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STUDY DESIGN Magnetic resonance images were obtained of the lumbar spines of three volunteers in neutral, flexed, and extended postures. OBJECTIVES To measure migration of the nucleus pulposus within the intervertebral disc during flexion and extension of the spine in living people. SUMMARY OF BACKGROUND DATA Results of experiments on bisected cadaveric(More)
Eighteen frozen ovine discs were bisected, in the mid-sagittal plane, to produce 36 specimens. The cut surfaces were marked at the inner and outer annulus boundaries of the annulus fibrosus, both anteriorly and posteriorly, with Alcian blue stain. The sections were sealed by a transparent plate, and thawed. A compression of 1mm at a rate of 0.2mms(-1) was(More)
Flexion-extension of the spine is defined in the sagittal plane, which divides the body into right and left halves, and can be measured from lateral radiographs, including those obtained by videofluoroscopy. The effects of axial rotation and lateral bending, which lead to movement out of the sagittal plane, were investigated by generating a(More)
AIM To evaluate evidence for involvement of the lower limb in spinal function and low back pain (LBP). DESIGN A hypothesis based on a critical review of the relevant biomechanical and clinical literature. RESULTS The spine resembles an inverted pendulum that supports the weight of the upper body; its stability requires a moving base that is provided by(More)
BACKGROUND Articular cartilage is a viscoelastic material, but its exact behaviour under the full range of physiological loading frequencies is unknown. The objective of this study was to measure the viscoelastic properties of bovine articular cartilage at loading frequencies of up to 92 Hz. METHODS Intact tibial plateau cartilage, attached to subchondral(More)
The upright thoraco-lumbar spine resembles an Euler column buckled in the second mode (n = 2) when viewed in the sagittal plane. An advantage of n = 2 buckling is that further load can be carried without adopting a stooped posture. Flexion of the spine is considered as the first quarter cycle of an Euler pendulum. This is possible if the antagonistic(More)
RATIONALE AND OBJECTIVES The authors investigated the feasibility of using a low-field open-magnet magnetic resonance (MR) scanner to acquire functional flexion-extension images for range of motion (ROM) measurements on the lumbar spine. METHODS Seventeen healthy subjects with no symptoms of back pain (age range, 22-59 years) were scanned in a low-field(More)
Posterior and anterior heights, cross-sectional area and shape were measured for all the intervertebral discs in four spines from elderly human cadavers. Disc height was a minimum at the T4-5 level; thoracic discs were less wedge-shaped than those in the cervical and lumbar regions. Cross-sectional area increased from the cranial to caudal extremity; at the(More)
BACKGROUND Polyurethane (PU) foam is widely used as a model for cancellous bone. The higher density foams are used as standard biomechanical test materials, but none of the low density PU foams are universally accepted as models for osteoporotic (OP) bone. The aim of this study was to determine whether low density PU foam might be suitable for mimicking(More)