biological principles
Last reviewed 01/2018
Modern principles of limb equalisation owe much of their foundation to Ilizarov who observed what known as the "tension stress effect" - stresses created by gradual distraction of living tissues stimulates active regeneration in responsive tissues. Applied to the leg, the controlled stress of axial lengthening will stimulate the formation of bone and soft tissue.
During distraction, there is osteogenesis at both sides of the lengthening site. The zone between the areas of new bone acts as an epiphyseal plate and ossifies once lengthening ceases. During lengthening, bone is laid down longitudinally; once lengthening ceases, it undergoes consolidation, increases in density, and develops both a cortex and finally, a medullary canal. Soft tissue formation is also stimulated with generalised regeneration of muscle, nerve and fibrous tissue throughout the limb but concentrated at the site of lengthening.