THE COMPARISON OF FES TO ORTHOSES FOR UPRIGHT MOBILITY IN CHILDREN AND ADOLESCENTS WITH SPINAL CORD INJURIES

M.J. Mulcahey, Randal Betz, Cecilia Mullin, Megan Moynahan, Brian T. Smith Research Department, Shriners Hospitals Philadelphia Unit 8400 Roosevelt Blvd., Philadelphia, PA 19152

ABSTRACT

As part of a larger study on lower extremity applications of functional electrical stimulation (FES), a laboratory-based comparison of the utility of a FES system to the utility of knee-ankle-foot orthoses (KAFOs) is being conducted for a standard set of mobility activities. Following FES and KAFO training, five repeated measures of independence level and time to completion are obtained on eight activities with FES and with KAFOs. The median independence score of each activity is obtained with FES and with KAFOs. The mean of the time score is calculated and a t-test is applied to determine if there is a significant difference between FES and KAFOs. Results of the first subject demonstrated that FES and KAFOs provided the same level of independence for seven of the eight mobility activities. For five activities, FES performance required significantly less time as compared to KAFOs. These pilot data suggest that FES was comparable to KAFOs in terms of independence level in the selected mobility activities and may have provided an advantage over KAFOs for some activities by decreasing the amount of time required.

BACKGROUND

Between 1986 and 1991, nine adolescents participated in a laboratory-based study of FES for reciprocal ambulation [1]. As part of this study, pediatric candidacy for FES systems was defined [2] and the effects of exercise and weightbearing with FES on bone mineral density [3], joint integrity [4] and muscle strength and endurance were studied. In 1991, the focus of the research on FES for lower extremity applications shifted from reciprocal ambulation to upright mobility. Between 1991 and 1994, five adolescents with SCI participated in a feasibility study of FES for upright mobility in the laboratory and their home environments [5]. Implementation of the FES system involved implantation of percutaneous intramuscular electrodes, participation in a four week program of stimulated exercise to reverse the effects of disuse atrophy and participation in a rigorous program of balance and mobility skills training. After four months of training, participants demonstrated the ability to use FES to perform wheelchair transfers to and from cars, high stools and the floor, step up a curb and a flight of stairs, negotiate small areas inaccessible from a wheelchair, reach high places and perform activities at a counter top while standing. These data suggested that FES is a feasible method to provide upright mobility skills for adolescents with complete paraplegia secondary to spinal cord injuries. However, it remains unknown how FES compares to other methods available for upright mobility.

RESEARCH QUESTION

How does FES compare to KAFOs in the independent and timely performance of mobility activities in children and adolescents with complete paraplegia secondary to spinal cord injury?

METHODS

Selection Criteria

Candidates are invited to participate if they meet the following selection criteria: (1) between 6 and 18 years of age, (2) intact lower motor neurons innervating lower extremity muscles required for FES, as confirmed by strength-duration curves, (3) < 300 hip flexion and < 150 knee flexion and ankle plantar flexion contractures, (4) motor complete SCI between T1 and T12 and, (5) no outstanding orthopedic problems or medical complications.

Implementation

The FES system consists of a multi-channel stimulator with the capability of generating pulse durations up to 150 microseconds and frequencies up to 50 Hz, percutaneous intramuscular electrodes and a four-button key pad worn on the index finger and activated by the thumb. The stimulator is worn around the waist with cables positioned underneath clothing to connect to the electrodes exiting from the anterior thighs. A molded shoe insert is worn to provide ankle and foot protection. Following implantation of percutaneous intramuscular electrodes into the muscles required for upright mobility (Table 1), a four week program of stimulated exercise is initiated to reverse the effects of disuse atrophy. Once the muscles are conditioned, stimulated mobility patterns are programmed and participants are trained in the donning and doffing, operation and care of the percutaneous FES system. During the same time period, each participant is also fitted with and trained in the donning and doffing of KAFOs. With FES and KAFOs, a walker, loftstrand crutches or a large suction-cup handle are used to provide balance support during standing and mobility.

Table 1. The muscles implanted with percutaneous intramuscular electrodes.

FES and KAFO Training

Training in FES and KAFOs progresses from static standing in the parallel bars to training in the activities described in Table 2. Starting with the easiest activity, research subjects are trained in each mobility activity with FES and with KAFOs until they reach their highest level of independence; "highest level of independence" is defined as the ability to complete an activity with the least amount of assistance in a timely and safe manner. When the highest level of independence is achieved for the first activity, data are collected with FES and with KAFOs on that activity and training in the next activity is initiated. This process continues until data are collected with FES and with KAFOs on each mobility activity.

