P133. Is preoperative resolution of leg pain at rest a predictor for successful indirect decompression in anterior and lateral lumbar interbody fusion

BACKGROUND CONTEXT The principle of indirect decompression via lateral and anterior interbody fusion has been investigated previously. Many patients respond well after such an approach, with good improvement in their pain and function. However, there is a group of patients in whom direct decompression may still be necessary. It remains unclear which patients will respond most favorably to indirect decompression. PURPOSE This study aims to investigate our hypothesis that preoperative improvement of leg pain at rest is predictive of pain relief via indirect decompression after anterior lumbar (ALIF) or lateral lumbar interbody fusion (LLIF). STUDY DESIGN/SETTING Retrospective review of prospectively collected data at a single institution between 2017 and 2018. PATIENT SAMPLE During the study period, 453 patients underwent ALIF or LLIF. Patients who lacked preoperative leg pain, those who underwent multilevel surgery, direct decompression and/or those who lacked three-month postop patient reported outcome measures were excluded. 43 patients met the inclusion criteria. OUTCOME MEASURES Patient-reported leg and back pain intensity via the numeric rating scale (NRS) and low back pain related disability scores via the Oswestry Disability Index (ODI) were analyzed. METHODS A linear regression model was used to determine whether improvement in leg pain at rest predicted improvements in pain using the NRS and low back pain-related ODI scores at 3 months and 1 year, adjusting for each individual's baseline values. RESULTS Forty-three patients (22M, 21F) with a mean age of 66±13 years underwent LLIF (n=34) or ALIF (n=9) with concomitant pedicle screw fixation. Mean NRS scores for preop leg and back pain were 6.2±2.5 and 6.8±2.2, respectively. Mean preop ODI was 44.6±17.6. Mean 3-month NRS leg and back pain scores were 2.0+2.4 and 3.8+2.3 respectively. Mean ODI at 3 months was 28.2+20.6. Preop leg pain improvement at rest was a significant predictor for postop reduction in pain at the 3-month time point when using indirect decompression (p=0.023). When adjusting for preop pain levels, individuals with preop leg pain improvement at rest demonstrated a 2.3±1.0 point greater improvement in NRS leg pain compared to those without preop leg pain improvement at rest (4.3±3.6 vs 1.8±2.3). Results did not differ when correcting for surgery type. Preop leg pain improvement at rest did not predict 1-year pain levels, or changes in disability at either timepoint (p>0.352). CONCLUSIONS In this study, improvement in leg pain at rest before surgery was a significant predictor of those patients who were successfully managed via indirect decompression with ALIF or LLIF. Preoperative improvement in leg pain at rest may be used as an important predictive tool for short-term success using indirect decompression. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.