A new concept for implant fixation: bone-to-bone biologic fixation

Area of Science:

• Biomaterials Engineering
• Orthopedic Surgery
• Spinal Fusion Technology

Background:

• Pedicle screw loosening is a common complication in spinal fusion surgery.
• Current fixation methods often struggle with achieving robust, long-term stability.
• Biologic augmentation strategies are being explored to improve implant osseointegration.

Purpose of the Study:

• To evaluate a novel bone-to-bone biologic fixation concept using recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded cannulated pedicle screws.
• To assess the efficacy of rhBMP-2 and beta-tricalcium phosphate (TCP) in enhancing pedicle screw fixation.
• To investigate the potential of this method for improving outcomes in challenging spinal surgeries.

Main Methods:

• Four types of titanium pedicle screws (uncannulated, cannulated, TCP-loaded, TCP/BMP2-loaded) were implanted in 16 miniature pigs.
• Radiological assessment, micro-computed tomography (µCT), and histologic examination were used to evaluate fusion and fixation.
• Peak torsional extraction torque was measured 12 weeks post-implantation.

Main Results:

• The TCP/BMP2-loaded group showed significantly higher radiological scores and distinct bone formation around screws.
• Mean extraction torque was over 10-fold higher in the TCP/BMP2-loaded group compared to controls.
• µCT and histology confirmed increased bone surface, bone volume, and bone-to-bone fixation at the screw-bone interface.

Conclusions:

• rhBMP-2 and TCP-loaded cannulated pedicle screws achieve robust bone-to-bone biologic fixation.
• This novel fixation method significantly enhances spinal implant stability and strength.
• The technique holds promise for treating patients with osteoporotic or tumor-affected spines.