Rescue of interfragmentary compression in screw stripping failures: The efficacy of NiTiNOL.

Abstract

Orthopedic screws are widely used to achieve bone reduction, compression, and construct stability. However, the relationship between insertion torque, interfragmentary compression, and fixation strength, especially when comparing standard screws with NiTiNOL/sustained dynamic compression (SDC), has not been thoroughly investigated. This study measured insertion torque, interfragmentary compression, and fixation strength for two types of headed orthopedic devices-standard and SDC-using solid foam bone replicates and cadaver validation. The study also assessed the interfragmentary compression produced by these devices in the context of simulated bone resorption. Results showed that compression force increased with insertion torque until thread stripping occurred, resulting in a 91.9 % loss of compression in the standard screw group. In contrast, the SDC device maintained significantly higher compression, even beyond the point of stripping. These findings suggest that SDC devices offer increased safety by continuing to apply interfragmentary compression after stripping. The SDC device's ability to generate internal compression allows it to re-engage threads into undamaged bone, potentially compensating for compression loss due to stripping. Clinically, these results indicate that surgeons might benefit from deliberately undershooting peak insertion torque, regardless of the device type, and may prefer NiTiNOL-based SDC devices for their resilience to stripping and bone resorption, ultimately optimizing patient outcomes in foot and ankle surgery.