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Finite element models were created to study the stress and strain distribution around a solitary Brånemark implant. The influence of a number of clinically relevant parameters was examined: bone-implant interface (fixed bond versus frictionless free contact), bone elastic properties, unicortical versus bicortical implant fixation and the presence of a lamina dura. Bone loading patterns in the vicinity of the implant seem to be very sensitive to these parameters. Hence they should be integrated correctly in numerical models of in vivo behaviour of oral implants. This necessitates the creation of patient-dependent finite element models.

This is the only cadaveric study of bridging vein rupture focused on short pulse durations, which are usually associated with falls. The data suggest a tolerance level of approximately 10,000 rad/second2 for pulse durations shorter than 10 msec, which seems to decrease for longer pulse durations.

Different methods for ultrasonic velocity determination using broad-band pulse transmission have been investigated in 70 human calcanae in vitro. The work took place within the context of the EC BIOMED1 concerted action Assessment of Quality of Bone in Osteoporosis. Ultrasonic velocities were determined using three different transit time definitions: first arrival (TTV1), thresholding (TTV2), and first zero crossing (TTV3). Phase velocity (PV) was determined over a range of frequencies from 200 to 800 kHz using a new phase spectral analysis technique. The different velocity measurements were compared in terms of their magnitudes and their inter-correlations. There were significant differences of up to 260 m s-1 between different transit time velocities (p < 0.0001), indicating the sensitivity of the measurement to the arrival criteria used. Phase velocities were lower than all of the transit time velocities (p < 0.0001) and decreased with increasing frequency (p < 0.005). A strong correlation (r2 = 0.968) was observed between PV at 400 kHz (PV400) and TTV3, with much weaker correlations between PV and the other transit time velocities. Reproducibility for transit time velocity measurement was optimal for TTV3 (coefficient of variation, cv = 0.41%), and for PV it was optimal at 600 kHz (cv = 0.34%). These data indicate that transit time measurements may be subject to errors due to the modification of the pulse shape during propagation through bone by attenuation and dispersion. Velocity measurement by phase spectral analysis appears to offer advantages over the transit time approach, and should be the method of choice for velocity measurement in trabecular bone. Where transit time velocity measurements are made, the first-zero-crossing criterion appears to be have some advantages over other arrival criteria. We also note that PV measurements provide new information on dispersion which could prove to be relevant to the structural and mechanical characterization of trabecular bone.

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Linear and depressed skull fractures are frequent mechanisms of head injury and are often associated with traumatic brain injury. Accurate knowledge of the fracture of cranial bone can provide insight into the prevention of skull fracture injuries and help aid the design of energy absorbing head protection systems and safety helmets. Cranial bone is a complex material comprising of a three-layered structure: external layers consist of compact, high-density cortical bone and the central layer consists of a low-density, irregularly porous bone structure.In this study, cranial bone specimens were extracted from 8 fresh-frozen cadavers (F=4, M=4; 81±11 yrs old). 63 specimens were obtained from the parietal and frontal cranial bones. Prior to testing, all specimens were scanned using a µCT scanner at a resolution of 56.9µm. The specimens were tested in a three-point bend set-up at different dynamic speeds (0.5, 1 and 2.5 m/s). The associated mechanical properties that were calculated for each specimen include the 2 nd moment of inertia, the sectional elastic modulus, the maximum force at failure, the energy absorbed until failure and the maximum bending stress. Additionally, the morphological parameters of each specimen and their correlation with the resulting mechanical parameters were examined.It was found that testing speed, strain rate, cranial sampling position and intercranial variation all have a significant effect on some or all of the computed mechanical parameters. A modest correlation was also found between percent bone volume and both the elastic modulus and the maximum bending stress.

Spinal bone mineral density (BMD) measurements and calcaneal ultrasound were compared in terms of their ability to predict the strength of the third lumbar vertebral body using specimens from 62 adult cadavers (28 females, 34 males). BMD was measured using dual X-ray absorptiometry (DXA) in both vertebra and calcaneus. Quantitative computed tomography (QCT) was used to determine trabecular BMD, cortical BMD, cortical area, and total cross-sectional area (CSA) of the vertebral body. Bone velocity (BV) and broadband ultrasonic attenuation (BUA) were measured in the right calcaneus.

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