Article

A new test set-up for skull fracture characterisation.

Division of Biomechanics and Engineering Design, K.U. Leuven, Celestijnenlaan 300C, 3001 Heverlee, Belgium.
Journal of Biomechanics (Impact Factor: 2.72). 02/2007; 40(15):3389-96. DOI:10.1016/j.jbiomech.2007.05.018
Source: PubMed

ABSTRACT Skull fracture is a frequently observed type of severe head injury. Historically, a variety of impact test set-ups and techniques have been used for investigating skull fracture. The most frequently used are the free-fall technique, the guided fall or drop tower set-up and the piston-driven impactor set-up. This document proposes a new type of set-up for cadaver head impact testing which combines the strengths of the most frequently used techniques and devices. The set-up consists of two pendulums, which allow for a 1 degree of freedom rotational motion. The first pendulum is the impactor and is used to strike the blow. The head is attached to the second pendulum using a polyester resin. Local skull deformation and impact force are measured with a sample frequency of 65 kHz. From these data, absorbed energy until skull fracture is calculated. A set-up evaluation consisting of 14 frontal skull and head impact tests shows an accurate measurement of both force and local skull deformation until fracture of the skull. Simplified mechanical models are used to analyse the different impacting techniques from literature as well as the new proposed set-up. It is concluded that the proposed test set-up is able to accurately calculate the energy absorbed by the skull until fracture with an uncertainty interval of 10%. Second, it is concluded that skull fracture caused by blunt impact occurs before any significant motion of the head. The two-pendulum set-up is the first head impact device to allow a well-controlled measurement environment without altering the skull stress distribution.

0 0
 · 
1 Bookmark
 · 
58 Views
  • [show abstract] [hide abstract]
    ABSTRACT: For illustration of the more precise variation of the plasma velocity of ; an electric wave with the frequency in a plasma column, the effect of the glass ; tube in which the discharge occurs and the effect of the Langmuir layer between ; plasma and glass tube were considered in the calculation of the wave broadening. ; (tr-auth);
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Implant survival rate is a primary concern for individuals receiving a primary total knee arthroplasty. Loosening is the primary reason for revision surgery and was therefore the focus of the current study. To better understand the mechanics of implant fixation, the time-dependent fixation of a femoral knee component was measured in vitro on three cadaveric femurs. The fixation of each femoral knee component was measured with strain gauged implants for at least 10min on each femoral component. Additionally, impaction forces were measured during the implantation of each component. These forces were 2-6 times less than previously reported. The implantation impact forces were higher for the bones with higher bone density. Power law regressions were fit to the absolute value of the principal strains measured on the components over time to quantify the relaxation of the bone. The average power coefficient value for the three bones was lower for the bones with higher bone density. The average power coefficient value for the maximum principal strains was significantly higher than that of the minimum principal strains in each bone. The results were extrapolated to approximate the fixation strength at 9 months after implantation. In this time period the strain was predicted to decrease to between 78 and 91% of the strain 1s after implantation where those with lower bone density will have decreased fixation strength.
    Medical Engineering & Physics 11/2010; 32(9):968-73. · 1.78 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Service data does not exist for the strength of enclosures for subdermally implanted biotelemetry devices intended for young wild animals. Developing adequate tests especially for implants intended for endangered species is difficult due to the very limited availability of live animals and cadaverous tissue, ethical concerns about using them, and high enclosure costs. In this research, these limitations were overcome by taking a conservative approach to design and testing. Reliability tests were developed and performed to establish the likelihood that a thin subdermally and cranially implanted alumina enclosure would fail due to typical external forces related to diving, fights, and falls over the expected 30-year life time of sea lions. Cyclic fatigue tests indicative of deep dives performed out of tissue and at the 90% reliability level indicated no failure after 70,000 stress cycles at stresses of approximately 15 MPa; dynamic fatigue tests indicated a 5% probability of failure at 250 MPa; and puncture tests indicative of fight bites showed a 5% probability of failure at 1500 N. These values were far outside of what the animals might expect to encounter in real life. On the other hand, the response of the enclosure to impact outside of the tissue was failure at a mean energy level of 6.7 J. Modeling results predict that head impacts due to trampling by fighting sea lion males and falls over 1 m onto a rocky ledge typical of haul out environments would likely fracture an infant’s head as well as the implant. The device can be implanted under an impact absorbing 1 cm blubber layer for extra protection. More service data for enclosures can be made more available despite limited availability of test animals if a conservative approach to testing is taken.
    Journal of Materials Engineering and Performance 21(9). · 0.92 Impact Factor