Radiofrequency Neurotomy Does Not Cause Fatty Degeneration of the Lumbar Paraspinal Musculature in Patients with Chronic Lumbar Pain-A Retrospective 3D-Computer-Assisted MRI Analysis Using iSix Software

Objective The present study aimed (1) to analyze the relative paraspinal autochthonous intramuscular fat volume before and after radiofrequency neurotomy (RFN) and (2) to compare it to the contralateral non-treated side. Design Retrospective cohort study. Setting Inselspital, University Hospital Bern, University of Bern. Subjects Twenty patients (59.60 +/- 8.49 years; 55% female) with chronic low back pain, treated with RFN (L2/3-L5/S1) due to symptomatic facet joint syndrome (FCS) between 2008 and 2017 were included. Methods All patients received a magnetic resonance imaging (MRI) of the lumbar spine before and at a minimum of 6 months after RFN. The absolute (cm(3)) and relative (%) paraspinal muscle and fat volume was analyzed three-dimensionally on standard T2-MRI sequences using a newly developed software (iSix, Osiris plugin). Both sides were examined and allocated as treated or non-treated side. Results A total of 31 treated and 9 non-treated sides (Level L2/3-L5/S1) were examined. There were no differences in the relative paraspinal intramuscular fat volume before and at a median of 1.4 [0.9 - 2.6] years after RFN (P = .726). We found no differences in the relative fat volume between the treated and non-treated side before (P = .481) and after (P = .578) RFN. Conclusions Our study shows that there are no differences in the paraspinal muscle/fat distribution after RFN. RFN of the medial branches for FCS does not seem to cause fatty degeneration of the lumbar paraspinal muscles as a sign of iatrogenic muscle denervation.