Mechanical principles of compressive interbody fusion

Area of Science:

• Spinal biomechanics
• Orthopedic surgery
• Fusion techniques

Background:

• Limited understanding of optimal internal fixator application for interbody bone block compression.
• Previous attempts to compress bone blocks with internal fixators lacked clear methodology.

Purpose of the Study:

• To demonstrate the correct application of internal fixators for achieving interfragmentary compression.
• To optimize the technique for enhanced bone block fixation and fusion.

Main Methods:

• Biomechanical analysis of ten cadaveric lumbar spines.
• Instrumentation with interbody bone blocks and dorsal transpedicular Arbeitsgemeinschaft Osteosynthesefragen (AO) internal fixators.
• Measurement of interfragmentary load and compression surface distribution using a capacitive measuring mat.

Main Results:

• Simple fixator compression yielded insufficient interfragmentary forces and contact areas.
• Lordotic contouring decreased interfragmentary forces and compression surfaces.
• Preloading the fixator in slight kyphosis followed by compression significantly improved forces and surfaces.

Conclusions:

• Preloading internal fixators in kyphosis with secondary compression is mandatory for adequate interfragmentary fixation.
• This technique facilitates compressive interbody fusion while preserving physiological spinal alignment.