Ti2448 pedicle screw system augmentation for posterior lumbar interbody fusion.
METHODS
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).


BACKGROUND
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.


CONCLUSIONS
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.
*Institute of Orthopedics, General Hospital of PLA, Beijing, China †Institute of Spine Surgery, Guangzhou Military Area General Hospital, Guangzhou, China; and ‡Institude of Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an Shanxi Province, P. R. China.
Zheng
Z
Wang
Suochao
S
Fu
Zi-Xiang
ZX
Wu
Yang
Y
Zhang
Wei
W
Lei
D000497:Alloys; D001696:Biomechanical Phenomena; D001863:Bone Screws; D003198:Computer Simulation; D055119:Elastic Modulus; D005240:Feasibility Studies; D020342:Finite Element Analysis; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008954:Models, Biological; D011474:Prosthesis Design; D015203:Reproducibility of Results; D013123:Spinal Fusion / Q000295:instrumentation*; D013314:Stress, Mechanical; D014025:Titanium
D000497:Alloys; C031462:titanium alloy (TiAl6V4); D014025:Titanium