Guan-Liang Chang

Effectiveness of Two Forms of Feedback on Training of a Joint Mobilization Skill by Using a Joint Translation Simulator

Background and Purpose Joint mobilization is a complicated task to learn and to teach and is characterized by great intersubject variability. This studys purpose was to investigate whether quantitatively augmented feedback could enhance the learning of joint mobilization and, more specifically, to compare the effects of training with concurrent or terminal feedback by using a joint translation simulator (JTS). Subjects Thirty-six undergraduate physical therapist students were randomly assigned to control (no feedback), concurrent feedback, and terminal feedback groups. Methods The JTS was designed to simulate tissue resistance based on load-displacement relationships of glenohumeral joint specimens. Subjects applied specific mobilization grades of force on the JTS while quantitative feedback was given to the feedback groups either during a trial (ie, concurrent feedback) or after a trial (ie, terminal feedback). The skill acquisition phase lasted a total of 40 minutes, and a total of 75 repetitions were performed for each grade of each joint model. Pretest and no-feedback retention tests were conducted. Results During acquisition and retention, both feedback groups performed more accurately than did the control group. No obviously superior performance was shown by the terminal feedback group compared with concurrent feedback group during retention testing. Discussion and Conclusion Subjects who trained with augmented feedback had less variability, and thus more consistency, than the control group subjects who received no feedback. Augmented feedback provides the student with a reference force and the status of his or her performance. The effectiveness of the JTS feedback compared with no feedback was clearly demonstrated. Skill acquisition in mobilization can be enhanced by either concurrent or terminal feedback.

Rate-related fatigue injury of vertebral disc under axial cyclic loading in a porcine body-disc-body unit

OBJECTIVE: Cyclic loading tests were performed on fresh mature porcine lumbar spines to investigate the mechanical responses at different loading rates, morphological changes in the disc and to produce the clinically relevant injuries of porcine intervertebral disc. DESIGN: Two-segment units of fresh porcine spine with all the posterior elements removed were used for a disc stress analysis and morphological observation during axial cyclic loading. BACKGROUND: The repetitive loading of the spine has been implicated as a risk factor in developing low back disorders. However, few studies have discussed morphologic changes in vertebral disc due to fatigue stress and no study has investigated the relationship between disc strength and bone mineral density. METHODS: 21 body-disc-body specimens divided into three groups were subjected to cyclic loading at test speeds of 0.5, 5 and 20 mm min(-1). The correlation between residual stress of specimen and bone mineral density was investigated and the disc morphological changes were observed through the middle cross section of the intervertebral disc using a zoom stereo microscope. RESULTS: There was no visible crack observed following testing in the 0.5 mm min(-1) test group. However, one disc in the 5 mm min(-1) and two discs in the 20 mm min(-1) test group exhibited disc herniation. The residual stress was found to be positively and linearly correlated with bone mineral density and decreased as the loading rates increased. CONCLUSION: Faster loading rate generates greater stress decay, and disc herniation is more likely to occur under higher loading rate conditions. The most common site of disc herniation is the posterolateral area which is in agreement with that of the human spine.

Geometric and morphological changes of the intervertebral disc under fatigue testing.

OBJECTIVE To understand the injury mechanism of the intervertebral disc at different loading rates and to explore the anatomic and histological changes of intervertebral discs. DESIGN Fresh porcine lumbar spines were used for fatigue testing to study the morphological changes of the intervertebral disc. BACKGROUND Intervertebral disc problem is one of the most common causes that lead to low back pain. Slow repetitive loading was considered to be the critical factor of spine and disc injuries. METHODS Twenty-four lumbar functional units were subjected to cyclic loading at three different loading rates. The geometric measurements and magnetic resonance image observations were conducted for the comprehension of morphological changes. The detail observation was taken through a stereomicroscope. RESULTS There was no significance in geometric changes between different loading rates. For magnetic resonance imagings, morphological changes included the changes of nucleus pulposus shape, bulge of anterior and posterior longitudinal ligaments, and dehydration in annulus fibrosus. CONCLUSION The morphological changes of intervertebral disc were revealed in certain kinds of lesions. The results imply that fatigue failure and degeneration or instability are strongly linked. The correlation of magnetic resonance imaging and anatomic observation showed a high correspondence in the comparison of shape and position of the nucleus pulpasus. RELEVANCE The changes of geometric measurements and relationship between anatomic observation and magnetic resonance imaging finding had been analyzed. It could help in understanding the mechanism of triggering cause in the early stage of disc degeneration.

Distribution and regional strength of trabecular bone in the porcine lumbar spine.

