Magnetic Resonance Neurography of the Lumbar Plexus at the L4–5 Disc: Development of a Preoperative Surgical Planning Tool for Lateral Lumbar Transpsoas Interbody Fusion (LLIF)

Abstract

Introduction The lateral transpsoas approach for lumbar interbody fusion (LLIF) is a minimally invasive surgical technique that is now frequently used to treat common spinal disorders. During LLIF, the course of the plexus within the surgical corridor places it at risk for iatrogenic intraoperative injury. Several previous studies have suggested that the risk of neurological injury during LLIF is higher at L4–L5. Current imaging techniques of assessing the proximity of neural tissue to the L4–L5 disc space have limited capabilities. Magnetic resonance neurography (MRN) is a noninvasive MR imaging tool developed for peripheral nerve imaging. A myriad of clinical applications exist including imaging assessment of lumbosacral plexopathies. In this study, we explored an additional clinical application for this technology as a preoperative planning tool for LLIF. Material and Methods Consecutive lumbar plexus MR neurograms ( n = 27 patients, 54 sides) were studied. All scans were performed on a Siemens 3 T Skyra MRI scanner. The imaging protocol included axial and coronal T1-weighted, axial and coronal T2-weighted spectral adiabatic inversion recovery (SPAIR; Siemens Healthcare), and coronal T2-weighted 3D inversion recovery (3D SPACE; Siemens Healthcare) sequences. Following acquisition, the images were postprocessed using TeraRecon Aquarius iNtuition v4.4 to generate T1- and T2- color-coded fusion maps. 3D models of the lumbosacral plexus with attention to the L4–L5 interspace were generated using the GE AW Suite v2 (General Electric). The L4–L5 intervertebral space was divided into six zones according to Moro method. Zones I to IV were distributed equidistantly between the anterior and posterior margins. The position of the plexus and the shape of the psoas muscle at the L4–L5 interspace was evaluated and recorded. Results Direct imaging of the lumbar plexus using MR neurography revealed variability in the position of the plexus relative to the L4–L5 interbody space. In this series of 27 patients, there was significant variability in the anatomic position of the lumbar plexus from patient-to-patient and right-to-left in individual patients. The left-side lumbar plexus was identified in zones III (55%) and zone IV (44%) ( p = 0.56). On the right side the plexus was most frequently identified in zones III (44%) or zone IV (44%) however was also identified in zone II (7.4%) or posterior (3.7%) ( p = 0.009). Right–left symmetry of the plexus relative to the disc space was found in 44% of the subjects. There was no correlation between the position of the plexus and the shape the overlying psoas muscle identified. Conclusion MRN is a noninvasive imaging technique for visualizing the lumbosacral plexus. The course of the lumbosacral plexus traversing the L4–5 disc space may be more variable than has been suggested by previous studies. MRN may provide a more reliable means of preoperatively identifying the plexus when compared with current methods. The ability to assess the location of the plexus may aid in preoperative planning and reduce neurological complications.

Integrated anatomy of the neuromuscular, visceral, vascular, and urinary tissues determined by MRI for a surgical approach to lateral lumbar interbody fusion in the presence or absence of spinal deformity

“…Another study examined the course of the lumbar nerve plexus using magnetic resonance neurography (MRN) in 35 patients. MRN imaging clearly showed the lumbar nerve plexus at the dorsal half of L4-5 on the left and right sides 16) .…”

“…Complications of bowel injury after LLIF surgery at L3-4 and L4-5 have been reported 1) . Older patients with a low BMI favorably show the existence of a retrorenal colon, possibly because of low adipose tissue content in the retroperitoneal space 13,15,16) . In these circumstances, it is more difficult for the bowel to move ventrally and easier to approach the anterior pararenal extraperitoneal space.…”

Recent advances in magnetic resonance neuroimaging of lumbar nerve to clinical applications: A review of clinical studies utilizing Dffusion Tensor Imaging and Diffusion-weighted magnetic resonance neurography

“…We excluded reviews, spinal cord studies and animal or in vivo studies. Our review identified a total of 35 articles: 24 DTI studies and 11 diffusionweighted MR neurography studies [31][32][33][34][35][36][37][38][39][40][41] . The number of lumbar nerve DTI studies has sharply increased in recent years ( Fig.…”

Quantitative magnetic resonance (MR) neurography for evaluation of peripheral nerves and plexus injuries

“…The use of DWI based neurographic sequences has demonstrated several advantages over conventional morphological neurographic studies (9,18,28,29). The strength of these techniques relies on providing functional and quantitative information, allowing a correct understanding of the normal physiology of PN and the pathophysiological processes that underlie the different conditions involving PN, with potential influence to improve their diagnosis and therapy monitoring.…”