Disclosures: Emilie Pinto, DO: No financial relationships or conflicts of interest

Background and/or Objectives: During radiofrequency ablation the medial branch of the dorsal rami is destructed to interrupt pain signal from the facet joint. Radiofrequency ablation is considered a low-risk procedure with only rare complications of nerve or vascular injuries. One potential long-term complication, based on the nerve intended to be damaged, is injury to the motor function of the multifidus muscle which also receives innervation from this medial branch. The primary objective of this study was to retrospectively measure the change in fat-subtracted cross-sectional area (CSA) of the L5 multifidus before and after radiofrequency ablation using MRI imaging. The L5 multifidus was the focus of this study as it is most likely to be affected by the common L3-L5 medial branch RFA. The CSA at the L3 level was obtained for reference as it would be less likely to be affected by L3-5 RFA.

Design: Retrospective Case-Control Study

Setting: Academic pain clinic

Participants: 36 patients who met criteria for pre and post MRI imaging with lumbar RFA of levels L3,4,5. Major exclusions included lumbar spine surgery or trauma in the time between the imaging and those under the age of 18.

Interventions: MRI imaging pre and post RFA were analyzed using ImageJ software to calculate fat-subtracted cross-sectional area of the bilateral multifidi at the L3 and L5 levels.

Main Outcome Measures: Change in fat subtracted cross-sectional area after bilateral L3-5 RFA.

Results: 36 patients (144 L3 and L5 multifidi) met our inclusion and exclusion criteria. The average change for CSA at L5 was –12.34% (p=0.0006). The average change for CSA at L3 was +16.98% (p=0.016). The average number of years between the compared MRIs was 5.8 years.

Conclusions: Radiofrequency ablation of the bilateral lumbar medial branch nerves is correlated with lumbar multifidus atrophy.

Level of Evidence: Level III

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/multifidus-atrophy-secondary-to-radiofrequency-ablation/