Artificial Organs and Assistive Devices: Basics
Scope
Artificial organs replace a failing physiological function; assistive devices support activity. The exam tests definitions, examples and basic fitting.
Examples
- Artificial organs: haemodialysis and peritoneal dialysis, ventricular assist devices, prosthetic heart valves, pacemakers, cochlear implants and insulin pumps.
- Assistive devices: wheelchairs, crutches, walkers, canes, commodes, reachers, hearing aids, and seating and positioning systems.
Fitting basics
- Wheelchair seat width = hip width + 2.5 cm; seat depth should leave 2.5–5 cm behind the knee.
- Axillary crutch length ≈ patient height − 41 cm; handgrip at the wrist crease with 20–30° elbow flexion.
- Devices are matched to the user's environment, transfers and endurance, not only to the diagnosis.
Worked example
A patient 170 cm tall: crutch length ≈ 170 − 41 = 129 cm. With the crutch tip placed about 15 cm lateral and 15 cm anterior to the foot, the handgrip should sit at the wrist crease with the elbow flexed about 30°. If the crutch presses into the axilla, it is too long and risks radial nerve compression.
Traps
Calling an orthosis an artificial organ; measuring crutches without shoes; fitting a wheelchair too wide; ignoring home accessibility; issuing a walker to a patient who cannot lift it.