Data Collection

An ordinal scale ranging from 1 to 7 is applied to measure the level of independence. A score of 1 represents complete dependence and 7 independence without the need for FES or KAFOs. During each mobility activity, the amount of time taken to perform the activity is also documented. Five repeated measures of independence and time are obtained for each mobility activity with FES and with KAFOs. Each data collection session is videotaped and reviewed to confirm measures.

Data Analysis

The median of the five independence scores and the mean of the five time scores are calculated. A t-test is applied to the time scores to determine if there is a significant difference between FES and KAFO performance.

Table 2. Abbreviated Description of Mobility Activities Used to Compare FES to KAFOs. Activities are listed from easiest to most difficult.

RESULTS

Table 3 summarizes the results of the first research subject. As shown, in four of the eight activities, the participant was independent (6) using FES and KAFOs. For the jeep transfer and ascending stairs, FES and KAFOs required supervision (5) and minimal assistance (4) respectively. For the "up from floor" activity, a minimal assist (4) was required with KAFOs; stance was achieved by assuming a prone position and using crutches to toggle into a standing position. With FES, "up from floor" was attempted by first assuming a squat position with the knees tucked; stimulation to the adductor longus assisted in maintaining the tucked position. Once positioned, stimulation was delivered to the vastus lateralis and medialis, gluteus maximus and medius and the adductor magnus and, simultaneously, the subject pulled to stand using a walker. A combination of inadequate stimulated strength of the vastus lateralis and medialis and the subject's body weight (174lbs) and spasticity contributed to his inability to safely perform the activity (1). While the level of independence obtained with FES and with KAFOs was comparable, with FES there was a significant decrease in the time required for five of the eight activities. Significant improvements in performance time with FES are denoted in the shaded areas of Table 3.

Table 3. Results of the first subject of five repeated measures in nine activities with FES and with KAFOs. The independence score reflects the median of five repeated measures. The time score reflects the mean of five repeated measures; standard deviation is shown in parenthesis. Significant improvements in timely performance with FES are shaded. *NT= not tested.

DISCUSSION

The equivalency of the independence level obtained with FES and KAFOs by the first subject is encouraging. Equally encouraging are the results of the time data. The time required to don the FES system was significantly less than the time required to don KAFOs. This time difference is appreciated since the donning time required of braces contributes to poor use [6, 7]. For children and adolescents, cosmesis is also an important factor in brace use. As documented with the first subject, if FES is less visible than KAFOs, easier to don and provides comparable levels of independence, youngsters may find FES more desirable when performing mobility activities in home and school environments. Additional data are needed to document the advantages of FES.

REFERENCES

[1] R.J. Triolo, R. Kobetic, R.R. Betz. "Standing and Walking with FNS: Technical and Clinical Challenges," in Human Motion Analysis, G. Harris, editor. IEEE Press, New York, NY, 1995. [2]R.J. Triolo, R.R. Betz, M.J. Mulcahey, E.R. Gardner. "Application of Functional Neuromuscular Stimulation to Children with Spinal Cord Injuries: Candidate Selection for Upper and Lower Extremity Research," Paraplegia, 32:824-843, 1994.

[3]R.R. Betz, R.J. Triolo, V.M. Hermida, M. Moynahan, E.R. Gardner. A. Mauer, S.D. Cook, J.T. Bennett. "The Effects of Functional Neuromuscular Stimulation on the Bone Mineral Content in the Lower Extremities of Spinal Cord Injured Children, " Journal of the American Paraplegia Society, 14(2):65- 66, April 1991.

[4] R.R. Betz, B. Boden, R.J. Triolo, E.R. Gardner, R.S. Fife. "The Effects of Functional Neuromuscular Stimulation on the Joints of Lower Extremity in Children with Spinal Cord Injuries, " Journal of the American Paraplegia Society, 17(2):119, 1994.

[5] M. Hunt, C. Mullin, M. Moynahan. "A Pilot Study of Functional Neuromuscular Stimulation for Standing by Adolescents with Paraplegia, " Journal of the American Paraplegia Society, 17(2):122, 1994.

[6]H. Hahn. "Lower Extremity Bracing in Paraplegics with Usage Follow-up, " Paraplegia, 147-153, 1974

[7] J.K. Coghlan, C.E. Robinson, B. Newmarch, G. Jackson. "Lower Extremity Bracing in Paraplegia-A Follow-up Study," Paraplegia, 18: 25-32, 1980.

ACKNOWLEDGEMENTS

This study is funded by Shriners Hospitals Grant #15953. June M. Akers and Sheryl E. Davis are acknowledged for their contributions to the design of this study.

M.J. Mulcahey Research Dept. Shriners Hospitals 8400 Roosevelt Blvd. Philadelphia, PA 19152 Phone: 215-332-4500 ext 254 FAX: 215-332-5766