Biomechanical Properties of Novel Porous Scaffold Core and Hollow Lateral Hole Pedicle Screws: A Comparative Study in Bama Pigs

TL;DR

A new type of pedicle screw with a porous scaffold design showed better stability and resistance to loosening in pig spine implants.

Contribution

The study introduces a novel porous scaffold core pedicle screw and demonstrates its superior biomechanical performance compared to existing designs.

Findings

PSCPSs showed significantly higher maximal pull-out forces than HLHPSs before and after cyclic bending.

PSCPSs exhibited better fatigue tolerance with only a 7.43% decrease in pull-out force after 800 cycles, compared to 14.89% for HLHPSs.

Both screw types buckled rather than broke in bending tests, with no significant differences in maximal bending load or modulus of elasticity.

Abstract

Screw loosening is a common complication of internal fixation of pedicle screw. Therefore, the development of a pedicle screw with low loosening rate and high biosafety is of great clinical significance. This study aimed to investigate whether the application of a porous scaffold structure can improve the stability of pedicle screws by comparing the biomechanical properties of novel porous scaffold core pedicle screws (PSCPSs) with those of hollow lateral hole pedicle screws (HLHPSs) in a porcine lumbar spine.

Thirty‐two pedicle screws of both types were implanted bilaterally into the L1–4 vertebrae of four Bama pigs, with our newly designed PSCPSs on the right and HLHPSs on the left. All the Bama pigs were sacrificed 16 weeks postoperatively, and the lumbar spine was freed into individual vertebrae. Biomechanical properties of both the pedicle screws were evaluated using pull‐out tests, as well as cyclic bending and pull‐out tests, while the mechanical properties were assessed using three‐point bending tests. The data generated were statistically analyzed using paired‐sample t‐tests and two independent sample t‐tests.

We found that the maximal pull‐out forces before and after cyclic bending of the PSCPSs (1161.50 ± 337.98 N and 1075.25 ± 223.33 N) were significantly higher than those of the HLHPSs (948.38 ± 194.32 N and 807.13 ± 242.75 N) (p < 0.05, p < 0.05). In 800 cycles of the bending tests, neither PSCPS nor HLHPS showed loosening or visible detachment, but their maximal pull‐out forces after cyclic bending tests decreased compared to those in cycles without cyclic bending tests (7.43% and 14.89%, respectively), with no statistical significance (p > 0.05 and p > 0.05, respectively). Additionally, both screws buckled rather than broke in the three‐point bending tests, with no statistically significant differences between the maximal bending load and modulus of elasticity of the two screws (p > 0.05 and p > 0.05, respectively).

Compared with the HLHPSs, the PSCPSs have greater pull‐out resistance and better fatigue tolerance with appropriate mechanical properties. Therefore, PSCPSs theoretically have significant potential for clinical applications in reducing the incidence of loosening after pedicle screw implantation.

Novel porous scaffold core pedicle screws (PSCPSs) had excellent pullout resistance and fatigue tolerance with appropriate mechanical properties. Therefore, PSCPSs theoretically had a significant potential for clinical application in reducing the incidence of loosening after pedicle screw implantation.

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