Phantom Limb Mobility May Influence Pattern Recognition Control

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Given the development of prosthetic devices with active joints and the need for systems to control them, one method of pattern recognition myoelectric control relies on the myoelectric activities of the residual limb associated with phantom limb movements (PLM). A report published October 18 in Scientific Reports, which involved patients with transradial and transhumeral amputations, aimed to describe the types, characteristics, potential influencing factors, and trainability of upper-limb PLM.

Seventy-six patients (12 women) 18 to 82 years old (48 ± 12 years) underwent a semidirected interview after admission to or follow-up at a rehabilitation center after major acquired upper limb amputation between June 2013 and July 2017. Thirty-seven patients had transradial amputations and 39 had transhumeral amputations. Median time post-amputation was 4.7 years (total range: one month to 52 years). Nine patients had multiple limb amputations (five bilateral, three quadrilateral, and one upper- and lower-limb amputation). Thirty-four patients had a medical-specific treatment for phantom limb pain and some also for residual limb pain. None had undergone targeted muscle reinnervation surgery.

Amputation level, elapsed time since amputation, chronic pain, and use of prostheseswere taken from the interviews. Thirteen different PLM were found involving the hand, wrist, and elbow. Seventy-six percent of the patients were able to produce at least one type of PLM; most of them could execute several. Seventy out of the 76 patients (92 percent) described various painless phantom sensations such as general awareness and non-painful somatic sensations (warmth, cold, pressure, tingling, etc.), all of them at least involving the fingers and often the entire hand. At the time of the interview, 76 percent of all patients (31 out of 37 patients with transhumeral amputations and 27 out of 39 patients with transradial amputations) described the ability to produce voluntary PLM. Only 16 percent of the patients had never produced any PLM, whereas 8 percent described an initial but temporary capacity to produce voluntary PLM.

Amputation level, elapsed time since amputation, chronic pain, and use of myoelectric prostheses were not found to influence PLM, researchers found. Five patients with transhumeral amputations participated in a PLM training program and consequently increased the endurance and speed of their PLM.