Increasing stability by pre-bending the nails in elastic stable intramedullary nailing

Abstract

Elastic stable intramedullary nailing (ESIN) is generally acknowledged to be the treatment of choice for displaced diaphyseal femoral fractures in children over the age of three years, although complication rates of up to 50% are described. Pre-bending the nails is recommended, but there are no published data to support this. Using synthetic bones and a standardised simulated fracture, we performed biomechanical testing to determine the influence on the stability of the fracture of pre-bending the nails before implantation. Standard ESIN was performed on 24 synthetic femoral models with a spiral fracture. In eight cases the nails were inserted without any pre-bending, in a further eight cases they were pre-bent to 30° and in the last group of eight cases they were pre-bent to 60°. Mechanical testing revealed that pre-bending to 60° produced a significant increase in the stiffness or stability of the fracture. Pre-bending to 60° showed a significant positive influence on the stiffness compared with unbent nails. Pre-bending to 30° improved stiffness only slightly.These findings validate the recommendations for pre-bending, but the degree of pre-bend should exceed 30°. Adopting higher degrees of pre-bending should improve stability in spiral fractures and reduce the complications of varus deformity and shortening.

Modification of elastic stable intramedullary nailing with a 3rd nail in a femoral spiral fracture model – results of biomechanical testing and a prospective clinical study

“…However, because of the high repeatability due to minimal inter-individual variability [40-42], it was used successfully in previous biomechanical studies [23,26,27]. Furthermore, due to the configuration of the synthetic bone model, the nails could not be placed as proximally as is ideal in real operations.…”

“…The biomechanical in-vitro setting is described in detail elsewhere [23,26,27]. Each mid-shaft fracture was identically sawed by Sawbones® with a fracture length of 100 mm and an identical spiral fracture from distal lateral rotating to cranial medial (AO pediatric comprehensive classification of long bone fractures: 32D51 [28]; LiLa classification for pediatric long-bone fractures: 3.2.s.3.2.…”

In-vitro characterization of stress corrosion cracking of aluminium-free magnesium alloys for temporary bio-implant applications

“…Temporary implants for osteosynthesis require good ductility for geometrical adaption by the surgeon [32]. In-vitro and animal studies also show each alloy to possess good cytocompatibility [5,8].…”

Additional Tension Screws Improve Stability in Elastic Stable Intramedullary Nailing: Biomechanical Analysis of a Femur Spiral Fracture Model

“…24 With our recently developed validated long spiral femur fracture model, we found advantages of steel over titanium nails 24 and demonstrated that using endcaps did not improve the stability of the ESIN-osteosynthesis, especially not in axial compression in a spiral fracture model. 25 Also, we proved the importance of prebending the nails of more than 30 degrees 26 and showed that an additional third nail reduced the risk of shortening and recurvation in the biomechanical model. 27 The transfer of this biomechanical results into clinical practice demonstrated that a third nail increases the stability of the fixation in a femoral fracture if the implantation and the prebending of the third nail is appropriate to the individual character of the fracture.…”