- Ilizarov developed the law of tension-stress, which describes the process of new bone and soft tissue regeneration under the effect of slow and gradual distraction. His biological principles can be summarized as follows:
Delay before distraction.
- Rate of distraction
- Rhythm of distraction
- Site of the osteotomy
- Unifocal or bifocal lengthening (number of lengthening sites)
- Minimal disturbance of bone. Ilizarov showed that formation of new bone at the osteotomy site is definitely influenced by the amount of damage to the bone, medullary cavity, and periosteum.He described the new concept of corticotomy, where only the cortex of the bone is cut, preserving the periosteum and medullary cavity.
The value of corticotomy has recently been questioned, because the medullary blood supply regenerates in 7 to 10 days following a complete osteotomy. The integrity of the periosteum is the only important factor for new bone formation at the site of the osteotomy.
Delay before distraction. This allows osteogenesis (or new bone formation) to begin. Duration of delay varies from 5 days in a child to about 10 days in a skeletally-mature patient
Deformity correction of upper and lower limb.