Publications

PURPOSE: Our objective was to use an open weight-bearing MRI to identify the effects of different loading conditions on the inter-vertebral anatomy of the lumbar spine in a post-discectomy recurrent lumbar disc herniation patient. METHODS: A 43-year-old male with a left-sided L5-S1 post-decompression re-herniation underwent MR imaging in three spine-loading conditions: (1) supine, (2) weight-bearing on standing (WB), and (3) WB with 10 % of body mass axial loading (WB + AL) (5 % through each shoulder). A segmentation-based proprietary software was used to calculate and compare linear dimensions, angles and cross sections across the lumbar spine. RESULTS: The L5 vertebrae showed a 4.6 mm posterior shift at L5-S1 in the supine position that changed to an anterior translation >2.0 mm on WB. The spinal canal sagittal thickness at L5-S1 reduced from supine to WB and WB + AL (13.4, 10.6, 9.5 mm) with corresponding increases of 2.4 and 3.5 mm in the L5-S1 disc protrusion with WB and WB + AL, respectively. Change from supine to WB and WB + AL altered the L5-S1 disc heights (10.2, 8.6, 7.0 mm), left L5-S1 foramen heights (12.9, 11.8, 10.9 mm), L5-S1 segmental angles (10.3 degrees , 2.8 degrees , 4.3 degrees ), sacral angles (38.5 degrees , 38.3 degrees , 40.3 degrees ), L1-L3-L5 angles (161.4 degrees , 157.1 degrees , 155.1 degrees ), and the dural sac cross sectional areas (149, 130, 131 mm(2)). Notably, the adjacent L4-L5 segment demonstrated a retro-listhesis >2.3 mm on WB. CONCLUSION: We observed that with weight-bearing, measurements indicative of spinal canal narrowing could be detected. These findings suggest that further research is warranted to determine the potential utility of weight-bearing MRI in clinical decision-making.

We read with great interest the recent review by de Bakker et al that summarized the state of several existing and emerging technologies for estimating bone strength and fracture risk in vivo. Much of their review focused on how well the measurements of selected technologies predicted experimental measurements of bone strength by ex vivo quasistatic mechanical testing (QMT) and on how well they tracked changes in mechanical properties of bone. The authors noted that the association of many common skeletal health measurements (e.g., DXA measures of trabecular bone score and areal and volumetric BMD) are only moderately associated with bone strength. The authors did not include mechanical response tissue analysis (MRTA) in their review. MRTA is a dynamic mechanical bending test that uses a vibration analysis technique to make immediate, direct, functional measurements of the mechanical properties (mass, stiffness, and damping) of long bones in humans in vivo. In this article we note our interest in the ability of MRTA to detect large changes in bone stiffness that go undetected by DXA. We also highlight results of our proprietary improvements to MRTA technology that have resulted in unmatched accuracy in QMT-validated measurements of the bending stiffness and estimates of the bending strength (both R2 = 0.99) of human ulna bones. To distinguish our improved technique from the legacy MRTA technology, we refer to it as Cortical Bone Mechanics Technology (CBMT). Further research will determine whether such CBMT measurements are clinically useful.

In recent years, there has been increasing interest in using low-load resistance exercise in combination with a reduction in blood flow to promote muscle adaptation (ie, blood flow-restricted exercise or KAATSU exercise). There has been 1 case study reported in the literature of this type of exercise resulting in exertional rhabdomyolysis, and herein, we report the second case of exertional rhabdomyolysis. In this case, a 20-year-old man performed 6 sets of blood flow-restricted exercise (3 sets of knee-extension and 3 sets of elbow-flexion exercise). The subject presented with high levels of delayed onset muscle soreness in the days after the exercise bout exhibited high levels of creatine kinase (peak recorded: 36 000 IU/L), and was hospitalized for exertional rhabdomyolysis. We urge that investigators and practitioners use caution with blood flow-restricted exercise protocols and to begin these exercise programs modestly and gradually progress them with time.

BACKGROUND: Single or biplanar video radiography and Roentgen stereophotogrammetry (RSA) techniques used for the assessment of in-vivo joint kinematics involves application of ionizing radiation, which is a limitation for clinical research involving human subjects. To overcome this limitation, our long-term goal is to develop a magnetic resonance imaging (MRI)-only, three dimensional (3-D) modeling technique that permits dynamic imaging of joint motion in humans. Here, we present our initial findings, as well as reliability data, for an MRI-only protocol and modeling technique. METHODS: We developed a morphology-based motion-analysis technique that uses MRI of custom-built solid-body objects to animate and quantify experimental displacements between them. The technique involved four major steps. First, the imaging volume was calibrated using a custom-built grid. Second, 3-D models were segmented from axial scans of two custom-built solid-body cubes. Third, these cubes were positioned at pre-determined relative displacements (translation and rotation) in the magnetic resonance coil and scanned with a T1 and a fast contrast-enhanced pulse sequences. The digital imaging and communications in medicine (DICOM) images were then processed for animation. The fourth step involved importing these processed images into an animation software, where they were displayed as background scenes. In the same step, 3-D models of the cubes were imported into the animation software, where the user manipulated the models to match their outlines in the scene (rotoscoping) and registered the models into an anatomical joint system. Measurements of displacements obtained from two different rotoscoping sessions were tested for reliability using coefficient of variations (CV), intraclass correlation coefficients (ICC), Bland-Altman plots, and Limits of Agreement analyses. RESULTS: Between-session reliability was high for both the T1 and the contrast-enhanced sequences. Specifically, the average CVs for translation were 4.31 % and 5.26 % for the two pulse sequences, respectively, while the ICCs were 0.99 for both. For rotation measures, the CVs were 3.19 % and 2.44 % for the two pulse sequences with the ICCs being 0.98 and 0.97, respectively. A novel biplanar imaging approach also yielded high reliability with mean CVs of 2.66 % and 3.39 % for translation in the x- and z-planes, respectively, and ICCs of 0.97 in both planes. CONCLUSIONS: This work provides basic proof-of-concept for a reliable marker-less non-ionizing-radiation-based quasi-dynamic motion quantification technique that can potentially be developed into a tool for real-time joint kinematics analysis.

