Original ArticleElimination of Subsidence with 26-mm-Wide Cages in Extreme Lateral Interbody Fusion
Introduction
Extreme lateral interbody fusion (ELIF) has become an increasingly popular minimally invasive technique in recent years for indirect spinal decompression.1 Initially described by Ozgur et al.,2 ELIF has proved to be an efficient means of treating various spinal pathologies, including low to moderate central canal, lateral recess and/or foraminal stenosis, low-grade spondylolisthesis (grade I–II), degenerative scoliosis, and degenerative disc disease (DDD).3 The lateral transpsoas approach provides anterior access to the lumbar spine, allowing for implantation of larger cages (Figure 1) compared with transforaminal lumbar interbody fusion or posterior lumbar interbody fusion.2 Another significant advantage of ELIF compared with traditional fusion procedures is the preservation of the anulus fibrosus and the anterior and posterior longitudinal ligaments during discectomy, thus maintaining segmental stability through ligamentotaxis, which offers the opportunity for “stand-alone” fusion procedures.5, 6, 7 However, some authors found higher rates of cage subsidence when ELIF was performed without additional instrumentation.8, 9 To date, 2 mm of cage settlement into the vertebral body is considered as cage subsidence.10, 11 Indirect decompression by ELIF results from restoration of native disc height and subsequent stretching and tightening of the remaining anulus, causing elongation of the posterior longitudinal ligament and distraction of the ligamentum flavum and ultimately leading to an increase of the epidural space.8, 12, 13 Significant limitations of ELIF, along with reported neurovascular complications, are anatomic limitations, subsidence, and loss of correction, decreasing the potential to sustainably restore spinal biomechanics.9, 10, 14
We previously investigated patient-related and surgery-related factors predicting successful indirect decompression in ELIF.15 Parameters unlikely to influence outcome in indirect decompression were cage position, cage type (lordotic vs. parallel), side of approach, presence of facet degeneration, spinal region (upper lumbar vs. lower lumbar spine), number of operated levels, and additional instrumentation.6, 15, 16 Implantation of wider cages solely has been found to be associated with successful and more sustained indirect decompression, as wider cages result in less subsidence, although contrary results also can be found.4, 10, 14, 17, 18, 19 However, the respective differences in radiographic outcome between cage dimensions could not yet be translated into improved clinical outcome. Cage subsidence jeopardizes segmental stability and the restoration of disc and foraminal heights, translating into indirect decompression, which consequently puts the patient at risk for recurrence of symptoms and potentially additional surgery.9, 11
Although 18-mm-wide and 22-mm-wide cages have been studied and compared with promising results, the effectiveness of the more recently introduced 26-mm-wide cages has yet to be analyzed.4, 14 Therefore, the aim of this study was first to expand on the current data and evaluate the clinical and radiographic outcome of ELIF surgeries in which 26-mm-wide cages were used.1 Second, we sought to compare these results with the results of our previous studies on 18-mm-wide and 22-mm-wide cages.4 Our hypothesis was that 26-mm-wide cages would further reduce cage subsidence in ELIF resulting in superior radiographic outcome compared with 18-mm-wide and 22-mm-wide cages. To our knowledge, this is the first study specifically analyzing 26-mm-wide cages in ELIF.
Section snippets
Materials and Methods
The study was approved by our local institutional review board, and informed consent was obtained from all patients before surgery. All studies have been performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Patient Demographics
The study enrolled 21 patients with 28 spinal levels (mean patient age 70 years ± 1.9; range, 54–85 years; 38% women) (Table 1). A positive history of smoking, diabetes, and steroid medication was present in 33%, 9.5%, and 28.6% of patients. Major indications for surgery were central stenosis (66.7%), foraminal stenosis (52.4%), degenerative scoliosis (28.6%), and spondylolisthesis (28.6%).
Surgical Details
Fusion was performed at spinal levels L1-L2, L2-L3, L3-L4, and L4-L5 in 10.7%, 42.6%, 39.3%, and 7.1% of
Discussion
The present study investigated whether it is possible to minimize subsidence in ELIF by using the widest interbody cage currently available. Additionally, the results were compared with previous studies conducted by our group on 18-mm-wide and 22-mm-wide cages in ELIF.4 It was hypothesized that 26-mm-wide cages would lead to minimal postoperative subsidence after ELIF, yielding superior radiographic outcomes compared with 18-mm-wide and 22-mm-wide cages. To our knowledge, this is the first
Conclusions
We assessed the impact of multiple parameters on radiographic subsidence, including width and height of interbody cages, anterior versus posterior positioning, parallel versus lordotic configuration, and side of approach. Of all these, only cage width has been associated with successful and more sustained indirect decompression in ELIF. Our results indicate that 26-mm-wide cages almost eliminate cage subsidence in ELIF. Compared with 18-mm-wide and 22-mm-wide cages, 26-mm-wide cages
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Conflict of interest statement: This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors. Rodrigo Navarro-Ramirez was supported by the Carol and Grace Hansen Spinal Research fund. Roger Härtl has received consulting fees from AO Spine, Brainlab, DePuy Synthes, and Lanx and support for contracted research from Baxter. Gernot Lang has received educational grants from DePuy Synthes and a travel grant from the GlaxoSmithKline Foundation. The other authors have nothing to disclose.
Gernot Lang and Rodrigo Navarro-Ramirez are co–first authors.