title: Biomechanical evaluation of two innovative locking implants for comminuted olecranon fractures under high-cycle loading conditions.
abstract: BACKGROUND
  The relatively high complication rate after fixation of olecranon fractures has led to an increasing application of anatomically pre-contoured locking plate systems. The purpose of the present study was to conduct a biomechanical comparison of olecranon osteosyntheses by applying the Olecranon VA-LCP and the 3.5mm LCP Hook Plate (LCP, locking compression plate) to an unstable fracture model under high-cycle loading conditions.
  
  
  METHODS
  After creating an unstable fracture (Schatzker type B), osteosynthesis was performed on eight pairs of fresh-frozen cadaveric ulnae by application of either the Olecranon VA-LCP (Synthes, Solothurn, Switzerland) or the 3.5mm LCP Hook Plate (Synthes, Solothurn, Switzerland). Loading (50,000 alternating loads, cyclic and sinusoidal 10-300 N) was conducted by application of tensile load with the elbow in 90° flexion to simulate the tensile strength of the triceps brachii. For statistical analysis, angular displacement in the region of the humeral trochlea was taken as a measure of olecranon dislocation.
  
  
  RESULTS
  In Group 1 (Olecranon VA-LCP), a median angular displacement of 0.36° (minimum 0.10°; maximum 0.80°) was observed after 500 alternating loads. In Group 2 (3.5-mm LCP Hook Plate), the medial displacement was 0.80° (minimum 0.13°; maximum 2.72°). The difference was nonsignificant (p = 0.128). The mean value for angular displacement in Group 1 after 50,000 cycles was 0.80° (minimum 0.31°; maximum 1.99°), whereas in Group 2 a mean angular displacement of 2.02° (minimum 0.71°; maximum 6.40°) was recorded. The difference was statistically significant (p = 0.017). In Group 2, implant failure in the form of proximal plate pullout occurred in one construct after 756 cycles.
  
  
  CONCLUSIONS
  A significantly higher biomechanical stability can be achieved in the fixation of unstable olecranon fractures by application of the Olecranon VA-LCP rather than the 3.5mm LCP Hook Plate.
authors.affiliation: Department of Orthopedic and Trauma Surgery, Freiburg University Medical Center, Freiburg, Germany. Electronic address: ferdinand.wagner@uniklinik-freiburg.de.
authors.forename: F C
authors.initials: FC
authors.lastname: Wagner
authors.affiliation: Department of Orthopedic and Trauma Surgery, Freiburg University Medical Center, Freiburg, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Konstantinidis
authors.affiliation: Department of Orthopedic and Trauma Surgery, Freiburg University Medical Center, Freiburg, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Hohloch
authors.affiliation: Department of Orthopedic and Trauma Surgery, Freiburg University Medical Center, Freiburg, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Hohloch
authors.affiliation: Department of Orthopedic and Trauma Surgery, Freiburg University Medical Center, Freiburg, Germany.
authors.forename: N P
authors.initials: NP
authors.lastname: Suedkamp
authors.affiliation: Department of Orthopedic and Trauma Surgery, Freiburg University Medical Center, Freiburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Reising
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D002102:Cadaver; D005593:Fracture Fixation, Internal / Q000379:methods*; D005594:Fracture Fixation, Intramedullary / Q000379:methods*; D018460:Fractures, Comminuted / Q000601:surgery*; D006801:Humans; D056740:Olecranon Process / Q000601:surgery*; D011474:Prosthesis Design; D013718:Tensile Strength; D014458:Ulna Fractures / Q000601:surgery*
keywords: Biomechanics; Cyclic loading; Elbow; Locking compression plate; Olecranon fracture fixation; Osteosynthesis