Journal of orthopaedic research : official publication of the Orthopaedic Research Society
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Dynamization of fracture fixation is used clinically to improve the bone healing process. However, the effect of early dynamization remains controversial. This study evaluated the effect of early dynamization, by reduced stiffness of fixation on callus stiffness and size after 5 weeks of healing in a rat diaphyseal femoral osteotomy. ⋯ The flexural rigidity of the R-group was 82% (tested in the anterior-posterior direction; p = 0.01) and 93% (tested in the medial-lateral direction; p = 0.002) greater than the flexural rigidity of the D-group. The rigid fixation led to a stiffer callus with a smaller callus volume, but better mineralized tissue in the whole callus and at the level of the osteotomy gap than the flexible or the dynamized fixation. Early dynamization did not improve healing compared to rigid or flexible fixation in a rat femoral osteotomy model.
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The aim of this study was to investigate whether preconditioned local somatotheral stimulation (LSTS) protects the muscle and nerve against ischemia-reperfusion (I/R) injuries. Male rats were randomly assigned to normal, preconditioned LSTS only, and I/R-injured groups with or without LSTS preconditioning. I/R injuries of the lower limb were induced by rubber band wrapping, followed by measurements of gait function and nerve conduction, muscle pathology, serum enzymatic activity, and the expression of heat-shock protein 70 (HSP-70) in the gastrocnemius muscles. ⋯ In contrast, gait stride length, compound motor action potential, and serum creatine phosphokinase MM isoenzyme were significantly improved on the eighth day after one or two doses of preconditioned LSTS and subsequent I/R injury. Western blot analysis disclosed no significant change of HSP-70 expression in the muscle of I/R injured limbs between LSTS (-) and LSTS (+) groups. We conclude that preconditioned LSTS is a safe modality that improves the neuromuscular plasticity against I/R injured limbs, which provides a new strategy for I/R injury in clinical applications, such as intraoperative use of tourniquets.
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In the treatment of polytrauma patients, multiple studies have shown how the timing and the type of the initial surgery of long bone fractures influence the incidence of systemic complications. Database analyses documented that unduly long surgical procedures undertaken early after trauma increase the risk of acute respiratory distress syndrome (ARDS), especially when femoral shaft fractures are stabilized. Animal research and prospective clinical studies also support the fact that the type of stabilization of a femoral shaft fracture may influence the systemic response to trauma. ⋯ The potentially negative impact of excessive surgery in high-risk patients can be avoided by using a new grading system for the assessment of the clinical status of the injured patient. Most recently, a large prospective randomized multicenter study has documented that this grading system is effective for identifying these borderline patients, and that in the borderline patient a staged surgical approach, such as temporary femoral stabilization with an external fixator, reduces the incidence of systemic complications. This work has changed the surgical management of multiply injured patients toward an approach that is tailored to the clinical condition of the patient, as indicated by well-defined clinical parameters as well as objective measurements of serum cytokine levels.
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The aim of this study is to establish a new experimental model of hematogenous implant-related infection (IRI) by a community-acquired methicillin-resistant S. aureus (CA-MRSA) strain. Cylindrical porous tantalum intramedullary implants were inserted in the proximal right tibia of 30 male white rabbits after administration of antibiotic prophylaxis. Four weeks later and without antibiotic prophylaxis, 20 animals received 1 ml of inoculum of two different concentrations (study groups A and B) of CA-MRSA strain through an ipsilatelar femoral artery catheter. ⋯ Histopathological semiquantitative scoring was used to compare the three groups. Comparison of groups A and B with control group and between group A and B showed statistically significant difference (p < 0.05) in all parameters except for periosteal reaction between groups B and C (p = 0.354). This novel, reproducible experimental model will facilitate the study of hematogenous CA-MRSA IRIs.
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Finite element (FE) models have become an important tool to study load distribution in the healthy and degenerated disc. However, model predictions require accurate constitutive laws and material properties. As the mechanical properties of the intervertebral disc are regulated by its biochemical composition and fiber-reinforced structure, the relationship between the constitutive behavior of the tissue and its composition requires careful consideration. ⋯ The goodness of fit ranged from 0.88 to 0.96 for the four experimental conditions evaluated. The constitutive law emphasized the interdependency of the strong swelling ability of the tissue and the viscoelastic nature of the collagen fibers. This is especially important for numerical models to further study the load sharing behavior with regard to disc degeneration and regeneration.