Key words: Ilizarov device, foot deformites surgery, children
The treatment of foot deformities in children using an Ilizarov device is described. Indications, Complications and treatment outcome is described. The authors experienced favorable results using this method.
Conventional surgical procedures in the treatment of foot deformities can be difficult to use and not completely reliable in some cases. Traditional methods consist in extensive bone resections with significant shortening of the foot and does not avoid the risks of vascular and nervous injuries.
The skin is often not sufficient to obtain a complete correction at the time of surgery. Sometimes, overall in post-traumatic deformities, the skin is atrophic and the position of neurovascular structures related to usual anatomical reference points may be changed. Moreover consolidation defects and retraction scars may be severe complications of this kind of surgery.
With external fixation we are able to progressively correct deformities using the tension-stress effect as suggested by Ilizarov with minimal bleeding and without neuro-vascular damage. In fact during the processes of elongation of bone and the correction of deformities by distraction osteogenesis, the adjacent soft tissues are elongated and rearranged.
Usually only a minimally invasive surgery like the elongation of tendons and release of soft tissues is combined to external fixation. Nevertheless, when mechanical obstacles, like severe bone anomalies, are present, it is possible to perform also a major open surgery with multiple osteotomies, using the Ilizarov apparatus either to complete or to maintain the correction obtained.
In the First Orthopaedic Unit of the University of Florence we treated with Ilizarov apparatus 21 foot deformities. There were 14 men and 7 women. The average age was 34 (min. 21, max. 63). The deformities were due to neuromuscular or congenital diseases in 13 cases. Post-traumatic deformities occurred in 8 cases.
A partial weight bearing using two crutches was permitted as soon as the patient was able to stand up without pain. The fixator was removed after a period ranging from 3 to 11 months (average 6 months).
Patients were controlled at an average follow-up of 18 months (min. 8, max. 3 y.)
According to Paley et al. 1993, the results were rated satisfactory or unsatisfactory. To be assigned to the first group a patient had to present a clinical and radiographic plantigrade foot, an improvement in gait (if previously abnormal) and absence of pain. A pre-operative planning was performed on the basis of X-rays and / or MNR images. The characteristics and the degree of the deformity were analyzed with computer assisted procedures.
No nervous or vascular complications occurred in the 18 patients, nor deep pin track infections. According to Checketts classification, superficial pin track infections (grade 1, 2) occurred rather frequently but all healed with just a more accurate local care and in some cases oral antibiotic therapy, without jeopardizing the end result. A particular assembly was used at the distal third of tibia. At this site traditional transfixation schema gives constantly problems of pain and onsequent limited joint motion because the wires pass close to tibialis anterior, extensor allucis longus and extensor digitorum communis tendons anteriorly and the Os calcis tendon posteriorly. These areas are subjected to sliding during walking and this leads to inflammation, pain, and at the end, stiffness of the ankle. So, we cross the wires of the tibial ring not on an horizontal plane but on a frontal one. In this way the wires pass through areas were the bone is only covered by skin and no tendons are closed. For this crossing, close to the center of rotation of the ankle, we use two olive stop wires. The wires are usually fixed with posts placed on the same plane to enhance the stability. Recently we employ a double post placed on the same plane, instead of the traditional combinations of single posts, so to make easier and quicker the assembling of the apparatus. This component is now produced by a French trade. Two types of frames may be used: constrained and unconstrained. In the first one the correction is performed around the axis of rotation of the joint involved in the deformity. A uniaxial hinge is used and must be exactly placed in line with the joint deformity. The success of the method depends on an accurate preoperative planning. In fact it is very important to establish the most adequate position of the hinges which must respect the anatomical axes of foot joints. So we use to perform a computer assisted planning which help us to define the exact position of the articular axes. An unconstrained system can also be used. In this case the correction is done around the natural axes of rotation of the joints and soft tissue hinges. This system is useful for the treatment of multiple joint deformity when it is not possible to locate a single axis of rotation.
In conclusion we think that Ilizarov apparatus find its best indication in the treatment of foot severe deformities in which traditional methods could meet some risks. In these cases the one-stage surgical procedure exposes the patient to the risks of traction injuries to the nerve and vessels which are stretched. Excessive scarring, skin slough and non union can also occur following complex surgical foot procedures. Furthermore with the circular fixation one is able to obtain the desired correction either acutely in the operative room or gradually after operation. The progressive correction starts usually after a period of 3-4 days, as soon as the patients are able to tolerate the decreasing pain. The disadvantages of the method are those found with all forms of external fixation and are predominantly related to pin sites. With local or general antibiotics we have never met deep infection. Sometimes we perform a minimal surgery on soft tissues, which helps us to correct the deformity through progressive distraction. In the presence of fixed bony deformity, if the patient is older than eight years, we use to perform at the same time an osteotomy procedure. To retain the obtained correction a brace or a cast may be required. If the stability obtained is considered not satisfactory, a surgical arthrodesis is performed decreasing the risks of a one time surgery.