Blount's disease / Tibia vara / Bow legs
Blount's disease is a disorder of the tibial growth plate (usually the medial aspect) leading to changes in the angle at the knee.
This results in bowing of the leg (usually the lower leg).
However, unlike bow legs it is pathological and progressively worsens.
Clinically it is difficult to distinguish between simple bowlegs and Blount's disease.
However, bow legs should resolve between the ages of 2-4 years - if not then one should suspect Blount's disease.[1]
Epidemiology
Presents at age 2-4 years
Risk factors
Repetitive trauma to a knee with an already varus abnormality
Presentation
Investigations
Plain radiographs show increased angulation between the metaphysis and the longitudinal axis of the tibia.
Physiological bow legs
Rickets
Osteomyelitis
Trauma
Ollier's disease
Metaphyseal chondrodysplasia
Focal fibrocartilaginous dysplasia
Management
Braces - these are long-legged and lock the knee and need to be worn whilst weight bearing.
However, if by the age of 4-5 years the condition has not corrected then surgery is usually required.
Surgery usually involves osteotomy of the tibia and realignment of the lower leg.
Prognosis
Bracing is usually unsuccessful in girls and in those with obesity.
If treatment is successful there is usually no residual disability or cosmetic abnormality.[4]
Usually the adolescent variety is less severe than infantile Blount's disease.
Risk factors
Bow legs
Females
Afro-Caribbean ethnicity
Obesity
Walking at an early age
Possible family preponderance
Presentation
Commonly unilateral
Varus deformity
Shortening of the involved leg by up to 3-4 cm
Pain at the medial prominence of the proximal tibia
Medial tibial torsion may also be present
Investigations
Plain radiographs, as for infantile Blount's disease.
Treatment
High tibial osteotomy is usually the procedure of choice. This is attractive, as limbs are not shortened; however, it requires the wearing of an external fixator for several months.