Metallosis-induced Facet Joint Synovial Cyst after Spinal Instrumentation Surgery

Metallosis is an uncommon complication of metal implantation. It most commonly occurs after knee and hip joint replacement, but it has also been reported in other joints such as the shoulder, wrist, and elbow. A 43-year-old man with L4-5 spondylolisthesis underwent L4-5 laminectomy and posterolateral fusion with pedicle screw instrumentation 7 years previously. Low back pain radiating to the bilateral lower limbs developed 2 months prior to presentation. The L3-4 facet joint synovial cyst compressing dura was diagnosed via magnetic resonance imaging. We removed the pedicle screws and performed a total excision of the cystic mass. At the 1-year follow-up, the patient was pain-free. Metallosis should be considered as a late complication of spinal implantation surgery. It can induce synovial cysts that cause radicular symptoms. Surgical intervention produced good results in this case.