An OLIF Cage Integrated with a Low-Profile Plate and Cross Screws Could Reduce the Risk of Postoperative Complications Biomechanically.

Background: Stand-alone oblique lumbar interbody fusion (OLIF) cannot provide credible postoperative stability; additional fixation devices (AFDs) have been used to optimize surgical segment stability. Anterior lateral single rod (ALSR) screw fixation can be performed without intraoperative body position changes and additional surgical incisions, but its biomechanical defect may trigger complications. Inspired by the cross screw in other fixation devices, we designed an OLIF cage integrated with a low-profile plate and cross screw (LPCS).

Methods: This study was designed to investigate whether the biomechanical performance of the LPCS OLIF cage is better than that of OLIF with ALSR fixation. The pullout and bending strength of the newly designed conical screw were tested by comparing it with a clinically used cylindrical screw. Different directional fixation strengths of the LPCS OLIF cage were tested by comparing the failure moment and stiffness with the ALSR fixation model. To test the fixation stability and potential risk for screw loosening in models with LPCS OLIF, we also compared the surgical segment's range of motions (ROMs) and stress distributions on OLIF models without and with different AFD fixation under physiological loading conditions.

Results: The bending and pullout strength of the conical screw was better than that of the clinically used screw, and the failure moment and stiffness of the LPCS OLIF model were higher than those of the ALSR model, especially under the extension loading conditions. In which, the maximum failure moment of ALSR fixed OLIF model was 0.88 Nm and 0.76 Nm, while that of the LPCS OLIF model was 9.79 Nm and 7.48 Nm in models with normal and osteoporotic BMD, respectively. Compared to the ALSR fixed OLIF model, failure moment of LPCS models increased by 1012.5% and 884.21% in normal and osteoporotic models, respectively. Moreover, under most physiological loading conditions, the ROM and stress values of the LPCS OLIF model were lower than those of the ALSR model and even slightly lower than those of the OLIF model with bilateral pedicle screw fixation under limited loading conditions.

Conclusions: Compared to OLIF with ALSR fixation, the newly developed LPCS OLIF cage demonstrates inherent biomechanical advantages in establishing immediate postoperative stability and reducing complications related to stress concentration. However, the conclusions of current research should still be validated through in vitro mechanical tests and clinical trials.