Brian T. Smith

Energy cost of walking in children with cerebral palsy: relation to the Gross Motor Function Classification System.

This study compared the energy cost of walking in children with cerebral palsy (CP) classified at different levels of the Gross Motor Function Classification System (GMFCS) with that in children with typical development. Sixteen female and 14 male children with CP (mean age 9 years 6 months, SD 2 years 4 months, range 6 years 4 months to 13 years 4 months) and 14 male and 13 female typically developing children (mean age 10 years, SD 1 year 6 months, range 7 years 1 month to 12 years 11 months) participated. Children with CP were classified at GMFCS level I, n=5; level II, n=10; level III, n=9; and level IV, n=6. Energy cost was assessed by the gas dilution method as each child walked around an oval track wearing a dilution mask. Significant differences were found across GMFCS levels (p < 0. 0001) and between adjacent levels (p < 0.013). Children with CP displayed a higher energy cost of walking than the typically developing children (p < 0.0001). A strong correlation (0.87) was found between the energy cost of walking and GMFCS level (p < 0.01) when children with typical development were assigned a GMFCS level of zero to allow statistical analysis. This indicates increasing energy cost of walking with increasing severity of functional involvement. These differences in energy cost across GMFCS levels provide another distinguishing factor between GMFCS levels and further emphasize the importance of considering metabolic demand in determining treatment options.

Evaluation of force-sensing resistors for gait event detection to trigger electrical stimulation to improve walking in the child with cerebral palsy

Force-sensing resistors (FSRs) were used to detect the transitions between five main phases of gait for the control of electrical stimulation (ES) while walking with seven children with spastic diplegia, cerebral palsy. The FSR positions within each childs insoles were customized based on plantar pressure profiles determined using a pressure-sensitive membrane array (Tekscan Inc., Boston, MA). The FSRs were placed in the insoles so that pressure transitions coincided with an ipsilateral or contralateral gait event. The transitions between the following gait phases were determined: loading response, mid- and terminal stance, and pre- and initial swing. Following several months of walking on a regular basis with FSR-triggered intramuscular ES to the hip and knee extensors, hip abductors, and ankle dorsi and plantar flexors, the accuracy and reliability of the FSRs to detect gait phase transitions were evaluated. Accuracy was evaluated with four of the subjects by synchronizing the output of the FSR detection scheme with a VICON (Oxford Metrics, U.K.) motion analysis system, which was used as the gait event reference. While mean differences between each FSR-detected gait event and that of the standard (VICON) ranged from +35 ms (indicating that the FSR detection scheme recognized the event before it actually happened) to -55 ms (indicating that the FSR scheme recognized the event after it occurred), the difference data was widely distributed, which appeared to be due in part to both intrasubject (step-to-step) and intersubject variability. Terminal stance exhibited the largest mean difference and standard deviation, while initial swing exhibited the smallest deviation and preswing the smallest mean difference. To determine step-to-step reliability, all seven children walked on a level walkway for at least 50 steps. Of 642 steps, there were no detection errors in 94.5% of the steps. Of the steps that contained a detection error, 80% were due to the failure of the FSR signal to reach the programmed threshold level during the transition to loading response. Recovery from an error always occurred one to three steps later.

Implanted functional electrical stimulation hand system in adolescents with spinal injuries: An evaluation

