Comparison of Different Pullout Test Setups for Evaluation of Bone–Implant Interfacial Strength of Anterior Lumbar Interbody Fusion Devices

Experimental approaches have been widely used to investigate the bone–implant interfacial strength of anterior lumbar interbody fusion (ALIF) devices. However, improper design of experimental jigs and inconsistencies in cadaveric specimens might significantly impede the evaluation of different ALIF device designs. Therefore, this study aimed to investigate and compare various test setups in terms of their feasibility for conducting pullout tests on ALIF devices. Three types of pullout test setups for evaluating the interfacial strength of the ALIF devices were investigated. Then, finite element models of the L4–L5 segment with different ALIF device designs were developed and numerical analysis was performed. Finally, the results from all the pullout test setups were compared with those obtained from numerical analysis. The results indicated that the quasi-material and boundary pullout test setup (QMBPTS), which considered the effects of the composite material of the test specimens and mimicked the lumbar posterior element’s anatomy and loading mechanism, revealed a more realistic bone failure pattern and interfacial pullout strength compared with the general pullout test setup and the quasi-boundary pullout test setup. The finite element models could accurately predict the experimental results obtained using the QMBPTS. It was confirmed that QMBPTS is a feasible and inexpensive pullout test setup for evaluating the bone–implant interfacial pullout strength of ALIF devices. Both the experimental and numerical approaches could provide useful information for designing a biomechanical experiment to solve bone–implant loosening problems.