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How evolutionary changes in body size are brought about by variance in developmental timing and/or growth rates (also known as heterochrony) is a topic of considerable interest in evolutionary biology. In particular, extreme size change leading to gigantism occurred within the dinosaurs on multiple occasions. Whether this change was brought about by(More)
OBJECTIVE To determine whether the human Achilles tendon has higher material properties than other tendons and to test for strain rate sensitivity of the tendon. DESIGN Mechanical testing of excised tendons. BACKGROUND While the human Achilles tendon appears to experience higher in vivo stresses than other tendons, it is not known how the Achilles(More)
STUDY DESIGN Measurement of the kinematics of the lumbar spine after insertion of an interspinous spacer in vitro. OBJECTIVES To understand the kinematics of the instrumented and adjacent levels due to the insertion of this interspinous implant. SUMMARY OF BACKGROUND DATA An interspinous spacer (X Stop, SFMT, Concord, California) has been developed to(More)
STUDY DESIGN The spinal canal and neural foramina dimensions of cadaver lumbar spines were quantified during flexion and extension using magnetic resonance imaging before and after placement of an interspinous process implant. OBJECTIVE To quantify the effect of the implant on the dimensions of the spinal canal and neural foramina during flexion and(More)
OBJECTIVE To examine the influence of strain rate, bone mineral density, and age in determining the mode by which human Achilles tendons fail. DESIGN Dual-energy X-ray absorptiometry and mechanical testing of excised Achilles tendon-calcaneus specimens. BACKGROUND The Achilles tendon can fail by tendon rupture or bony avulsion. These injuries are caused(More)
STUDY DESIGN A biomechanical study on the stabilization of thoracolumbar burst fractures. OBJECTIVE To demonstrate that the addition of a calcium phosphate cement into the fractured vertebral body through a transpedicular approach is a feasible technique that improves the stiffness of a transpedicular screw construct. SUMMARY OF BACKGROUND DATA Short(More)
STUDY DESIGN A static nondestructive bending analysis of pedicle screws inserted into vertebral analogues was conducted. Pedicle screw load was studied as a function of variables in insertion technique. OBJECTIVES To determine how the sagittal bending moment in pedicle screws is affected by changes in pedicle screw length, insertional depth, and sagittal(More)
STUDY DESIGN Anatomic analysis of L4 vertebral morphometry comparing specimens harvested from humans and five common large animal species. OBJECTIVE To compare fundamental structural similarities and differences in the vertebral bodies of commonly used experimental animals relative to human vertebrae. SUMMARY OF BACKGROUND DATA Animal models are(More)
STUDY DESIGN This biomechanical study of fractures in cadaver vertebrae used specially designed pedicle screws to determine screw strains during loading of two different fixation constructs. OBJECTIVES The authors determined the relative benefit of adding offset sublaminar hooks to standard pedicle screw constructs to reduce screw bending moments and(More)