Braces are very helpful in treatment of children below three years of age and in case of severe development of bowing.
- Surgery: Surgery is performed only when braces fail to work properly for correction of bowing and if the Blount’s disease is diagnosed before the child becomes adult. Surgical procedure is performed by placing the tibia in its proper position. This also lengthens the tibia. The growth process of the outer half of the shin bone is restricted by performing surgery in few other cases to neutralize the angle allowing correction of the child’s natural growth and reversal of bowing.
Investigations for Blount’s Disease or Tibia Vara
A complete subjective and physical examination is necessary to diagnose the Blount’s disease. Typically an x-ray of the lower leg and the knee is required for confirming the severity.