Coflex interspinous implant placement leading to synovial cyst development: case report

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Interspinous process devices (IPDs) have been developed as less-invasive alternatives to spinal fusion with the goal of decompressing the spinal canal and preserving segmental motion. IPD implantation is proposed to treat symptoms of lumbar spinal stenosis that improve during flexion. Recent indications of IPD include lumbar facet joint syndrome, which is seen in patients with mainly low-back pain. Long-term outcomes in this subset of patients are largely unknown. The authors present a previously unreported complication of coflex (IPD) placement: the development of a large compressive lumbar synovial cyst. A 64-year-old woman underwent IPD implantation (coflex) at L4–5 at an outside hospital for low-back pain that occasionally radiates to the right leg. Postoperatively, her back and right leg pain persisted and worsened. MRI was repeated and showed a new, large synovial cyst at the previously treated level, severely compressing the patient’s cauda equina. Four months later, she underwent removal of the interspinous process implant, bilateral laminectomy, facetectomy, synovial cyst resection, interbody fusion, and stabilization. At the 3-month follow-up, she reported significant back pain improvement with some residual leg pain. This case suggests that facet arthrosis may not be an appropriate indication for placement of coflex.

ABBREVIATIONS IPD = interspinous process device; LSS = lumbar spinal stenosis.

Article Information

Correspondence Ali Bydon: The Johns Hopkins Hospital, Baltimore, MD.

INCLUDE WHEN CITING Published online June 15, 2018; DOI: 10.3171/2018.1.SPINE171360.

Disclosures Dr. Sciubba: Consulting relationships with Medtronic, DePuy-Synthes, Stryker, NuVasive, K2M.

© AANS, except where prohibited by US copyright law.



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    Pre-coflex sagittal (A) and axial (B) T2-weighted MR images showing a diffuse disc bulge at the L4–5 level and significant facet hypertrophy with widening of the joint spaces. No listhesis is noted.

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    Post-coflex sagittal and axial T2-weighted (A–C) and T1-weighted (D–F) MR images obtained 3 months after coflex insertion, illustrating bilateral synovial cyst herniation at the L4–5 level causing severe thecal sac compression.

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    Post-coflex midsagittal (A) and axial (B) CT scans showing the coflex device at the L4–5 interspinous process. Right (C) and left (D) parasagittal scans demonstrating the distracted facet joint at the L4–5 level where the coflex implant was placed. The distance between the inferior articulating process and the superior articulating process at the L4–5 facet joint was 4.2 mm compared with 1.1 mm at the L3–4 facet joint.

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    Sagittal (A) and axial (B) T2-weighted MR images obtained after L4–5 laminectomy and posterior lumbar interbody fusion surgery, showing resolution of the synovial cyst and the neural foraminal stenosis.

  • View in gallery

    Postoperative radiograph showing posterior segmental fixation at L4–5 with intervertebral graft.


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