The high rigidity of metal implants may be a cause of failure after fixation of proximal humerus fractures. Carbon fiber-reinforced polyetheretherketone (PEEK) plates with a modulus similar to human cortical bone may help to overcome this problem. The present study assesses the biomechanical behavior of a PEEK plate compared with a titanium locking plate.
Materials and methods
Unstable two- and three-part fractures were simulated in 12 pairs of cadaveric humeri and were fixed with either a PEEK or a titanium locking plate using a pairwise comparison. With an optical motion capture system, the stiffness, failure load, plate bending, and the relative motion at the bone–implant interface and at the fracture site were evaluated.
Results
The mean load to failure for two- and three-part fracture fixations was, respectively, 191 N (range 102–356 N) and 142 N (range 102–169 N) in the PEEK plate group compared with 286 N (range 191–395 N) and 258 N (range 155–366 N) in the titanium locking plate group. The PEEK plate showed significantly more bending in both the two- and three-part fractures (p < 0.05), an increased relative motion at the bone–implant interface and lower stiffness values (p < 0.05).
Conclusion
In this biomechanical study on unstable proximal humerus fractures, fixation with a PEEK plate showed lower fixation strength and increased motion at the bone–implant interface compared with a titanium locking plate.
