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Unloading mechanism in the total contact cast
Efraim D Leibner1, James W Brodsky, Fabian E Pollo
1Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
Foot & Ankle International
|April 21, 2006
Summary
Total contact casts reduce plantar pressure effectively. Removing the upper part of the cast significantly increases walking pressure, indicating the shank portion is crucial for unloading the foot.
Area of Science:
- Biomechanics
- Orthopedics
- Podiatry
Background:
- Total contact casts (TCC) are believed to reduce plantar pressure.
- The exact mechanism of off-loading the plantar surface is debated.
- This study investigates whether intimate molding or the below-knee cast is responsible.
Purpose of the Study:
- To evaluate the mechanism of plantar unloading by total contact casts.
- To determine the contribution of the cast's shank portion to pressure reduction.
- To compare plantar loads between a TCC and a shoe-cast (SC).
Main Methods:
- Plantar pressures and forces were measured in 12 healthy subjects using a pedobarographic system.
- Measurements were taken with a full TCC and a modified shoe-cast (SC) after removing the shank.
- Data were collected during single-leg standing and over-ground walking.
Main Results:
- Removing the shank portion of the TCC significantly increased average plantar force by 31% during walking.
- Peak plantar pressure increased by 53% during walking after shank removal.
- No significant changes in pressure or force were observed during single-leg standing.
Conclusions:
- The proximal 'shank' portion of a total contact cast plays a critical role in unloading the plantar foot.
- This unloading effect is likely due to the reduction of ankle motion.
- Well-molded shoes or insoles are less effective than TCCs due to the absence of this shank component.