Chapter 1
Chapter 1
A study evaluating differences in three-D upper limb kinematics and surface electromyography measures in adults with and without facioscapulohumeral dystrophy
ABSTRACT
Background: Facioscapulohumeral dystrophy is a rare disease that causes progressive muscle wasting and loss of function, with the upper limb being the most affected. Factors leading to loss of arm function are poorly understood. A better understanding of movement profiles determined using three-D movement analysis could help inform treatment selection and development; however, limited evidence is available for combined three-D movement and surface electromyography studies that include the scapula. Our null hypothesis is that there are no differences between the movement and muscle activity of people with facioscapulohumeral dystrophy and age- and sex-matched controls.
Methods: Adults were recruited into three groups: one. Facioscapulohumeral dystrophy with scapulothoracic arthrodesis (scap fix); two. Facioscapulohumeral dystrophy and no surgery (no surgery); or three. Age- and sex- matched control group (CG). Participants attended a single session and carried out seven motion tasks in which their movements and muscle activity was measured using three-D movement analysis and surface electromyography. Descriptive statistics and normalized movement and muscle activity plots were used to compare joint angles, surface electromyography patterns, and scapulohumeral rhythm between groups.
Results: Data were collected for fourteen participants (ten males to four females), seven with facioscapulohumeral dystrophy and seven age- and sex- matched controls, with a mean (standard deviation) age of forty-one point six (fifteen point seven). The facioscapulohumeral dystrophy (no surgery) group achieved lower mean (standard deviation) thoracohumeral elevation, most notably in flexion, seventy-four point six degrees (twenty-nine point two), and abduction eighty point eight degrees (thirty-one point two), compared to the control group, who achieved one hundred twenty-six point nine degrees (twelve point seven) and one hundred thirty point one degrees (ten point eight), respectively. Despite these differences, range of movement for glenohumeral elevation was similar between groups. Considerable variability across the acromioclavicular and sternoclavicular joints was noted in all facioscapulohumeral dystrophy groups, with no clear between group differences. Scapulohumeral rhythm was reduced in the facioscapulohumeral dystrophy (no surgery) group. Facioscapulohumeral dystrophy groups demonstrated prolonged and higher
Facioscapulohumeral dystrophy is a rare muscle disease that causes progressive muscle damage, wasting and loss of function. The presentation and progression of the disease is highly variable and asymmetric between individuals. Despite this, changes to the morphology of muscles which control movements of the scapular and shoulder girdle is one of the most prevalent and apparent consequences. This can result in altered scapular kinematics and biomechanical changes to the glenohumeral joint, which present alongside limited shoulder range of movement and pain. People with facioscapulohumeral dystrophy can experience difficulties with functional tasks such as reaching, lifting, carrying objects and management of personal care. Maintaining arm elevation is important as reduced arm function is linked to a loss of independence and participation, which negatively impacts quality of life.
Establishing large scale effectiveness trials in rare disease subtypes such as facioscapulohumeral dystrophy is challenging. Currently, there is limited evidence to inform management of the upper limb and engagement with exercise-based rehabilitation is low. Some people with facioscapulohumeral dystrophy may be offered surgical fixation of their scapula to reduce pain or increase arm elevation. However, these benefits diminish over time, long-term outcomes are variable, and some people experience complications. In the absence of data derived from robust clinical trials, movement analysis may provide an alternative method for evaluating effectiveness and the disease mechanism.
Movement analysis is already used to inform clinical decision making in other rare diseases; however, a lack of standard reference tasks and protocols for assessing upper limb movements is known to be a barrier to wider use in clinical practice. Previous research has used movement analysis to evaluate the movement and control strategies of people with facioscapulohumeral dystrophy. This has involved three-dimensional kinematic analysis or surface electromyography. Studies have identified that people with facioscapulohumeral dystrophy have slower movement speeds (between twenty-five and forty percent) and increased elbow flexion (possibly to reduce the overall moment at the shoulder), in addition to increased levels of muscle activation, compared to controls. Movement analysis studies investigating the biomechanical effects of scapulothoracic fixation are limited. While these studies have provided valuable information to the field, there are still some gaps in our current understanding. Existing studies have either only included people with higher levels of arm function (Brooke scale greater than four), assessed a limited number of movements, not combined assessment of three-D joint angles with surface electromyography, used simple kinematic measures or models which did not include the scapula, or modeled simplified representations of the shoulder complex such as scapulothoracic and thoracolumbar segments only. While other measures of arm function such as reachable workspace provide useful information regarding an individual's global level of arm function, they do not always provide information for individual joints or muscles of the shoulder girdle, which may be required for understanding disease mechanisms or tailoring interventions. Accepted conventions that allow for the identification of deviations within the condition and clear links between the activity, impairment, and intervention are required for informing decision making.
Further evidence for movement and muscle activity pattern differences in people with facioscapulohumeral dystrophy, based on combined surface electromyography and more detailed kinematic representations of the shoulder girdle, which include scapular movement, is needed. The aim of this study was therefore to quantify the movement and muscle activity patterns of people with and without facioscapulohumeral dystrophy using three-D motion capture, surface electromyography and a physiologically representative model of the shoulder girdle which includes scapula kinematics.
Materials and methods
Materials and methods
Ethical approval for this study was gained from the West Midlands - Black Country Research Ethics Committee twenty-one WM zero two seven five. This trial is registered on ClinicalTrials.gov Identifier: NCT zero five two three nine five two zero.