Clinical biomechanics
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Clinical biomechanics · Jun 2010
The influence of the axial, antero-posterior and lateral positions of the center of rotation of a ball-and-socket disc prosthesis on the cervical spine biomechanics.
Previous studies documented the importance of the positioning and the design parameters of the prosthesis in determining the biomechanics of the implanted spine. However, a comprehensive biomechanical evaluation of the significance of these parameters is still lacking. Therefore, the paper is aimed to the quantification of their influence on the flexibility of the implanted spine and the force transmitted through the facet joints. ⋯ The effects of the positioning of a cervical disc prosthesis were estimated. A wide range of mechanical behaviors can be obtained by the manufacturers by appropriately manipulating the position of the center of rotation. A proper positioning of the artificial disc during the surgery, in particular in the antero-posterior direction, was found to be of critical importance.
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Clinical biomechanics · Jun 2010
In vivo intersegmental motion of the cervical spine using an inverse kinematics procedure.
The main functions of the cervical spine are the stabilization and the orientation of the head. Pathologies are complex and difficult to diagnose. The first sign of the dysfunction is an abnormal intervertebral motion. It is the purpose of this feasibility study to determine the intersegmental motions and loading conditions of the cervical spine in vivo with standard clinical investigation methods. ⋯ A subject-specific rigid body model merged data from classical flexion-extension radiographs and noninvasive external motion capture. Our approach is based on inverse kinematics allowing the estimation of the intervertebral motion and mechanical behavior of the cervical spine in vivo, which gives valuable information concerning biomechanics of the cervical spine in vivo for cervical spine clinical investigation.
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Clinical biomechanics · May 2010
Proximal humerus fracture rotational stability after fixation using a locking plate or a fixed-angle locked nail: the role of implant stiffness.
Fixed-angle locked devices have been developed to improve internal fixation of proximal humerus fractures. Available low-profile precontoured locking plates and intramedullary nails with fixed-angle interlocks are currently favored by most surgeons in this setting. The aim of this study was to assess the relative stability of these two methods of fixation under torsion load. ⋯ Both locking plates and locked intramedullary nails may provide enough stability to avoid secondary displacement of proximal humerus fractures during early physical therapy. Locking plates demonstrated superior biomechanical properties under high rotational loads than locked intramedullary nails in a cadaveric proximal humerus two-part osteotomy model, and could provide more protection against unexpected high torsion loads.
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Clinical biomechanics · May 2010
Biomechanical effects of patellar positioning on intraoperative knee joint gap measurement in total knee arthroplasty.
Balancing both the lateral/medial and extension/flexion joint gaps is a prerequisite for soft tissue balance in total knee arthroplasty. The purpose of this study was to quantify the effects of patellar positioning and quadriceps load during total knee arthroplasty on knee joint gap measurements. ⋯ The patellar positioning and quadriceps muscle loading in total knee arthroplasty have a strong influence on intraoperative joint gap measurements.
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Clinical biomechanics · May 2010
Gait parameters and stride-to-stride variability during familiarization to walking on a split-belt treadmill.
Subjects unfamiliar to walking on a split-belt treadmill may initially demonstrate an altered gait pattern or increased variability of gait parameters. While previous investigations have examined kinematic variables associated with familiarization time, the objective of this study was to determine the familiarization period required to obtain the most reproducible gait pattern through the assessment of kinetic, kinematic and spatio-temporal parameters during a single session of treadmill walking. ⋯ The results suggest that in order to collect accurate data for gait analysis, subjects should be familiarized to the split-belt treadmill for at least 5 min prior to data collection.