Oblique lateral interbody fusion: role of the elastic modulus of the cage material in mechanically induced osteogenesis.

BACKGROUND AND

OBJECTIVE

The elastic modulus of cage material (cage-E) is a key determinant of fusion outcomes in oblique lateral interbody fusion (OLIF), as it modulates the efficiency of mechanically induced osteogenesis (EMIO). Here, we establish a logarithmic predictive model linking cage-E to EMIO and delineate the underlying biomechanical mechanisms via computational biomechanical analysis.

METHODS

A customized mechano-regulation algorithm was applied to finite element models of the L4/5 OLIF construct to simulate the iteration of tissue differentiation and regeneration, which was driven by mechanical stimulation (MechSt). The regenerative bone fraction at the final iteration was defined as EMIO. A total of 23 cage-E values ranging from 0.1 GPa to 110 GPa were evaluated.

RESULTS

As cage-E increased from 0.1 GPa to 110 GPa, the OLIF construct stiffness increased from 3.29 to 6.02 N/mm to 4.95-6.13 N/mm across iterations; the stress-shielding MechSt region expanded from 0 to 0.92% to 9.75-53.67%, whereas the stress-growth MechSt region contracted from 100 to 99.08% to 90.25-46.33%. Correspondingly, EMIO declined from 92.05% to 55.44%. Logarithmic regression revealed strong correlations (R²=0.72-0.89) between cage-E and construct stiffness, MechSt distribution, and tissue regeneration.

CONCLUSIONS

Reduced cage-E enhances OLIF EMIO via a defined cascade biomechanical mechanism: cage-E logarithmically regulates construct stiffness, with lower cage-E mitigating stress shielding and preserving the osteogenic MechSt domain, in turn promoting osteoblastic differentiation of mesenchymal stem cells and bone regeneration. The established logarithmic model characterizes the cage-E-EMIO relationship and serves as a potential tool for cage-E screening to optimize OLIF fusion outcomes.