帮忙理解一下这句话

这是一篇有关游离组织移植修复颅底缺损的论文。

Results: Four patients with recurrent nasopharyngeal carcinoma, one with recurrent craniopharyngioma, one with clival-cervical chordoma, and one with meningioma of the middle cranial fossa were analyzed. Six defects were closed with an anterolateral thigh free flap and one with a radial forearm free flap. In two patients, the flap was secured in an onlay fashion to the defect via a Caldwell-Luc transmaxillary approach. In one patient, the flap was passed transorally, and the pedicle was delivered into the neck via Penrose drain. In two patients, a parapharyngeal technique and in two others, a retropharyngeal was used for nasopharyngeal inset with endoscopic assistance. There were no flap failures, with an average follow-up time of 20.1 (range 3.2–47.1) months. One patient required flap repositioning on postoperative day three due to midline shift and intracranial contents compression. The transoral inset flap necessitated flap repositioning on postoperative day 13 to improve the nasopharyngeal airway.

这句话没看懂，皮瓣是咋到达颈部的？谢谢~