Ankle Arthrodesis By External Fixation:

Ayman Mohamed Mansour

The ankle joint is a synovial joint of the modified hinge variety . The weight bearing surfaces are the upper facet of the talus and the inferior facet of the tibia. The stabilizing surfaces are those of the medial and lateral malleoli which group the sides of the talus. The average thickness of the ankle articular cartilage is approximately 1.6 mm .In general, the ankle joint cartilage can be damaged by several different etiologies: degeneration, trauma, infection, metabolic, autoimmune or neuropathy.Posttraumatic osteoarthritis is far more common than primary osteoarthritis in the ankle. Symptomatic ankle osteoarthritis can be found in < 1% of the adult population.Ankle arthrodesis can eliminate pain and improve function in even the most severely disabled patient when the technique is clinically indicated.The goal of ankle arthrodesis is to create a broad, flatcancellous surfaces, that allow fusion to occur.The arthrodesis site should be stabilized with rigid internal fixation ,if possible ,or with external fixation.Internal fixation is the method of choice for ankle arthrodesis.Cancellous screws ,plate and screws, interlocking nail, or bone graft may be used ,however this method of fixation may not be satisfying in certain conditions such as inadequate soft tissue covering, poor bone quality and in case of chronic infection of the ankle which necessitate the use of external fixation.External fixation is a method of skeletal immobilization that uses percutaneous pins placed in bone and linked with external connectors.Sir John Charnley first described the use of an external fixation device for compression ankle arthrodesis, using his uniplanar bilateral frame in 1951.Since then severaldifferent techniques for ankle fusion have been described including more sophisticated external devices. These techniques may be unilateral (orthofix), bilateral(Charnley),triangular(Calandruccio), (hybrid) and circular (Ilizarov).Selecting the type of external fixator depends on the availability of the device and the experience of the using surgeon as the results of all types were nearly the sameThis method has several advantages:*The method provides rigid fixation of the bones.*The method allows direct surveillance of the limb and wound status.*Associated treatment, for example, dressing changes, skin grafting, bone grafting, and irrigation.*Immediate motion of the proximal and distal joints is allowed*The extremity is elevated without pressure on the posterior soft tissues.The disadvantages of external fixation may be :1- Pin tract infection.2- Neurovascular impalement.3- Muscle or tendon impalement.4- Delayed union.5- Compartment syndrome.6- Re fracture.