Deformity correction and extremity lengthening in the lower leg: comparison of clinical outcomes with two external surgical procedures

OBJECTIVE Distraction osteogenesis is a method of stimulating the growth of new bone tissue in order to lengthen the extremities or bridge resected bone defects. In addition to the now-established intramedullary procedures, two different fixator systems are in use. The present study investigated the classical Ilizarov ring fixator (IRF) and a hexapod to assess the precision of lower-leg lengthening and complications classified using the Paley criteria for problems, obstacles, and complications. The study also examined the follow-up results in functional tests to assess outcomes in terms of range of motion in adjacent joints, daily activities, and quality of life. PATIENTS AND METHODS A total of 43 patients (53 segments) who were treated over a period of 16 years were re-assessed. In 33 segments, treatment was carried out with the hexapod Taylor Spatial Frame (TSF); the conventional IRF was used in 20 segments. The patients' mean age was 13.5 years (range 2-54 years). The follow-up examinations were carried out 2-15 years postoperatively and comprised measurement of a current leg axis view with the patient standing, calculation of a knee score, activity scores, ankle joint scores, and assessment of motor function and sensory function using appropriate scores in the lower leg and foot. The post-treatment health-related quality of life was assessed using the Short-Form Health Survey-36 questionnaire. RESULTS Using the Paley criteria, far fewer problems occurred in the TSF group in comparison with the IRF (TSF 12.1%, IRF 50%). In the problems category, significant differences were observed with regard to axial deviation (TSF 0%, IRF 36.8%) and pin infections (TSF 9.1%, IRF 40%). Comparison of the obstacles and complications did not identify any significant differences between the two groups. Analysis of the scores for the knee, activity, and motor function/sensory function also did not show any marked discrepancies, apart from a major difference in mobility in the upper and lower ankle joints with poorer findings in the TSF group. CONCLUSIONS During treatment, the TSF ring fixator leads to fewer problems, fewer secondary axial translations, and fewer pin infections. However, with temporary transfixation of the ankle joints, the TSF system is also associated with postoperative deterioration in mobility in the upper and lower ankle joint.