Short- and Mid-Term Outcomes Following ALIF and TLIF in L5-S1 Isthmic Spondylolisthesis Patients

Discussion

Multiple surgical approaches have been devised to treat isthmic spondylolisthesis; however, a definitive consensus on the optimal technique remains elusive. ALIF and TLIF stand out as the most commonly used techniques utilized for addressing isthmic spondylolisthesis, with each technique carrying distinct risks and benefits. ALIF may be performed as a stand-alone procedure or in combination with a posterior pedicle screw construct. However, performing ALIF alone increases the risk of instrument failure.12 In the context of isthmic spondylolisthesis, our goal is to restore the spine’s proper alignment and rebuild lumbar stability. Therefore, ALIF with posterior instrumentation creates circumferential fixation, thus enhancing stability and promoting interbody fusion. On the other hand, TLIF techniques require dissection of the paravertebral lumbar musculature, with insufficient exposure of the intervertebral disc and inadequate correction of lumbar lordosis. Furthermore, there is a higher risk of dural tears or cerebrospinal fluid leakage.9,13,14 The primary objective of the present study was to compare the medical and surgical complications of ALIF and TLIF treatments for L5 to S1 isthmic spondylolisthesis.

Many sources suggest that ALIF is associated with a higher incidence of deep vein thrombosis, gastrointestinal complications, and anemia, even with a 1.5 times higher mortality rate compared with posterior approaches.15,16 During anterior approach surgery, there are varying degrees of disruption to the abdominal tissues when exposing the surgical field. The traditional method for performing ALIF involves placing the patient in a supine position while using an inflated back cushion to enhance the lumbar lordosis. The procedure is carried out through a retroperitoneal approach. Although ALIF approaches offer wider access to the disk space, the dissection involves considerable potential risks due to the exposure of major vessels, ureter, organs, and the hypogastric plexus. Our data confirmed that there is an increased occurrence of ileus in the ALIF group. A retrospective database analysis conducted by Fineberg et al reported an increased incidence of postoperative ileus with anterior approaches for lumbar fusion.17 Beyond that, the incidence rates of complications, such as pneumonia, deep vein thrombosis, pulmonary embolism, sepsis, and others, were not significantly different between ALIF and TLIF. Additionally, the incidence rates of cerebrovascular accidents, delirium, and myocardial infarctions also did not demonstrate significant differences.

The 2013 North American Spine Society guidelines on the diagnosis and treatment of isthmic spondylolisthesis indicated that there was currently insufficient evidence to suggest which surgical approach is more advantageous for improving long-term prognosis in adult patients undergoing surgical treatment. So far, several large-scale retrospective reviews and meta-analyses have emphasized the respective complication characteristics of anterior and posterior surgical approaches, with no significant differences in terms of reoperation rates, nerve root injuries, and infection rates.16–19 There are also differing findings. Alhammoud et al, through a meta-analysis, arrived at results showing a higher incidence of surgical site infections, dural injuries, and implant misplacements in posterior approach surgeries.20 Phan et al also demonstrated that TLIF carries a higher risk of dural tear or cerebrospinal fluid leakage.13 However, our results indicated that there were no clear differences in rates of infection, nerve root injury, dural tear, or wound complications.

Alhammoud et al also found that there was no significant difference in fusion rate between ALIF and TLIF approaches.20 Alhauge et al found no significant difference in reoperation rates between ALIF and TLIF for isthmic spondylolisthesis,21 consistent with our findings. However, they noted that the subgroup sample was too small to yield statistically robust conclusion. Nevertheless, according to the clinical guidelines on isthmic spondylolisthesis from the North American Spine Society, circumferential fusion has been identified as capable of improving clinical outcomes in adult patients and achieving higher radiographic fusion rates.1 At the same time, there is also a large amount of literature showing that for the restoration of lumbar lordosis, ALIF is superior to TLIF.13,14,22,23 Nonetheless, Prost et al concluded that ALIF provides faster relief of postoperative low back pain than TLIF, but there are no significant clinical differences between techniques. Despite better restoration of disc height and lumbar lordosis in the ALIF group, there was no difference in the restoration of global lordosis.9 Similarly, Thompson et al also found similar long-term reductions in pain and functional disability between ALIF and TLIF. Additionally, they noted that ALIF patients experienced faster reductions in pain and disability within 1 year.24

