Abstract
This manuscript introduces a programable active bone fixator system that enables systematic investigation of bone healing processes in a sheep animal model. In contrast to previous systems, this solution combines the ability to precisely control the mechanical conditions acting within a fracture with continuous monitoring of the healing progression and autonomous operation of the system throughout the experiment. The active fixator system was implemented on a double osteotomy model that shields the experimental fracture from the influence of the animal’s functional loading. A force sensor was integrated into the fixator to continuously measure stiffness of the repair tissue as an indicator for healing progression. A dedicated control unit was developed that allows programing of different loading protocols which are later executed autonomously by the active fixator. To verify the feasibility of the system, it was implanted in two sheep with different loading protocols, mimicking immediate and delayed weight-bearing, respectively. The implanted devices operated according to the programmed protocols and delivered seamless data over the whole course of the experiment. The in vivo trial confirmed the feasibility of the system. Hence, it can be applied in further preclinical studies to better understand the influence of mechanical conditions on fracture healing.
Highlights
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.license.Despite decades of research on the mechanobiology of bone repair and the development of new orthopedic implants and procedures, 5% to 10% of fractures still fail to heal properly, leading to non or delayed union [1]
The active systematically execute defined stimulation protocols with simultaneous monitoring of the fixator was actuated by a Brushless Direct Current (BLDC) motor connected to a spindle healing response
The sling system allows the sheep to fully bear all prevents protocolsexcessive that werepeak tested duringonthe in vitro tests, stimulation weightInbut loading thedynamic osteotomies when thethe animals lie down corresponded wellanimals to the commanded with
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.license (https://creativecommons.org/licenses/by/4.0/).Despite decades of research on the mechanobiology of bone repair and the development of new orthopedic implants and procedures, 5% to 10% of fractures still fail to heal properly, leading to non or delayed union [1]. The vast majority of bone fractures heal via indirect bone healing by development of an external callus that overgrows the fracture gap to provide stabilization and later remodels into bone [3]. It is long established that development of the fracture callus is mechanically stimulated by interfragmentary motion (IFM) in the fracture gap [4]. Effects on fracture healing have been reported for many parameters, such as amplitude of IFM [5,6], loading mode [7,8] and number of loading cycles [9,10]. Claes et al [11] reported that early dynamization does not improve fracture healing in a rat model and Augat et al [12] claimed that early, full weight-bearing with a flexible external fixator delays healing in sheep. Tufecki et al [13]
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