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. 2024 Aug 30;9(2):202-210.
doi: 10.22603/ssrr.2024-0169. eCollection 2025 Mar 27.

Advantages of Combined Use of Claw Hooks and Sublaminar Wires as the Upper Foundation of Long Fixation from the Thoracic Spine to the Pelvis in Osteoporotic Cases: A Finite Element Analysis of Proximal Junction Stress

Takuhei Kozaki  1 , Takachika Shimizu  2 , Akimasa Murata  1 , Ryuichiro Nakanishi  1 , Takahiro Kozaki  1 , Ei Yamamoto  3 , Shunji Tsutsui  1 , Mamoru Kawakami  4 , Hiroshi Yamada  1
Affiliations

Advantages of Combined Use of Claw Hooks and Sublaminar Wires as the Upper Foundation of Long Fixation from the Thoracic Spine to the Pelvis in Osteoporotic Cases: A Finite Element Analysis of Proximal Junction Stress

Takuhei Kozaki et al. Spine Surg Relat Res. .

Abstract

Introduction: This study aimed to compare the biomechanical stress at the proximal junctional aspect between the conventional pedicle screw (PS) fixation (PSF) and the low PS density fixation (LPF) method.

Methods: This study involved 10 patients, half of whom have non-osteoporosis and the other half have osteoporosis. We made two types of intact models (one is from the upper thoracic-to-pelvis model, and the other is from the lower thoracic-to-pelvis model). From the intact models, we constructed two kinds of fusion models: (1) PSF and (2) LPF. The LPF method was as follows: The claw hooks (the combination of the down-going transverse process hooks and facet hooks) were set at the upper instrumented vertebra (UIV) and sublaminar wires at the thoracic spine and PSs at the lumbo-pelvis.

Results: Upper thoracic to pelvis fixation model In non-osteoporosis, no significant difference between the PSF and LPF is found. In osteoporosis, the von Mises stresses of the vertebra body at UIV, UIV+1, and disc were significantly lower in LPF than in PSF. Lower thoracic-to-pelvis fixation model In non-osteoporosis, the average von Mises stress of the vertebral body at UIV+1 and the maximum stress at UIV were lower in LPF than in PSF; however, no significant difference was found in the others. In osteoporosis, the von Mises stress was significantly lower in LPF than in PSF.

Conclusions: The claw hooks stabilized the vertebra body at UIV firmly, and sublaminar wires reduced load translation from the fixed spine.

Keywords: finite element analysis; low pedicle screw density fixation; osteoporosis; proximal junctional kyphosis; sublaminar wires; thoracic claw hooks.

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Conflict of interest statement

Conflicts of Interest: The authors declare that there are no relevant conflicts of interest.

Figures

Figure 1.
Figure 1.
A 68-year-old female underwent spinopelvic fusion surgery for kyphoscoliosis using multiple hooks (a, b). Three years later, the alignments were preserved, and no implant failure was observed (c, d). The upper foundation of this case was claw hooks (down-going transverse process hooks and facet hooks) at T9 and facet hooks at T10 (e, f).
Figure 2.
Figure 2.
The range of motion of the lumbar spine of our finite element (FE) models was validated with a previous study.
Figure 3.
Figure 3.
Upper thoracic spine to pelvis fixation model by all pedicle screw fixation (a, b) and low pedicle screw density fixation (c, d).
Figure 4.
Figure 4.
Lower thoracic spine to pelvis fixation model by pedicle screw fixation (a, b) and low pedicle screw density fixation (c, d).
Figure 5.
Figure 5.
The setting of the claw hooks (the combination of the bilateral down-going transverse hooks and facet hooks) at T2, facet hooks at T3 (a), and sublaminar wires (b) from T4 to L1 in the upper thoracic spine to pelvis fixation model. The setting of claw hooks at T10 (c) and sublaminar wires from T11 to T12 in the lower thoracic spine to pelvis fixation model.
Figure 6.
Figure 6.
The view of the stress distribution in all pedicle screw fixation (PSF) model and low pedicle screw fixation (LPF) model. In osteoporosis, the stress concentration has occurred in the PSF but not in the LPF model. Conversely, in non-osteoporosis, the stress concentration has not made a difference between PSF and LPF.
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