The Effects of Targeted Phantom Motor Execution on Phantom Limb Control

Overview

Lower limb amputations account for more than 85% of all amputations. In Canada, it has been reported that transtibial amputation (TTA) is the most common level of amputation. Many people with limb amputation have awareness and feel that their missing limb still exists (phantom limb), with perceptions of sensation or pain, and the ability to move the limb with or without intention. Phantom limb sensation (PLS) is defined as all non-painful somatic sensations (e.g. sense of the limb position, touch, pressure, warmth or cold, or movement) in the missing part of the limb. The incidence of PLS is about 60% in adults after 17 months. In addition to PLS, 60-70% of people with amputation experience phantom limb pain (PLP), an intense chronic pain perception in their phantom limb, in the first year after amputation. Although PLP is well known to decrease the quality of life and lessen function, little is known about PLS and phantom limb control (PLC), the ability to intentionally move or control movements of the phantom limb. Enhancing PLS and PLC especially in the immediate months after amputation, could decrease painful perception, facilitate prosthetic control, and improve the function of people with amputations. Keeping this therapeutic and rehabilitative significance in mind, it is hypothesized that a targeted program of phantom motor execution, designed to address phantom limb awareness (PLA), the general knowledge of the presence or existence of the missing limb as one's own, could be associated with improving PLC in people with TTA. Furthermore, prosthetic embodiment, the sense that the prosthesis is accepted as a part of the body with the same functional abilities, may play a role in PLC. Investigating the association of PLC, as one of the phantom phenomena (i.e. PLA, PLS, PLP, and PLC), with surgical, clinical, and demographic characteristics of people with TTA will provide better insight into how phantom phenomena develop. The association of PLC with physical function has significant clinical importance that has never been investigated in people with TTA.

This research explores testing of the following hypotheses with four independent but interrelated studies: Study #1: In people with TTA, post-amputation exercises focus on strength, balance, flexibility, and endurance training of the residual limb and intact limb muscles. Phantom limb motor execution, the active movement of the amputated body part, is not usually encouraged until a patient complains of PLP with the hypothesis that this intervention could re-organize the motor cortex to pre-amputation neural network and function. It was shown that phantom motor execution promoted by mirror therapy, virtual reality, and augmented reality could be used as a non-invasive therapy to relieve PLP in people with limb amputation. However, it is not clear if training with phantom motor execution improves peripheral control over the phantom limb. Therefore, this study explores the effects of a targeted phantom motor execution program on PLC in people with unilateral TTA. Specific aim: To determine if targeted phantom motor execution improves control of the phantom limb, as measured by EMG patterning, in people with unilateral TTA. Research hypothesis: People with unilateral TTA will improve control of their phantom limb after completion of a targeted phantom motor execution program. Study #2: Prosthetic embodiment is a sense that people with limb amputation feel that their prosthesis is integrated into their body and acts like their limb before amputation. It has been shown that higher prosthesis embodiment is associated with less PLP with the thought that it reverses brain plasticity after amputation. It is not clear whether prosthetic embodiment has any effect on PLC. This study explores the potential association between prosthetic embodiment and PLC in people with unilateral TTA. Specific aim: To determine if there is a correlation between prosthetic embodiment, as measured by the self-reported TAPES-R and PEmbS-LLA questionnaires, and PLC (self-report), in people with unilateral TTA. Research hypothesis: There is a strong positive association between prosthetic embodiment and PLC in people with unilateral TTA. Study #3: Surgical closure of the dissected muscles of the residual limb has been shown to impact PLP in people with limb amputation. The two most common surgical closure techniques are myodesis connection of the dissected muscles to bone/periosteum, and myoplasty, the connection of the dissected muscles to antagonist muscles. Residual limb muscles activity and PLA could be influenced by the distal closure of the dissected muscles. However, there is a scarcity of evidence on how surgical closure impacts the PLC. This study explores the association of surgical closure with PLC by measuring the symmetry of EMG muscle activity between the amputated and intact sides in people with unilateral TTA. Specific aim: To determine if PLC, as measured by the symmetry of EMG muscle activity, is influenced by the surgical closure technique of the dissected muscles. Research hypothesis: People who undergo unilateral TTA and myodesis surgical closure of the dissected muscles will have better PLC, as measured by the symmetry of EMG muscle activity, than those who undergo unilateral TTA and myoplasty surgical closure of the dissected muscles. Study #4: The previous three studies investigate the effects of the targeted phantom motor execution, prosthetic embodiment, and surgical closure on PLC. In the literature, it has been shown that improvement of PLC has been correlated with decreased PLP, and reduced PLP is associated with better function in people with limb amputation. However, it is not clear whether PLC has an association with physical function in people with TTA. Specific aim: To determine if there is a correlation between PLC (self-report) and physical function, as measured by the four-square step test (FSST), in people with unilateral TTA. Research hypothesis: There is a strong positive association between PLC and physical function in people with unilateral TTA.