BACKGROUND AND OBJECTIVES

Mouth retractors are essential in ensuring efficient yet safe exposure of the oral cavity and oropharynx. However, when applied improperly or haphazardly, retractors can cause tissue injuries and compromise patient safety. In addition, there are gaps in the usability of existing designs. This study aimed to identify the issues encountered by otorhinolaryngology surgeons in the use of commercially available mouth retractors, design and fabricate an improved retractor, and explore the use of additive manufacturing (popularly known as 3D printing) for retractor prototyping.

METHODS

The study used the United States Food and Drug Administration (US FDA) Design Control as its framework. End-user requirements from otorhinolaryngologists were collected through key informant interviews. Results were organized into a Design Input template which was used to guide the design and development process. Prototype designs were iteratively created using computer-aided design software and 3D printing. Once design specifications were satisfied, a beta prototype was fabricated and given to another cohort of otorhinolaryngologists. The participants assessed the usability of the beta prototype. System Usability Scale (SUS) was used to quantify participant's feedback.

RESULTS

Five designs were created in the course of the study. The final prototype was fabricated using a Stereolithography (SLA) 3D printer. Several features were developed to address user requirements. The primary modification was to make the retractor modular to facilitate easier and shorter mounting and assembly. Gingival injury was addressed with the replacement of the maxillary alveolus hook with support bars. Five participants evaluated the beta prototype which received a mean SUS score of 75, well above the 50th percentile threshold.

CONCLUSION

This study demonstrates the applicability of the US FDA Design Control Process in the local setting to improve the mouth retractor design. Clinical and ergonomic issues were identified and design solutions were proposed and some have been implemented in a low-fidelity prototype. Results of the small-scale usability test suggest that the present form factor can be the basis for further iterations. Future studies can implement the proposed features to address other clinical and ergonomic needs.

Human ; 3d Printing ; Printing, Three-dimensional ; Devices, Medical ; Equipment And Supplies

BACKGROUND: Instrumented posterior cervical spine surgery (IPCSS) can be conducted using screws inserted through the pedicles of the vertebra. A safe IPCSS method uses 3D-printing to produce templates that will serve as drill guides for screw placement. OBJECTIVES: This study describes the generation of 3D-printed drill guides using low-cost general purpose 3D modeling software and the comparison of screw insertion accuracy scores against the traditional landmark method and guides created using commercial grade software. METHODS: Twenty-five (25) subaxial pedicles of five cadaveric spines were selected and scanned using computed tomography (CT). A digital reconstruction of the five cadaveric spines were created based on the CT DICOM data. A low-cost 3D modeling software, Rhinoceros 3D, was utilized for trajectory planning and generation of a patientspecific drill template using the digital reconstruction. The templates were then fabricated in ABS plastic using a fused deposition modeling (FDM) 3D printer. Insertion of cervical pedicle screws on the cadaveric spines was done by an orthopedic resident using the 3D printed guides. Postoperative CT scans were obtained, and placement accuracy of the screws were scored by two assessors utilizing a four-point rating system. Screws in correct placement were scored Grade 0 while misplaced screws with neurovascular damage were given a score of Grade 3. RESULTS: Accuracy scores for the 3D-printed drill guides were 52% for assessor 1 and 44% for assessor 2. For assessor 1, screw placement in C3, C6, and C7 received the highest scores. For assessor 2, the highest scores were achieved in C3 and C7. The hybrid method of Bundoc et al. achieved scores of 94% while 3D printed guides utilizing commercial software like Materialise Mimics, Geomagic Freeform, or UG Imageware achieved scores of 80-100%. The traditional landmark method had scores ranging from 12% to 94% depending on the skill of the surgeon. CONCLUSION Commercial medical 3D image-based engineering software has high acquisition costs that might be beyond the reach of most institutions. A sub-$1000 general purpose 3D modeling software can be used to create drill templates. Several factors were identified in the design and fabrication of the template that can be addressed to increase accuracy. Trajectory planning can also be improved by automating the process. The researchers recommend further studies in these areas specially in the context of developing 3D printing as a support service for surgical operations in the Philippines.