Elsevier

World Neurosurgery

Volume 143, November 2020, Pages e351-e361
World Neurosurgery

Original Article
Effect of Fenestrated Pedicle Screws with Cement Augmentation in Osteoporotic Patients Undergoing Spinal Fusion

https://doi.org/10.1016/j.wneu.2020.07.154Get rights and content

Objective

Osteoporosis is a well-known risk factor for instrumentation failure and subsequent pseudoarthrosis after spinal fusion. In the present systematic review, we analyzed the biomechanical properties, clinical efficacy, and complications of cement augmentation via fenestrated pedicle screws in spinal fusion.

Methods

We conducted a systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Reports appearing in the PubMed database up to March 31, 2020 were queried using the key words “cement,” “pedicle screw,” and “osteoporosis.” We excluded non-English language studies, studies reported before 2000, studies that had involved use of cement without fenestrated pedicle screws, nonhuman studies, technical reports, and individual case reports.

Results

Twenty-five studies met the inclusion criteria. Eleven studies had tested the biomechanics of cement-augmented fenestrated pedicle screws. The magnitude of improvement achieved by cement augmentation of pedicle screws increased with the degree of osteoporosis. The cement-augmented fenestrated pedicle screw was superior biomechanically to the alternative “solid-fill” technique. Fourteen studies had evaluated complications. Cement extravasation with fenestrated screw usage was highly variable, ranging from 0% to 79.7%. However, cement extravasation was largely asymptomatic. Thirteen studies had assessed the outcomes. The use of cement-augmented fenestrated pedicles decreased screw pull out and improved fusion rates; however, the clinical outcomes were similar to those with traditional pedicle screw placement.

Conclusions

The use of cement-augmented fenestrated pedicle screws can be an effective strategy for achieving improved pedicle screw fixation in patients with osteoporosis. A potential risk is cement extravasation; however, this complication will typically be asymptomatic. Larger comparative studies are needed to better delineate the clinical efficacy.

Introduction

Osteoporosis, defined as a bone mineral density that is >2.5 standard deviations less than the mean for young healthy women, is a relative contraindication for instrumented fusion surgery owing to the decreased fixation strength of pedicle screws. This will manifest by increased screw pull out, pseudoarthrosis, and construct failure. An abundance of reported data have supported the correlation between pedicle screw stability and bone mineral density.1, 2, 3

The elderly population has a high incidence of osteoporosis and also constitute a large proportion of those undergoing spinal surgery.1, 2, 3, 4 Strategies to mitigate the risk of implant failure in elderly osteoporotic patients are, therefore, exceedingly important. Several strategies are available to mitigate the effects of osteoporosis, including treatment of the underlying condition with bone induction agents such as teriparatide, using larger diameter and longer length pedicle screws, the use of expandable screws, and the use of cement augmentation, frequently with polymethylmethacrylate.

Historically, cement injection into the vertebral body was first used to provide anterior column stabilization in the setting of metastatic disease.5 The first reported case of cement use was for treatment of a vertebral body hemangioma in France in 1984.5,6 Cadaveric studies involving the use of cement augmentation for pedicle screw stabilization were performed in the late 1980s and throughout the 1990s.7, 8, 9, 10, 11 These early cadaveric studies provided promising data on the potential for cement augmentation to improve pedicle screw purchase in the osteoporotic spine.

The first reported cases of cement augmentation for improved pedicle screw fixation as a salvage technique appeared in the late 1990s.12, 13, 14 The initial approaches for cement augmentation were performed by cement injection through a tapped pedicle screw tract.15 With the advent of minimally invasive spine surgery16 and the introduction of cannulated screws, reports of the use of fenestrated screws for cement augmentation appeared in the 2000s.17,18 Fenestrated screws have the theoretical advantage of cement penetration into the vertebral body directly around the screw, with less opportunity for cement extravasation through pedicle breaches.15

The use of cement augmentation, however, is not without risk. Cement augmentation has been associated with several neurologic and cardiopulmonary complications. Specifically, cement extravasation into the epidural space or neural foramen can cause neurologic injury. The cement can also embolize into the venous system via the epidural veins and travel to the right atrium and pulmonary arteries, potentially causing right heart strain or respiratory failure.19,20

The goal of the present review was to systematically identify and analyze the reported data on cement-augmented fenestrated pedicle screws, with specific attention to the biomechanics, outcomes, and complications.

Section snippets

Literature Search and Inclusion Criteria

We conducted a systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.21 Using the PubMed database, we first identified relevant studies using the search terms “cement” AND “pedicle screw” AND “osteoporosis” that had been reported through March 31, 2020. We elected to use the PubMed database because of its broad accessibility, author familiarity, and access to ahead-of-print citations with the most up-to-date reported information.

Study Selection

The database search identified 120 studies. After title and abstract review, 81 studies were excluded, and the full text of 39 reports was reviewed, which resulted in the exclusion of another 16 studies. After a review of the references, another 2 studies were included. The reason for study exclusion included non-English language, publication before 2000, use of cement without fenestrated pedicle screws, lack of cement use, nonhuman study, technical report, and individual case report. A total

Discussion

Given the increasingly elderly population with symptomatic degenerative disease, the ability to treat patients with osteoporosis is essential. The introduction of fenestrated pedicle screws has facilitated the broader use of cement augmentation in spinal fusion, especially because cement augmentation can now be performed using minimally invasive surgical techniques.

One of the greatest concerns with osteoporotic bone is the loss of screw fixation and subsequent pull out with construct failure.

Conclusions

The use of cement-augmented fenestrated pedicle screws is a recent innovation that has been shown to improve screw fixation strength in osteoporotic bone. The results from the included studies have suggested that cement-augmented fenestrated pedicle screws have an adequate safety profile. However, extravasation of cement can be common. Despite this complication, the patients with cement extravasation were largely asymptomatic according to most reports and the extravasation was not clinically

CRediT authorship contribution statement

Yamaan S. Saadeh: Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Writing - original draft, Writing - review & editing. Kevin N. Swong: Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Writing - original draft, Writing - review & editing. Timothy J. Yee: Formal analysis, Validation, Writing - original draft, Writing - review &

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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