One of the main success criteria of interbody fusion is the formation of a solid, bony fusion between vertebrae. The primary objective of this study was to compare vertebral endplate bulging between an open and a single-strutted Titanium interbody cage during dynamic loading. Endplate bulging may have potential importance in bone graft remodeling as it is believed to contribute to bone graft compression. The secondary objective was to compare vertebral deformation between the two implant groups. This is significant as a greater vertebral deformation could constitute a greater extent of bone remodeling within the vertebra in vivo. In this study, fourteen porcine lumbar vertebrae, including an even number of L4’s and L5’s, were used. Endplate deflection and vertebral deformation data was collected during dynamic loading of the implant/vertebra construct for both implants. Specimens were loaded from –50N to –500N at 1 Hz for 525 cycles. Load versus deformation data was collected at cycle 5 and at 20 cycle intervals thereafter. The difference in vertebral deformation between minimum and maximum loads was calculated and averaged across all cycle counts. Endplate deflection was measured using a self-fabricated displacement transducer capable of submicron resolution. A non-linear exponential analysis was performed to obtain parameters (K-value, half-life, and span) characterizing the dynamic responses. An F-test (α = 0.05) indicated that a single phase decay best fit the endplate deflection data for both implant groups. For vertebral deformation data, the F-test revealed that a dual phase decay provided a better fit for the open interbody cage (P = 0.0006). However, because the strut implant group vertebral deformation data did not converge under a dual phase decay, the results of the single phase decay were used for comparison. A two-tailed unpaired t-test (α = 0.05) compared endplate deflection and vertebral deformation parameters between the implant groups. The span parameter revealed that the open implant allowed for a statistically greater endplate deflection and vertebral deformation than the strut implant (P < 0.0001 for both). This indicates that the open implant may be superior to the strut implant in regards to its contribution to a stronger fusion (endplate bulging) and a stronger vertebral core (vertebral deformation).
|Commitee:||Gray, Marissa, Hazelwood, Vikki|
|School:||Stevens Institute of Technology|
|School Location:||United States -- New Jersey|
|Source:||MAI 57/05M(E), Masters Abstracts International|
|Subjects:||Biomedical engineering, Biomechanics|
|Keywords:||Cage, Deflection, Endplate, Implant, Interbody, Vertebral|
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