Uses of Phantom Sensations Induced by Global and Local Modifications of the Prosthetic Socket as Somatosensory Feedback During Walking in Lower Limb Amputees

Overview

Following lower-limb amputation, the loss of somatosensory information from the missing limb renders walking less automatic, more cognitively demanding, and often asymmetric, which can lead to secondary pathologies. Hypothesis: This study is based on the hypothesis that phantom limb sensations (PLS), when coherent with the prosthetic device's movements and the phases of the gait cycle, can compensate for the loss of somatosensory feedback and thereby improve locomotion for individuals with amputation. It is further hypothesized that it is possible to artificially induce these coherent and useful sensations, notably through "referred sensations" elicited by stimulation of the residual limb (e.g., via the prosthetic socket). Objectives: The project aims to: * Determine whether the natural presence of phantom limb sensations during walking impacts gait parameters. * Confirm in a larger patient population that modifications to the prosthetic socket can induce or enhance phantom sensations that are perceived as useful for walking. * Investigate whether these perceptual changes (induced or enhanced) are associated with objective, measurable improvements in gait quality.

Interventions

• Other Gait analysis
  Participants with unilateral amputations and a control group will undergo a comprehensive walking analysis. In a lab setting (on a treadmill or floor), their gait will be recorded using inertial sensors, EMG, force plates, and motion capture, while an EEG cap and a NASA-TLX questionnaire will assess cognitive load. Capable participants will also perform a walking test on a real-world outdoor course with varied terrain. The data will be analyzed to compare walking patterns between groups (amputee
• Other Mapping of referred sensations.
  Participants reporting referred sensations in gait analysis phase will undergo further testing. The study will investigate whether prosthesis pressure or a specific socket interaction causes these sensations. A 3x3 cm grid will be drawn on the residual limb to systematically map referred sensations using various stimuli (brush, pressure tip, electrical stimulation). Participants will rate the intensity and describe the location of any resulting phantom sensations. This mapping will be repeated a
• Other Exploration of the areas of the brain activated during referred sensations
  Unilateral transfemoral amputees with detailed referred sensation maps will have their brain activity recorded using a 64-electrode EEG cap. Non-invasive stimuli will be applied to four specific sites: an area on the residual limb that elicits a referred sensation, the corresponding location on the intact foot, a neutral area on the residual limb, and its corresponding location on the intact thigh. This process, involving 400 total stimulations, will be repeated after 6 months to track cortical
• Other Evaluation of the effects of socket modifications on phantom sensations and walking
  This phase will evaluate how socket modifications affect phantom sensations and walking in 10 transfemoral amputees. First, the best material to comfortably induce referred sensations will be determined in a small sub-study. Then, each participant will be tested under four conditions: their usual socket and a socket with different rigidity, both with and without a specific local pressure point added inside. The location of this pressure point is based on the user's sensation map. Participants' w
• Other Phantom limb interview
  A semi-structured interview will be conducted to ask participants to describe their phantom limb sensations (type, location, intensity) under three conditions: without their prosthesis, while standing with it, and while walking with it. This aims to identify factors influencing these sensations. Additionally, a brief physical examination of the residual limb will be performed to see if touch in specific areas triggers any referred sensations.

Primary outcome measures

• Characterization of phantom limb sensations [Time frame: The first day of the study]
• Walking speed under laboratory conditions [Time frame: The first day of the study for the control group and the second day of the study for participants with amputation]
• Step length symmetry index. [Time frame: The first day of the study for the control group and the second day of the study for participants with amputation]
• Changes in the surface area of sensory maps referred to the residual limb [Time frame: 2nd or 3rd day of the study depending on whether the participant with an amputation was included in phase 2 or not and during the 6-month follow-up visit.]
• Change in the average intensity of reported phantom sensations. [Time frame: 2nd or 3rd day of the study depending on whether the participant with an amputation was included in phase 2 or not and during the 6-month follow-up visit.]
• Localization of the cortical source of somatosensory evoked potentials (SEPs) during stimulation of referred sensation areas [Time frame: The second day of the study for participants with amputation]
• Participant's subjective preference for one of the four socket conditions tested. [Time frame: Day 7 of the study]
• Change in the spatiotemporal parameters of walking in ecological situations [Time frame: Days 4 to 7 to the study]

Secondary outcome measures (12)

• Walking pace under laboratory conditions [Time frame: The first day of the study for the control group and the second day of the study for participants with amputation]
• Analysis of muscle co-activation in the lower limbs and trunk during walking. [Time frame: The first day of the study for the control group and the second day of the study for participants with amputation]
• Maximum vertical reaction force during walking. [Time frame: The first day of the study for the control group and the second day of the study for participants with amputation]
• Assessment of mental workload during walking using the NASA-TLX questionnaire [Time frame: The first day of the study for the control group and the second day of the study for participants with amputation]
• Analysis of brain activity related to cognitive load during walking [Time frame: The second day of the study for participants with amputation]
• Gait speed in ecological situation [Time frame: The first day of the study for the control group and the second day of the study for participants with amputation]
• Qualitative description of the interaction between phantom sensations and walking [Time frame: The second day of the study for participants with amputation]
• Change in phantom limb sensation intensity at 6 months for recent amputees [Time frame: The first day of the study and during the 6-month follow-up visit.]
• Effect of focal stimulation on phantom sensations [Time frame: Day 3 of the study]
• Change in perceived cognitive load (NASA-TLX score) during walking in an ecological setting [Time frame: Day 4 to 7 of the study]
• Evaluation of socket comfort [Time frame: Day 4 to 7 of the study]
• Qualitative description of the sensations reported for each socket condition [Time frame: Day 4 to 7 of the study]

Eligibility criteria

Inclusion criteria

• Participants with amputations:

• Major lower limb amputation
• Understand and be able to express oneself in the French language (for semi-structured interviews)
• Affiliated with a social security scheme
• Asymptomatic volunteer participants:

• No major surgery on the lower limbs for at least 3 years
• No minor injury to the trunk, lower or upper limbs that could influence walking for at least 1 year
• Understand and be able to express oneself in the French language
• Affiliated with a social security scheme

Exclusion criteria

• History of psychiatric disorders
• Pregnant or breastfeeding woman
• Minor
• Adult subject to a legal protection measure
• Person under guardianship or conservatorship
• Person under a judicial protection order
• Pain affecting walking (trunk, residual limb, phantom limb, contralateral limb)
• Medical treatment incompatible with walking

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Non-randomized

Model

Sequential

Masking

Open label

Primary purpose

Health services research

Study locations

France · 1 center

• Institut Régional de Médecine Physique et de Réadaptation — Nancy

Identifiers

NCT: NCT07191795 · 2022-A01647-36 · ANR-23-CE17-0067-02

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