Preoperative predictors of difficult hypopharyngeal exposure by retractor for transoral robotic surgery

Transoral endoscopic surgeries provide excellent oncologic outcomes while preserving speech and swallowing ability. However, feasibility has been a major concern about transoral surgery. Therefore, ensuring visualization of the surgical field and sufficient working space is required. The aim of this study was to evaluate the parameters in the preoperative assessment that affect hypopharyngeal exposure.

Before transoral surgery, parameters regarding the patient's neck and face such as modified Mallampati index, thyroid-mental distance (TMD), and ability to fully open the mouth were evaluated. Cephalometry and cervical spine radiography were performed preoperatively to evaluate the size of the mandible bone, mouth opening, and cervical spine extension. Mandibular bone parameters such as intergonion distance, mental-gonion distance, articulare-gonion distance, and aperture angle were measured. According to hypopharyngeal exposure using FKWO retractor, patients were divided into difficult hypopharyngeal exposure group (DHE) and non-difficult hypopharyngeal exposure group (non-DHE). Parameters were enrolled to evaluate the relationship between these parameters and DHE status.

This study included 51 patients, 37 in the non-DHE group and 14 in the DHE group. On radiographic evaluation, there was a significant difference in the degree of cervical lordosis between non-DHE and DHE patients. A significantly higher proportion of DHE patients had a history of radiotherapy compared with non-DHE patients.

Patients with limited cervical extension and a history of previous radiotherapy might have difficult hypopharyngeal exposure during transoral surgery. This is the first report to suggest a classification system for hypopharyngeal exposure during transoral surgery.