Determination of stresses in below-knee walking casts

Area of Science:

• Orthopedics
• Biomedical Engineering
• Materials Science

Background:

• Glass fibre bandages are increasingly used for below-knee walking casts, replacing plaster of Paris due to superior stress resistance.
• Understanding stress distribution and failure points in these casts is crucial for improving patient outcomes and reducing revision rates.

Purpose of the Study:

• To develop and demonstrate a technique for measuring strain in glass fibre below-knee walking casts.
• To quantify stress levels experienced by these casts during patient and volunteer ambulation.
• To correlate measured stresses with common sites of cast failure.

Main Methods:

• A novel technique using strain gauges was employed to record cast strains in glass fibre bandages.
• Measurements were taken during gait in both patient and volunteer subjects to capture real-world stress conditions.
• Stress variation maps were generated to visualize strain distribution across the cast.

Main Results:

• High stress concentrations were identified along the medial and lateral borders of the foot in below-knee walking casts.
• These findings align with clinical observations, where cast failure most frequently occurs at these specific locations.
• Typical stress levels during gait were successfully recorded and mapped.

Conclusions:

• The current generation of polyurethane-impregnated glass fibre bandages are often too brittle for the demands of below-knee walking casts.
• A more flexible fabric material is recommended to decrease the incidence of cast breakdown and improve durability.
• Further research into advanced composite materials for orthopedic casting is warranted.