Metabolic Cost and Mechanical Efficiency of a Novel Handle-Based Device for Wheelchair Propulsion.

OBJECTIVE: To investigate differences in metabolic cost and gross mechanical efficiency of a novel handlebased wheelchair propulsion device and to compare its performance with conventional push-rim propulsion. DESIGN: Double-group comparative study between 2 different propulsion methods. PARTICIPANTS: Eight paraplegic individuals and 10 non-disabled persons. METHODS: Participants performed the same exercise using a push-rim device and the novel handle-based device on a wheelchair- based test rig. The exercise consisted of a combined submaximal and maximal test. Power output, oxygen uptake, ventilation, respiratory exchange ratio and heart rate were recorded continuously during the tests. Analysis of variance was performed to determine the effects of group, mode and on power output. RESULTS: Submaximal exercise resulted in a higher efficiency for the novel device and significant main effects of propulsion mode on all investigated parameters, except heart rate. On the respiratory exchange ratio, a significant interaction effect was found for both mode and group. The maximal exercise resulted in a higher peak power output and lower peak heart rate during propulsion using the handle-based device. A significant main effect on mode for mean peak power output, ventilation and heart rate was also observed. CONCLUSION: Wheelchair propulsion using the handle-based device resulted in lower physical responses and higher mechanical efficiency, suggesting that this novel design may be well suited for indoor use, thereby offering an attractive alternative to pushrim wheelchairs.

In Vivo Biomechanical Assessment of a Novel Handle-Based Wheelchair Drive.

Push-rim wheelchair propulsion frequently causes severe upper limb injuries in people relying on the wheelchair for ambulation. To address this problem, we developed a novel handle-based wheelchair propulsion method that follows a cyclic motion within ergonomic joint ranges of motion. The aim of this study was to measure hand propulsion forces, joint excursions and net joint torques for this novel propulsion device and to compare its performance against traditional push-rim wheelchair propulsion. We hypothesized that under similar conditions, joint excursions of this novel handle-based device will remain within their ergonomic range and that the effectiveness of the propulsion forces will be higher, leading to lower average propulsion forces compared to push-rim propulsion and reducing the risk of injury. Eight paraplegic subjects propelled the new device at two different loads on a custom-made wheelchair-based test rig. Video motion capture and force sensors were used to monitor shoulder and wrist joint kinematics and kinetics. Shoulder and wrist loads were calculated using a modified upper-extremity Wheelchair Propulsion Model available in OpenSim. The results show that with this novel propulsion device joint excursions are within their recommended ergonomic ranges, resulting in a reduced range of motion of up to 30% at the shoulder and up to 80% at the wrist, while average resultant peak forces were reduced by up to 20% compared to push-rim propulsion. Furthermore, the lower net torques at both the shoulder and wrist demonstrate the potential of this novel propulsion system to reduce the risk of upper-extremity injuries.

Impact of Functional Capacity Evaluation on Patient-Reported Functional Ability: An Exploratory Diagnostic Before-After Study.

Introduction Work capacity in patients with orthopedic trauma and long-lasting inactivity is significantly reduced. Functional capacity evaluation (FCE) is a diagnostic approach for developing recommendations for a return to work and further occupational rehabilitation when the ability to carry out previous job demands is uncertain. However, FCE may also have direct effects on the patients' appraisal of their functional ability. Our study therefore evaluated the change in patient-reported functional ability after the performance of an FCE. Methods We performed a diagnostic before-after study in 161 consecutively recruited patients with trauma who were referred for FCE at the end of an interdisciplinary inpatient rehabilitation program in Austria. Patients completed the Spinal Function Sort to assess patient-reported functional ability both prior to the FCE and after completing it. Results Patient-reported functional ability (0-200 points) improved by 14.8 points (95% CI 11.3-18.2). The number of participants who rated their functional ability below their functional capacity as observed by the FCE decreased from 82.6 to 64.6% by about 18 percentage points. Conclusions The performance of the FCE in patients with trauma was associated with an improvement of patient-reported functional ability. The performance of an FCE in trauma rehabilitation may possibly have a direct therapeutic effect on the patient by allowing a more realistic appraisal of the ability to perform relevant work activities.

Monitoring of spasticity and functional ability in individuals with incomplete spinal cord injury with a functional electrical stimulation cycling system.

BACKGROUND: The aim of this study was to investigate the integration of motor function and spasticity assessment of individuals with spinal cord injury into cycling therapy. METHODS: Twenty-three participants with incomplete spinal cord injury performed 18 training sessions (standard deviation (SD) 14) on an instrumented tricycle combined with functional electrical stimulation. Each therapy session included a power output test to assess the participants' ability to pedal actively and a spasticity test routine that measures the legs' resistance to the pedalling motion. In addition, the required time for the therapy phases was monitored. RESULTS: The results of the power output test showed a monthly increase in power output of 4.4 W (SD 13.7) at 30 rpm and 18.2 W (SD 23.9) at 60 rpm. The results of the spasticity assessment indicate a 12.2 W (SD 9.7) reduction in resistance at 60 rpm after the FES training for the subject group with spasticity. CONCLUSION: In clinical use over a time-period of 2 years this combined form of therapy and motor function assessment was well accepted by participants. The active power output test and the spasticity test routine offered a proper tool to monitor participants' progress in functional rehabilitation and changes in spasticity.

A chronic pressure ulcer model in the nude mouse.

The pathophysiology of pressure ulcers is not yet fully understood. Widely used experimental models lead to pressure ulcers in the skin and the subcutaneous tissue only. The aim of the present study was to develop a clinically relevant deep pressure ulcer model in nude mice involving all relevant tissue layers. Balb/c nude mice were anesthetized and a steel disk was implanted under the great gluteus muscle. Full recovery was allowed for 10 days. Pressure was then periodically applied (2 hours compression, 1 hour recovery) using a Neodymium magnet in conjunction with the disk in the unanesthetized mouse. Cycles were repeated for 1, 4, 6, 8, or 10 times. Controls underwent the same procedure without placement of the magnet. The pressure ulcer grade was found to be cycle dependent,with the highest degree after 10 cycles. Histological evaluations revealed signs of necrosis in the skin and subcutaneous fat after four, and in the muscle after eight and 10 cycles of compression. Polymorphnuclear granulocyte infiltration in certain layers was found to be dependent on the number of cycles. We conclude that this clinically relevant nude mouse model can be used to investigate the mechanism of pressure ulcer development and to study new therapeutic approaches.