Experimental evaluation of the bone fragments fixation rigidity using standard transosseous elements and extracortical clamp device in the model of femoral lengthening over the intramedullary nail

Abstract

Introdu ction. Fe mur lengthening over nail is an ef-fective method to reduce the rate of typical complica-tions of external fixation. However, the technical feature of the method is the tangential insertion of half-pins and wires and problems of nail jamming related with this. Ex-tracortical clamp device is one of the solutions to these problems. External fixation device used in this technique requires additional studies of fixation rigidity, including in the presence of the internal fixator. Aim: Compare ex- ternal fixation rigidity during femur lengthening over the nail using traditional half-pins and wires and extracorti-cal clamp device. Materials and m ethods. The fixation rigidity of 8 variants of the complete arrangement of the external fixation device in combination with an intra-medullary nail inserted both antegrade and retrograde were studied: 4 modules using only half-pins and wires and 4 modules with combination of half-pins, wires and extracortical clamp device. The studies were carried out using a biomechanical testing bench with the definition of longitudinal rigidity, angular and rotational stability. Results. Antegr ade modules had lower fixati on rigidi-ty, except for the longitudinal ones, compared to retro-grade modules. It can be associated with a technically more complex tangential insertion of half-pins in the proximal femur due to the nail in the canal. The retro-grade modules using extracortical clamp device had the highest fixation rigidity compared to other models in all series of experiment. The use of the extracortical clamp device increased the fixation rigidity of external fixation 1.5–2 times. Conclusion. The use of extracortical clamp device increases the fixation rigidity of bone fragments in combined osteosynthesis (external fixation device with intramedullary nail) and can be recommended for femur lengthening over the nail.