Nerve Injury in Lateral Lumbar Interbody Fusion
After transpsoas LLIF, approximately 20% to 40% of patients have thigh pain, and 10% to 20% report numbness or dysesthetic pain.1,2 Psoas pain as a distinct entity has been described by physical therapists and total joint surgeons as activity-related pain that worsens with exertion. It radiates to the ipsilateral groin and anterior thigh and is exacerbated by active flexion of the hip while sitting and while navigating stairs. Psoas pain is expected after transpsoas surgery and must be differentiated from neural injury. A 22% incidence of posttraumatic stress disorder and associated inferior outcomes have been associated with open spinal fusion.3 It is clear that no matter the approach, one must consider the given morbidity and goals before obtaining informed consent.
Neural injury may be seen in discectomy, open spinal fusion, and LLIF. Subcostal, iliohypogastric, and ilioinguinal nerves may be injured during skin incision, resulting in thigh pain after LLIF. Direct visualization and intraoperative magnification will assist the surgeon in avoiding these nerves. Tracing out the given pain pattern on the patient's leg will assist the surgeon in understanding the pain pattern, and will likely reveal that the neural injury is not a root level problem (i.e., L4 or L5). In addition to direct injury, excessive retractor time (>20 to 40 min per level) and table flexion without ipsilateral hip flexion may injure the nerves of the lumbar plexus. Shallow docking may help reduce thigh symptoms by avoiding direct damage to involved nerves.
Direct visualization, appropriate positioning, and differentiation of psoas pain as compared with neural injury will aid surgeons in understanding the approach-related morbidity of LLIF. Realistic comparisons of morbidity as compared with open surgical methods will substantiate the role of LLIF in the modern spine surgeon's armamentarium.