Text

Background: Part-task trainers are essential for skills acquisition in health professions education but are subject to intensive mechanical stress and material degradation. At our skills lab, removable ears used in an otoscopy trainer presented three recurring challenges: frequent tearing caused by repeated traction on the helix to straighten the ear canal for tympanic membrane inspection, occasional inappropriate handling, and intentional cutting of the ears to replace embedded tympanic membrane images with pathological findings for assessment purposes. These factors resulted in high replacement costs and limited sustainability. This project aimed to analyse the ear material systematically and to evaluate suitable repair and sealing strategies to extend usability.

Methods: The ear replicas were examined macroscopically to document manufacturing features and damage patterns. Material identification was performed using Fourier-Transform Infrared Spectroscopy (FTIR) and hardness testing. Based on the identified material properties, relevant literature on plastisol (plasticized PVC) and adhesive bonding was reviewed. Adhesives and joining techniques were evaluated theoretically with respect to adhesion mechanisms, elasticity, resistance to plasticizer migration, application feasibility, and thermal compatibility. Exploratory practical tests included solvent-based PVC cold welding and localized thermal re-fusion of tear edges. In a practical trial, 20 ears were modified by opening them, replacing the findings, and resealing them using the proposed approach.

Results: FTIR analysis suggested a plastisol-based PVC material containing plasticizers. The ears exhibited Shore A15 hardness approximately (i.e., soft, elastic) but showed structural weaknesses at thin sections and pre-existing air inclusions. Elastic adhesives were deemed unsuitable due to required layer thickness and geometric constraints. Solvent-based diffusion bonding (PVC cold welding) demonstrated promising results, enabling cohesive rejoining of tears and effective sealing of cut openings with minimal material addition. Thermal fusion was technically feasible but associated with a higher risk of deformation. All ears used in the field trial were inserted into and removed from the trainer without renewed tearing; a systematic evaluation of the re-sealing strategy is pending.

Discussion: Material-informed repair strategies can substantially extend the service life of otoscopy trainer ears. Integrating basic material analysis into simulation management may facilitate more durable and flexible use of part-task trainers in medical education.

Competing interests: The authors declare that they have no competing interests.