Endonasal endoscopic procedures have replaced many open nasal surgeries since their introduction in the late 1980s for the treatment of various sinonasal tumors as well as inflammatory sinonasal diseases [1,2]. External approaches, including the canine fossa puncture or Caldwell-Luc approaches, however, are commonly combined with the endonasal approach to treat maxillary sinus lesions such as antrochoanal polyps, inverted papilloma, and severely diseased maxillary sinus [3,4]. This is because surgeons treating maxillary sinus lesions, particularly inverted papilloma or recalcitrant sinusitis, require direct visualization, sufficient working space for manipulation, and possible access to all aspects of the antrum.

Endoscopic maxillary mega-antrostomy and endoscopic medial maxillectomy (EMM) are endonasal surgical techniques for treating refractory maxillary sinusitis and maxillary sinus tumors, respectively, without an external approach [5,6]. EMM can be used for lesions involving the zygomatic recess, anterior wall, or floor of the antrum and includes removal of the inferior turbinate (IT), medial maxillary wall, and nasal valve area [6]. Preservation of the IT and anatomical integrity of the nasal valve area should be considered because these units are important in nasal physiology in terms of humidification and dynamics of nasal air flow [7].

To preserve the IT in situ and not violate the nasal valve area when performing EMM, we developed a novel technique called endoscopic trans-turbinal medial maxillectomy (ETTMM). Using this technique, we could access most aspects of the antrum from the middle and inferior meatuses through the extended antrostomy under direct visual control while preserving the IT in situ. In addition to achieving good intraoperative visualization and accessibility, we attained satisfactory post-operative results in 10 cases of various tumorous and nontumorous maxillary lesions. Here we present the procedures and results.

ETTMM was performed by two experienced surgeons (S.W.K. and S.Y.J.) in 10 patients from October 2014 to October 2017. We conducted a retrospective chart review of these patients. This study was approved by the Institutional Review Board of Gyeongsang National University Hospital (IRB 2017-12-008).

The mean age of the patients was 61.0 years (range, 48-87 years, with a male:female ratio of 8:2). Five patients received ETTMM to treat nontumorous lesions in the maxillary sinus, such as recalcitrant maxillary sinusitis, dental implant-related maxillary sinusitis, postoperative cheek cyst (POCC) in the zygomatic recess (Fig. 2A and B), and inflammatory antral polyps (Fig. 2C and D). The other five patients underwent ETTMM to resect tumors arising from the antrum, including cavernous hemangioma, inverted papilloma (Fig. 2E and F), and locally recurrent myxofibrosarcoma (Fig. 2G and H). All lesions were successfully addressed using ETTMM. The mean follow-up duration was 17.4 months (range, 3-35 months). We performed postoperative disease surveillance using rigid endoscopes of various angles (Fig. 3A-D) and/or imaging studies such as CT (Fig. 3E and F). Recirculation of a mucus was observed in no cases. Disease recurrence was observed in a single patient who had undergone ETTMM for recurrent myxofibrosarcoma 14 months postoperatively (Table 1).

Since its introduction, EMM has become a preferred endonasal surgical approach in many cases of inverted papilloma spreading throughout the maxillary sinus. When it was first introduced, the IT and NLD were resected depending on the area involved and the pathology of the lesion [6]. Because the IT performs important functions in nasal physiology, including warming and humidifying inhaled air, some modifications to preserve the IT have been introduced [7,8]. Some modifications involved cutting the head of the IT, positioning the IT medially or posteriorly during surgery, and repositioning the IT at the original site [7,8]. In other modifications, called the medial shift of IT or prelacrimal approaches, a vertical incision was made more anteriorly on the mucosa of the lateral nasal wall along the anterior margin of the IT. These modifications included osteotomy of the medial maxillary wall, identification, and preservation of the NLD [9-12]. Using these modifications, the prelacrimal recess of the maxillary antrum was opened and access to the maxillary antrum was achieved through the anterior side of the preserved NLD. Despite the changes in a more functional direction, however, these modifications violate the anatomical integrity of the nasal valve area through mucosal incisions and removal of bone at the anterior end of the IT, which may result in nasal functional disturbance.

