The contribution of the cortical shell to pedicle screw fixation

Pelletier, Matthew H.; Bertollo, Nicky; Al-Khawaja, Darweesh; Walsh, William R.

doi:10.21037/jss.2017.06.07

Cited by 15 publications

(10 citation statements)

References 47 publications

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“…In addition to insertion torque and POF, there are other methods of measuring implant fixation force, such as the toggle test, 44 which is a fixation force test for cyclic motion that has different characteristics from the above methods. There are also attempts to predict from imaging parameters, and there are studies that attempt to define fixation force from dual‐energy X‐ray absorptiometry 45 and CT imaging values.…”

Section: Discussionmentioning

confidence: 99%

Laser resonance frequency analysis of pedicle screw stability: A cadaveric model bone study

Nakashima

Mikami

Kikuchi

et al. 2021

Journal Orthopaedic Research

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There is no evaluation method currently available to assess intraoperative pedicle screw fixation (PSF) strength. In this study, we established a laser-based resonance frequency analysis (RFA) system with high-speed, noncontact, quantitative measurements of PSF. Clinical investigations in the future can assess surgical failure risk of implants. We investigated the characteristics of the laser RFA and compared them with the conventional methods. We inserted a pedicle screw in the vertebral pedicle of human cadaver or model bone, followed by screw pull-out, peak torque, implant stability quotient (ISQ) value obtained by the magnetic dental RFA system, and fixation force of laser RFA. We compared the outcomes using best-fit linear or logarithmic approximations. For the model bone study, the resonance frequency (RF) versus peak torque/pull-out force (POF) demonstrated strong correlations using logarithmic approximation (vs. peak torque: R = 0.931, p < .001, vs. POF: R = 0.931, p < .001). RF strongly correlated with the ISQ value using linear approximation (R = 0.981, p < .001). For the cadaveric vertebrae study, the correlation coefficients between RF and the peak torque/POF were significant regardless of approximation method (peak torque: logarithmic: R = 0.716 vs. linear: R = 0.811; p < .001) (POF: logarithmic: R = 0.644 vs. linear: R = 0.548; p < .05). Thus, the results of this study revealed a constant correlation between RFA and conventional methods as a measurement validation, predicting favorable support for intraoperative PSF. RFA has the potential to be a new index for evaluating the implant fixation force.

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Section: Discussionmentioning

confidence: 99%

Laser resonance frequency analysis of pedicle screw stability: A cadaveric model bone study

Nakashima

Mikami

Kikuchi

et al. 2021

Journal Orthopaedic Research

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“…This condition should be considered when comparing the results with other studies. Various authors used a unilateral hinge or ball joint instead of a rigid connection between the rod and the machine actuator and expected to observe a craniocaudal loosening of the screws [8,9,[25][26][27][28]. Consequently, the applied load did not simulate the situation of dorsal rigid instrumentation, limiting the comparison to the conclusions of the previous studies on primary stability at the boneto-implant interface.…”

Section: Discussionmentioning

confidence: 99%

Complex biomechanical properties of non-augmented and augmented pedicle screws in human vertebrae with reduced bone density

Schulze

Riesenbeck

Wähnert

et al. 2020

BMC Musculoskelet Disord

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Background: In osteoporotic bone, the quality of the bone-to-implant interface is decreased, which may lead to early implant failure. Screw anchorage can be improved by augmentation. This effect is mainly investigated with a pull-out test. To our knowledge, the effect of cement augmentation in an in vivo physiological setup focusing on screw movement has not been investigated to date. The aim of this work was to investigate and compare augmented and native screw behavior in a physiologically related setup. Methods: Twelve fresh-frozen human lumbar vertebrae were divided into two groups. Each vertebra was bilaterally instrumented with either non-augmented or augmented pedicle screw systems and loaded in a recently developed test setup that provided cyclic conditions comparable to a physiological gait. The cyclic loading should test the primary implant stability, comparable to the postoperative period of two months in a worst-case scenario in the absence of osseous remodeling. Screws were tracked optically, and screw movement and failure patterns were observed. Results: Mutual influence between the left and right sides resulted in a successive, rather than simultaneous, failure. Augmentation of the screws in vertebrae with poor bone quality reduced screw subsidence and thus improved the rigidity of the screw-to-implant interface by up to six-fold. The non-augmented condition was significantly related to early screw failure. Conclusions: Pedicle screw system failure involves a complex bilateral-coupled mechanism. The cyclic loading based on physiological conditions during walking has allowed the postoperative conditions and clinical failure mechanisms to be simulated in vitro and clarified. Future implant systems should be investigated with a physiologically related setup.

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“…The toggling effect can be further exacerbated if there is loss of bone mineral density which allows the screws to pivot easily with movements and torsion of the spine. These motions can also result in loss of cortical bone which weaken the screw fixations. Eventually, this can lead to proximal and distal screw loosening and affect the cemented region as in this case.…”

Section: Discussionmentioning

confidence: 94%

Technical Note: Pedicle Cement Augmentation with Proximal Screw Toggle and Loosening

Choy

Walsh

Phan

et al. 2019

Orthopaedic Surgery

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Background Cement augmentation is a technique used to increase the stability and purchase of pedicle screws in poor quality bone. Various methods can be applied for cement delivery, such as cement injection before screw placement and the use of fenestrated screws. However, potential problems can arise with the use of cement augmentation. Case Presentation A 66‐year‐old man with a lower trunk deformity, severe kyphosis, and sagittal imbalance following fusion (L2‐5), with minimal comorbidities, was referred to our unit 9 months after surgery. Pain and progressive kyphosis were investigated clinically and radiographically with computed tomography (CT) scans to assess the status of the hardware and fusion. CT imaging revealed that cement was present only at the distal tip of the fenestrated screws at the L4 vertebral level. A non‐union was present along with loosening and a halo around the body of the pedicle screws, and there was evidence of pullout of inferior screws. Conclusion Single‐level cement augmentation of pedicle screw in a posterior construct and distal tip cement augmentation of the screw results in a fixed pivot point. Micromotion in cranio‐caudal loading during flexion and extension may result in screw toggling with the single‐level cement‐augmented tip as a fulcrum. This may cause screw loosening, which can lead to pullout and loss of construct stability. The halo around the screw suggests bone loss and/or a fibrous tissue interface, which further complicates revision surgery. Stress shielding and polymethylmethacrylate cement present additional difficulties. The findings of this technical note question the risks and benefits of cement‐augmented fenestrated pedicle screw fixation for spinal fusion. Although incidences of such cases are uncommon, surgeons should perform this technique with caution. Accurate restoration of lumbar lordosis during index procedures is important to minimize the risk of construct failure.

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The contribution of the cortical shell to pedicle screw fixation

Cited by 15 publications

References 47 publications

Laser resonance frequency analysis of pedicle screw stability: A cadaveric model bone study

Laser resonance frequency analysis of pedicle screw stability: A cadaveric model bone study

Complex biomechanical properties of non-augmented and augmented pedicle screws in human vertebrae with reduced bone density

Technical Note: Pedicle Cement Augmentation with Proximal Screw Toggle and Loosening

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