title: The Humerusblock NG: a new concept for stabilization of proximal humeral fractures and its biomechanical evaluation.
abstract: BACKGROUND
  The Humerusblock NG represents a new semi-rigid angular stable fixation device for minimally invasive stabilization of proximal humeral fractures. This study evaluates the function and stability of the Humerusblock NG and its biomechanical properties on the basis of two different fracture models under cyclic loading.
  
  
  METHODS
  Six fresh frozen human humeri were tested in a dynamic shoulder joint abduction motion test bench, simulating abduction between 15° and 45°. A stable wedge fracture with intact medial hinge and an unstable fracture with 5-mm gap were loaded for 500 cycles. Radiological measurement of implant migration was performed.
  
  
  RESULTS
  The stable fracture model showed a slow constant fracture settling. The unstable fracture model showed initial fracture settling with closure of the medial fracture gap during the first 20 cycles. Thereafter, a slow constant settling of the fracture was measured comparable to the stable fracture model. Maximum varus tilt was 3.17° for the stable and 3.68° for the unstable fracture pattern. Radiological analysis showed no change in the tip apex distance and a significant settling of the implants fixation pins in the unstable fracture model. None of the specimen failed during the testing.
  
  
  CONCLUSIONS
  The Humerusblock NG allows for angular stable dynamic fixation of two-part proximal humeral fractures. It enables closure of the fracture gap and maintains fracture compression during loading, a concept already established in the stabilization of femoral neck fractures (dynamic hip screw). Clinical trials will be necessary to evaluate the value of this device in daily practice.
  
  
  METHODS
  Basic science study.
authors.affiliation: Department for Trauma Surgery and Sports Medicine, Medical University Innsbruck, Anichstrasse 35, Innsbruck, Austria. a-r.brunner@web.de
authors.forename: Alexander
authors.initials: A
authors.lastname: Brunner
authors.forename: Herbert
authors.initials: H
authors.lastname: Resch
authors.forename: Reto
authors.initials: R
authors.lastname: Babst
authors.forename: Susanne
authors.initials: S
authors.lastname: Kathrein
authors.forename: Johann
authors.initials: J
authors.lastname: Fierlbeck
authors.forename: Alfred
authors.initials: A
authors.lastname: Niederberger
authors.forename: Werner
authors.initials: W
authors.lastname: Schmölz
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging / Q000502:physiology; D016268:Internal Fixators; D011859:Radiography; D012784:Shoulder Fractures / Q000601:surgery*; D016474:Weight-Bearing