An implantable upper extremity neuroprosthesis in a growing child with a C5 spinal cord injury

Objectives: To implement a functional electrical stimulation (FES) hand neu roprosthesis called the Freehand System in a growing child with spinal cord injury (SCI) using extra lead wire to accommodate limb growth, and to eval uate 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 wile associated with each electrode was pathed subcutaneously up the al-m with 4 cm of extra lead distributed throughout the path to accommo date expected limb growth. All leads were attached to a stimulator placed i n the upper chest. Measures of lead unwinding, limb growth, stimulated musc le 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 close d and humeral and radial bone growth combined was 2.7 cm from the time of s urgery. For all eight leads, lead unwinding in the upper arm was approximat ely 1.2 cm and was comparable to humeral bone growth (1.4 cm). Lead unwindi ng ill the lower arm was also measurable for the two electrodes in hand mus cles. Six of eight electrodes maintained grade 3 or better stimulated muscl e strength throughout the growth period according to a manual muscle test. Of the two other electrodes, one appeared to have lost function due to depl etion of excess lead. However, hand function with FES was comparable at 6 a nd 16 months post implant suggesting that growth did not negatively impact performance with the FES system. Hand function with FES was improved over v oluntary 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 p inch force. Scores on the Functional Independence Measure (FIM) increased b y 9 points what FES was used as compared to voluntary function. Improvement s occurred primarily in eating and grooming. Independence in writing was ac hieved only with FES. Conclusions: For this child. hand function with the Freehand System was sus tained over the growth period and was a significant functional improvement over voluntary hand function. By using excess lead wire, the Freehand Syste m was successfully implemented before skeletal maturity, affording the chil d improved hand function earlier than would be otherwise indicated.