OBJECTIVE: The regional strength and distribution of trabecular bone in the porcine lumbar spine were examined to understand the mechanical responses in quadrupedal vertebrae. DESIGN: The cancellous bone columns prepared from different regions of porcine lumbar vertebrae were subjected to axial compression to investigate the regional strength related to disc structure. Some vertebrae were also serially sectioned sagittally and transversely to observe the trabecular patterns. BACKGROUND: Animal spines were often used in biomechanical testing and the results were said to be similar to those of humans. However, none of them are truly like human bipedal locomotion. The understanding of regional variations in compressive properties may help us to explain the similarity and interpret the data of animal experiments. METHODS: The dried, defatted cancellous bone columns were subjected to uniaxial compression of different regions at a deformation rate of 5 mm/min. The mechanical properties in different regions were compared. The main trabecular orientation was also observed using a zoom stereo microscope. RESULTS: The ultimate strength of the posterior column tended to be larger than that of the anterior column. The ratio of bony strength overlying the nucleus pulposus to that overlying the annulus fibrosis was constant and averaged 1.16. The main trabecular struts were noted to be parallel to the spinal canal and cross-bridged by thinner trabeculae. CONCLUSIONS: The trabecular morphology and regional mechanical properties of the porcine spine were comparable to those of other similar studies on the human spine. Its significance needed further study.

Effects of a functional electrical stimulation-assisted leg-cycling wheelchair on reducing spasticity of patients after stroke.

OBJECTIVE To determine whether short-term propulsion of a functional electrical stimulation-assisted leg-cycling wheelchair (FES-LW) in patients with stroke can reduce spasticity of the affected leg and whether FES has additional effects on reducing spasticity. DESIGN Within-subject comparison. SUBJECTS A total of 17 patients after stroke were recruited from the university hospital. METHODS Subjects propelled 2 leg-cycling wheelchairs (the FES-LW and the LW) and a manual wheelchair along an oval pathway. The Modified Ashworth Scale (MAS), H reflex/maximal M response (H/M ratio) and relaxation index were used to evaluate the immediate effects on leg spasticity. The changes in MAS, H/M and relaxation index were used to evaluate the effect of FES in comparing 2 leg-cycling wheelchairs. RESULTS The MAS and H/M ratio were significantly decreased and the relaxation index significantly increased by FES-LW and LW usage. For subjects with higher muscle tone, significant lowering of the changes in MAS, H/M ratio and higher relaxation index were found for FES-LW usage compared with LW usage. CONCLUSION Leg spasticity is reduced after short-term propulsion of the FES-LW and LW. The application of FES has an additional effect on reducing spasticity in subjects with higher muscle tone.

Biomechanical properties of muscle-tendon unit under high-speed passive stretch.

OBJECTIVE The purpose of this study was to investigate the strain injury mechanisms of the Achilles muscle-tendon unit during high-speed passive stretch. DESIGN The high-speed traction device consisted of an impactor which dropped freely to hit one end of a lever, transferring the impact energy to traction energy at the other end. A muscle-tendon unit was attached to the other end of the lever via a force link, and the elongation was recorded with a high-speed camera. BACKGROUND The muscle-tendon unit is thought to act viscoelastically. It is generally strain rate dependent, exhibiting higher tensile stress at faster strain rates. However, previous studies of passive stretch in muscle-tendon units usually employed low strain rates. METHODS 16 fresh Achilles muscle-tendon units were subjected to passive stretch at a test speed of 310 cm s(-1). The history of elongation and the traction force of the muscle-tendon unit during the elongation process were analyzed. RESULTS The muscle-tendon units exhibited highly nonlinear mechanical behavior. Most of the elongation occurred in muscle and resulted in structural failure. Failure was not found in the tendon or muscle-tendon junction. Muscle fibers during stretching reached their maximum mechanical strength and then progressively ruptured. CONCLUSION The strain rate is an important factor in strain injuries of the muscle-tendon unit due to passive stretch. The muscle is a good energy absorber; the rupture process can absorb a great deal of external energy and prevent complete failure of the muscle, while also protecting bone and joints. RELEVANCE The study of muscle-tendon unit under high-speed stretch could help us to understand the mechanism of strain injuries over passive stretch in real-life situations.

Differences in mechanical response between fractured and non-fractured spines under high-speed impact.

