Fig. 3

Intraoperative photographs. a An encapsulated mass lesion (suspected old hematoma) is observed in the epidural space beneath the ligamentum flavum at the right L4–5 level (arrowheads) after the L4–5 laminectomy and the right L4 inferior facetectomy. Arrows indicate the cartilage surface of the right L5 superior facet that was blackened, presumably by hemosiderin deposits. b Photograph taken following the removal of the dark-brownish mass lesion (suspected old hematoma). Arrows indicate the right L4 nerve root. c The encapsulated reddish-brownish mass (arrowhead) is observed in the cavity of the scalloped area at the posterior wall of the L4 vertebra, with the right L4 nerve root pulled to the caudal side with a spatula