OBJECTIVE To study the utility and functional benefits of an implanted functional electrical stimulation (FES) system for hand grasp and release in adolescents with tetraplegia secondary to spinal cord injuries. DESIGN Intervention study with before-after trial measurement with each subject as his or her own control. SETTING Nonprofit pediatric orthopedic rehabilitation facility specializing in spinal cord injury. PARTICIPANTS A convenience sample of five adolescents between 16 and 18 years of age with C5 or C6 level tetraplegia at least 1 year after traumatic spinal cord injury. Key muscles for palmar and lateral grasp and release were excitable by electrical stimulation. INTERVENTIONS A multichannel stimulator/receiver and eight electrodes were surgically implanted to provide stimulated palmar and lateral grasp and release. In conjunction with implantation of the FES hand system, surgical reconstruction in the form of tendon transfers, tendon lengthenings and releases, and joint arthrodeses was performed to augment stimulated hand function. Rehabilitation of the tendon transfers and training in the use of the FES hand system were provided. MAIN OUTCOME MEASURES Measurements of pinch and grasp force, the Grasp and Release Test (GRT), and an assessment of six activities of daily living (ADL) were administered before implantation of the FES hand system and at regular follow-up intervals. Results of the stimulated response of individual muscles and surgical reconstruction were evaluated using standard and stimulated muscle testing techniques and standard assessment of joint range of motion. All subjects completed followup testing. RESULTS Lateral and palmar forces were significantly greater than baseline forces (p = .043). Heavy objects on the GRT could only be manipulated with FES, and FES increased the level of independence in 25 of 30 ADL comparisons (5 subjects, 6 activities) as compared to baseline. After training, FES was preferred in 21 of 30 comparisons over the typical means of task completion. Of the 40 electrodes implanted, 37 continue to provide excellent stimulated responses and all of the implanted stimulators have functioned without problems. The surgical reconstruction procedures greatly enhanced FES hand function by either expanding the workspace in which to utilize FES (deltoid to triceps transfer), stabilizing the wrist (brachioradialis to wrist extensor transfer), or stabilizing joints (intrinsic tenodesis transfer, FPL split transfer). CONCLUSION For five adolescents with tetraplegia, the combination of FES and surgical reconstruction provided active palmar and lateral grasp and release. Laboratory-based assessments demonstrated that the FES system increased pinch force, improved the manipulation of objects, and typically increased independence in six standard ADL as compared to pre-FES hand function. The study also showed that the five adolescents generally preferred FES for most of the ADL tested. Data on the benefits of the implanted FES hand system outside of the laboratory are needed to understand the full potential of FES.

Application of a neuro-fuzzy network for gait event detection using electromyography in the child with Cerebral palsy

An adaptive neuro-fuzzy inference system (ANFIS) with a supervisory control system (SCS) was used to predict the occurrence of gait events using the electromyographic (EMG) activity of lower extremity muscles in the child with cerebral palsy (CP). This is anticipated to form the basis of a control algorithm for the application of electrical stimulation (ES) to leg or ankle muscles in an attempt to improve walking ability. Either surface or percutaneous intramuscular electrodes were used to record the muscle activity from the quadriceps muscles, with concurrent recording of the gait cycle performed using a VICON motion analysis system for validation of the ANFIS with SCS. Using one EMG signal and its derivative from each leg as its inputs, the ANFIS with SCS was able to predict all gait events in seven out of the eight children, with an average absolute time differential between the VICON recording and the ANFIS prediction of less than 30 ms. Overall accuracy in predicting gait events ranged from 98.6% to 95.3% (root mean-squared error between 0.7 and 1.5). Application of the ANFIS with the SCS to the prediction of gait events using EMG data collected two months after the initial data demonstrated comparable results, with no significant differences between gait event detection times. The accuracy rate and robustness of the ANFIS with SCS with two EMG signals suggests its applicability to ES control.

Evaluation of the lower motor neuron integrity of upper extremity muscles in high level spinal cord injury

