Biomechanics of external fixation and limb lengthening.

Surgeons who use external fixators for foot and ankle conditions need to understand the biomechanical principles to ensure good outcomes. Fixators can be used for fracture fixation, correction of contractures, distraction osteogenesis, and distraction arthroplasty. A two-ring fixator with wire fixation remains the gold standard with which all other frames are compared. Small changes in mechanical characteristics can have major implications on new bone or cartilage formation.