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. 2023 Mar 29;15(3):e36845.
doi: 10.7759/cureus.36845. eCollection 2023 Mar.

Endplate Trauma During Implant Insertion Affects the Expulsion Risk of Anterior Lumbar Interbody Fusion Devices

Annette Kienle  1 , Nicolas Graf  1 , Youping Tao  2 , Frank Heuer  3
Affiliations

Endplate Trauma During Implant Insertion Affects the Expulsion Risk of Anterior Lumbar Interbody Fusion Devices

Annette Kienle et al. Cureus. .

Abstract

Background Anterior cage migration in anterior lumbar interbody fusion is a serious complication. To address this risk, cage designs are now available with integrated screw or blade fixation or specially designed surface geometries with large teeth or ridges. However, the implantation technique itself has not yet been addressed as a potential risk factor for cage migration. This study aimed to investigate whether a cage that is implantable without gouging the vertebral endplates has improved resistance to anterior migration. Methodology A novel three-piece modular cage was inserted between two vertebral body replacements (polyurethane (PU) foam grade 15 pcf) in two ways. In group 1 (modular), the cage was inserted in a wedge within a wedge fashion according to the manufacturer's instructions such that damage to the PU foam was minimized. In group 2 (mono-bloc), the modular cage was inserted pre-assembled as a one-piece, mono-bloc device. This insertion method required impaction and increased the potential of gouging the PU surfaces. Then, an axial preload was applied to the PU test blocks to simulate the preload on the spine in vivo and an anteriorly direct expulsion force was applied to the cages. Results The mean expulsion yield load in the test group with modular implantation was 392 ± 19 N compared to 287 ± 16 N in the test group where the mono-bloc implants were inserted and endplate gouging occurred. This difference was statistically significant (p < 0.05). Thus, the onset of cage migration occurred at significantly higher loads in the test group with modular insertion without endplate gouging compared to one-piece impaction with gouging taking place. In contrast, the stiffness and the ultimate load were similar in both test groups (p > 0.05). Conclusions This study showed that the cage insertion technique may have a significant effect on the cage migration risk. Prevention of endplate gouging during cage implantation has the potential to improve the primary stability of the cage.

Keywords: alif; anterior lumbar interbody fusion; biomechanics; endplate gouging; expulsion; failure; implant migration; mechanical test; stand-alone cages.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Novel modular anterior lumbar interbody fusion cage.
Implantation is carried out with each of the two implant endplates (upper row, left, and right) and the implant body (upper row, middle) separately. After successful implantation, the implant body securely snaps into the endplates forming its final, locked mono-bloc condition (lower row).
Figure 2
Figure 2. Test setup of the static expulsion test with the axial loading device mounted in the static material testing machine.
The lordosis angle (20°) was considered by tilting the caudal and the cranial test blocks. Fexpulsion = expulsion load; Fax = constant axial preload.
Figure 3
Figure 3. Test procedure of the static expulsion test.
Left: start of testing; right: end of testing. Fexpulsion = expulsion load; Fax = constant axial preload
Figure 4
Figure 4. Test procedure of cage insertion in the mono-bloc test group.
This insertion was not required in the modular group because there the implant components were inserted one after the other Fexpulsion = expulsion load; Fax = constant axial preload
Figure 5
Figure 5. Individual load-displacement curves in the static expulsion test.
In the modular group, the implant was stepwise inserted and assembled inside the disc space. In the mono-bloc group, the implant was preassembled and inserted as a whole into the simulated disc space.
Figure 6
Figure 6. Mean load-displacement curve of the mono-bloc samples in the static expulsion test, calculated from all tested samples with stiffness, 0.1 mm offset displacement, yield load (Fyield), deformation at yield load (Dyield), ultimate load (Fult), and deformation at ultimate load (Dult).
Figure 7
Figure 7. Mean load-displacement curve of the modular samples in the static expulsion test, calculated from all tested samples with stiffness, 0.1 mm offset displacement, yield load (Fyield), deformation at yield load (Dyield), ultimate load (Fult), and deformation at ultimate load (Dult).
Figure 8
Figure 8. Gouging marks on the surface of the polyurethane test blocks after expulsion.
In the modular test group, the gouges were smaller than in the mono-bloc group.
See this image and copyright information in PMC

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