Ankle contractures in people with multiple sclerosis : Implications, measurement and treatment

Contractures (loss of passive joint range of motion) are common in people with Multiple Sclerosis (MS) and the ankle joint is the most common site. Ankle contractures are disabling as they impede ankle range of motion (ROM). Full ankle ROM is essential for normal ambulation therefore, ankle contractures play a role in the loss of mobility and physical independence in people with MS. Methods explored in this thesis focused on the implications, measurement and subsequent treatment of ankle contractures in people with MS.

Implications
Reduced ankle ROM was associated with compromised heel-to-toe progression. Compared to healthy controls, people with MS spent less time in contact phase (7.8% vs 25.1%) and more time in the mid stance phase of gait (57.3% vs 33.7%). Significant differences were detected in people with MS between the affected and less-affected limbs for contact (7.8% vs 15.3%) and mid stance (57.3% and 47.1%) phases. Our method of heel-to-toe progression revealed subtle gait impairments that were not detectable using standard spatiotemporal gait parameters.

Reduced ankle ROM was associated with an increase in compensatory head and pelvic movements that influenced gait stability in people with MS. Compared to healthy controls, people with MS had greater asymmetry in head and pelvic movements (Cohen’s d=1.85 & 1.60) and were less stable (Cohen’s d=-1.61 to -3.06) even after adjusting for slower walking speeds. Our method of screening for excessive compensatory movements provided clinically-important information that impacted on mobility, symmetry and stability in people with MS.

Measurement
Current measurement techniques lack sensitivity to detect ankle impairments in people with MS. We developed a device (Flexometer) to produce standardised (torque-controlled) and reproducible measurements of passive ankle dorsiflexion. The Flexometer proved to be a valid and reliable method (ICC’s 0.94 – 0.99) for assessing ankle ROM in people with MS. The accuracy of this device provides clinicians and researchers with a tool capable of accurate diagnoses and subsequent treatment of ankle contractures in people with MS.

Treatment
Ankle contractures alter muscle morphology leading to shorter, stiffer muscle fascicles in people with MS. According to our systematic review, there appears to be evidence to support the use of eccentric exercise to improve muscle fascicle length and ankle ROM. Therefore, adaptations from eccentric exercise could potentially target deficits present within muscles affected by contracture in people with MS. We explored the effects of backwards-walking-downhill (eccentric exercise) as a therapeutic modality for the management of ankle joint contractures in people with MS. Results indicated backwards-walking-downhill is a novel, safe and feasible training modality in people with MS with an ankle contracture. Additionally, compared to baseline measurements, MS participants improved by approximately 10 degrees in both passive and active ROM. While clinical outcomes (passive and active ROM) were promising, translation to clinically meaningful changes in walking function require further examination.