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Epidural Migration of Bone Graft Material: An Unusual Complication of Lumbar Interbody Fusion with Polyethylene Mesh Containment Device 2013

Category Interventional Sundeep Patel, MD
Jeffrey Wilseck, DO
Purpose We briefly review a technique of performing lumbar interbody fusion which utilizes an expandable polyethylene mesh bone graft containment system. Furthermore, we present a rare complication of this procedure with migration of graft material from this mesh device, which manifests as an unusual appearing epidural process on CT and MRI. After reviewing this unique case, the reader should better understand this procedure and recognized this complication and its imaging appearance. Materials & Methods This is a case report of a 64 year-old female who underwent lumbar interbody fusion at L3-L4 and L4-L5 utilizing a polyethylene mesh bone graft containment system. The patient developed progressive back pain and right lower extremity radiculopathy two years after the surgery. With progressive symptoms, a CT myelogram of the lumbar spine was performed followed by an MRI. Both studies showed the post-surgical changes at L3-L4 and L4-L5 and an unusual appearing epidural process at the L5-S1 level with compression of the thecal sac and impingement of the right L5 and S1 nerve roots. The patient underwent surgical decompression and removal of the epidural material, which proved to represent migrated graft material from the mesh device. Results CT myelogram shows post-surgical changes at L3-L4 with high-density material within the disc space, compatible with the interbody grafting system. There are also similar post-surgical changes at L4-L5, but with disc space narrowing and relatively smaller amount of high-density graft material compared to the L3-L4 level. At L5-S1, there is hyperdense extradural material at the right lateral aspect of the right L5 nerve root and the right lateral recess and foramen with mass effect upon thecal sac and impingement of right S1 nerve root. A follow-up MRI of the lumbar spine redemonstrates the epidural process at L5-S1 on the right side. The epidural material has unusual hypointense signal on T2 and T1WIs and does not enhance. At surgery, the right L5 and S1 nerve roots were impinged by multiple fragments of migrated bone graft material. This was removed and confirmed by microscopic analysis. Conclusion A polyethylene mesh bone graft containment system can be used to perform lumbar interbody fusion. We present a rare complication of this mesh containment system with migration of the bone graft material from the device causing post-operative radiculopathy. This was manifested as an epidural process, which was hyperdense on CT and T1 and T2 hypointense on MRI. We believe that radiologists should be aware of this rare complication and its unusual CT and MRI appearance. References Zheng X, Chaudhari R, Wu C, Mehbod A, Erkan S, Transfeldt, E: Biomechanical evaluation of an expandable meshed bag augmented with pedicle or facet screws for percutaneous lumbar interbody fusion. The Spine Journal 2010;10:987-993.