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Cadaveric-biomechanical evaluation of bone-implant construct of proximal humerus fractures (Neer type 3)
Florian Fankhauser1, Gert Schippinger, Kurt Weber
1University Clinic of Traumatology, Medical School of graz, Austria. florian.fankhauser@klinikum-graz.at
Background:
A biomechanical cadaver study was performed to test the stability and strength of screw osteosynthesis of surgical neck fractures of the humerus.
Methods:
After bone density measurement, 64 cadaver proximal humerus bones were bent to create a subcapital fracture. The fracture was then stabilized by means of screw osteosynthesis randomly assigned to subgroups of screw positioning, size of screw, and stress test (torsion/bending).
Results:
Two screws applied laterally and parallel were 34.2% more stable than the normal arrangement. Bone density had a dominant role with regard to maximal bending and torsion force, but no significance was found with respect to additional screws through the major tuberculum or diameter of screws.
Conclusion:
Two of the smaller 4.5-mm cannulated screws should be applied parallel from the lateral direction. Only range-of-motion exercises that produce a bending stress should be considered early after surgery, avoiding axial stress.
