Implantable FES system for upright mobility and bladder and bowel function for individuals with spinal cord injury.

STUDY DESIGN: Postintervention. OBJECTIVES: To determine the effectiveness of the Praxis multifunctional implantable functional electrical stimulation (FES) system (Neopraxis Pty. Ltd, Lane Cove, NSW, Australia) to provide standing and stepping ability and bladder and bowel management for individuals with motor complete thoracic level spinal cord injuries (SCI). SETTING: Pediatric orthopedic hospital specializing in SCI. SUBJECTS: Three males, ages 17 and 21 years, with motor-complete thoracic level SCI and intact lower motor neurons to the muscles targeted for stimulation. METHODS: Each subject was successfully implanted with the Praxis FES system. All three subjects received electrodes for upright mobility and the first two subjects received additional electrodes for stimulated bladder and bowel management. Following training, subjects were evaluated in their ability to use FES for nine mobility activities. Acute and chronic experiments of the effect of stimulation on bowel and bladder function were also performed. RESULTS: All three subjects could independently stand up from the wheelchair and could walk at least 6 m using a swing through gait pattern. Two subjects were able to independently perform swing through gait for 6 min and one subject was able to independently ascend and descend stairs. Suppression of reflex bladder contractions by neuromodulation (subject 1) and stimulated contractions of the rectum (subject 2) were observed in acute experiments. When stimulation was applied over the course of several weeks, a positive effect on bowel function was measured. Stimulated bladder contractions were not achieved. CONCLUSION: The feasibility of using the Praxis FES system for upright mobility and aiding aspects of bladder and bowel function was demonstrated with three subjects with thoracic level SCI.

Paraplegia: prolonged standing using closed-loop functional electrical stimulation and Andrews ankle-foot orthosis.

One T10 paraplegic male (CS) implanted in 1991 with a Nucleus FES-22 stimulator has been able to achieve closed-loop standing for 1 h. The knee angles are monitored by electrogoniometers, resulting in the quadriceps stimulation time being less than 10%. Stance stability is achieved by the Andrews anterior ankle-foot orthosis (AFO). The use of accelerometers for trunk inclination and vertical acceleration during controlled stand-to-sit, diminishes slamming onto the seat. CS does one-handed tasks with objects of 2.2 kg. In another T10 paraplegic male (FR), surface stimulation was applied over 1.5 years to both femoral nerves at the groin for conditioning and prolonged standing. With quadricep conditioning, 55 Nm at 45 degrees of knee flexion is produced. With the AFO and knee monitoring, FR can stand uninterrupted for up to 70 min and perform one-handed tasks. In August 1998, he was implanted with the multifunctional Praxis FES 24-A stimulator for restoration of limb movements, bladder and bowel function, and pressure sore prevention.

Paraplegia: prolonged closed-loop standing with implanted nucleus FES-22 stimulator and Andrews' foot-ankle orthosis.

Our object is to develop a reliable, implantable and closed-loop functional electrical stimulator (FES) hybrid system for safe prolonged standing in paraplegic individuals. Open-loop FES systems rapidly induce muscle fatigue that limits paraplegic standing to less than 20 and typically 10 min. Since December 1991, a paraplegic male (CS: 23 years old, T10 level, Asia: A) has been implanted with the first Nucleus FES-22 channel stimulating system (Cochlear Ltd., Lane Cove, N.S.W., Australia). Epineural platinum disc electrodes (2.5 mm) were placed on branches of the femoral, gluteal and sciatic nerves, which can be activated to produce controlled lower extremity movements for exercise and standing. No medical complications have occurred during these 5 1/2 years of implantation. The ankles are stabilized with Andrews' ankle-foot braces, the knees are free to flex. With bilateral knee goniometers fitted to sense a 10 degrees angle flexion, this hybrid closed-loop stimulation system allows the patient to achieve safe uninterrupted standing for over 60 min. The stimulator has needed to be activated 'on' for 8% (range: 3-17%) of the standing times, preventing muscle fatigue, with little or no changes found in the vital signs. The patient can manipulate and transfer objects at arm length up to 2.2 kg with good stability. New, less obstrusive sensors are currently being tested for a safer and more reliable closed-loop system.