18. Fatty infiltration of the lumbar multifidus (LM) may be associated with adjacent segment degeneration after fusion for spondylolisthesis

BACKGROUND CONTEXT Paraspinal muscle fat infiltration has been shown to be associated with back pain. However, it is unclear if fat infiltration of the lumbar multifidus (LM) increases the rate of adjacent segment degeneration after fusion. PURPOSE To investigate if fatty infiltration of LM is associated with adjacent segment degeneration after L4-5 transforaminal lumbar interbody lumbar fusion (TLIF) for spondylolisthesis. STUDY DESIGN/SETTING Retrospective study. PATIENT SAMPLE Single academic center with degenerative spondylolisthesis patients undergoing L4-5 TLIF. OUTCOME MEASURES Radiographic measures included: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL) and PI-LL. Fat infiltration (L3, L4 and L5) was measured with Goutallier classification on preop MRI. METHODS A total of 178 patients undergoing L4-5 TLIF for spondylolisthesis (2006 to 2016) were retrospectively analyzed. Inclusion criteria were: minimum 2-year follow-up, preop MRI and preop X-rays, L4-5 TLIF. Twenty-three patients underwent revision surgery for adjacent segment degeneration during the follow-up. Another 23 patients without adjacent segment degeneration were collected to match the patients with adjacent segment degeneration. RESULTS A total of 46 patients were evaluated (18 males, mean age 61years). The average follow-up was 40 months. There was no difference in age, sex, BMI and spinopelvic parameters with regard to the patients with and without adjacent segment disease (p>0.05). Fatty infiltration of LM was more significant in the patients with adjacent segment disease than those in the patients without adjacent segment disease (p=0.029). The fatty infiltration was most significant at L3 in patients with adjacent segment disease compared to patients without ASD (p=0.017). At L4 and L5, there was an increasing trend of fatty infiltration in the patients with adjacent segment disease compared to patients without adjacent segment disease, but the difference was not statistically significant (p>0.05) CONCLUSIONS In patients who underwent revision surgery for adjacent segment disease, fatty infiltration of LM was more significant compared to patients without adjacent segment disease. Fatty infiltration of LM may be associated with adjacent segment disease after fusion. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.