Endplate Deformation Due to Open and Strutted Intervertebral Devices

Area of Science:

• Spinal fusion biomechanics
• Orthopedic implant design
• Vertebral endplate mechanics

Background:

• Limited research exists on vertebral endplate response to loading after disc removal and interbody fusion.
• Endplate deflection into the interbody space may promote fusion mass development through beneficial strain.
• Investigating implant design's effect on endplate motion is crucial for optimizing spinal fusion outcomes.

Purpose of the Study:

• To quantify endplate deformation under peripheral loading using a custom transducer.
• To determine if interbody implant design influences endplate motion.
• To compare endplate deformation between open and strutted implant designs.

Main Methods:

• 14 porcine vertebrae (L4, L5) were used, allocated to open or strutted implant groups.
• A custom transducer measured endplate motion during cyclic loading (500 N at 1 Hz for 500 cycles).
• Endplate deformation rates and magnitudes were compared between implant designs using unpaired t-tests.

Main Results:

• Peripheral loading induced endplate deflection into the interbody space for both implant designs.
• The open implant design exhibited a significantly higher rate and magnitude of endplate deformation compared to strutted implants.

Conclusions:

• Interbody cage design critically affects vertebral endplate dynamic motion during cyclic loading.
• Increased endplate deflection in open designs may enhance strain rate, duration, and magnitude on the fusion mass.
• This dynamic strain pattern is associated with improved bone formation and remodeling, potentially leading to faster, stronger spinal fusion.