BACKGROUND: Decreased cortical excitability has been proposed as a potential mechanism underlying task failure during sustained muscular contractions, and cortical excitability may decrease with old age. We tested the hypothesis that transcranial direct current stimulation, which has been reported to raise cortical excitability, would prolong the time to task failure during a sustained muscular contraction in older adults. METHODS: Thirteen older adults (68.3+/-2.0 years; eight women and five men) performed isometric, elbow flexions to failure while receiving sham or anodal transcranial direct current stimulation. Order of stimulation was randomized, and the subjects and investigators were blinded to condition. Time to task failure was measured alongside selected psychological indices of perceived exertion and affect. RESULTS: Anodal transcranial direct current stimulation prolonged mean time to task failure by approximately 15% (16.9+/-2.2 vs 14.7+/-1.8 minutes) and slowed the rate of increase in rating of perceived exertion (0.29+/-0.03 vs 0.31+/-0.03) relative to the sham condition. CONCLUSIONS: These preliminary findings suggest that anodal transcranial direct current stimulation enhances time to task failure of a sustained, submaximal contraction in older adults by potentially increasing cortical excitability and/or influencing the perception of exertion. These results raise the question of whether interventions that acutely increase cortical excitability could enhance physical function and/or exercise-induced adaptations in older adults.

BACKGROUND: Single or biplanar video radiography and Roentgen stereophotogrammetry (RSA) techniques used for the assessment of in-vivo joint kinematics involves application of ionizing radiation, which is a limitation for clinical research involving human subjects. To overcome this limitation, our long-term goal is to develop a magnetic resonance imaging (MRI)-only, three dimensional (3-D) modeling technique that permits dynamic imaging of joint motion in humans. Here, we present our initial findings, as well as reliability data, for an MRI-only protocol and modeling technique. METHODS: We developed a morphology-based motion-analysis technique that uses MRI of custom-built solid-body objects to animate and quantify experimental displacements between them. The technique involved four major steps. First, the imaging volume was calibrated using a custom-built grid. Second, 3-D models were segmented from axial scans of two custom-built solid-body cubes. Third, these cubes were positioned at pre-determined relative displacements (translation and rotation) in the magnetic resonance coil and scanned with a T1 and a fast contrast-enhanced pulse sequences. The digital imaging and communications in medicine (DICOM) images were then processed for animation. The fourth step involved importing these processed images into an animation software, where they were displayed as background scenes. In the same step, 3-D models of the cubes were imported into the animation software, where the user manipulated the models to match their outlines in the scene (rotoscoping) and registered the models into an anatomical joint system. Measurements of displacements obtained from two different rotoscoping sessions were tested for reliability using coefficient of variations (CV), intraclass correlation coefficients (ICC), Bland-Altman plots, and Limits of Agreement analyses. RESULTS: Between-session reliability was high for both the T1 and the contrast-enhanced sequences. Specifically, the average CVs for translation were 4.31 % and 5.26 % for the two pulse sequences, respectively, while the ICCs were 0.99 for both. For rotation measures, the CVs were 3.19 % and 2.44 % for the two pulse sequences with the ICCs being 0.98 and 0.97, respectively. A novel biplanar imaging approach also yielded high reliability with mean CVs of 2.66 % and 3.39 % for translation in the x- and z-planes, respectively, and ICCs of 0.97 in both planes. CONCLUSIONS: This work provides basic proof-of-concept for a reliable marker-less non-ionizing-radiation-based quasi-dynamic motion quantification technique that can potentially be developed into a tool for real-time joint kinematics analysis.

For well over twenty centuries the muscle wasting (sarcopenia) and weakness (dynapenia) that occurs with old age has been a predominant concern of mankind. Exercise has long been suggested as a treatment to combat sarcopenia and dynapenia, as it exerts effects on both the nervous and muscular systems that are critical to positive physiological and functional adaptations (e.g., enhanced muscle strength). For more than two decades scientists have recognized the profound role that progressive resistance exercise training can have on increasing muscle strength, muscle size and functional capacity in older adults. In this review article we discuss how resistance exercise training can be used in the management and prevention of sarcopenia and dynapenia. We first provide an overview of the evidence for this notion and highlight certain critical factors- namely exercise intensity, volume and progression- that are key to optimizing the resistance exercise prescription. We then highlight how many, if not most, of the commonly prescribed exercise programs for seniors are not the 'best practices', and subsequently present easy-to-read guidelines for a well-rounded resistance exercise training program designed for the management and prevention of sarcopenia and dynapenia, including example training programs for the beginner through the advanced senior resistance exerciser. These guidelines have been written for the academician as well as the student and health care provider across a variety of disciplines, including those in the long term care industry, such as wellness instructors or activity directors.