The rising psoas sign: an analysis of preoperative imaging characteristics of aborted minimally invasive lateral interbody fusions at L4–5

Abstract

<jats:p>Minimally invasive lateral interbody fusion for the treatment of degenerative disc disease, spondylolisthesis, or scoliosis is becoming increasingly popular. The approach at L4–5 carries the highest risk of nerve injury given the proximity of the lumbar plexus and femoral nerve. The authors present 3 cases that were aborted during the approach because of pervasive electromyography responses throughout the L4–5 disc space. Preoperative imaging characteristics of psoas muscle anatomy in all 3 cases are analyzed and discussed. In all cases, the psoas muscle on axial views was rising away from the vertebral column as opposed to its typical location lateral to it. Preoperative evaluation of psoas muscle anatomy is important. A rising psoas muscle at L4–5 on axial imaging may complicate a lateral approach.</jats:p>

Prevention of neurological complications using a neural monitoring system with a finger electrode in the extreme lateral interbody fusion approach

“…[1][2][3]9,12,[16][17][18]21,24 Reduction of neurological complications is likely to improve the surgical outcome of XLIF and expand the indication. For this reason, we developed a new neural monitoring system using a finger electrode to reach the intervertebral region in patients undergoing XLIF.…”

“…25 A case in which the posterior border of the psoas major muscle is anterior to the center of the anteroposterior diameter of the intervertebral disc is defined as having a rising psoas sign, and the lateral approach is difficult in such cases. 24 The rising psoas sign is common at L4-5 and L5-6, and in many of these cases the patients cannot be treated with a conventional XLIF procedure. 18,24,25 In this study, the positional relationship between the psoas major muscle and nerve was quantified using the psoas position (PP%) calculated by dividing the distance (P) between the posterior margin of the intervertebral disc and posterior border of the psoas major muscle by the anteroposterior diameter (D) of the intervertebral disc, based on data from preoperative axial MR images of the inter- vertebral disc.…”

“…24 The rising psoas sign is common at L4-5 and L5-6, and in many of these cases the patients cannot be treated with a conventional XLIF procedure. 18,24,25 In this study, the positional relationship between the psoas major muscle and nerve was quantified using the psoas position (PP%) calculated by dividing the distance (P) between the posterior margin of the intervertebral disc and posterior border of the psoas major muscle by the anteroposterior diameter (D) of the intervertebral disc, based on data from preoperative axial MR images of the inter- vertebral disc. The PP% was ≥ 50% (a rising psoas sign) in 6 of the 36 patients in whom surgery was performed using the finger electrode, indicating a significant correlation between PP% and the pre-dissection threshold of the initially inserted dilator electrode.…”

“…19 Such surgery should be suspended when the insertion route is close to the lumbar plexus because of the invasive risk to the lumbar plexus. 24 This concern may lead to XLIF being excluded in preoperative planning.…”

“…The incidence of XLIF-induced postoperative neurological manifestations is 1%-60%, 24 with causes including direct subcutaneous and between-muscle procedures, compression by retractors, and postoperative hematoma. 2,3,7,9,11,12,17,21,24 No serious neurological complications occurred in any patients in the current study, but the incidence of neurological complications of 38.9% in the conventional group was comparatively high, as also seen in past reports.…”