INTRODUCTION: A postoperative facet joint cyst (FJC) can occasionally be incidentally observed in follow-up magnetic resonance imaging (MRI) scans after lumbar decompression surgery. However, the impact of FJC on surgical outcomes and its progression are not well understood. This study aimed to investigate the occurrence of postoperative latent FJC following decompression surgery for degenerative lumbar disease, and evaluate the impact of FJC on postoperative outcomes and its long-term progression.
METHODS: Among 138 consecutive patients who underwent lumbar decompression surgery from April 2019 to June 2020, 127 patients with one-year MRI were included in this retrospective analysis (82 men, 45 women; mean age of 61.4 years). All patients were scheduled for routine follow-up MRI scans one year postoperatively, regardless of symptoms. In the surgical procedures, microendoscopic decompression was utilized for one- or two-level decompressions, while spinous process splitting laminectomy was employed for more than two-level decompressions. Disc herniations were removed as necessary. FJC was diagnosed based on the presence of a cystic mass with high T2-weighted signal intensity extending into the spinal canal from the decompressed facet joint, as observed on the one-year postoperative MRI. Cases with FJC were further evaluated with a three-year postoperative MRI. Surgical outcomes were assessed using the Oswestry Disability Index (ODI) and visual analog scale (VAS).
RESULTS: Out of the 127 patients, 70 (55%) underwent microendoscopic decompression, while 57 (45%) underwent laminectomy. One year post-surgery, 17 (13%) patients (14 with laminectomy, 3 with microendoscopic decompression) developed postoperative FJC. Patients with FJC were predominantly male, older, and had preoperative facet joint effusion on imaging; further, a higher proportion of open surgery cases was seen. Multivariable regression analysis identified two independent predictors of postoperative FJC development: male sex (odds ratio [OR]: 6.996; 95% confidence interval [CI]: 1.346–36.359) and presence of preoperative facet joint effusion (OR: 4.193; 95% CI: 1.270–13.836). Among the 17 patients with FJC, none received additional treatment for radiculitis and/or back pain related to FJC. There were no statistically significant differences in preoperative ODI, and back and leg pain VAS scores between patients with and without FJC. Additionally, there were no statistically significant differences in ODI (20.1±16.9% vs. 17.9±13.8%, P = 0.55) and back (20.9±22.2 vs. 18.0±20.1, P = 0.58) and leg (14.1±19.7 vs. 14.4±21.0, P = 0.96) pain VAS scores at one year postoperatively between the two groups. In the 13 patients with FJC (excluding 4 dropouts) with three-year postoperative MRI, 3 cases showed cyst disappearance, while 10 cases exhibited no change in size. None of the 13 cases required revision surgery due to FJC.
DISCUSSION: Postoperative FJC developed in 13% of patients who underwent lumbar decompression surgery. Male sex and preoperative facet joint effusion were independently associated with development of postoperative FJC. Latent FJC discovered after lumbar decompression surgery did not exhibit any signs of enlargement, and had minimal impact on postoperative outcomes.