Dwarfism is where an individual is short in stature as a result of slow growth and is defined when an adult height of less than 4ft 10in. There are two main types of dwarfism: Harmonious and Disharmonious dwarfism.
Harmonious dwarfism is where both limbs and body are reduced in size, but the ratio of the limb to height remains proportionate. With this form of dwarfism, the bone deformity can cause hyper-anteversion around the hips, typically with a 40° varus (inward) and a flexum of 40°. For limb lengthening, a 3-D correction must be performed to treat any hyper-anteversion before surgery.
In disharmonious dwarfism, limbs are disproportionately shorter than the body. This is attributed to a disorder in bone growth, often genetically linked to chromosomes and affects conditions such as achondroplasia, hypochondroplasia and dyschondroplasia.
Treatment for this type of dwarfism consists of correcting any problems with joints and then lengthening the limb bones according to an individual’s needs.
For correcting joints in dwarfism deformities, hips present the greatest problem because the condition often includes a decreased femoral head by the pelvic acetabulum. If the socket is too small, the ball at the head of the femur may pop out during lengthening. For cases like this, an earlier operation to increase the size of the socket is required.
Lengthening for dwarfism is generally performed with an intramedullary nail or external fixator.