INTRODUCTION: Spinal fusion is generally recommended when lumbar spinal instability exists. A correlation between excessive facet joint fluid levels detected on magnetic resonance images and radiological instability has been reported. However, excessive facet fluid levels are occasionally found in cases without radiological instability. This study examined the correlation between facet joint fluid levels and surgical outcomes after decompressive surgery without fusion.
METHODS: Seventy‐three patients without significant radiological instability who underwent lumbar decompressive surgery (≤ three levels) were divided into the “fluid‐group” and the “no‐fluid‐group,” by the presence of excessive facet fluid. Severity of pain and numbness (visual analogue scale: VAS), intermittent claudication (IC), subjective surgical outcomes (Odom scale) and disability scores for lumbar spinal disorders (Japanese Orthopaedic Association Back Pain Evaluation Questionnaire: JOABPEQ) were compared pre‐ and post‐operatively.
RESULTS: Of the 73 patients, 16 patients had excessive facet joint fluid (21.9%). The mean follow‐up period was 16.6 (6‐30) months. Pre‐operative VAS scores (lower‐back pain, leg pain, numbness) were 5.2, 5.4, and 7.5 in the fluid‐group, and 5.8, 6.0, and 6.5 in the no‐fluid‐group, whereas post‐operative scores were 2.3, 3.3, and 3.7 in the fluid‐group, and 2.7, 2.7, and 2.8 in the no‐fluid‐group. When comparing the pre‐ and post‐operative states, and post‐operative improvements, no significant difference was found between the groups in any of the VAS scores. There were no significant differences in IC, Odom scales, and any of the five subscales of the JOABPEQ scores.
DISCUSSION: The present study revealed that excessive facet joint fluid levels did not predict poor surgical outcomes after decompressive surgery without fusion when patients have no radiological instability, suggesting that spinal fusion is not necessary in patients with excessive facet fluid, if they have no radiological instability. Further studies are required to determine the clinical significance of excessive levels of facet joint fluid.