ABSTRACT
Objective:To compare the biomechanical properties of different circular external fixators for the fracture site of oblique long bone fractures.Methods:15 polyethylene (PE) plastic rods with the same batch were selected to make the model of oblique fractures in the middle of long bones. According to the connection between PE rods and external fixators, the PE rods were randomly divided into: the group that was simply used kirschner wires (group kirschner wires), the group that was simply used olive wires (group olive wires), the group that was simply inserted half pins (group half pins), the group that was inserted single cortical fixed half pins at either side of the fracture site after being fixed by the tensioned olive wires (group olive wires+ half pin), the group that was inserted tensioned trans-fracture olive wires after being fixed by the tensioned olive wires (group olive wires+ olive wires). The axial compression tests were carried out, and the interfragmentary displacements under axial loads of 200 N, 400 N, 600 N and 800 N were measured and the axial stiffness was calculated. Then, the torsional tests were carried out, and the interfragmentary torsional angles were measured under torsional loads of 4 N·m, 7 N·m and 10 N·m, and the torsional stiffness was calculated.Results:With the increase of axial load from 200 N to 800 N, the axial interfragmentary displacement in each group gradually increased. The interfragmentary axial displacement of each group in ascending order was: group olive wires+ olive wires, group olive wires+ half pins, group half pins, group olive wires, group kirschner wires. The axial stiffness of each configuration under 800 N axial load in descending order was: group olive wires+ olive wires [863.93 (824.32, 875.87) N/mm], group olive wires+ half pins [119.92 (113.16, 123.58) N/mm], group half pins [81.92(79.42, 82.40) N/mm], group olive wires [76.83 (72.45,79.47) N/mm], group kirschner wires [70.80 (67.49, 71.59) N/mm]. The pairwise comparisons of the axial stiffness data of each configuration had statistical significance (all P <0.05). With the increase of the torque load from 4 N·m to 10 N·m, the interfragmentary rotational angle in each configuration gradually increased. The interfragmentary torsion angle of each group in ascending order was: group half pins, group olive wires+ olive wires, group olive wires+ half pins, group olive wires, group kirschner wires. The torsional rigidity of each configuration under 10 N·m torsional load in descending order was: group half pins [1.80 (1.63, 1.85) N·m/°], group olive wires+ olive wires [1.05 (1.02, 1.07) N·m/°], group olive wires+ half pins [0.99 (0.98, 1.03) N·m/°], group olive wires [0.81 (0.78, 0.82) N·m/°], group kirschner wires [0.75 (0.74, 0.76) N·m/°]. The pairwise comparisons of the torsional rigidity data of each configuration had statistical significance (all P < 0.05). Conclusion:The axial stiffness and torsional stiffness of circular external fixators can be increased by using tensioned olive wires or half pins at the fracture site. Due to the insufficient support between oblique fracture site, when the load is applied, the axial displacement and torsion angle of the fracture site will still be fairly large after being fixed the fracture site with half pins. Treating with tensioned trans-fracture olive wires after being fixed by the tensioned olive wires at either side of the fracture site can effectively control the interfragmentary shear and displacement, thus providing an ideal mechanical environment for fracture healing.
ABSTRACT
Bone defects are usually resulted from traumatic injuries,infections,and bone tumors.The treatments mainly include autologous bone graft,allograft bone graft,distraction osteogenesis,vascularized bone grafting and amputation.All of the procedures show their inherent limitations due to different operative indications and different surgical techniques.The emergence of Masquelet technique provides a simple,safe,and more cost-effective solution in treating bone defects.The present article reviews the relevant literatures and summarizes the progress of Masquelet technique in the treatment of bone defects.The technique mainly includes two-step process which involves the induction of the induced membrane prior to the introduction of graft material into induced membrane.The first stage involves radical debridement of all infected or necrotic tissue,fracture stabilization,and filling the segmental bone defect with a cement spacer,composed of polymethyl methacrylate (PMMA) cement.Based on the results of culture performed on the wound samples,the sensitive antibiotics are mixed with cement for the infected bone defect.The second stage of bone grafting is performed within 6-8 weeks after the primary surgery.A longitudinal incision is performed through the induced membrane.The cement spacer is removed carefully and autogenous cancellous bone graft is placed to fill the bone defect and to close the induced membrane.A large number of experimental studies and clinical observations show that the induced membrane is a highly vascularized biological membrane rich in vascular endothelial growth factor (VEGF),transforming growth factor-β1(TGF-β1),bone morphogenetic protein 2 (BMP-2) and other growth factors,which can promote bone regeneration and repair.Masquelet technique can effectively treat multiple parts of posttraumatic bone defects,infectious bone defects,bone defects after tumor resection,congenital tibial pseudarthrosis,and so on.Masquelet provide a choice to treat bone defect for maxillofacial.The complications of Masquelet technique include infection recurrence,bone graft absorption,nonunion and pseudarthrosis.This study is to summarize the recent development of Masquelet technique,and to provide theoretical guidance for the application of Masquelet technique.