The Humerusblock NG: a new concept for stabilization of proximal humeral fractures and its biomechanical evaluation
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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.
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.
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.
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.
Level of evidence
Basic science study.
KeywordsProximal humerus Fracture Percutaneous Minimally invasive Semi-rigid Fixation
Conflict of interest
The biomechanical lab of the University of Innsbruck received institutional funds from Synthes GmbH, Austria as reimbursement for material and personal costs for conducting the experiments. The authors or their immediate family did not receive any personal funding or benefits.
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