OBJECTIVE: The differences in mechanical response between fractured and non-fractured spines were investigated using a porcine spine impact model. DESIGN: Ten three-vertebrae segments (C3-C5) of porcine spine were subjected to a single impact to study the trauma mechanism. Small steel balls glued to the vertebra and a high-speed camera were used to observe the deformation of vertebral body and disc during impact. After trauma, the episodes of fractured specimens were compared with those of non-fractured specimens. BACKGROUND: Experimental trauma models using the spines of mature animals have rarely been evaluated. Finding a well-controlled, reproducible protocol based on an easily accessible specimen was therefore important. These models will be promising if clinical fractures can be produced. METHODS: All of the specimens were subjected to high-speed flexion-compression loading. The impact to the load cell and the operation of the high-speed camera were synchronized. The force-time sequence and disc deformation curve were recorded. The results from fractured and non-fractured spines were then compared. RESULTS: There were three burst fractures, four pedicle fractures, one facet joint fracture, one compression fracture and one fracture-dislocation. All of these fractures were similar to clinical fractures. Compared to non-fractured specimens, the fractured specimens had lower maximal force and longer reaction time. The characteristic steep decline in the middle region of the force-time curve was also consistently noted in the fractured spines. CONCLUSIONS: Spinal fractures similar to those found clinically were successfully produced in porcine spines. The characteristics of the mechanical responses observed should be helpful in the interpretation of events which occur during impact.

Determining the resting position of the glenohumeral joint in subjects who are healthy

Background and Purpose: The resting position is frequently used by clinicians in the examination and early treatment of patients with joint impairments. However, there is a lack of research on the kinematic characteristics of the resting position of the glenohumeral (GH) joint. The aim of this study was to define the resting position of the GH joint by quantifying the humeral head translation and axial rotational range of motion (ROM). Subjects and Methods: The anterior and posterior translation of the humeral head and the rotational ROM of the dominant arm were assessed in the seated position at multiple abduction positions in 15 subjects who were healthy by use of an electromagnetic tracking device. A force of 80 N and a torque of 4 N·m were applied during the measurement procedures for the translation of the humeral head and the rotational ROM, respectively. Results: The mean resting position determined by rotational movement was located at 49.8 degrees of GH abduction. However, the mean resting position determined by translational movement was located at 23.7 degrees of GH abduction and was significantly lower than the resting position determined by rotational movement (t=5.45, P=.000). Discussion and Conclusion: The mean resting position for rotational movement is consistent with the already accepted range of 30 to 60 degrees for a “loosely packed” position of the GH joint. The mean resting position for translational movement appears to be lower than 30 to 60 degrees. The results of this study suggest that, at least for the GH joint, different resting positions should be assessed with different movement criteria (accessory or physiological movement).

Differences of lumbosacral kinematics between degenerative and induced spondylolisthetic spine

OBJECTIVE To investigate the differences of lumbosacral kinematics between degenerative and induced spondylolisthetic subjects. DESIGN Translations and angulations of spondylolisthetic spine from L1-L2 to L5-S1 were documented by taking X-ray films at flexion, standing and extension positions. BACKGROUND The unstable mechanism of spondylolisthesis leads to lower back pain. It is important to determine the kinematics and the process of spondylolisthesis. METHODS Nineteen subjects with spondylolisthesis participated in this research, seven subjects with diagnosis of degenerative and 12 with induced spondylolisthesis, were taken lateral radiographs at three positions including flexion, standing and extension. RESULTS The differences of angulation among three positions (flexion, standing, and extension) at different levels were statistically significant (P<0.05) in both spondylolisthetic groups. The differences of translation among three different positions in induced spondylolisthetic group had a statistical significance (P<0.05) except at the level of L5-S1 (P>0.05). CONCLUSIONS Segmental total translation and angulation at each level of induced spondylolisthetic spine were greater than those of degenerative spondylolisthetic spine except L5-S1 level, which illustrated the evolution of spondylolisthesis from unstable to less unstable. RELEVANCE The results showed induced spondylolisthesis may link to degenerative spondylolisthesis. It provided essential knowledge to detect the evolution of degenerative spondylolisthesis clinically earlier.

Evaluation of functional electrical stimulation-assisted leg-propelled wheelchair in hemiplegic patients

BACKGROUND Manual wheelchairs are an important mobility device for hemiplegic stroke patients, but understandably difficult to operate. A novel mobility device termed the functional electrical stimulation-assisted leg-propelled wheelchair (FES-LW) was proposed and a field test conducted to evaluate its clinical performance by comparison against a manual wheelchair (MW). METHODS A total of 20 hemiplegic patients were recruited from the National Cheng Kung University Hospital. They were instructed to successively propel the FES-LW and MW comfortably, as fast as possible, in along an oval pathway. The finish time, deviation frequencies, deviation percentage, physiological cost index (PCI), and modified Ashworth scale (MAS) of affected ankle were measured and compared. FINDINGS Subjects can propel the FES-LW with 40.1% less finish time (P=0.003); 23.7% lower deviation frequencies (P=0.009) and 36.7% lower deviation percentage (P=0.001); and 17.7% lower PCI (P=0.022) than the MW. In addition, the MAS of the affected ankle was noticeably reduced (P=0.002) after propelling the FES-LW. INTERPRETATION The FES-LW showed better controllability, cardiopulmonary response and positive effects on reducing spasticity versus the MW. The FES-LW is a suitable alternative to a MW for the needs of hemiplegic stroke patients.