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Axis for dynamic measurement of flexion and extension torques about the lumbar spine. A computer simulation.

Most reports of trunk testing with an isokinetic dynamometer describe the axis of the machine aligned with the lumbosacral junction. A computerized mathematical simulation of motion of the lumbar spine under three conditions was performed, representing variations on the physiologic motion of the lumbar spine. The instantaneous center of rotation of the T12 vertebral body moving about a fixed pelvis was calculated and displayed. Under normal conditions, the center of rotation started close to the center of the L3 vertebral body and moved in an arc similar to that of L3 during flexion and extension. Dynamic testing of the trunk musculature in the lumbar region, therefore, should be performed with the axis of the isokinetic dynamometer aligned with the L3 vertebral body, and motion of the pelvis and thoracic spine should be minimized. This position of the axis provides the best approximation of the fixed axis of the testing machine to the physiologic axis. Failure to observe these precautions would tend to make the motion of the lumbar spine nonisokinetic and, thus, interfere with angular measurement of the spinal motion.

Adult↗

Devices for lung isolation used by anesthesiologists with limited thoracic experience: comparison of double-lumen endotracheal tube, Univent torque control blocker, and Arndt wire-guided endobronchial blocker.

BACKGROUND: Lung isolation is accomplished with a double-lumen tube or a bronchial blocker. Previous studies comparing lung isolation methods were performed by experienced anesthesiologists in thoracic anesthesia. Therefore, the results of these studies may not be relevant to the anesthesiologist with limited experience. This study compared the success rates of lung isolation devices among anesthesiologists with limited experience in thoracic anesthesia. METHODS: A prospective, randomized trial was designed to determine the success and time required for proper placement of the left-sided double-lumen tube (n = 22), the Univent tube (Vitaid Ltd., Lewiston, NY; n = 22), and the Arndt Blocker (Cook Critical Care, Bloomington, IN; n = 22). Anesthesiologists with less than two lung isolation cases per month were included (faculty n = 17 and senior residents n = 11). Variables recorded included (1) successful placement (as determined by an independent observer), (2) time of placement, and (3) the number of times the fiberoptic bronchoscope was used. RESULTS: Participants failed to place or position their assigned device in 25 of 66 patients (failure was 39% among faculty and 36% among senior residents). The failure rate did not differ among the three devices (P = 0.65). The median (25th-75th percentile) times to complete the placement procedures were as follows: (1) double-lumen tube: 6.1 min (4.6-9.5 min), (2) Univent tube: 6.7 min (4.9-8.8 min), and (3) Arndt Blocker: 8.6 min (5.8-17.5 min) (P = 0.45 comparing all devices). After device malposition was identified, it took 1 min or less for the investigating anesthesiologist to achieve optimal position. CONCLUSIONS: Anesthesiologists with limited experience in thoracic anesthesia frequently fail to successfully place lung isolation devices. Rapid successful device placement by an experienced anesthesiologist excluded any contribution of uniquely difficult anatomy. The nature of the malpositions suggests that the most critical factor in successful placement was the anesthesiologist's knowledge of endoscopic bronchial anatomy.

Adult↗

Dynamic EMG analysis of torque transfer in professional baseball pitchers.

Fifteen professional baseball pitchers underwent active pitching motion analysis of the abdominal oblique, rectus abdominis, lumbar paraspinous and gluteus maximus muscles bilaterally via surface electrode evaluation. Baseline resting and isometric maximum values were obtained and active data referenced against these for comparison. The muscle activity then was measured during the pitching sequence and analyzed in each of the five pitching phases. The abdominal oblique, lumbar paraspinous and rectus abdominis contralateral to the pitching arm and the ipsilateral gluteus maximus all had increases in activity level of 75 to 100% during the active pitching motion. Using these data indicating specific muscle group patterns with clinical and performance data, we hope to minimize injuries and maximize pitching performance.

Abdominal Muscles↗

Assessment of unicortical and bicortical fixation in a quasistatic cadaveric model. Role of bone mineral density and screw torque.

STUDY DESIGN: The stabilizing potential of the Caspar Trapezial Osteosynthetic Plate was studied using unicortical and bicortical screw placement in cadaveric cervical spines. OBJECTIVE: To determine if Caspar plates secured with unicortical screws provide the same degree of stability as those anchored with unlocked bicortical screws. SUMMARY OF BACKGROUND DATA: Previous work has demonstrated that bicortical cervical vertebral screws are superior to unicortical screws in terms of pullout strength and decreased wobble. However, these two methods of plate fixation have not been directly compared in a clinically relevant cadaveric model. METHODS: The immediate and post-fatigue stabilizing potential of Caspar plates secured with unicortical or bicortical screws was assessed using a model of complete segmental instability. RESULTS: Unicortical screw placement resulted in inadequate stabilization in half of the cervical specimens. CONCLUSIONS: Our results suggest that, for the Caspar screw, bicortical fixation provides greater flexion-extension stability.

Biomechanical Phenomena↗