Purpose: To evaluate the lower motor neuron (LMN) integrity of upper extremity muscles of persons with high tetraplegia (C1-C4) in order to determine muscles available for stimulation. Methods: Fourteen subjects (23 arms) were evaluated for LMN integrity. Muscles that elicited a functional response (grade 3 or better) to surface electrical stimulation were considered to have intact LMN and good candidates for FES. Strength-duration (S-D) curves were generated on muscles that showed weak (less than grade 3) or no response to surface stimulation. Muscles were considered denervated if S-D curves were discontinuous or depicted steep, increasing amplitude for pulse durations greater than 1 m. Results: Muscles for grasp and release had intact LMN in 19 of 23 (83%) arms. The wrist extensors and flexors and pronator were excitable in 17 (74%), 20 (87%) and 19 (83%) arms, respectively. The supinator demonstrated LMN lesion in 80% of the arms. Over 90% of the biceps muscles were unresponsive to electrical stimulation and 85% and 87% of the deltoid and supraspinatus muscles, respectively, were not electrically excitable. The latissimus dorsi and triceps muscles were typically innervated (78% and 91%, respectively) and slightly more than half (52%) of the pectoralis major muscles were excitable. Conclusion: These data suggest that application of FES in high tetraplegia for hand and arm function would require augmentation because of the inability to stimulate the elbow flexors, deltoid and rotator cuff muscles. These data also show that several paralyzed proximal muscles with intact LMN that have been historically transferred to address shoulder paralysis in other patient populations are available for transfer and stimulation in the population with high level spinal injuries.

Development of an upper extremity FES system for individuals with C4 tetraplegia

The application of functional electrical stimulation (FES) to provide upper extremity function for individuals with C4 tetraplegia is under investigation. In this study, a FES system was designed that allowed one individual with complete C4 tetraplegia to coordinate stimulated lateral or palmar prehension with stimulated arm movements using contralateral shoulder position. The system consisted of percutaneous intramuscular electrodes implanted to muscles for hand grasp and release, supination, elbow flexion, and extension and arm adduction. Due to peripheral denervation, transposition and subsequent stimulation of the paralyzed latissimus dorsi muscle provided elbow flexion and transfer and stimulation of the paralyzed extensor carpi ulnaris muscle provided forearm supination. A suspended sling provided shoulder joint stability. The subject controlled stimulation proportionally using contralateral shoulder motion sensed by a position transducer. Control of stimulated hand grasp and release were coupled with stimulated arm motions so that hand-to-mouth activities could be accomplished with one motion of the contralateral shoulder. With this system, the subject was able to grasp a milk carton placed in the hand and lift and lower it from his mouth to drink from a short straw. He could also scoop a semisolid substance with an adapted spoon and lift and lower it from the work surface to his mouth to eat. The subject required assistance to place the milk carton or spoon in his hand and position the plate for scooping. Further investigation is needed to generate the necessary arm movements to make completion of these tasks possible without assistance and to expand the range of activities possible with the FES system.

Quantitative comparison of grasp and release abilities with and without functional neuromuscular stimulation in adolescents with tetraplegia

In this study, a functional neuromuscular stimulation (FNS) hand system designed by Case Western Reserve University (CWRU) was implemented in 5 adolescents with C5 tetraplegia and hand function with FNS was evaluated and compared to tenodesis abilities using a grasp and release test designed specifically for this purpose. The test involved the unilateral acquisition, movement and release of 6 objects of various sizes and weights. During a single test session, five 30-second trials were performed with each object with and without the FNS system where the number of completions and failures were recorded for each trial. At least 4 and as many as 8 test sessions were conducted with each subject over periods of 1.5 to 3 years. For each subject, test performance with FNS was compared statistically to tenodesis performance and session-to-session consistency was analyzed. Of 30 comparisons (5 subjects and 6 test objects), FNS was more effective in 23 cases (77%), tenodesis was better in 5 instances (17%) and in 2 cases (6%) there was no difference. Subjects were able to manipulate the 3 heaviest test objects only with FNS and in 60% of all cases involving the 3 lighter test objects there were significantly more trials in which there were more completions or fewer failures with FNS. Performance with FNS and tenodesis was generally inconsistent across sessions; possible reasons for these variations are discussed. Overall, the results of this study support those of the only previous investigation that used the grasp and release test to evaluate hand function with FNS in C5 and C6 tetraplegia.

Implanted functional electrical stimulation: an alternative for standing and walking in pediatric spinal cord injury.

