PMC7382722_01
(a) Standing lateral radiograph where L4-L5 segmentary instability (4 mm) can be seen. (b) Laminar inclination angle. In (a), we can appreciate vacuum phenomenon and facet hypertrophy, with 10  of facet tropism that suggests segmentary instability.
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fig1
Standing and dynamic radiographs demonstrated a 4 mm instability at the L4-L5 level and a laminar inclination angle of 120  (it is the angle measured between the line that connects the top and bottom edges of the superior articular process and the line that connects the anterior cortex with the posterior cortex of the vertebral body) (Figure 1(a)). The CT study showed degenerative facet changes and vacuum phenomenon at the left L4-L5 level, with a 10  of facet tropism (difference between the right and left L4-L5 facet angle in an axial view) (Figure 1(b)).
MR images on T1, T2, and STIR sequences. Hypointensity on T1 sequences and hyperintensity on T2 sequences. In sagittal cuts, we can see the cyst and how it compromises the spinal canal, as well as degenerative changes in L4-L5/L5-S1. In axial cuts, L4-L5 bilateral cysts can be seen (white arrows).
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fig2
MR images showed moderated to severe disc degenerative changes at L4-L5/L5-S1, as well as lesions that were hypointense on the T1 sequence and hyperintense on the T2 and STIR sequences in both L4-L5 facet joints, compatible with bilateral synovial cysts, the largest being on the left, which relates to her radicular symptoms (Figure 2).
(a, b) Fluoroscopic images obtained during the aspiration and infiltration of the synovial cyst. The end of the needle was slightly bent to ease the access due to the morphology of the cyst. In (c) and (d), we can observe the cyst contents inside the syringe and the subsequent infiltration (2 cc of betamethasone + 2 cc of mepivacaine).
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fig3
A 22 G x 100 mm spinal needle was used and, to ease joint access, the end of the needle was slightly bent (Figures 3(a) and 3(b)). A percutaneous aspiration of the cyst was performed, obtaining 3 mm of a light liquid, followed by the infiltration of 2 cc of 2% mepivacaine and 2 cc of betamethasone (Figures 3(c) and 3(d)).
Standing radiographs in anterior-posterior and lateral projections. Postoperative study of the 5-year follow-up. We can observe the obtained fusion with and adequate position of the implants.
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fig4
The radiology study shows an adequate implant position, without signs of loosening, compatible with solid fusion (Figure 4).