Clinical biomechanics
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Clinical biomechanics · Dec 2006
Comparative StudyBiomechanical comparison of a unique locking plate versus a standard plate for internal fixation of proximal humerus fractures in a cadaveric model.
Newer internal fixation devices with a locking mechanism between the plate and the screw have recently been released. The efficacy of these plates in the proximal humerus has yet to be fully described. There is a need to compare the biomechanical properties of efficacy of plate fixation with or without locking screws for surgery of two-part proximal humerus fractures. Multiple-plane locking plate and cloverleaf plate designs were tested to determine their ability to maintain fixation on the humeral head. ⋯ In the cadaveric, two-part proximal humerus fracture model that was created, the locking plate displayed significantly greater holding power of the humeral head. Clinical relevance is unproven but may be manifested in vivo as improved early range of motion exercises and functional outcome.
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Clinical biomechanics · Dec 2006
Outer annulus tears have less effect than endplate fracture on stress distributions inside intervertebral discs: relevance to disc degeneration.
Annulus tears and endplate fracture are common lesions in human intervertebral discs. Both cause degenerative changes in animal models, but the time course appears to be different. The purpose of the present experiment is to compare the effects of outer annulus tears and endplate fracture on intradiscal stresses. We hypothesise that endplate fracture provides a greater stimulus for disc degeneration. ⋯ Outer annulus tears have less (immediate) effects on intradiscal compressive stresses than endplate fracture, supporting our hypothesis.
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Clinical biomechanics · Dec 2006
Clinical TrialThe effect of three levels of foot orthotic wedging on the surface electromyographic activity of selected lower limb muscles during gait.
Some types of foot orthoses have been researched for their effect on lower limb electromyographic muscle activity during walking. However, foot orthoses with high levels of medial rearfoot wedging ('inverted' foot orthoses) have not been investigated. ⋯ Footwear and orthoses can significantly alter the maximum EMG amplitude of leg muscles during walking. Foot orthoses appear to increase peroneus longus EMG amplitude compared to footwear alone. However, the level of medial rearfoot posting within an orthosis does not appear to significantly alter maximum EMG amplitude. The individual responses to foot orthoses are highly variable. The changes in EMG amplitude with the use of foot orthoses and shoes may have clinical implications.
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Clinical biomechanics · Dec 2006
Buck's direct repair of lumbar spondylolysis restores disc stresses at the involved and adjacent levels.
Lumbar spondylolysis was reported to cause disc degeneration at both caudal and cranial adjacent level. However, basic disc biomechanics in the spondylolytic spine is not fully understood. Purpose of this study was to analyze the disc stresses at cranial and caudal adjacent level of lumbar spondylolysis. Also, the biomechanical effects of Buck's technique on disc stresses at these two segments were evaluated. ⋯ Spondylolysis increases disc stresses at the affected as well as cranial adjacent level, and it may lead to disc degeneration at both levels. However, the increase in stresses is higher at the affected caudal level, when compared to the cranial level. Buck's technique may restore the disc stresses back to normal at both disc levels. Thus, this technique may be beneficial from a biomechanical perspective as well.