Treatment of distal humeral fractures using conventional implants. Biomechanical evaluation of a new implant configuration

Background: In the face of costly fixation hardware with varying
performance for treatment of distal humeral fractures, a novel
technique (U-Frame) is proposed using conventional implants in a
180 degrees plate arrangement. In this in-vitro study the
biomechanical stability of this method was compared with the
established technique which utilizes angular stable locking
compression plates (LCP) in a 90 degrees configuration. Methods: An
unstable distal 3-part fracture (AO 13-C2.3) was created in eight
pairs of human cadaveric humeri. All bone pairs were operated with
either the "Frame" technique, where two parallel plates are
distally interconnected, or with the LCP technique. The specimens
were cyclically loaded in simulated flexion and extension of the
arm until failure of the construct occurred. Motion of all
fragments was tracked by means of optical motion capturing.
Construct stiffness and cycles to failure were identified for all
specimens. Results: Compared to the LCP constructs, the "Frame"
technique revealed significant higher construct stiffness in
extension of the arm (P = 0.01). The stiffness in flexion was not
significantly different (P = 0.16). Number of cycles to failure was
found significantly larger for the "Frame" technique (P = 0.01).
Conclusions: In an in-vitro context the proposed method offers
enhanced biomechanical stability and at the same time significantly
reduces implant costs.