What is a trunk orthosis?

ALS can lead to weakness of the spinal muscles as well as the rib and abdominal muscles. This form of muscle weakness causes trunk instability. It manifests itself in an unintentional misalignment of the trunk with a forward tilt of the head and upper body or a tilt of the trunk at the level of the lumbar spine. At the beginning of the disease, trunk stability may consist of a slight forward tilt, which appears as a “hunchback”. As the disease progresses, trunk instability (also known as “axial instability”) can increase in severity, resulting in gait disturbance.

Patients with trunk instability feel relief when pushing a shopping cart (which gives them stability) and benefit from using a rollator. In the case of severe trunk instability, it may make sense to fit a trunk orthosis. Trunk orthoses can be designed in different ways. The most common form of trunk orthosis is a corset that provides greater stability to the thorax (in conjunction with the thoracic spine or lumbar spine). Other forms of orthosis consist of a backpack-like tension belt (with stabilization of the trunk) or abdominal supports (with stabilization of the lumbar spine).

Adaptation to the individual symptoms and treatment goals (e.g. support for walking and standing), but also the strain caused by an orthosis, must be considered and weighed up. In fact, a trunk orthosis can be associated with restrictions and “side effects”. For example, stabilizing the rib cage with a trunk orthosis can make it more difficult to lift the rib cage, which in turn can hinder inhalation motor skills. Patients with respiratory dysfunction should therefore be aware of this potential limitation and the orthosis should be adjusted accordingly.

Overall, trunk orthoses are relatively rarely used aids, but they can be highly effective in restoring stability to the trunk and thus the ability to walk. Due to the relative rarity and complexity of orthosis fabrication for the trunk, it is recommended that the orthosis is selected, fabricated and fitted by a specialist provider.