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An implantable upper extremity neuroprosthesis in a growing child with a C5 spinal cord injury
B T Smith1, M J Mulcahey, R R Betz
1Research Department, Shriners Hospitals for Children, Philadelphia, Pennsylvania 19140, USA.
Insights
Functional electrical stimulation (FES) using the Freehand System improved hand function in a child with spinal cord injury (SCI) throughout growth. Extra lead wire accommodated limb growth, maintaining grasp and release capabilities and enhancing independence in daily activities.
Area of Science:
- Neuroprosthetics
- Biomedical Engineering
- Rehabilitation Medicine
Background:
- Spinal cord injury (SCI) in children presents challenges for neuroprosthetic device adaptation due to growth.
- The Freehand System offers functional electrical stimulation (FES) for grasp and release in individuals with SCI.
Observation:
- A novel implantation technique using extra lead wire was employed to accommodate limb growth in a pediatric SCI patient.
- Performance metrics including lead unwinding, bone growth, muscle strength, and hand function were tracked over 16 months.
Findings:
- The Freehand System successfully adapted to a 2.7 cm limb growth, with lead unwinding comparable to bone growth.
- Six of eight electrodes maintained functional muscle strength, and overall hand function with FES was sustained and improved compared to voluntary function.
- FES enabled a 15 N pinch force versus 1.3 N voluntary, and improved Functional Independence Measure (FIM) scores, particularly in eating, grooming, and writing.
Implications:
- This study demonstrates the feasibility of using FES neuroprostheses in growing children with SCI.
- The adaptive lead wire technique allows for earlier implementation of FES, providing functional benefits during maturation.
- FES neuroprostheses can significantly enhance independence and quality of life for pediatric SCI patients.
Objectives:
To implement a functional electrical stimulation (FES) hand neuroprosthesis called the Freehand System in a growing child with spinal cord injury (SCI) using extra lead wire to accommodate limb growth, and to evaluate the performance of the Freehand System during the subject's maturation.
Setting:
Pediatric orthopedic hospital specializing in SCI rehabilitation.
Subject:
Ten-year-old female patient with a C5 level SCI.
Method:
The Freehand System was implanted. Eight electrodes were implanted to targeted forearm and hand muscles to provide grasp and release function. The lead wire associated with each electrode was pathed subcutaneously up the arm with 4 cm of extra lead distributed throughout the path to accommodate expected limb growth. All leads were attached to a stimulator placed in the upper chest. Measures of lead unwinding, limb growth, stimulated muscle strength, and hand function were made at 6 and 16 months after implant.
Results:
By 16 months post implant, the upper limb growth plates were closed and humeral and radial bone growth combined was 2.7 cm from the time of surgery. For all eight leads, lead unwinding in the upper arm was approximately 1.2 cm and was comparable to humeral bone growth (1.4 cm). Lead unwinding in the lower arm was also measurable for the two electrodes in hand muscles. Six of eight electrodes maintained grade 3 or better stimulated muscle strength throughout the growth period according to a manual muscle test. Of the two other electrodes, one appeared to have lost function due to depletion of excess lead. However, hand function with FES was comparable at 6 and 16 months post implant suggesting that growth did not negatively impact performance with the FES system. Hand function with FES was improved over voluntary hand function as well. Using the Freehand System, a pinch force of approximately 15 N was achieved compared to 1.3 N of voluntary tenodesis pinch force. Scores on the Functional Independence Measure (FIM) increased by 9 points when FES was used as compared to voluntary function. Improvements occurred primarily in eating and grooming. Independence in writing was achieved only with FES.
Conclusions:
For this child, hand function with the Freehand System was sustained over the growth period and was a significant functional improvement over voluntary hand function. By using excess lead wire, the Freehand System was successfully implemented before skeletal maturity, affording the child improved hand function earlier than would be otherwise indicated.
