A lower limb orthosis is an external device applied or attached to a lower body segment to improve function by controlling motion, providing support through stabilizing gait, reducing pain through transferring load to another area, correcting flexible deformities, and preventing progression of fixed deformities.
Orthosis is the medical term for what most people would refer to as a brace or splint. Orthoses generally are named by the body regions that they involve, as demonstrated by the following abbreviations:
- AFO is an ankle-foot orthosis.
- KAFO is a knee-ankle-foot orthosis.
- HKAFO is a hip-knee-ankle-foot orthosis.
- THKAFO is a trunk-hip-knee-ankle-foot orthosis.
Regarding human gait, the purpose of using an orthosis is to enhance normal movement and to decrease abnormal posture and tone. Lower extremity orthoses can be used to correct abnormal gait patterns and to increase the efficiency of walking.
Classes of Lower extremity Orthoses
An orthosis may be classified as a static or dynamic device. A static orthosis is rigid and is used to support the weakened or paralyzed body parts in a particular position. A dynamic orthosis is used to facilitate body motion to allow optimal function. In all orthotic devices, 3 points of pressure are needed for proper control of a joint.
Principles of Orthotics
A lower limb orthosis should be used only for specific management of a selected disorder. The orthotic joints should be aligned at the approximate anatomic joints. Most orthoses use a 3-point system to ensure proper positioning of the lower limb inside the orthosis.
The orthosis selected should be simple, lightweight, strong, durable, and cosmetically acceptable. Considerations for orthotic prescription should include the 3-point pressure control system, static or dynamic stabilization, flexible material, and tissue tolerance to compression and shear force.
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