Theory 18/Prosthetics & Rehabilitation Engineering
Socket Failure Is an Impedance Ratio
The claim
Prosthetic socket failure is set by the ratio of mechanical impedance mismatch to tissue tolerance rather than by pressure alone, so a compliant interface can tolerate higher load.
01The mechanism
Load transfers through the interface. Mismatch between the device's stiffness and the tissue's creates shear concentrations that damage skin at loads well below the pressure limit.
The ratio determines whether load is distributed or concentrated, which is why interface material matters more than fit pressure.
02What this is not
Pressure-distribution models
Those target peak pressure. This targets mismatch, which explains failures at acceptable pressure.
03Predictions
- P1Failure should track the ratio.
- P2Compliant interfaces should tolerate higher load.
04Refutation
Failure tracking peak pressure at controlled mismatch would favour pressure models.