Abstract

Background: Lumbar synovial cysts (LSC), best diagnosed on MR studies, may cause symptoms/signs ranging from unilateral radiculopathy to cauda equina compressive syndromes. Attempts at percutaneous treatment of LSC typically fail. Rather, greater safety/efficacy is associated with direct surgical resection with/without fusion.

Methods: Treatment of LSC with percutaneous techniques, including cyst aspiration/perforation, injection (i.e., with/without steroids, saline/other), dilatation, and/or disruption/bursting, classically fail. This is because LSCs’ tough, thickened, and adherent fibrous capsules cause extensive thecal sac/nerve root compression, and contain minimal central “fluid” (i.e., “crank-case” and non-aspirable). Multiple percutaneous attempts at decompression, therefore, typically cause several needle puncture sites risking dural tears (DT)/cerebrospinal fluid (CSF) leaks, direct root injuries, failure to decompress the thecal sac/nerve roots, infections, hematomas, and over the longer-term, adhesive arachnoiditis.

Results: Alternatively, many studies document the success of direct or even partial resection of LSC (i.e., partial removal with marked cyst/dural adhesions with shrinking down the remnant of capsular tissue). Surgical decompressions of LSC, ranging from focal laminotomies to laminectomies, may or may not warrant additional fusions.

Conclusions: Symptomatic LSC are best managed with direct or even partial operative resection/decompression with/without fusion. The use of varying percutaneous techniques classically fails, and increases multiple perioperative risks.

Keywords: Lumbar, Synovial Cysts: Operative Management, Avoid Cyst Aspiration, Failure Percutaneous Treatment, Adverse Events, Cyst Perforation, Cyst Disruption, Bursting, Lumbar Decompression, Fusion

INTRODUCTION

Lumbar synovial cysts (LSC), best diagnosed on MR studies, may cause symptoms ranging from unilateral radiculopathy to cauda equina syndromes/compression [ Table 1 ].[ 1 - 16 ] Typically, attempts at percutaneous cyst aspiration, injection (i.e. with/without steroids/other), dilatation, and/or disruption typically fail. Further, these procedures risk producing; multiple dural tears (DT)/persistent CSF leaks, direct nerve root injuries, inadequate decompression of the thecal sac/nerve roots, infections, hematomas, and over the longer-term, adhesive arachnoiditis. Rather, here we reviewed how direct or partial (i.e., with LSC capsular/dural adhesions leaving a small segment of capsule behind to avoid a DT/CSF leak) LSC resections/decompressions with/without fusion usually offer the best outcomes.

Table 1:

Lumbar Synovial Cysts: Demographics, Diagnostic Studies, and Management.

6.5% Frequency of Symptomatic/Asymptomatic Lumbar Synovial Cysts

In 2018, Janssen et al. found that in 19,010 lumbar MR scans (2004-2015 obtained at 2 tertiary care spine centers), lumbar synovial cysts (LSC) occurred in 6.5% or 1236 patients; 54% were symptomatic, while 46% were asymptomatic [ Table 1 ].[ 10 ] The 1 of 15 patients with LSC were typically older, exhibited significant degenerative facet disease, and developed larger and more anteriorly located LSC more likely to be associated with radicular pain.

Etiology and Level of Lumbar Synovial Cysts (LSC)

The etiology of lumbar synovial cysts (LSC) occurring in patients in their sixties who developed radicular deficits were ascribed by Epstein (2004) and others to disruption of the facet capsule [ Table 1 ].[ 3 ] Notably, 40% of the time, patients had accompanying degenerative spondylolisthesis (DS) located in descending order at the L45, followed by the L5S1, L34 and L23 levels. Surgical intervention could involve unilateral or bilateral laminotomies/laminectomies with/without attendant non-instrumented vs. instrumented fusions.

Failure of Non-Surgical Management of LSC

Lalanne et al. (2022) observed that 100% of 69 patients with LSC failed to improve following 3 months of non-surgical management; all 69 underwent decompressions/instrumented posterolateral lumbar fusions that resulted in no LSC recurrence [ Table 1 ].[ 11 ] Further, utilizing Macnab’s Outcomes Criteria, 91.3% demonstrated good/excellent results (63 patients), with only 8.6% (6 patients) showing fair/poor outcomes.

SF-36 Postoperative Outcomes for Patients with Lumbar Synovial Cysts, Stenosis with/without DS Treated with Decompressions Alone

Utilizing the Short-Form 36 (SF-36) patient-based outcome measure, Epstein (2004) compared postoperative results for patients undergoing decompressions for resection of LSC/Stenosis (45 patients) vs. 35 with LSC/Stenosis/DS [ Table 1 ].[ 4 ] Two years postoperatively, 5 of 45 without DS became unstable (i.e. developed a Grade I olisthy), while 11 of 35 who originally had Grade I DS showed an increase in olisthy to Grade II; nevertheless, both groups demonstrated comparable good/excellent postoperative SF-36 Physical Function Scores (+44 vs +38). Here, the author commented: “As synovial cysts reflect disruption of the facet joint and some degree of instability, primary fusion should be considered to improve operative results for patients in both categories”.

