Background: To determine the temperature, time and biomechanical properties of free-form polyurethane external skeletal fixation (PUESF) and compare them with acrylic external skeletal fixation (ACESF). 
 
Methods: Three different configurations (uniplanar, multiplanar and circular) (n=4 for each configuration) were subjected to compression and bending (n=24 PUESF, n=24 ACESF) and only the uniplanar configuration was subjected to pullout testing (n=4 PUESF, n=4 ACESF). The temperatures of the connecting bar and K-wire were recorded when creating the multiplanar and circular configurations. All the configurations were subjected to axial and bending tests and the uniplanar configuration was subjected to pullout tests. 
 
Result: Regarding the connecting bar temperature and the temperature delivered to the K-wires, the PUESF group reached maximum temperatures of 75.7&deg;C and 38.1&deg;C at 3 minutes and the ACESF group reached maximum temperatures of 87.6&deg;C and 60&deg;C at 9 minutes, respectively (p&lt;0.001). Under compression force, the PUESF group showed similar strength to the ACESF group in the uniplanar and circular configurations (p&gt;0.05), while it showed less strength than the ACESF group in the multiplanar configuration (p&lt;0.05). The PUESF group showed similar strength to the ACESF group in all three configurations under the bending force (p&gt;0.05). The ACESF group showed approximately 2 times as much pullout strength as that of the PUESF group (p&lt;0.05). Polyurethane showed acceptable mechanical performance compared to acrylic in several test configurations. Polyurethane can be used in clinical trials for free-form external skeletal fixations (ESFs).

In vitro Biomechanical Testing of Polyurethane External Skeletal Fixator as a Novel Polymer in Fracture Treatment