Biomechanical and clinical comparative study of the new elastic stable intramedullary nailing “MJ-FLEX Orthofix”

Denis, Delphy, Maucort-Boulch, Delphine, Suchier, Yanneck, Mamadou, T. Bah and Metaizeau, Jean Damien (2018) Biomechanical and clinical comparative study of the new elastic stable intramedullary nailing “MJ-FLEX Orthofix”. Journal of Pediatric Orthopaedics. (doi:10.1097/BPO.0000000000001206).

Abstract

Background: The objectives of this study were first to compare the results of osteosynthesis with standard Metaizeau (MS) nails versus Metaizeau Junior Flex or MJF Orthofix (MJF) in terms of the stability of long-bone fractures in children, and to study the preoperative and postoperative safety of these new nails. We also carried out an analysis by computer modeling of a femur, in order to compare the biomechanical stability of the 2 nails. The interest in the MJF nails lies in the improvements they bring in terms of stability for long-bone fractures in pediatric patients, as well as the simplification of the surgical procedure. Methods: A study by numerical computer modeling of a femur was conducted to compare the biomechanical stability of the 2 assemblies with MS versus MJF nails. A retrospective single-center study of 137 fractures treated with MS and MJF was added to this biomechanical study. The onset of angular misalignment during follow-up was identified by radiographic measurements. Results: The biomechanical study showed greater stiffness of MJF in the frontal and sagittal plane and in torsion for modeled comminuted and simple transverse fractures. Use of MJF nails significantly reduced the risk of frontal and sagittal misalignment, by a factor of 5 and 12, respectively. The amplitude of this misalignment was also significantly reduced by 30% in the frontal plane with the MJF nail. The use of MJF compared with MS significantly diminished not only the quantity of preoperative radiation by 66% but also operative time by 30%. The complication rate in our population was 33.4% with a 6-fold lower risk of complications with MJF. Conclusions: MJF nails provide greater stability in the frontal and sagittal plane with regard to both the onset and amplitude of misalignment in the treatment of long-bone fractures in children. This improvement was confirmed by the biomechanical study. Preoperative and postoperative safety was also better with these new nails, and surgery was easier.

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