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Spine (Phila Pa 1976). 2013 Nov 1;38(23):2008-15. doi: 10.1097/BRS.0b013e3182a76fec.

Ti2448 pedicle screw system augmentation for posterior lumbar interbody fusion.

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  • 1*Institute of Orthopedics, General Hospital of PLA, Beijing, China ‚ĆInstitute of Spine Surgery, Guangzhou Military Area General Hospital, Guangzhou, China; and ‚Ä°Institude of Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an Shanxi Province, P. R. China.

Abstract

STUDY DESIGN:

A finite element analysis was used.

OBJECTIVE:

To evaluate the feasibility of using the Ti-24Nb-4Zr-7.9Sn (Ti2448) pedicle screw system to augment single-level posterior lumbar interbody fusion (PLIF).

SUMMARY OF BACKGROUND DATA:

The Ti-6Al-4V pedicle screw system increases the risk of adjacent disc degeneration and stress-shielding effect due to enormous rigidity. A titanium alloy with much lower elastic modulus, Ti2448, may help to resolve the complications.

METHODS:

A finite element model of intact L3-S1 was established and then validated. Single-level PLIF at L4-L5 with or without a supplementary titanium-alloy pedicle screw system was simulated. A pure moment of 7.6 Nm and a 400 N preload was applied to the finite element model of PLIF, PLIF with the Ti-6Al-4V screw system, and PLIF with the Ti2448 screw system in flexion, extension, axial rotation, and lateral bending.

RESULTS:

The axial displacement at the fusion level decreased to 64%, 72%, 84%, and 92% of screw-free status in flexion, extension, axial rotation, and lateral bending, respectively, after augmentation of the Ti2448 screw system, which was 1% to 3% lower than the performance of the Ti-6Al-4V system. The angular displacement at the fusion level with the Ti2448 system was similar to that of the Ti-6Al-4V system, only 2% lower in flexion. Compared with the Ti-6Al-4V system, the Ti2448 system suppressed the increase of intradiscal pressures at the upper adjacent disc in all bending directions, but only in extension and axial rotation at the lower adjacent disc; the maximum stress experienced by cages and screws was higher in all bending directions when augmented with the Ti2448 system.

CONCLUSION:

Using the Ti2448 screw system is suggested for augmenting single-level PLIF because it induces less disc intradiscal pressure at adjacent levels and the stress-shielding effect at implant-bone surface with stabilization performance compared with the Ti-6Al-4V screw system.

PMID:
23921332
DOI:
10.1097/BRS.0b013e3182a76fec
[PubMed - indexed for MEDLINE]
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