Laura Peeters

124 | Chapter 6 movement when performing daily tasks. As this balance of effects is likely to change with the disease stage, this research should be extended to a range of disease stages in DMD and SMA. Spinal deformities Spinal deformities are often seen in patients with DMD and SMA due to trunk muscle weakness already being present while the spine is still growing [34, 35]. Severe scoliosis can have an effect on sitting balance and cardio-respiratory function and is generally treated by spinal surgery [36]. After spinal surgery, sitting balance is often improved, but ROM is reduced because spinal flexibility is lost [37]. Despite the fact that movement between spinal segments is used to perform daily tasks (chapter 2), people with sufficient muscle strength do not experience major restrictions in performing daily activities after surgery [38, 39]. Their muscle strength is large enough to create sufficient torque to move the rigid trunk; when spinal segments are fused the amount of force needed to stabilize and move the rigid trunk increases (increase in inertia). However, patients with neuromuscular disorders will lose function due to the spinal surgery [40]. Compensatory trunk movements cannot be performed anymore and it is more difficult, or even impossible, to create enough muscle force to move the rigid trunk towards higher inclination angles. The level of spinal fixation is determined by the surgeon and can be limited to the thoracolumbar region or can involve fixation of the lumbosacral joint too. There is still controversy whether it is necessary to extent the fixation to the sacrum. The major argument for inclusion of the lumbosacral joint is to correct for pelvic obliquity and thereby creating a leveled and stable base. However, we found that movement between the lower lumbar spine and pelvis segment contributes substantially to trunk ROM in the sagittal plane (chapter 2), so restricting movement at the lumbosacral joint would likely decrease functionality even more. In addition, some studies showed that improvement of pelvic obliquity in the frontal plane could also be seen when fixation was done down to the L5 level, although this only applied to patients with less severe pelvic obliquity [41, 42]. These arguments together would plead for fixation down to the L5 level as long as further fixation is not strictly necessary, which is also suggested in the Dutch guideline for scoliosis treatment in neuromuscular disorders [43]. Development of dynamic supportive devices Another solution to reduce fatigability and assist patients in their trunk and head movement would be the development of dynamic supportive devices. The development of such devices was the aim of the Symbionics project. Both passive systems (i.e. spring based) and control methods for active systems (i.e. actuated by