Biomechanical effects of polyaxial pedicle screw fixation on the lumbosacral segments with an anterior interbody cage support

Chen, Shih Hao; Lin, Ray–Ming; Chen, Hsiang Ho; Tsai, Kai Jow

doi:10.1186/1471-2474-8-28

Cited by 21 publications

(16 citation statements)

References 28 publications

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“…When using monoaxial screws, the addition of an intermediate forces the surgeon to bend the connecting rod to accommodate the additional screw. Polyaxial screws, on the other hand, facilitate the installation of the connecting rod, and their biomechanical properties have been reported in several studies 14–1623. Stanford et al 15.…”

Section: Discussionmentioning

confidence: 99%

Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study

Wang

Liu

et al. 2012

IJOO

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Background:Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing lumbar fracture, but there is a paucity of biomechanical studies to support the claim. The aim of this study was to evaluate the effect of adding intermediate pedicle screws at the level of a fracture on the stiffness of a short-segment pedicle fixation using monoaxial or polyaxial screws and to compare the strength of monoaxial and polyaxial screws in the calf spine fracture model.Materials and Methods:Flexibility of 12 fresh-frozen calf lumbar spine specimens was evaluated in all planes. An unstable burst fracture model was created at the level of L3 by the pre-injury and dropped-mass technique. The specimens were randomly divided into monoaxial pedicle screw (MPS) and polyaxial pedicle screw (PPS) groups. Flexibility was retested without and with intermediate screws (MPSi and PPSi) placed at the level of fracture in addition to standard screws placed at L2 and L4.Results:The addition of intermediate screws significantly increased the stability of the constructs, as measured by a decreased range of motion (ROM) in flexion, extension, and lateral bending in both MPS and PPS groups (P < 0.05). There was neither any significant difference in the ROM in the spines of the two groups before injury, nor a difference in the ROM between the MPSi and PPSi groups (P > 0.05), but there was a significant difference between MPS and PPS in flexion and extension in the short-segment fixation group (P < 0.05).Conclusions:The addition of intermediate screws at the level of a burst fracture significantly increased the stability of short-segment pedicle screw fixation in both the MPS and PPS groups. However, in short-segment fixation group, monoaxial pedicle screw exhibited more stability in flexion and extension than the polyaxial pedicle screw.

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Section: Discussionmentioning

confidence: 99%

Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study

Wang

Liu

et al. 2012

IJOO

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Section: Discussionmentioning

confidence: 99%

Infected primary non-Hodgkin lymphoma of spine

Liu

Tsai

et al. 2012

IJOO

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Primary bone lymphoma (PBL) comprises less than 5% of all malignant bone tumors and almost 7% of all extranodal lymphomas. Only 1.7% of all PBLs have been reported to involve the vertebrae. In our case, osteomyelitis was accidentally found during surgery, which might have resulted in the rapid collapse of vertebral body. This is the first report on primary lymphoma of the vertebrae with superimposed osteomyelitis in the English literature to the best of our knowledge. The patient reported here received anterior vertebrectomy and posterior interbody fusion with instrumentation for spinal instability. Tumor mass and the necrotic debris were removed. After the procedure, the patient received treatment with antibiotics and six cycles of chemotherapy. This case reminds us the possibility of hematologic seeding of bacteria in the tissue, especially with tumor necrosis. We suggest percutaneous needle aspiration for pathology and culture before making a decision whether or not to proceed with surgical decompression for fear of missing the occult bacterial infection.

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“…Quigley et al [5] reported that offset positioning of interbody cages places higher strains upon posterior instrumentation than a central cage, and lower load to failure than an anteriorly placed cage. In another study, Chen et al [6] described how polyaxial screw systems used in conjunction with anterior cage support yield higher contact ratios, compressive stiffness and flexion stiffness of spinal constructs than monoaxial screw systems do in the same model when the spinal segment is set at large lordotic angles. The authors used strain gauges attached to the posterior surface of the cage and to the posterior rod connecting the pedicle screws.…”

Section: Clinical Applicationsmentioning

confidence: 96%