Pullout performance comparison of pedicle screws based on cement application and design parameters

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Spinal instrumentation

Background:

• Pedicle screws are crucial for spinal fixation.
• Osteoporotic bone increases the risk of pedicle screw loosening.
• Cement augmentation and specialized screw designs are used to improve fixation.

Purpose of the Study:

• To evaluate the pullout strength of dual lead dual core pedicle screws with cement augmentation.
• To compare this novel design against standard and cannulated pedicle screws with augmentation.
• To assess the potential of this screw type for osteoporotic patients.

Main Methods:

• Five groups of pedicle screws were tested: dual lead dual core (with and without augmentation), standard pedicle screw with augmentation, and cannulated pedicle screw with augmentation.
• Tests were conducted on healthy bovine vertebrae and synthetic polyurethane foams (grade 20).
• Pullout tests followed ASTM F543 standards using an Instron 3300 testing frame.

Main Results:

• Dual lead dual core pedicle screws with poly-methyl methacrylate (PMMA) augmentation demonstrated the highest pullout strength.
• The dual lead dual core screw without augmentation showed comparable strength to augmented standard and cannulated screws.
• Augmented dual lead dual core screws offer significantly improved fixation.

Conclusions:

• Dual lead dual core pedicle screws with PMMA augmentation provide superior fixation strength.
• This enhanced fixation makes them a viable option for patients with osteoporotic or severely osteoporotic bone.
• The study supports the use of augmented dual lead dual core screws in challenging spinal fusion cases.