Biomechanical analysis of plate osteosynthesis systems for proximal humerus fractures.

OBJECTIVES: To biomechanically assess five proximal, humeral, fracture-plate-fixation systems. METHODS: Surgical neck fractures, with and without cortical contact, were created in 25 fresh-frozen cadaveric humeri. Five methods of plate fixation were used for repair: construct A [an eight-hole, low contact dynamic compression (LCDC) plate contoured into a blade shape, supported by one, 70-mm-long, 4.5-mm-diameter cortical screw acting as a truss], construct B (a 10-hole LCDC plate arrangement identical to construct A, but using one, 70-mm-long, 3.5-mm-diameter cortical screw as a truss), construct C [a five-hole dynamic compression (DC) blade plate with one, 6.5-mm-diameter cancellous screw], construct D (a five-hole T-plate supported by three, 6.5-mm-diameter cancellous screws), and construct E (a five-hole cloverleaf plate supported by five, 4-mm-diameter cancellous screws). Plates were posterior to the bicipital groove, 10 mm distal to the greater tuberosity tip, on the lateral aspect of the humeral shaft. Screw fixation was done using standard AO compression plating techniques. Stiffness of constructs was measured in bending and axial compression. Locked plates were not assessed. RESULTS: For cortical contact [abduction of 20 degrees (P=0.02), flexion of 20 degrees (P=0.02), flexion of 90 degrees (P=0.005)] and no cortical contact [flexion of 90 degrees (P=0.0001)], construct A was significantly stiffer than other constructs. For no cortical contact in abduction of 90 degrees (P=0.05), construct A was significantly stiffer than other constructs. CONCLUSIONS: Construct A was significantly stiffer than other constructs.

The biomechanical analysis of three plating fixation systems for periprosthetic femoral fracture near the tip of a total hip arthroplasty.

BACKGROUND: A variety of techniques are available for fixation of femoral shaft fractures following total hip arthroplasty. The optimal surgical repair method still remains a point of controversy in the literature. However, few studies have quantified the performance of such repair constructs. This study biomechanically examined 3 different screw-plate and cable-plate systems for fixation of periprosthetic femoral fractures near the tip of a total hip arthroplasty. METHODS: Twelve pairs of human cadaveric femurs were utilized. Each left femur was prepared for the cemented insertion of the femoral component of a total hip implant. Femoral fractures were created in the femurs and subsequently repaired with Construct A (Zimmer Cable Ready System), Construct B (AO Cable-Plate System), or Construct C (Dall-Miles Cable Grip System). Right femora served as matched intact controls. Axial, torsional, and four-point bending tests were performed to obtain stiffness values. RESULTS: All repair systems showed 3.08 to 5.33 times greater axial stiffness over intact control specimens. Four-point normalized bending (0.69 to 0.85) and normalized torsional (0.55 to 0.69) stiffnesses were lower than intact controls for most comparisons. Screw-plates provided either greater or equal stiffness compared to cable-plates in almost all cases. There were no statistical differences between plating systems A, B, or C when compared to each other (p > 0.05). CONCLUSIONS: Screw-plate systems provide more optimal mechanical stability than cable-plate systems for periprosthetic femur fractures near the tip of a total hip arthroplasty.