Original ArticleEvaluating Outcomes of Stand-Alone Anterior Lumbar Interbody Fusion: A Systematic Review
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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2022, Spine JournalCitation Excerpt :Anterior lumbar interbody fusion (ALIF) is an appealing technique as it allows for the increase of disc height and lumbar lordosis, enhances fusion potential, decompresses foramina, and improves sagittal and coronal balance, thereby restoring normal anatomy and stability, while conserving posterior spinal elements [1–9].
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2022, World NeurosurgeryCitation Excerpt :First described by Capener in 1932, ALIF provides direct anterior access to the lumbar disc space via a muscle-splitting retroperitoneal approach, allowing for less disruption of the posterior spinal elements, with the most-cited approach-specific complications relating to vascular and visceral injury when achieving exposure.1,6,18 The technique was supplemented with posterior pedicle screw fixation to address concerns of posterior instability and inconsistent fusion rates.19 Through direct anterior access, the ALIF approach has increased in popularity, likely secondary to its efficient discectomy, enhanced visualization and access to disc space (which facilitates removal of disc material and detailed preparation of lumbar end plates), and favorable geometry, allowing for angulated placement of lordotic stabilizing devices (providing both greater disc height and lordotic restoration compared with a posterior approach).1,12
Clinical and radiologic outcomes of stand-alone anterior lumbar interbody fusion at L4-L5
2021, Interdisciplinary Neurosurgery: Advanced Techniques and Case ManagementCitation Excerpt :Therefore, it is difficult to generalize the effect of ALIF on pelvic parameters, with differences across studies possibly due to the heterogeneity of indications, procedures, and levels fused. Recent ALIF implant designs demonstrated excellent fusion rates [39,40] with minimal complications [40–42]. The present study achieved a fusion rate of 91%, and reported only 3 (6%) minor complications (2 intraoperative wounds and 1 hematoma), all of which healed successfully, with these three patients having a postoperative ODI score that improved by 16 to 26 points.
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.