High Lumbar Synovial Cyst Occurrence Rates Following Decompressions Alone

Two studies highlighted 6.7% to 12.3% rates of postoperative LSC occurrences in patients undergoing bilateral lumbar decompressions [ Table 1 ].[ 12 , 13 ] Morishita et al. (2021) performed 107 unilateral and 277 bilateral lumbar laminectomy/decompressions without fusions (i.e. 326 total patients, at 384 levels) [ Table 1 ].[ 12 ] All 18 (6.7%) postoperative LSC occurred in the 277 patients undergoing bilateral laminectomies (i.e. reflecting greater instability) vs. none following unilateral procedures. Over a 20-year period, Page et al. (2022) found an even higher 12.3% (i.e. 11 of 89) incidence of postoperative LSC requiring reoperation out of an initial series of patients undergoing bilateral lumbar decompressions without fusions [ Table 1 ].[ 13 ] Risk factors predisposing these patients to developing postoperative LSC included; “...facet angle of > 45%, canal stenosis of > 50%, T2 facet joint hyperintensity, and grade I degenerative spondylolisthesis”.

LSC/Lumbar Stenosis Treated with Primary Decompressions/Fusions Reduced LSC Recurrence Rates vs. Decompressions Alone

Five studies showed that patients with LSC/Stenosis undergoing primary decompressions/fusions resulted in lower LSC recurrence rates vs. for those having decompressions alone [ Table 1 ].[ 1 , 7 , 9 , 14 , 16 ] Utilizing 4 databases (i.e., 17 studies; 824 patients), Ramhmdani et al. (2019) found that patients with LSC/Stenosis/DS were; “...more likely to undergo spinal fusion surgery than laminectomy alone compared with patients with LSC and no preoperative DS” [ Table 1 ].[ 4 ] Notably, preoperative LSC were located at the same level of DS (42.5%), and this correlated with facet arthropathy (89.3%), and degenerative disc disease (48.8%). In 2016, Epstein documented that 66 of 336 patients undergoing average 4.7 level lumbar laminectomies/1.4 level non instrumented fusions had LSC at the primary surgery along with DS (i.e., 195 patients with Grade I, and 67 patients with Grade II DS); only 1 (1.5% or 1 of 66 patients with LSC) of 9 patients required secondary surgery for a recurrent LSC [ Table 1 ].[ 7 ] Over a 20-year period, Wun et al. (2019) found that 11.5% (i.e., 10 of 55) of patients exhibited recurrent LSC following decompressions alone vs. 0% recurrences of LSC after decompressions with initial fusions (i.e. involving 32 patients); notably, second operations for the decompression alone group included 4 additional decompressions, but warranted 6 decompressions/fusions [ Table 1 ].[ 16 ] In their meta-analysis of 6 studies (i.e. including 657 patients), Benato et al. (2023) found that treating symptomatic LSC with decompressions/fusions resulted in less postoperative low back pain, fewer recurrent LSC, but comparable reoperation and complication rates vs. laminectomy alone [ Table 1 ].[ 1 ] When Gonzalez et al. (2023) evaluated 1631 patients with LSC undergoing primary laminectomy/instrumented fusions vs. 2212 with LSC having initial laminectomies alone, they found the laminectomy/fusion group had a lower 1.7% incidence of postoperative LSC recurrences requiring additional surgery vs. a much higher 3.1% recurrence rate of LSC for those undergoing initial decompressiona alone [ Table 1 ].[ 9 ]

Low Failure Rates for Incomplete Surgical Resection of Lumbar Synovial Cysts

Scholz et al. (2015) documented that 8 (5.4%) of 148 patients with lumbar stenosis and LSC underwent incomplete microsurgical cyst resections [ Table 1 ].[ 15 ] Partial LSC resections were largely attributed to marked cyst/dural adhesions, where dissection was carried around the residual capsule to avoid/limit the risk of dural tears/cerebrospinal fluid fistulas. With adequate surrounding neural decompressions, partial LSC removals did not negatively impact patients’ outcomes.

Stenosis with/without DS Treated with Lumbar Decompressions/Non-Instrumented Fusions Result In Few Dural Fistulas Attributed to LSC

In 2015, Epstein found an overall 7.14% frequency (i.e. 24 patients) of dural tears occurring in 336 patients undergoing average 4.7 level lumbar laminectomies/1.4 level non-instrumented fusions for stenosis with/without DS [ Table 1 ].[ 6 ] Notably, 6 (1.7%) DT were uniquely attributed to LSC, while the remainder were due to; 7 epidural steroid injections (ESI), 5 ossification of the yellow ligament (OYL), 3 postoperative scar, and 3 elective durotomies for tumor removal.

High Failure Rates for Multiple Percutaneous Procedures Addressing LSC

Three studies summarized the multiple failures for various attempts at percutaneous treatment of LSC [ Table 1 ].[ 2 , 5 , 8 ] Bureau et al. (2001) documented 3 (25%) treatment failures out of 12 patients with LSC managed with percutaneous steroid injections for distension of LSC capsules; 1 had only short-term relief and required additional procedures, while 2 were not improved [ Table 1 ].[ 2 ] In 2012, Epstein reviewed the 50-100% rate of failed attempts at LSC utilizing unilateral/bilateral aspiration or dilatation under CT-guidance or fluoroscopy; notably, good outcomes were achieved with operative decompression with/without fusion (i.e. > 90% resolution of low back pain/radiculopathy). [ Table 1 ].[ 5 ] Further, in 2016, Eshraghi et al. (2016) looked at the efficacy of attempted percutaneous LSC rupture in 30 patients with low back/radicular complaints; 9 (30%) attempts failed, resulting in recurrent/residual synovial cysts, with 6 (20%) requiring surgery (2006-2013) [ Table 1 ].[ 8 ]

CONCLUSION

Symptomatic LSC are best managed with operative decompression/fusion. Notably, the various percutaneous cyst aspiration, distension, dilatation/other techniques typically fail, unnecessarily exposing patients to added perioperative/postoperative adverse events.

Ethical approval

Institutional Review Board approval is not required.

Declaration of patient consent

Patient’s consent not required as there are no patients in this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflict of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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