119 - A Prospective, Multi-center Evaluation of Anterior Thigh Symptoms Following Lateral Transpsoas Interbody Fusion in 87 Patients: 2 year follow up

Introduction
The occurrence of access-side thigh pain present immediately following lateral lumbar interbody fusion (LLIF) is frequently described in literature as a common and expected occurrence with rates often not reported. When stated, however, rates range from 1.4% to 25% with most being transient and resolving within 3 months after surgery. Considering the divergent opinions expressed in literature we sought to further explore the presence, severity and frequency of post procedure-related thigh pain and motor and sensation disturbance in a prospective, real-world population undergoing LLIF through a small tissue-sparing protective portal with a large-footprint expandable cage.
Methods
A sub-analysis of patients with little or no baseline anterior thigh pain was performed on data collected by 11 surgeons at 10 sites that participated in a larger post-market study. Multiple serial evaluations were employed from preoperative through 2-years for thigh symptoms including a highly detailed direct patient self-reporting survey and provider neurological testing. The survey evaluated anterior thigh pain severity on a 0-100mm Visual Analog Scale (VAS) and frequency on a 5-point scale ranging from Never to Always. Consistent with literature, a 20mm change in VAS score was deemed clinically meaningful. Quadriceps weakness was assessed subjectively in flexion/knee extension as measured on the survey 0-100mm scale and thigh numbness was subjectively assessed on a self-rated 5-point scale ranging from Never to Always. Objectively, neurological testing was performed for thigh dysesthesia and motor weakness against resistance.
Results
Age, BMI, gender, and operative levels are 64 years, 31, 65.5% female, and 104 levels (80.5% single-level and 19.5% 2-level, 47.6% at L4-L5) respectively with 94.3% left-sided access. Perioperative findings include mean portal time of 30.8 minutes, 150.4cc blood loss and 2.6 days to discharge. Postoperative thigh pain was reported in 21.8% (19) patients with all resolving between 2 and 6 weeks. For postoperative access-side leg pain, 92.8% of patients were improved or maintained at 6-weeks through 2-years. Low rates of subjective weakness (6.9%, 6/87) and subjective numbness (6.9%, 6/87) were reported immediately postoperative. Eleven patients experienced transient neurological worsening immediately postoperative: 5 demonstrated a quadriceps motor weakness, 5 had thigh dysesthesia and 1 had both. While most (80%, 8/10) symptoms resolved on or before the 6-week visit, 2 resolved by the 3-month visit. For the patient with both motor/sensation deficits, the thigh radiculopathy was present preoperative and was improved, but not entirely resolved, by 3-months when the patient exited the study early.
Conclusions
Literature indicates an increased prevalence of thigh symptoms immediately after LLIF surgery with a frequency of 0-75% for sensory deficits, 0.7%-33.6% for motor weakness, and 1.4%-25% for anterior thigh pain. Our findings suggest postoperative thigh pain occurs and confirms the occurrence as transient with early resolution. The results of this study appear specific to the device used resultant of the technology employing a smaller access portal and thereby reducing trauma to the surrounding neural structures. Results may differ from other devices used. Larger studies are recommended to further explore the frequency/severity of procedure-related thigh pain symptoms.