Study design: Post intervention, repeated measures design, comparing two interventions.Setting: Orthopedic pediatric hospital specializing in spinal cord injury.Methods: Nine subjects, ages 7–20 years, received an eight-channel implanted lower extremity functional electrical stimulation (FES) system for standing and walking. Electrodes were placed to stimulate hip and knee extension, and hip abduction and adduction. Standing and walking were achieved through constant stimulation to the implanted muscles, allowing a swing through gait pattern with an assistive device. After training with FES and long leg braces (LLB), subjects were tested in eight upright mobility activities, which were scored based upon completion time and level of independence.Results: Seven subjects completed data collection. These subjects completed four activities faster (P<0.02) and five activities more independently (P<0.025) with FES as compared to LLB. Transitions between sitting and standing, which were scored in isolation for two mobility activities, were achieved faster and with more independence with FES. In addition, subjects reported preferring FES for the majority of activities. No activity required more time or more assistance to complete with FES as compared to LLB.Conclusion: The implanted FES system provided these subjects with enhanced functional abilities over traditional LLB and decreased the need for physical assistance by a caregiver, suggesting that it is a realistic alternative for upright mobility in a pediatric population with spinal cord injury.Sponsorship: This study was funded by Shriners Hospitals for Children, Grant #8530.

Effects of cycling and/or electrical stimulation on bone mineral density in children with spinal cord injury

Study design:Randomized clinical trial.Objectives:To determine the effect of cycling and/or electrical stimulation on hip and knee bone mineral density (BMD) in children with spinal cord injury (SCI).Setting:Childrens hospital specializing in pediatric SCI.Methods:A total of 30 children, aged 5–13 years, with chronic SCI were randomized to one of three interventions: functional electrical stimulation cycling (FESC), passive cycling (PC), and non-cycling, electrically stimulated exercise (ES). Each group exercised for 1 h, three times per week for 6 months at home. The hip, distal femur and proximal tibia BMD were examined via dual-energy X-ray absorptiometry (DXA) pre- and post-intervention.Results:In all, 28 children completed data collection. The FESC group exhibited increases in hip, distal femur and proximal tibia BMD of 32.4, 6.62 and 10.3%, respectively. The PC group exhibited increases at the hip (29.2%), but no change at the distal femur (1.5%) or proximal tibia (−1.0%). The ES group had no change at the hip (−0.24%) and distal femur (3.3%), but a loss at the proximal tibia (−7.06%). There were no differences between groups or within groups over time. Significant negative correlations were found between baseline BMD and the amount of BMD change.Conclusion:Although not achieving statistical significance, hip BMD changes observed were greater than the reported 0.9–10% gains after exercise for children with and without disability. Thus, cycling with and without electrical stimulation may be beneficial for skeletal health in pediatric SCI, but further research is needed with a larger sample size.

Technical Perspective Functional Electrical Stimulation For Augmented Walking In Adolescents With Incomplete Spinal Cord Injury

Abstract Background/Objective: This study evaluated the effects of functional electrical stimulation (FES) applied to the muscles acting on the pelvis, hip, and knee on muscle strength, energy cost of walking, maximum walking distance and speed, step length and cadence, and joint kinematics during gait in 3 ambulatory adolescents with incomplete spinal cord injury (SCI). Methods: Percutaneous FES was used to strengthen weakened muscles and to augment walking. After training, participants walked as desired at home with FES for 1 year. Data were collected at baseline (preintervention), and with FES on and FES off immediately following the training period and with FES on and FES off at 3, 6, and 12 months posttraining. Results: Voluntary strength improved in 12 out of 13 stimulated muscles. Decreased energy cost, increased maximum walking distance and speed, increased step length, and improved joint kinematics during gait were demonstrated with FES on and FES off Discussion: FES was able to achieve selective stimulation of key weakened muscles for augmented walking. The data suggest that FES had both direct and carryover effects.