Spring technique for correction of multilevel deformity using hexapod external fixator

Abstract

Context: Osteotomies in several parts of one long bone are recommended for correction of a long, curved, and wide-angled deformity. Hexapod external fixators (HEFs) allow for the single-stage correction of multiplanar deformity, but they are heavy, expensive, and requires continuous management of 12 struts, if at more than one level. Aims: We proposed the use of springs with HEF to support the intermediate ring. Deformity between the proximal and distal rings is corrected using one HEF, and the intermediate fragment is automatically corrected by the tension of the springs. Settings and Design: This was a retrospective descriptive study. Subjects and Methods: We treated seven males and eight females with 17 affected limbs. Four patients with familial hypophosphatemic rickets, five posttraumatic deformities, two osteogenesis imperfectas, three fibrous dysplasias, and one neurofibromatosis were included. The mean preoperative angle between the most proximal and distal fragments was 62.5°. First, small distraction at each level was initiated with one HEF fixed to the most proximal and distal rings, and Ilizarov hinges applied between the proximal and intermediate rings. Then, a set of three springs was applied for each interval between the rings. Gradual correction using HEF was performed, considering only the axes of the proximal and distal bone fragments. Results: Good alignment was achieved in all patients without severe complications. The mean correction period was 5.5 weeks and mean fixation period was 33.8 weeks. Conclusion: Combination of HEF and springs is capable of correcting severe deformity.