Extended maxillary antrostomy or maxillary mega-antrostomy, which involves resecting the posterior half or greater portion of the IT, has been used to treat refractory maxillary sinus inflammatory lesions since its introduction in the late 1990s [5,13,14]. Because the scope of maxillary antrostomy has increased, including partial resection of the IT, its surgical procedures overlap with those of EMM [15]. Accordingly, EMM, including maxillary mega-antrostomy, is now considered a suitable surgical technique for treating recalcitrant maxillary sinusitis as well as for extirpating sinonasal tumors [16].

Our modified technique, ETTMM, involves elevating a turbinate mucosal flap on the superior aspect of the IT after MMA, developing a trans-turbinal window to expose the inferior meatus, extending MMA inferiorly to make an extended maxillary antrostomy, and then repositioning the turbinate mucosal flap after completely removing the antral lesions. The repositioned mucosal flap covers the remaining IT bone, and thus postoperative stenosis of the trans-turbinal window is minimized. Unlike the aforementioned IT-preserving tech-niques that rely on vertical mucosal incision at the head of the IT or lateral nasal wall, our technique does not disrupt the anatomical integrity of the nasal valve area. Moreover, our modification is easy to perform and allows for a smooth transition from MMA to extended antrostomy because the posteroinferior margin of MMA and the inferior meatus are well visualized by the creation of the trans-turbinal window. The trans-turbinal window also provides more working space for surgical instruments such as microdebriders of various angled tips all over the antrum to the zygomatic recess compared to simple combination of MMA and inferior meatal antrostomy (IMA). While preserving the IT in situ, our technique achieves extended endoscopic visualization and unrestricted surgical manipulation of the zygomatic recess laterally, the antral floor inferiorly, and the anterior maxillary wall by two separate channels above and below the IT. Finally, the trans-turbinal window enables wider endoscopic visualization during follow-up than combination of MMA and IMA. Preventing the stenosis of the trans-turbinal window by mucosal flap coverage is a key procedure for this purpose.

One limitation of this technique is that tumors growing from the anterior region to the NLD, such as the prelacrimal recess and pyriform aperture, cannot be optimally addressed; thus, other techniques, such as the prelacrimal approach or Caldwell-Luc approach, would be more suitable. However, given that removal of the frontal process of the maxilla included in some types of the prelacrimal approach [17] may potentially lead to nasal valve problems or facial asymmetry, our technique may be more appropriate in cases of maxillary tumors that do not involve the prelacrimal recess and pyriform aperture.

In our case series, a case of POCC in the zygomatic recess (Fig. 2A and B) and a case of inverted papilloma originating from the zygomatic recess (Figs. 2E, 2F, 3E, and 3F) showed good surgical accessibility of ETTMM to the zygomatic recess laterally. Although the lesions in these two cases were located far lateral in the maxillary sinus, the wide endoscopic view through the trans-turbinal window allowed clear postoperative surveillance. In other two cases (Fig. 2C and D, G and H), the origins of lesions were medial maxillary wall. The trans-turbinal window created during ETTMM provided simultaneous visualization of the maxillary sinus and the inferior meatus, and thus the masses could be resected in a safe and efficient manner. In the single case of recurrence after ETTMM, the first site of the tumor recurrence was the medial wall of the maxillary sinus (Fig. 2G and H). Because the tumors were pedunculated with a small stalk, they were successfully removed by ETTMM, including partial resection of the posterior region of the IT with clear resection margins. During the follow-up period, the maxillary antrum was well visualized using rigid endoscopes of various angles (Fig. 3A-D) until the second recurrence, which occurred at the posterior maxillary wall. Given the negative resection margins during ETTMM, the recurrence site (the posterior maxillary wall), and the 14-month interval between ETTMM and the second recurrence, the cause of the second recurrence was not ascribed to ETTMM.

In conclusion, in our experience, ETTMM appears to be a safe and efficient modification of EMM that provides clear visualization and great accessibility to all aspects of the maxillary antrum while preserving the IT in situ and the anatomical integrity of the nasal valve area.