Effect of interspinous ligament fluid sign on postoperative outcome of single-level lumbar interbody fusion.

PURPOSE

This study aims to investigate the relationship between interspinous ligament fluid (ISF) sign and low back pain, and the effect of ISF on the outcome of lumbar interbody fusion (LIF).

METHODS

This retrospective analysis evaluated patients who underwent single-level LIF for lumbar degeneration from January 2012 to December 2019. Patients were divided into ISF (+) and ISF (-) groups based on preoperative lumbar MRI. Data collected included demographic information, surgical data, preoperative and postoperative VAS and ODI scores, and surgical satisfaction. Imaging data assessed intervertebral disc degeneration, lumbar spondylolisthesis, and stability of surgical segments. Differences in VAS, ODI, and satisfaction scores before and after surgery were compared, and regression analysis identified imaging factors linked to residual low back pain. Two-sided p < 0.05 was considered statistically significant.

RESULTS

A total of 328 patients participated in the study, with 108 in the ISF (+) group and 220 in the ISF (-) group. There were no significant differences in mean age, BMI, sex ratio, hypertension, or diabetes rates between the groups. However, the ISF (+) group had a significantly longer hospital stay (16.13 ± 6.83 days) compared to the ISF (-) group (14.51 ± 6.59 days) (p = 0.040). No significant differences were found in operative level, operation time, intraoperative blood loss, or complication rates. At 1 and 3 months postoperatively, VAS scores for low back pain were significantly higher in the ISF (+) group than in the ISF (-) group (p < 0.001 for both). ODI scores showed no significant differences at any postoperative time point (p > 0.05). A significant difference was observed in the proportion of patients with residual low back pain at both 1 and 3 months post-surgery, with more patients in the ISF (+) group reporting pain. Residual low back pain at 1 and 3 months post-surgery positively correlated with a positive ISF sign at the preoperative fusion level (R = 0.213, p < 0.001; R = 0.123, p = 0.025). Logistic regression analysis indicated that a positive ISF sign at the preoperative fusion level was an independent risk factor for residual low back pain at both 1 month and 3 months post-surgery [OR (95% CI) = 2.528 (1.552, 4.118), p < 0.001; OR (95% CI) = 2.146 (1.076, 4.277), p = 0.030].

CONCLUSION

A positive ISF sign observed at the fusion level may significantly influence the outcomes of lumbar fusion procedures. Specifically, the presence of a positive ISF sign is associated with an elevated risk of unfavorable early postoperative results following lumbar fusion. Furthermore, patients exhibiting a positive ISF sign are more likely to experience residual low back pain during the early postoperative phase compared to those with a negative ISF sign.