Radiculopathy due to microfibrillar collagen hemostat mimicking recurrence of disc herniation.

Microfibrillar collagen hemostat (Avitene) is an absorbable topical hemostatic agent prepared from purified bovine corium collagen. A 65-year-old woman presented with left buttock and lower extremity radicular pain. The patient underwent a disc excision in which Avitene was used to control venous bleeding from the epidural space. Leg pain decreased postoperatively, but she developed radicular pain when she started walking 3 days after the operation. Magnetic resonance imaging (MRI) performed post-operatively showed there was a mass lesion located between the dural sac and L5 nerve root. The lesion exhibited high signal intensity on T1-weighted images and higher signal intensity at the rim of the mass on T2-weighted images. A second operation performed 10 days later revealed that the nerve root was adherent to an extradural granulomatous mass associated with Avitene. Macroscopically, the resected mass was found to be composed mainly of microfibrillar collagen hemostat materials. Hemostat agents may produce a clinically symptomatic, radiologically apparent mass lesion. When considering a mass lesion arising after spine surgery, the differential diagnosis should include foreign body granuloma along with recurrent disc herniation and peridural scar formation.