Fixation of three-part proximal humeral fractures: A biomechanical evaluation

Objectives: To examine the biomechanical stability of three constructs curr ently used for the management of three-part proximal humerus fractures. Ten sion band wires (TBW) with supplemental Enders nails, modified cloverleaf p late and screws, and intramedullary (IM) nailing with proximal and distal i nterlocks were tested to determine relative stability. Design: A reproducible three-part fracture was made in fresh-frozen strippe d proximal humeri. The fracture was stabilized using TBW/Enders nail (n = 6 ), plate/screws (n = 5), or IM nailing (n = 5). Main Outcome Measurements: Mechanical testing was performed with a small pr eload followed by deflection of five millimeters at a rate of one millimete r per second in flexion, extension, and varus and valgus relative to the hu meral shaft. A load-displacement curve was obtained. Torsional testing was performed in internal and external rotation, and torque-rotation curves wer e recorded. Results: In cantilever bending, the plate/screws construct and the IM nail construct were superior to the TBW/Enders nail construct for all parameters except extension. There was no statistically significant difference betwee n the IM nail and the plate/screws groups. Torsional stiffness testing reve aled that the plate/screws and the IM nail were superior to the TBW/Enders nail construct. There was no statistical difference between the IM nail and the plate/screws groups. Conclusions: In a cadaveric model of three-part proximal humerus fractures stripped of soft tissue, plate/screws fixation and IM nailing provide great er torsional and bending stiffness than does fixation with TBW/Enders nail. There was no statistically significant difference in torsional or bending stiffness between IM nailing with interlocks and plate/screws fixation in t his model.