Pullout strength of reinserted pedicle screws using the previous entry point and trajectory

Huang, Xuanwu; Huang, Zixiang; Xu, Liang‐Guo; Zhang, Meichao; Zhang, Hui

doi:10.1186/s13018-019-1240-8

Cited by 7 publications

(1 citation statement)

References 21 publications

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“…For repositioned screws, the pullout strength in sequence from smallest to largest, was 80%, 60%, 40%, and 20% overlap. The most important reason for this result was the difference in the degree of engagement between the screw and the bone, 6,30,31 the more the screw engaged with the bone, the larger the pullout strength. The screw path left when the unsatisfactory screw was removed resulted in less contact between the repositioned screw and the bone, which further led to a lower pullout strength of the screw, as well as decreased the time and displacement required to achieve the maximal pullout force 12,13 …”

Section: Discussionmentioning

confidence: 99%

Screw Pullout Strength After Pedicle Screw Reposition: A Finite Element Analysis

Huang²,

Hao³

et al. 2022

Spine

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Research design. Finite element analysis based on computed tomography images from the lumbar spine. Objective. Determined the pullout strength of unsatisfactorily placed screws and repositioned screws after unsatisfactory place in lumbar spine surgery. Background. Pedicle screws are widely used to stabilize the spinal vertebral body. Unsatisfactory screws could lead to surgical complications, and may need to be repositioned. Screw removal and reposition, however, may decrease pullout strength. Methods. We conducted a three-dimensional finite element analysis based on high-resolution computed tomography images from a 39-year-old healthy woman. Pullout strength was determined with the screw placed in different orientations at the same entry point (as selected by the Magerl method), as well as after removal and reposition. The material properties of the vertebral body and the screw were simulated by using grayscale values and verified data, respectively. A load along the screw axis was applied to the end of the screw to simulate the pullout. Results. The pullout strength was 1840.0 N with the Magerl method. For unsatisfactorily placed screws, the pullout strength was 1500.8 N at 20% overlap, 1609.6 N at 40% overlap, 1628.9 N at 60% overlap, and 1734.7 N at 80% overlap with the hypothetical screw path of the Magerl method. For repositioned screws, the pullout strength was 1763.6 N, with 20% overlap, 1728.3 N at 40% overlap, 1544.0 N at 60% overlap, and 1491.1 N at 80% overlap, with the original path. Comparison of repositioned screw with unsatisfactorily placed screw showed 14.04% decrease in pullout strength at 80% overlap, 5.21% decrease at 60% overlap, 7.37% increase at 40% overlap, and 17.51% increase at 20% overlap, with the screw path of the Magerl method. Conclusions. Removal and reposition increased the pullout strength at 20% and 40% overlap, but decreased the pullout strength at 60% and 80% overlap. For clinical translation, we recommend removal and reposition of the screw when the overlap is in the range of 20% to 40% or less. In vitro specimen studies are needed to verify these preliminary findings.

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Section: Discussionmentioning

confidence: 99%

Screw Pullout Strength After Pedicle Screw Reposition: A Finite Element Analysis

Huang²,

Hao³

et al. 2022

Spine

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Clinical outcomes of short rod technique in posterior lumbar interbody fusion surgery: a minimum of 2-year follow-up

Yang,

Pu,

Liu

et al. 2023

Eur Spine J

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We rst introdue a novel entry point of pedicle screws (Short Rod Technique, SRT), which could avoid violation of superior facet and has been veri ed as a safe screw placement method. The aim of this study is to detcte the clinical outcomes of SRT in posterior lumbar interbody fusion (PLIF) surgery. Methods 89 patients who received SRT and 109 patients who received PLIF surgery with regular entry point of pedicle screws were recruited with a minimum of 2-year follow-up. Patientes were further divided into three groups according to the number of fusion segments, and clinical outcomes including surgical variables, radiological parameters and HRQOL were analyzed and compared. ResultsThe length of wound and the length of rods was sigi cantly shorter in SRT group in both patients fused with single segment, two segments and three segments, respectively. Less intraoperative blood loss was observed in SRT group in patients fused with single segment and two segments, rather than three segments. Less degenerations of upper adjacent segment were observed in SRT group in both patients fused with single segment and three segments. In addition, less postoperative wound pain was observed in PLIF surgery with SRT group in patients fused with two and three segments. ConclusionSRT was an effective technique and good clinical outcomes were observed, especially for the reduction of the occurrence of upper ASD in PLIF surgery with single segment and three segments. We hope this article could provide a novel method for spinal surgeons in PLIF surgery.

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Gandhi¹,

Phillips²

2022

Revision Lumbar Spine Surgery

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Pullout strength of reinserted pedicle screws using the previous entry point and trajectory

Cited by 7 publications

References 21 publications

Screw Pullout Strength After Pedicle Screw Reposition: A Finite Element Analysis

Screw Pullout Strength After Pedicle Screw Reposition: A Finite Element Analysis

Clinical outcomes of short rod technique in posterior lumbar interbody fusion surgery: a minimum of 2-year follow-up

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