Decoupling the Wrist: A Cadaveric Experiment Examining Wrist Kinematics Following Midcarpal Fusion and Scaphoid Excision

At the wrist, kinematic coupling (the relationship between flexion-extension and radial-ulnar deviation) facilitates function. Although the midcarpal joint is critical for kinematic coupling, many surgeries, such as 4-corner fusion (4CF) and scaphoidexcision 4-corner fusion (SE4CF), modify the midcarpal joint. This study examines how 4CF and SE4CF influence kinematic coupling by quantifying wrist axes of rotation. Wrist axes of rotation were quantified in 8 cadaveric specimens using an optimization algorithm, which fit a 2-revolute joint model to experimental data. In each specimen, data measuring the motion of the third metacarpal relative to the radius was collected for 3 conditions (nonimpaired, 4CF, SE4CF). The calculated axes of rotation were compared using spherical statistics. The angle between the axes of rotation was used to assess coupling, as the nonimpaired wrist has skew axes (ie, angle between axes approximately 60°). Following 4CF and SE4CF, the axes are closer to orthogonal than those of the nonimpaired wrist. The mean angle (±95% confidence interval) between the axes was 92.6° ± 25.2° and 99.8° ± 22.0° for 4CF and SE4CF, respectively. The axes of rotation defined in this study can be used to define joint models, which will facilitate more accurate computational and experimental studies of these procedures.

A proof-of-concept study of the VeinScrew: A new percutaneous venous closure device

Objective This study evaluated the concept of percutaneous closure of insufficient veins using the VeinScrew principle. Methods The VeinScrew is designed to place a spring-shaped implant that contracts and clamps around the vein. The ability of the device to occlude adequately was tested in a bench model experiment. The feasibility of accurate placement and adequate venous occlusion was evaluated in an animal experiment and in a human cadaveric experiment. Results The VeinScrew implant occluded up to a pressure of 135 mmHg. In vivo studies confirmed that deployment was challenging but technically feasible, and subsequent phlebography showed closure of the vein. The cadaveric study showed that percutaneous placement of the evolved VeinScrew around the great saphenous vein was feasible and accurate. Conclusions The current studies show the feasibility of the VeinScrew concept. Future developments and translational studies are necessary to determine the potential of this technique as a new option in the phlebologist’s toolbox.

The effect of spinal osteotomies on spinal cord tension and dural buckling: a cadaveric study

OBJECT The standard surgical release of a tethered cord may result in recurrent scar formation and occasionally be associated with retethering. The application of spinal shortening procedures to this challenging problem potentially can reduce tension on the retethered spinal cord while minimizing the difficulties inherent in traditional lumbosacral detethering revision. Although spinal shortening procedures have proven clinical benefit in patients with a recurrent tethered cord, it is unclear how much shortening is required to achieve adequate reduction in spinal cord tension or what impact these osteotomies have on dural buckling. METHODS The authors calculated mean values from 4 human cadavers to evaluate the effect of 3 different spinal shortening procedures—Smith-Petersen osteotomy (SPO), pedicle subtraction osteotomy (PSO), and vertebral column resection (VCR)—on spinal cord tension and dural buckling. Three cadavers were dedicated to the measurement of spinal cord tension, and 3 other cadavers were devoted to myelography to measure dural buckling parameters. RESULTS The SPO was associated with a maximal decrease in spinal cord tension of 16.1% from baseline and no dural buckling with any degree of closure. The PSO led to a mean maximal decrease in spinal cord tension of 63.1% from baseline at 12 mm of closure and demonstrated a direct linear relationship between dural buckling and increasing osteotomy closure. Finally, VCR closure correlated with a mean maximal decrease in spinal cord tension of 87.2% from baseline at 10 mm of closure and also showed a direct linear relationship between dural buckling and increases in osteotomy closure. CONCLUSIONS In this cadaveric experiment, the SPO did not lead to appreciable tension reduction, while a substantial response was seen with both the PSO and VCR. The rate of tension reduction may be steeper for the VCR than the PSO. Adequate tension relief while minimizing dural buckling may be optimal with 12–16 mm of posterior osteotomy closure based on this cadaveric experiment.

Novel Axillary Approach for Brachial Plexus in Robotic Surgery: A Cadaveric Experiment

Brachial plexus surgery using the da Vinci surgical robot is a new procedure. Although the supraclavicular approach is a well known described and used procedure for robotic surgery, axillary approach was unknown for brachial plexus surgery. A cadaveric study was planned to evaluate the robotic axillary approach for brachial plexus surgery. Our results showed that robotic surgery is a very useful method and should be used routinely for brachial plexus surgery and particularly for thoracic outlet syndrome. However, we emphasize that new instruments should be designed and further studies are needed to evaluate in vivo results.

Investigation of Material Properties and Force of 6-Year-Old Children Lumbar FEM

The purpose of this study was to investigate injury mechanism and injury biomechanical response of children lumbar segment L4-L5. Firstly, the geometric model of lumbar segment at L4-L5 was extracted from CT scan images of a healthy 6-year-old child for from repairing and refining by reverse engineering software Geomagic to finite element (FE) pre-processing by Hypermesh. The FE model was calculated by LS-Dyna under the conditions given by cadaveric experiments, in which a static load was applied to the center of lumber segment at L4-L5 by a metal plate. The static load was subsequently moved forward and backward 10mm in sagittal plane, respectively. The interfacial force between articular surfaces was the objective to investigate for the comparison between the simulation and the cadaveric experiment as well as the simulation by adult FE model. The simulated results showed that the displacement between L4 and L5 of children was, to some extent, smaller than that of adults. The ratio of calculated force between articular surfaces of L4-L5 of children to the applied force moreover was, to a great extent, smaller than that of adults. Children are much easier to be rendered injury at L4-L5 than adults are, because articular surfaces of children relatively more slightly contribute to distributing the force that nucleus pulposus undergoes than those of adults do. Hence, the current study could be perceived as a theoretical basis for the product design toward vehicle safety.