Biomechanical Comparison of Polymethylmethacrylate Augmentation Methods in Failed Pedicle Screw Revision

Area of Science:

• Spinal surgery
• Biomechanical engineering
• Orthopedic research

Background:

• Lumbar pedicle screw fixation is crucial for spinal stability.
• Screw loosening and pull-out are common complications, especially in osteoporotic bone.
• Polymethylmethacrylate (PMMA) augmentation is used to enhance screw fixation strength.

Purpose of the Study:

• To compare the biomechanical effectiveness of different polymethylmethacrylate (PMMA) augmentation techniques.
• To evaluate the pull-out strength (POS) of revised lumbar pedicle screws with various PMMA augmentation methods.
• To determine the optimal PMMA augmentation strategy for failed pedicle screw models in animal vertebrae.

Main Methods:

• Animal vertebrae (n=30) were used to create failed lumbar pedicle screw models.
• Four groups underwent different PMMA augmentation procedures: syringe injection, bone graft with roll-shaped PMMA, bone graft with syringe PMMA, and bone graft with fenestrated screw PMMA injection.
• Pull-out tests were conducted using an Instron machine to measure the pull-out strength (POS) of primary and revised screws.

Main Results:

• No significant difference in bone mineral density (BMD) was observed between the groups (p > 0.05).
• Post-revision POS values showed no statistically significant difference among the four PMMA augmentation groups (p > 0.05).
• All augmentation methods successfully increased the POS compared to primary screw fixation.

Conclusions:

• Different polymethylmethacrylate (PMMA) augmentation techniques do not yield statistically significant differences in pull-out strength for revised lumbar pedicle screws.
• The choice of PMMA augmentation method may not critically impact biomechanical stability in this animal model.
• Further research may explore long-term outcomes and clinical applicability of these findings.