Individualized 3D-Printed Tissue Retraction Devices for Head and Neck Radiotherapy

Abstract

Background: Radiotherapy for head and neck cancer may cause various oral sequelae, such as radiation-induced mucositis. To protect healthy tissue from irradiation, intraoral devices can be used. Current tissue retraction devices (TRDs) have to be either individually manufactured at considerable cost and time expenditure or they are limited in their variability. In this context, a 3D-printed, tooth-borne TRD might further facilitate clinical use.

Methods: A novel approach for the manufacturing of TRDs is described and its clinical application is analysed retrospectively. The devices were virtually designed for fabrication by 3D-printing technology, enabling-in only a single printing design-caudal or bi-lateral tongue displacement, as well as stabilization of a tongue-out position. For a total of 10 patients undergoing radiotherapy of head and neck tumors, the devices were individually adapted after pre-fabrication. Technical and clinical feasibility was assessed along with patient adherence. Tissue spacing was calculated by volumetric analysis of tongue retraction. In one exemplary case, radiotherapy treatment plans before and after tissue displacement were generated and compared. The reproducibility of maxillomandibular relation at device re-positioning was quantified by repeated intraoral optical scanning in a voluntary participant.

Results: 3D-printing was useful for the simplification of TRD manufacture, resulting in a total patient treatment time of less than 30 min. The devices were tolerated well by all tested patients over the entire radiation treatment period. No technical complications occurred with the devices. The TRDs caused an effective spacing of the healthy adjacent tissue, e.g., the tongue. Position changes of maxillomandibular relation were limited to a mean value of 98.1 µm ± 29.4 µm root mean square deviation between initial reference and follow-up positions.

Conclusions: The presented method allows a resource-efficient fabrication of individualized, tooth-bourne TRDs. A high reproducibility of maxillomandibular relation was found and the first clinical experiences underline the high potential of such devices for radiotherapy in the head and neck area.

Keywords: 3D printing; HNSCC; advances in management; intraoral splints; oral stents; radiation therapy; tissue retraction; tongue displacement.

Figure 1

Design file of the tissue retraction device; the fixation part (FP) is shown in green and the tongue retraction part (TP) in red. The connection bar (yellow) bridges upper and lower parts of the TRD. (A) front view, (B) lateral view, (C) top view.

Figure 2

View of a pre-fabricated TRD. After size selection, different tongue displacements can be realized by removal of tongue retraction parts (TPs). (A) If no parts are removed, caudal tongue displacement can be achieved. (B) The left part of the TP was removed along defined breaking points enabling tongue displacement to the left side. (C) TRD (top view) after removal of TP for tongue-out position, after customization with silicone material.

Figure 3

Patient with pleomorphic sarcoma of the nasal sinus: (A) diagnostic MR imaging without TRD, (B) baseline planning CT with incorporated TRD: the tongue is displaced to a caudal position, (C) irradiation plan without involvement of mandibular soft or hard tissues.

Figure 4

RMS differences between initial reference and follow-up scans.