Lower back pain, an important symptom of degenerative lumbar disease (DLD), is common in patients over 65 years1. Other symptoms of DLD include radiculopathy and claudication. When non-surgical treatment fails, surgical decompression or, if indicated, interbody fusion of the spine may be a viable treatment option2. Several techniques and approaches have been developed to achieve interbody fusion or decompression of the segment. Traditional approaches include posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF). Approaches to the lumbar spine are illustrated in Figure 1.

Figure 1: Different approaches to the lumbar spine for interbody fusion12. Overview of the different approaches used for lumbar interbody fusion. LLIF is a trans-psoas approach, and OLIF is a pre-psoas approach. Please click here to view a larger version of this figure.
Over the last decades, minimally invasive techniques for interbody fusion of the lumbar spine have been developed to reduce tissue damage and complications, allowing for quicker patient recovery, reducing complications, and surpassing the technical limitations of traditional approaches to the spine. In 2001, Pimenta et al. introduced a minimally invasive retroperitoneal approach to the lumbar spine by splitting the psoas, providing direct disc exposure by expanding the retroperitoneal space. This has been introduced as the lateral trans-psoas approach3,4. This technique was modified with the use of special retractors and popularized by Ozgur et al.5. In recent years, extreme lateral interbody fusion in a prone patient position has been developed. This technique offers efficiency with combined posterior procedures and improved lumbar lordosis6,7.
Lateral interbody fusion (LLIF) can be achieved utilizing various approaches. These include trans-psoas approaches (extreme lateral interbody fusion (XLIF8), direct lateral interbody fusion (DLIF9) using different instruments), and a pre-psoas approach (oblique lateral interbody fusion (OLIF10). The approach used for the procedure depends on the patient and the surgeon's training, among others. Anatomical studies showed notable benefits for trans-psoas approaches (minimal blood loss, preservation of the posterior musculature and ligamentous chain, the ability to perform an extensive discectomy, and placement of a large intervertebral graft) but also disadvantages (post-operative nerve palsies, visceral abdominal injuries)11. Reported major but rare complications include intestinal perforation, common iliac vein injury, cage subsidence, vertebral body fractures around the interbody device, retroperitoneal hematoma, and pneumoretroperitoneum with an associated pneumoscrotum12. Overall, pre-psoas approaches are associated with a slightly lower complication rate and fewer postoperative neurological deficits13. To allow optimal outcome, the indication for a lateral interbody fusion needs to be done carefully. We advise obtaining a computed tomography (CT) and magnetic resonance (MR)-scan of the lumbar spine. To assess the segment hypermobility or instability, obtain flexion-extension X-ray images besides regular anteroposterior (AP) and lateral. Common indications are patients with segmental instability and concurrent radiculopathy who have failed non-surgical treatment. In the case of segmental instability or deformity surgery, additional internal fixation may be necessary. LLIF may be limited in the lower lumbar spine, depending on the height of the iliac crest. Supplemental posterior fixation may add valuable construct stiffness and deformity reduction for patients with high-grade instability, deformity, or questionable bone stability. Contraindications for this procedure are typically malignancy, high-grade deformities, or bifurcation abnormalities. A history of retroperitoneal infection or disease and previous retroperitoneal surgery or injury are important considerations. Risk factors for poor outcomes include osteoporosis, smoking, long-term steroid use, severe deformities, and segment hypermobility due to facet effusion or previous laminectomy14,15,16. Also, patients with very low body mass index and anterior psoas location are potentially adverse patients for increased complexity of access. In revision surgery, a pre-psoas approach may be favorable to avoid scar tissue.
The aim of this article is to provide step-by-step guidance to surgeons on a stand-alone lateral trans-psoas interbody fusion, including pitfalls and complication rates after 10 years of single-center experience.