The Biomechanical Evaluation Of Internal Fixation For Proximal Humerus Fractures (Neer Type 3)

ObjectiveThe purpose of this study was to investigate the mechanical stability and durability of cannulated compression screws(ccs) and percutaneous pinning (PP) ,and cloverleaf plate(cp) for fixation of three-part proximal humeral fractures using a cadaveric model.MethodsWe used a cadaveric three-part proximal humeral osteotomy model to perform a biomechanical evaluation of three types of internal fixation devices: cannulated compression screws, a cloverleaf plate, and Kirschner wires.Thirty six (18 fresh frozen, 18 embalmed) proximal humerus specimens were selected and divided into two groups: fresh frozen specimens represented a nonosteopenic group and embalmed specimens an osteopenic group. The bone-mineral density of each specimen was measured with dual energy x-ray absorptiometry . Simulated three-part proximal humeral fractures were created, reduced, and randomly assigned to one of three methods of fixation (six fresh frozen and six embalmed specimens per fixation group). The specimens were tested cyclically in abduction and in flexion- extend for 250 cycles to evaluate interfragmentary motion and rotation. The specimens were tested in torsional load and loaded to failure in external rotation to measure torsional load to failure and torsional stiffness.ResultsFresh frozen humerus specimens have higher BMD than the embalmed. The Cannulated compression screws had greater stiffness than percutaneous pinning ,but less than cloverleaf plate . Bone-mineral density was strongly correlated with the stiffness of the CCS and the PP,but there is no significant difference for the CP between two kind of humerus specimens .ConclusionThe Cannulated compression screws is an effective method of minimal invasion to treat proximal humerus fracture,which is strong enough for internal fixation and can provid sufficient stability allow postoperative functional exercise.