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Biomedical subjects

N J Madeley

Publications and source records attributed to N J Madeley.

4 recordsLinked to original sources
PubMed2006

Changes in scaphoid bone density after acute fracture.

The radiographic density of the proximal fragments of 16 scaphoid fractures was assessed on scaphoid series radiographs taken at 6 to 12 weeks. In addition, dual energy X-ray absorptiometry measurements of bone mineral density in the distal radius and proximal and distal fracture fragments were performed at 1 to 2 weeks and 6 to 12 weeks. Median reductions of 9% and 10% were observed in bone mineral density in the proximal fracture fragment and the distal radius respectively, but these did not correlate with the radiographic density of the proximal fragment. A greater median reduction in bone mineral density (27%) was observed in the distal fracture fragment and more bone loss occurred at this site when there was an apparent increase in the radiographic density of the proximal fragment (median fall of 0.23 g/cm2 versus 0.14 g/cm2). Thus, apparent increased radiographic density of the proximal fragment may be due to increased bone loss from the distal fragment.

Absorptiometry, Photon↗
PubMed2004

Retrospective analysis of malleolar fractures in an impact environment.

To protect against malleolar fractures in frontal crashes it is important to understand the mechanisms of injury. We have investigated the accuracy of Orthopaedic Specialists in deducing the injury mechanisms of experimentally generated malleolar fractures from radiographs; and the applicability of classic descriptors of injury mechanisms, such as the Lauge-Hansen classification system, in analysing impact induced trauma. Orthopaedic Specialists did not consistently deduce the mechanism of ankle injuries suggesting there may not be a unique fracture pattern for every injury mechanism and that the Lauge-Hansen classification system does not reliably describe ankle fractures created in the impact environment.

Accidents, Traffic↗
PubMed2003

Muscle tetanus and loading condition effects on the elastic and viscous characteristics of the thorax.

Thoracic deformation under an applied load is an established indicator of injury risk, but the force required to achieve an injurious level of deformation currently is not understood adequately. This article evaluates how two potentially important factors, loading condition and muscle tensing, affect the structural response of the dynamically loaded thorax. Structural models of two human cadaver thoraxes and two porcine thoraxes were used to quantify the effects. The human cadavers, which represent anthropometric extremes, were subjected to anterior loading from (1) a 5.1-cm-wide belt oriented diagonally (i.e., seatbelt-like loading), (2) a 15.2-cm-diameter rigid hub, and (3) a 20.3-cm-wide belt oriented laterally (i.e., a distributed load). A structural model having the mathematical formulation of a quasilinear viscoelastic material model was used to model the elastic and viscous response, with ramp-hold tests used to determine the model coefficients. The effect of thoracic musculature was assessed using similar ramp-hold tests on the porcine subjects, each with and without forced muscle contraction. Even maximally contracted thoracic musculature is shown to have a minimal effect on the response, with similar elastic and viscous characteristics exhibited by each subject regardless of muscle tone. The elastic response is shown to be approximately a factor of three stiffer for diagonal belt loading and for this distributed loading condition than for the hub loading, indicating that the response is influenced most by the particular anatomical structures that are engaged and, secondarily, by the area of load application. Specifically, shoulder involvement is shown to have a strong influence. The force relaxation is found to be pronounced, but insensitive to the loading condition, with long-time force relaxation coefficients (G( infinity )) in the range of 0.1 to 0.3. The findings of this study provide restraint-specific guidelines for the force-deflection characteristics of both physical and computational thoracic models.

Animals↗