Researchers determine algorithm for bionic hand treatment

Algorithm for bionic hand reconstruction in patients with global brachial plexopathies. The long arrow pointing downward indicates the order of clinical steps of the algorithm. If two electromyographic (EMG) signals are detected during EMG signal identification, the third step (nerve transfer and/or free functional muscle transplantation) is left out (curved arrow).

No longer only an image conjured by science fiction, bionic hands can return functionality in cases of traumatic nerve and muscle loss. A new article published in the Journal of Neurosurgery offers a treatment algorithm for identifying patients with global (flail arm) brachial plexus injuries who are likely to benefit from trading in their insensate and nonfunctional hand for a myoelectric prosthetic device.

Laura A Hruby, and colleagues from the Medical University of Vienna and the University of Applied Sciences FH Campus (Vienna, Austria) recounted their experience with patients who sought treatment for global brachial plexus injuries at the Center for Advanced Restoration of Extremity Function in Vienna between 2011 and 2015. In 16 patients, the nerve injury was so severe that no currently available biological intervention could restore adequate hand function. The authors offered these patients the opportunity to replace the useless biological hand with a myoelectric prosthetic device—a bionic hand.

The authors developed the following protocol for bionic hand reconstruction. It comprises several steps:
1. Physical and psychological assessment of the patient: Patients must have useful shoulder and elbow function but no motor ability or sensation in the hand. In addition, patients must be able to face the challenges ahead.

2. Identification of electromyographic signals in muscles of the forearm: Two separate signals are necessary to control a bionic hand. If fewer than two signals are present, surgical procedures may be performed.

3. Optional: Surgery to perform selective nerve transfer and/or transplantation of healthy muscle to improve nerve conduction and muscle activation in the forearm when at least two electromyographic signals are not present.

4. Brain training: This biofeedback training allows the patient to target reinnervated muscles to control movement of the hand and forearm.

5. Hybrid hand fitting: Patients are trained to use a prosthetic device with their own biosignals prior to hand amputation.

6. Elective amputation of the useless biological hand.

7. Replacement of the biological hand with a myoelectric prosthetic device, followed by additional training and testing of bionic hand function.

The authors report outcomes in the five patients in whom sufficient follow-up was obtained (at least three months after final prosthetic fitting). At the time the paper was written, the other 11 patients were still moving through earlier steps of the algorithm.

Functional outcomes were assessed using the Action Research Arm Test (ARAT), the Southampton Hand Assessment Procedure (SHAP), and the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire. Significant improvements in hand function were seen in all five patients and continued throughout the follow-up period.

Interestingly, deafferentation pain, which had been severe in three of the five patients, lessened after patients became accustomed to working with the bionic hand. According to the authors, “patients reported a subjectively observed correlation between daily wearing time of the prosthesis and pain reduction. Thus when the prosthetic device could not be worn due to regular maintenance, pain was reported to increase again within days.”

When asked about the study, the senior investigator, Oskar C Aszmann, stated, “For more than 25 years, I have dealt with patients suffering from devastating peripheral nerve lesions. Bionic reconstruction, as described in this paper, has been a real game changer since it offers hope and real help for patients who otherwise have none.”