There are many reasons bones may become deformed. These reasons include:
- congenital (from birth)
- developmental (from abnormal growth during childhood)
- posttraumatic (from healing in a deformed position after a fracture)
Bones may be deformed in four ways:
- angulation (a bend in the bone)
- rotation or torsion (a twist in the bone)
- translation or displacement (a shift in the position of the bone after a fracture or osteotomy)
- limb length discrepancy (a difference in the length of a bone compared with the other side)
Although each of the different types of bone deformities can exist on its own, combinations these deformity components together are common. The surgical techniques developed and used allow the simultaneous correction of combinations of deformities. The most common combination is correction of angulation with lengthening. The most common way the we treat deformities is with corrective osteotomy (cutting of the bone). Corrective osteotomy requires either internal or external fixation to stabilize the broken bone. Internal fixation is used in cases of acute correction (corrected all at once). External fixation is used when it is preferable or safer to correct the deformity gradually to avoid stretch injury to soft tissues, such as nerves or blood vessels. Gradual correction of deformities is similar to limb lengthening. It follows the same protocols. One of the newer methods for gradual correction is using the spatial frame external fixator. This new powerful correction tool can simultaneously correct all four deformity components. It requires computer analysis of the deformity.
In children, gradual deformity correction can also be achieved by stapling one side of the growth plate. This tethers the growth of that side while the other side of the same growth plate continues to grow. Once the bone is straight, the staple can be removed to permit symmetric growth of the entire growth plate. This procedure has the advantage of being minimally invasive and is often performed on an outpatient basis.