Quantifying Accuracy of Self-Tapping Screw Models.

Area of Science:

• Biomaterials Engineering
• Orthopedic Biomechanics
• Medical Device Design

Background:

• Proper bone screw torquing is critical for preventing fixation failures and improving patient outcomes in orthopedic surgery.
• Patient-specific bone material properties are essential for accurate torque recommendations, but are difficult to obtain.
• Model-based methods have been proposed for identifying bone material properties but lack experimental validation.

Purpose of the Study:

• To experimentally test the accuracy of proposed model-based methods for identifying patient-specific bone material properties.
• To evaluate the performance of these models across a range of material densities.
• To assess the potential clinical applicability of model-based torque recommendations for bone screws.

Main Methods:

• Utilized two previously proposed models for parameter identification on experimental data.
• Employed rigid polyurethane foams of varying densities and standard bone screws for testing.
• Compared identified material property values with datasheet values to quantify model accuracy.

Main Results:

• Models demonstrated reasonable accuracy in identifying material properties for medium-density polyurethane foam.
• A slight under-prediction of strength was observed for lower-density foam materials.
• A significant under-prediction of strength occurred for the highest density foam, indicating limitations.

Conclusions:

• The tested model-based method shows promise for identifying bone material properties for torque recommendations.
• The method's accuracy appears dependent on material density, suggesting applicability primarily to lower-to-medium strength materials.
• Further calibration and testing are necessary to confirm accuracy and define the reliable density range for clinical use.