30.1 Introduction to Bilayer Button

Extended endoscopic transnasal approaches have benefited greatly from the development of multilayered closures to dramatically decrease the incidence of postoperative cerebrospinal fluid (CSF) leaks. In 2010, we described our initial experience with a technique developed at Thomas Jefferson University for the primary closure of skull base defects using a “bilayer button graft” of fascia lata to repair high-flow CSF leaks. ¹ Since 2010, we have utilized this closure technique to primarily repair the dural defect in cases with high-flow CSF leaks, along with the nasoseptal flap as an adjunct, ² which has yielded a CSF leak rate of ≤3%.

30.2 Procedure

The “bilayer button graft” consists of two layers of fascia lata sutured together to form an inlay and an onlay component. The inlay portion sits within the subdural space, while the onlay portion covers the epidural space to create a tight primary dural closure (▶ Fig. 30.1). A vascularized mucosal second layer, often a nasoseptal flap, can then lay over the button graft and cranial base defect for a multilayered closure.

A pituitary rongeur or cottonoid is first used to measure the size of the dural defect. A template is created from a piece of sterile paper the exact size of the dural defect. A 4- to 6-cm linear incision is made along the lateral thigh halfway between the greater trochanter and the knee. The incision is carried through the subcutaneous tissue, fat is removed, and the fascia lata is identified (▶ Fig. 30.2). A piece of fascia lata is harvested with blunt and sharp dissection. The graft harvest size is individualized to the defect size and allows two pieces of fascia: one 10% larger than the defect for the onlay portion, and the other approximately 25 to 30% larger for the inlay portion. The rationale for the smaller onlay is to allow the nasoseptal flap direct contact with the dural edge circumferentially, since, in our experience, nasoseptal flap heals to exposed dura more robustly than exposed bone. The inlay and onlay fascial layers are then sutured together with four 4–0 Nurolon sutures (Ethicon, Bridgewater, NJ), with all sutures placed just inside the size of the actual dural defect (▶ Fig. 30.3a, b). One side of the graft is colored with a surgical marker to aid with orientation when placing the graft (▶ Fig. 30.3c). The bilayer button graft is placed into the defect with a pituitary rongeur. It is then maneuvered into position with ring curettes such that the inlay portion is inserted through the defect and made flush with the surrounding inner dural surface, while the onlay portion only sits over the defect flush with the outer dural surface (▶ Fig. 30.1). Since the two layers are sutured together, the inlay portion can be manipulated and positioned by grasping and moving the onlay portion. The onlay portion is sequentially lifted to confirm the inlay graft is completely approximated to the dura. The nasoseptal flap is then reflected over the button graft, biological glue is applied along its edges, and a single piece of absorbable packing is placed centrally along the flap for stability.