External fixation design evolution enhances biomechanical frame performance

Sellei, Richard Martin; Kobbe, Philipp; Dadgar, Azad; Pfeifer, Roman; Behrens, Markus; Oldenburg, Geert von; Pape, Hans-Christian

doi:10.1016/s0020-1383(15)30007-3

Cited by 19 publications

(14 citation statements)

References 11 publications

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“…However, assessing the overall effective performance of a low-cost external fixator must consider more than just stiffness [6]. In addition to these fundamental requirements [6,8], the external fixator must be inexpensive [4]. These constructs should also be compatible with patient care and allow the recovery of the softtissue envelope [19].…”

Section: Discussionmentioning

confidence: 99%

“…Six external fixation frames were tested. Pins of 5 mm in diameter and 180 mm in length, with a 50-mm threaded portion, were used for all tests [6,8]. Three pins were fixed in each bony fragment for UUEF and H3-SR ( Fig.…”

Section: Positioningmentioning

confidence: 99%

“…When used for fracture management, the stiffness should be sufficient to overcome the forces a patient is subjected to during mobilization to prevent fracture displacement and to avoid nonunion [7]. It is also needed to foster sound callus formation [8]. The aim of this study was to determine the biomechanical characteristics of a low-cost external fixator in comparison with a validated reference fixator.…”

Section: Introductionmentioning

confidence: 99%

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Biomechanical study of a low-cost external fixator for diaphyseal fractures of long bones

et al. 2020

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Background: External fixation improves open fracture management in emerging countries. However, sophisticated models are often expensive and unavailable. We assessed the biomechanical properties of a low-cost external fixation system in comparison with the Hoffmann® 3 system, as a reference. Methods: Transversal, oblique, and comminuted fractures were created in the diaphysis of tibia sawbones. Six external fixators were tested in three modes of loading-axial compression, medio-lateral (ML) bending, and torsion-in order to determine construction stiffness. The fixator construct implies two uniplanar (UUEF1, UUEF2) depending the pin-rods fixation system and two biplanar (UBEF1, UBEF2) designs based on different bar to bar connections. The designed low-cost fixators were compared to a Hoffmann® 3 fixator single rod (H3-SR) and double rod (H3-DR). Twenty-seven constructs were stabilized with UUEF1, UUEF2, and H3-SR (nine constructs each). Nine constructs were stabilized with UBEF1, UBEF2, and H3-DR (three constructs each). Results: UUEF2 was significantly stiffer than H3-SR (p < 0.001) in axial compression for oblique fractures and UUEF1 was significantly stiffer than H3-SR (p = 0.009) in ML bending for transversal fractures. Both UUEFs were significantly stiffer than H3-SR in axial compression and torsion (p < 0.05), and inferior to H3-SR in ML bending, for comminuted fractures. In the same fracture pattern, UBEFs were significantly stiffer than H3-DR (p = 0.001) in axial compression and torsion, while only UBEF1 was significantly stiffer than H3-DR in ML bending (p = 0.013). Conclusions: The results demonstrated that the stiffness of the UUEF and UBEF device compares to the reference fixator and may be helpful in maintaining fracture reduction. Fatigue testing and clinical assessment must be conducted to ensure that the objective of bone healing is achievable with such low-cost devices.

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Section: Discussionmentioning

confidence: 99%

Section: Positioningmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Biomechanical study of a low-cost external fixator for diaphyseal fractures of long bones

et al. 2020

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“…The bending force applied was constantly increased up to 400 N, corresponding to a bending moment of 20 Nm, at a rate of 1 mm/min. The bending stiffness was calculated by dividing the bending moment by the bending angle and was expressed in Nm/deg [26,27]. Afterwards, sinusoidal loading with a constant amplitude was applied for each configuration.…”

Section: Four-point Bending Testmentioning

confidence: 99%

Investigating the biomechanical function of the plate-type external fixator in the treatment of tibial fractures: a biomechanical study

Shi

Liu

Zhang

et al. 2020

BMC Musculoskelet Disord

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Background: The design of an external fixator with the optimal biomechanical function and the lowest profile has been highly pursued, as fracture healing is dependent on the stability and durability of fixation, and a low profile is more desired by patients. The plate-type external fixator, a novel prototype of an external tibial fixation device, is a low profile construct. However, its biomechanical properties remain unclear. The objective of this study was to investigate the stiffness and strength of the plate-type external fixator and the unilateral external fixator. We hypothesized that the plate-type external fixator could provide higher stiffness while retaining sufficient strength. Methods: Fifty-four cadaver tibias underwent a standardized midshaft osteotomy to create a fracture gap model to simulate a comminuted diaphyseal fracture. All specimens were randomly divided into three groups of eighteen specimens each and stabilized with either a unilateral external fixator or two configurations of the plate-type external fixator. Six specimens of each configuration were tested to determine fixation stiffness in axial compression, four-point bending, and torsion, respectively. Afterwards, dynamic loading until failure was performed in each loading mode to determine the construct strength and failure mode. Results: The plate-type external fixator provided higher stiffness and strength than the traditional unilateral external fixator. The highest biomechanics were observed for the classical plate-type external fixator, closely followed by the extended plate-type external fixator. Conclusions: The plate-type external fixator is stiffer and stronger than the traditional unilateral external fixator under axial compression, four-point bending and torsion loading conditions.

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“…The bending force applied was constantly increased up to 400 N, corresponding to the bending moment of 20 Nm, at a rate of 1 mm/min. Bending stiffness was calculated by dividing the bending moment by the bending angle, and was expressed in Nm/deg [26,27]. Afterwards, sinusoidal loading with a constant amplitude was applied for each configuration.…”

Section: Four-point Bending Testmentioning

confidence: 99%

Investigating the biomechanics function of the plate-type external fixator in the treatment of tibial fractures: a biomechanical study

Shi

Liu

Zhang

et al. 2019

Preprint

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Background People have been pursuing to design an external fixator with the optimal biomechanics function and the lowest profile, since the fracture healing is dependent on the stability and durability of fixation and a low profile is more acceptable to patients. The plate-type external fixator, a novel prototype of an external tibial fixation device, is a low profile construct. However, the biomechanical properties remained unclear. The objective of the study was to investigate stiffness and strength of the plate-type external fixator and the unilateral external fixator. We hypothesized that the plate-type external fixator could provide higher stiffness, while retaining sufficient strength. Methods Fifty-four cadaver tibias underwent a standardized midshaft osteotomy to create a fracture gap model to simulate a comminuted diaphyseal fracture. All specimens were randomly divided into three groups of eighteen specimens each and stabilized with either the unilateral external fixator or the two configurations of the plate-type external fixator. Six specimens of each configuration were tested to determine fixation stiffness in axial compression, four-point bending, and torsion, respectively. Afterwards, dynamically loading until failure was performed in each load mode to determine construct strength and failure modes. Results The plate-type external fixator provided higher stiffness and strength compared with the traditional unilateral external fixator. The highest biomechanics was observed for the classical plate-type external fixator, with the extended plate-type external fixator close behind. Conclusions The plate-type external fixator is stiffer and stronger than the traditional unilateral external fixator under axial compression, four-point bending and torsion loading conditions.

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External fixation design evolution enhances biomechanical frame performance

Cited by 19 publications

References 11 publications

Biomechanical study of a low-cost external fixator for diaphyseal fractures of long bones

Biomechanical study of a low-cost external fixator for diaphyseal fractures of long bones

Investigating the biomechanical function of the plate-type external fixator in the treatment of tibial fractures: a biomechanical study

Investigating the biomechanics function of the plate-type external fixator in the treatment of tibial fractures: a biomechanical study

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