While some literature has shown strong evidence that ALIF and TLIF have similar rates of reoperation,18,19 other reviews demonstrated that TLIF has a higher reoperation rate compared with ALIF.7,20 This reason could be due to the bigger footprint of ALIF cages, resulting in greater stability, hence leading to fewer instances of internal fixation failure. However, in our study, no significant differences were found in terms of reoperation rate and instrument failure rate. The reoperation rate mainly depends on instrumentation failure and pseudarthrosis. This is likely explained by the fact that both techniques involve anterior column support using interbody cages, as well as posterior stability with pedicle screws, resulting in similar circumferential biomechanical stability. Javernick et al discovered that in TLIF, a unilateral transforaminal approach can remove around 69% of disc volume, while a bilateral approach can remove approximately 80% of the volume.25 They concluded that the removal of disc material through unilateral TLIF was sufficient to achieve a solid and stable joint fusion while minimizing neural retraction and dural exposure. The similar reoperation rates between TLIF and ALIF may be attributed to TLIF having sufficient biomechanical stability and removing an adequate volume of intervertebral disc material.

One important consideration when selecting between ALIF and TLIF is cost. ALIF has been shown to be associated with higher costs compared with posterior fusion alone,16,26 primarily due to longer operative times, the need for changing patient positions during surgery, and the increased cost of implants and BMP usage. Moreover, ALIF often requires coordination with an access surgeon, which can lead to scheduling challenges and potential delays, further increasing resource utilization. These additional costs contribute to a higher overall financial burden. While ALIF may offer superior outcomes in specific cases, the increased resource utilization should be carefully considered in the context of patient care and healthcare economics. Future research should continue to investigate strategies for reducing these costs without compromising patient outcomes, particularly in healthcare systems where resource allocation is critical.

This study leverages the strength of large national databases, enabling the examination of rare conditions on a grand scale, which is a challenge for single institutions. With 1656 patients, our study avoids the pitfalls of small sample sizes and regional biases common in single-center studies. The PearlDiver database stands out with its capability to track postoperative patient data longitudinally, unlike databases like the National Inpatient Sample and National Surgical Quality Improvement Program, which can only monitor complications occurring during the hospital stay or within 30 days postsurgery. These extensive data offer a reliable source of both short and mid-term outcomes, making it a valuable reference for surgeons and patients evaluating surgical treatments for isthmic spondylolisthesis.

Unfortunately, the use of a large retrospective database has inherent limitations. The study’s reliability hinges on the precision of database coding, and though human error might lead to coding inaccuracies, it is estimated to affect only about 1.1% of all entries.27 Our comprehensive multivariate regression analysis helps mitigate some coding-related biases. Still, it cannot account for variables outside the database, such as operative time, blood loss, minimally invasive vs traditional open spine surgery, use of hyperlordotic cage, and most importantly classification/grade of isthmic spondylolisthesis, which might influence the results. Furthermore, radiographical and patient-reported outcomes could not be assessed due to the nature of nongranularity of the database, and those could have provided additional insights into the course of development of complications, including nonsignificance in reoperation rate. It is important to recognize that both techniques are essential to the development of the surgical treatments of lumbar pathologies, with each offering unique advantages and disadvantages. Therefore, the spine surgeon should choose the superior technique based on patient-specific factors; clinical judgment should encompass a patient’s unique anatomy as well as certain medical comorbidities/history that might further predispose a patient to surgical complications such as ileus.