Biomechanical comparison of traditional plaster cast and 3D-printed orthosis for external coaptation of distal radius fractures

Introduction

Distal radius fractures make up around 20% of adult fractures, varying in type and severity, thus requiring different treatments. Cast immobilization is effective in indicated fractures, but is associated with several disadvantages such that 3D-printed orthoses (3D-Braces) have been introduced as a potentially advantageous alternative. The present study was designed to test the hypothesis that short-arm 3D-printed Polylactic Acid (PLA) orthoses would provide superior biomechanical properties when compared to plaster of Paris short-arm casts for immobilization of distal radial fractures.

Methods

Modified mannequin forearms were utilized as human models for the creation of both the circular casts and the 3D Braces. A total of five plaster cast prototypes were produced, based on a standard cylindrical plaster cast application technique used in the treatment of distal radius fractures, and another five samples were 3D printed braces. Each sample was then subjected to a three-point bend load test, using an Instron 68SC2 testing machine, and the data was collected and exported to an Excel spreadsheet and analyzed using SPSS Statistics version 26 (IBM Corp., Armonk, N.Y., USA).

Results

The 3D-Braces can withstand significantly higher forces at yield and maximum force, implying they may offer superior mechanical stability. Moreover, our findings indicated a higher strain at yield for the 3D-Braces compared to conventional plaster casts.

Conclusions

3D-printed Polylactic Acid short-arm orthoses demonstrated superior biomechanical properties when compared to plaster of Paris short-arm casts designed for immobilization of distal radial fractures. Taken together with data from previous studies, preclinical evidence suggests that PLA 3D-Braces can effectively maintain distal radius fracture alignment and stability with potential advantages over traditional casts with respect to biomechanical properties as well as post-fabrication adjustment, patient hygiene, comfort, and daily activities.