Background: Lumbar synovial cysts are thought to signal facet joint degeneration and possible instability, leading some surgeons to routinely add a fusion to the decompressive procedure. These recommendations were formulated before the minimally invasive surgery (MIS) era. Here we describe our outcomes in surgical treatment of lumbar synovial cysts using MIS techniques.

Methods: The charts of 117 patients who underwent MIS resection of a synovial cyst were retrospectively reviewed. All surgeries were carried out in an ambulatory surgery center (ASC). The preoperative and postoperative visual analog scale (VAS) and Oswestry Disability Index (ODI) were collected prospectively. Surgical variables and complications were also reviewed. The subset of 48 patients followed for over 1 year was analyzed, and the outcome of patients with and without a spondylolisthesis was compared.

Results: A total of 117 patients underwent MIS decompression of a synovial cyst. Postoperative follow-up ranged from 3 to 12 months. There were no perioperative complications or 30-day readmissions. Preoperative mean VAS and ODI were 6.2 and 46.7. The postoperative VAS and ODI declined by 3.0 and 22.0 over a mean of 125 days. There were 48 patients with a mean follow-up of 15 months, where the VAS and ODI declined by 2.8 and 22.5, respectively. In this subset, the 23 patients with a spondylolisthesis (all grade 1), were compared to the 25 patients without. The spondylolisthesis group VAS and ODI, preoperatively and postoperatively, declined by 3.3 and 26.1, respectively, while the nonspondylolisthesis group declined by 2.6 and 19.2. These results for each group in this study surpass the standard for a minimal clinically important difference.

Conclusions: Patients with lumbar synovial cysts may safely undergo MIS decompression in an ASC setting, with a low risk of perioperative complications. The reduction in pain and disability is meaningful in the short term and sustained over the next 15 months. The presence of a grade 1 spondylolisthesis did not adversely impact patient outcomes over this time period. For patients undergoing MIS resection of a lumbar synovial cyst, with either the presence or absence of a grade 1 spondylolisthesis, the mandatory inclusion of a concomitant spinal fusion is brought into question.

Clinical relevance: This work is among the largest series of synovial cysts published in which the MIS technique is applied. It demonstrates the efficacy of the procedure, along with its safety and appropriateness for performance in an ambulatory care setting. Moreover, it describes the outcomes using the patient-reported outcome measures VAS and ODI. Finally, the long-term outcomes of patients with and without spondylolisthesis are compared, further supporting the position that when performing a decompression of a synovial cyst with an associated grade 1 spondylolisthesis, a concomitant fusion may not always be necessary.