1. Percentage of Canal Compromise
Novel Grading System for the Classification of Lumbar Facet Joint Cysts: A single-centre retrospective cohort study
Ryan J Campbell, Ralph J Mobbs, Prashanth Rao, Kevin Phan
Prince of Wales Hospital
University of New South Wales
Methods picture, go onto paint and make the two images on the left less wide, so the whole picture is less wide and more room for caption without decreased image size.
INTRODUCTION
RESULTS
CLINICAL IMPLICATIONS
Facet joint cysts (FJC) of the lumbar spine are benign cystic lesions, frequently associated with radiculopathy, lower back pain and neurogenic claudication. FJCs may arise in both the cervical and thoracic regions, but are most commonly found in the lumbar spine, especially the L4-L5 facet joints1. Although the exact aetiology remains incompletely understood, FJCs are believed to develop due to degeneration and instability2 (figure 1). As the FJC develops and bulges into the vertebral canal, the thecal sac and nerve roots becomes compressed.
After diagnosis through magnetic resonance imaging (MRI) scans, discussion with the patient will be conducted regarding the most appropriate treatment option3. This may initially involve non-operative management, though this is frequently unsuccessful. Further intervention will then be considered through percutaneous aspiration techniques and operative techniques such as laminotomy for cyst removal, with or without fusion. Currently, there is a lack of conclusive evidence outlining when a particular treatment should be undertaken, nor what patient indications suit each approach. The development of a grading system may predict groups of patients most susceptible to recurrence, and optimistically allow identification of patient groups best suited to a particular approach.
From a prior meta-analysis, it has been shown that percutaneous cyst aspiration and decompressive surgeries with or without fusion are viable treatment options for lumbar FJCs4. Currently though, no subgroups of the population best suited to a particular intervention have been identified. To the best of our knowledge, this proposed system is the first attempt to grade symptomatic lumbar FJCs using a simple classification system based on presenting radiology. The aim here is to provide a structured framework to assist the medical practitioner with the choice of treatment.
As clinical symptom presentation is too diverse to base a classification system, the current proposal utilizes two easily calculated measurements: canal compression and listhesis. The measurement of canal compression is included as it is likely to correlate with clinical factors such as radiculopathy, neurogenic claudication and cauda equina symptoms. The presence of listhesis on the other hand correlates with underlying joint pathology and instability.
Analysis of the current series suggests that grades IV and V FJCs have an increased rate of recurrence, and should therefore be considered for surgical decompression with concomitant fusion or other stabilisation techniques.
Grade
Percentage of Canal Compromise
Degree of listhesis I
0-25%
< 15% II
25-50%
III
>50% IV
<50%
≥ 15% V
≥50%
Table 1: Grading system for lumbar FJCs. Percentage of canal compromise determined using T2-weighted axial MRI sequence demonstrating the FJC. Degree of listhesis determined from sagittal MRI.
Characteristics
n = 166
Mean age (range)
68.6 (44-94)
Men/Women
75/91
Side – Right/Left
78/86 (2 bilateral)
Level n (%): L1-L2
L2-L3
10 (6%)
L3-L4
33 (20%)
L4-L5
111 (67%)
L5-S1
12 (7%)
Graded (n)
139
GRADE n (%): I
35 (25%) II
62 (45%)
III
18 (13%) IV V
5 (4%)
Mean canal compression
34.9%
Mean degree of spondylolisthesis
8.3%
Recurrences n (%)
17 (12.2%)
Figure 1: Facet joint degeneration and cyst formation. The illustration demonstrates degeneration from a normal facet joint (A) through to a severely degenerated facet joint with a large FJC (D).
Table 2: Patient characteristics from retrospective cohort treated surgically for lumbar FJCs. 166 patients were included, of which access to past MRI scans allowed 139 to be completely graded.
CONCLUSIONS
GRADE I
GRADE II
FJCs can be safely and effectively treated with surgical decompression. However, the lack of cyst recurrence after concomitant fusion supports a need to investigate which groups of patients should undergo fusion to avoid a recurrence. The same rationale can be used to identify patient populations suited to percutaneous aspiration techniques and conservative / non-surgical management. A grading system to stratify patient presentation based on radiological features would assist with this important clinical decision making process. The importance of such a system is to provide surgeons and practitioners of spine care, the tools to assist in decision making on appropriate treatment algorithms for this patient cohort.
METHODS
GRADE III
GRADE IV
A classification system, grading FJCs based on various input factors was proposed (Table 1). Over a 7 year period, data from 166 patients treated surgically at the Prince of Wales Hospital for a lumbar FJC were retrospectively collected. 158 were treated by decompression procedures, while 8 underwent decompression with fusion. Utilising the Surgimap program, MRI scans were then graded by two observers according to the new classification system. Sagittal MR images were used to measure the degree of listhesis, and axial T2-weighted MR images were used to determine the percentage of vertebral canal compression. Details of the current surgical intervention, any prior treatment interventions and baseline demographic data were also recorded. The rate of cyst recurrence and need for subsequent surgery was then analysed against the given grades.
GRADE V
Figure 3: Axial and sagittal MRI scans graded using Surgimap. Grades I-III have <15% degree of listhesis, whilst grades IV and V have ≥ 15%. The grading is then subdivided based on the percentage of canal compromise.
REFERENCES
Bydon A, Xu R, Parker SL, et al. (2010). Recurrent back and leg pain and cyst reformation after surgical resection of spinal synovial cysts: systematic review of reported postoperative outcomes. The spine journal 10,
Boviatsis E, Stavrinou L, Kouyialis A, et al. (2008). Spinal synovial cysts: pathogenesis, diagnosis and surgical treatment in a series of seven cases and literature review. European spine journal 17,
Doyle AJ & Merrilees M (2004). Synovial cysts of the lumbar facet joints in a symptomatic population: prevalence on magnetic resonance imaging. Spine 29,
Campbell R, Mobbs R & Phan K, (2016). Percutaneous, decompression and fusion treatments for lumbar FJC: A meta-analysis. In Press
Figure 2: Lumbar Facet Cyst Surgery. A. Grade 3 L3/4 Facet cyst resulting in significant central canal stenosis. B. Unilateral hemilaminotomy and exposure of facet cyst (arrows). C. Removal of cyst with restoration of normal canal diameter.
CONTACT Ryan Campbell
University of New South Wales
Phone: