Comparative analysis of the reduction capabilities of orthopedic hexapod Ortho-SUV frame and its minimized (pediatric) version (experimental study)

Introduction Currently, orthopedic hexapods have been effectively used for long bone, foot and large joint deformity correction in both adults and children. Previous studies demonstrated the superiority of the reduction capabilities of the orthopedic hexapod Ortho-SUV Frame (OSF) in comparison with other designs of external fixation devices. However, the reduction capabilities of the minimized version of this hexapod (minimized Ortho-SUV Frame, OSFm) have not been studied yet. Purpose To identify the reduction capabilities of OSFm compared to OSF. Materials and methods The bench test was performed using plastic models of the tibia osteotomized at the middle third of the shaft. One-ring modules were used to fix each of the bone fragments. In the first series of the experiment, the reduction capabilities of OSFm with a standard strut size and in the second series OSF with a short strut size were studied. In each series of experiments, three groups were studied depending on the method of fixing the struts to the rings: directly to the ring, using straight plates, and using Z-shaped plates. Reduction capabilities were assessed by the maximum displacement of the distal bone fragment relative to the proximal one in distraction, translation, angulation, and rotation. Results The magnitude of the maximum distraction of OSF and OSFm with fixation of the struts directly to the rings and with the use of straight plates is the same (p > 0.05). With Z-plates, OSFm outperforms OSF by 27.3 %. OSFm surpasses OSF by 2.8-29.3 % in terms of the planar-parallel movement. OSFm surpasses OSF by 29.6-55.4% in terms of angular movement capabilities. The study of rotational movement found that OSFm exceeds the capabilities of OSF by 20.3-41.3%. Conclusion The findings obtained indicate that OSFm, in comparison with OSF, has better deformity correction capabilities.