Virtual Rehabilitation of Elbow Flexion Following Nerve Transfer Reconstruction for Brachial Plexus Injuries Using the Single-Joint Hybrid Assisted Limb

PURPOSE: The upper limb single-joint hybrid assistive limb (HAL), a wearable robot that can support elbow flexion and extension motions, was originally used to rehabilitate patients with stroke. We report the preliminary outcomes of serial HAL use for rehabilitation following nerve transfer (NT) for elbow flexion reconstruction in brachial plexus injuries. METHODS: Hybrid assistive limb training consisted of virtual and power training courses. Virtual training was started before HAL picked up motor unit potentials (MUPs) from the target muscle through electrodes attached to the skin overlying the original donor muscles. Power training was started after the maturation of MUPs, the stage where the MUPs were strong to be recognized to arise from the target muscles. Hybrid assistive limb assist at this stage was carried out by decreasing the settings in an inversely proportionate manner to the increase in target muscle strength. Fourteen patients underwent HAL training following NT. Eight patients had the intercostal nerve to musculocutaneous nerve (ICN-MCN) transfer, and their postoperative functional outcomes and rehabilitation performance were compared to 50 patients with ICN-MCN transfer who underwent conventional postoperative rehabilitation with electromyographic biofeedback (EMG-BF) techniques. RESULTS: Comparison of the long-term results following ICN-MCN transfer between EMG-BF and HAL groups showed similar follow-up times, elbow flexion range of motion, or power of elbow flexion assessed using the British Medical Council grade, and quantitative measurement using Kin-Com dynamometer. However, the number of rehabilitation sessions was significantly fewer in the HAL than EMG-BF group. CONCLUSION: HAL training accelerated patients’ learning to convert the original muscle function into elbow flexion following NT by replicating elbow flexion during the pre-MUP detection stage and shortening the rehabilitation time. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.