Elsevier

World Neurosurgery

Volume 104, August 2017, Pages 259-271
World Neurosurgery

Original Article
Evaluating Outcomes of Stand-Alone Anterior Lumbar Interbody Fusion: A Systematic Review

https://doi.org/10.1016/j.wneu.2017.05.011Get rights and content

Background

Stand-alone anterior lumbar interbody fusion (ALIF) is an effective surgical approach for selected spinal pathologies. It avoids the morbidity and complications associated with instrumented ALIF, such as plate fixation and the traditionally used posterior approach. Despite improved disc space visualization and clearance, the associated posterior instability and increased risk of nonfusion present major challenges to this approach. The integral cage design aims to address these challenges by providing the necessary stabilization through intracorporeal screws. However, there is limited and controversial data available for stand-alone ALIF and integral cage fixation. To our knowledge, this is the first systematic review to evaluate recent findings on outcomes of stand-alone ALIF devices to explore areas of controversy and identify directions for future research.

Methods

Two reviewers conducted independent, systematic literature searches for appropriate studies in 5 electronic databases as per Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies were filtered by the use of specified selection criteria, particularly exclusion of studies with supplementary fixation to ALIF and studies published before the year 2000. A total of 17 studies met the criteria, and their data were comprehensively extracted and analyzed.

Results

The current literature is supportive of stand-alone ALIF due to acceptable clinical outcomes, promising fusion rates and disc height restoration. However, data and outcomes remain preliminary, and there are numerous areas of controversy.

Conclusions

There is evidence for the efficacy and safety of stand-alone ALIF. However, the extent of improvement based on specific indications for surgery remains unclear. Further investigation utilizing more methodologically rigorous studies of long-term outcomes is necessary to address these issues.

Introduction

Lumbar interbody fusion is an effective intervention, with reasonable clinical and radiologic outcomes for certain symptomatic spinal pathologies, particularly degenerative diseases. Common indications for surgery include degenerative disc disease (DDD), low-grade spondylolisthesis, and foraminal stenosis.1 The prevalence of anterior lumbar interbody fusion (ALIF) has increased dramatically in the last 2 decades, with 2-fold increases in the Australian private sector and the United States disproportionate to the aging population, and it is correlated potentially with the increase in access to magnetic resonance imaging and new cages.2, 3 Although posterior approaches are successful, they are correlated with greater morbidity, including paravertebral musculature disruption, sagittal imbalance, and pseudarthrosis.4, 5 This sparked the advancing development of alternate approaches, including the anterior approach (ALIF) in 1932.6, 7

ALIF allows for improved visualization and efficient discectomy to target discogenic pain directly, an angulated approach to allow the placement of stabilizing lordotic devices, increased bone graft contact area, and better fusion rates.7, 8, 9, 10 However, this approach requires extensive peritoneal and vascular manipulation and distraction, particularly at more caudal levels, because of the aortic bifurcation in addition to other complications such as subsidence, retrograde ejaculation, and adjacent segment degeneration.1, 9, 11, 12, 13 Also, ALIF is contraindicated in patients with unfavorable vascular, abdominal, and spinal pathologies and anatomies.8

Troublingly, posterior instability in ALIF may impair fusion, as seen with the controversial fusion rates reported in literature, necessitating additional instrumentation.6, 9, 14, 15, 16 ALIF with anterior tension band plating or posterior pedicle screw fixation has demonstrated similar outcomes to instrumented posterior lumbar interbody fusion (PLIF),15, 17, 18 but the increased dissection may risk implant failure and adjacent-segment disease.6, 9, 15, 19 Thus, stand-alone ALIF, with the use of a threaded device or intracorporeal “integrated” screws without additional instrumentation, was developed to address the limitations of instrumented ALIF,20 following earlier threaded or tapered stand-alone cages.21, 22, 23 These integral fixation devices demonstrated biomechanical stabilization and were favorable to mixed outcomes in clinical studies.13, 19, 24, 25, 26, 27

The current literature supports stand-alone ALIF, with reports of reduced pain, disability, and, with some contention, promising fusion rates and disc height restoration associated with the technique. However, the data and outcomes remain preliminary, and there are numerous areas of controversy.4, 7, 9, 13, 22, 23, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 For example, individual studies often have small sample sizes of ≤50 subjects and heterogeneously cover diverse outcomes. To address these unresolved questions,14 we conducted a systematic review of original studies published since the year 2000 to analyze outcomes of stand-alone ALIF in modern practice and draw conclusions regarding clinical and radiologic efficacy and safety of this technique.

Section snippets

Methods

Systematic literature searches for stand-alone ALIF outcomes were performed in 5 electronic databases, including Ovid Medline, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and EBM Reviews. Variations of appropriate Medicine Subject Heading terms and key words were used to increase search sensitivity, including “Spinal Fusion/,” “lumbar vertebrae/,” “exp treatment outcome/,” “anterior lumbar interbody fusion,” and “stand-alone” in conjunction

Studies Evaluating Stand-Alone ALIF

A total of 83 studies initially were identified through 5 electronic database searches and from other sources such as reference lists (Figure 1). After we excluded duplicate or irrelevant references, 32 potentially relevant articles remained. Detailed evaluation of these articles ultimately yielded the 17 studies to be used for assessment of stand-alone ALIF. Study characteristics are summarized in Table 1.4, 9, 13, 22, 23, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 39

Discussion

Although there are studies reporting data on the safety and efficacy of stand-alone ALIF, the rigor and cohort sizes of these studies are limited. Of the 17 studies included in this systematic review from the last 15 years of literature, only 3 RCTs were identified. They compared Stabilis SAC and BAK cages,28 stand-alone ALIF and lumbar disc arthroplasty,29 and threaded InterFix device and femoral ring allograft.30 These respectively scored 8, 8, and 7 (maximum and ideal being 11) on the PEDro

Conclusions

There currently exists a reasonable body of literature that reports outcomes for stand-alone ALIF for the treatment of various pathologies, most commonly DDD and/or spondylolisthesis. Although there is general consensus that stand-alone ALIF results in positive functional and radiographic outcomes, key studies reported the opposite leading to dissimilitude in the extent to which this is true. Further studies, using more robust methodology, are required to investigate the efficacy and safety of

Acknowledgments

Dr. Prashanth Rao provided insight into the study design and feedback on some early drafts.

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    Conflict of interest statement: Dr. Ralph Mobbs is a consultant and design surgeon for Stryker, Kasios Biomaterials, A-Spine Asia, and K2M. There are no other financial or other conflicts of interest in relation to this research and its publication.

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