PROGRAM | Biomechanics & Movement Science

By: Emma Beisheim Chair: Megan Sions

ABSTRACT

As many as 80% of adults with lower-limb loss experience persistent post-amputation pain in the phantom limb (i.e., amputated portion of the limb) and/or residual limb (i.e., remaining portion of the limb), which is associated with depressive symptoms and reduced quality-of-life. Despite its prevalence, persistent post-amputation pain remains poorly understood and under-addressed in clinical practice. Localized treatments targeting persistent post-amputation pain generally lack efficacy, warranting further investigation into whether central nervous system impairments should be the focus of clinical pain evaluation and management following lower-limb loss.

The overarching objective of this dissertation was to use low-cost, clinical measurement techniques to identify whether underlying central nervous system impairments are present and associated with pain characteristics among adults with persistent post-amputation pain. Aim 1 was a secondary analysis of data compiled from six, cross-sectional research studies, which evaluated the prevalence and patterns of multisite pain, a symptom of central nervous system hypersensitivity, among a sample of 303 adults with lower-limb loss. Aim 2 was a secondary analysis of cross-sectional data which (1) evaluated whether adults with persistent amputation pain demonstrate greater pressure-induced pain sensitivity within and remote to the amputated region and (2) compared signs and symptoms of central nervous system hypersensitivity among subgroups of participants with persistent post-amputation pain. Finally, Aim 3 utilized an online, pilot study to evaluate whether adults with persistent post-amputation pain demonstrate impaired body representation (i.e., altered detection or perception of the amputated limb), which may be attributed to maladaptive changes in the central nervous system. When possible, considerations were made for sex-specific differences, as research in other chronic pain conditions suggests pain perception, experience, and processing may differ between males and females.

Findings from Aim 1 indicate over 60% of adults with lower-limb loss experience multisite pain, with females being disproportionately affected. Findings from Aim 2 indicate adults with persistent post-amputation pain demonstrate increased amputated-region pain sensitivity as compared to pain-free peers and adults with intact limbs; however, increased remote-site pain sensitivity was only found among a subgroup of adults with persistent post-amputation pain. Self-reported pain characteristics (e.g., intensity, interference, symptoms of nervous system hypersensitivity) did not differ between adults with and without amputated-region sensitivity. Findings from Aim 3 indicate adults with post-amputation pain demonstrate greater difficulty completing a body representation task as compared to adults with intact limbs; however, adults with post-amputation pain performed similarly to pain-free peers with lower-limb loss, suggesting body representation impairments may be attributed to overarching changes associated with limb amputation. Finally, body representation impairments were indicated by increased phantom limb hypervigilance and more negative body image among adults with post-amputation pain as compared to pain-free peers with lower-limb loss.

Collectively, this dissertation identified potential central nervous system impairments among adults with persistent post-amputation pain, which can be identified using a battery of clinical outcome measures and non-invasive techniques. Evaluation of multisite pain involvement, increased pain sensitivity, and body representation impairments may guide pain management in clinical practice, including implementation of novel rehabilitation interventions (e.g., treatments targeting impaired body representation) to reduce pain-related disability and improve quality of life following lower-limb loss.

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