Biomechanical comparison of two side plate fixation techniques in an unstable intertrochanteric osteotomy model: Sliding Hip Screw and Percutaneous Compression Plate.

BACKGROUND

Our objective was to determine the biomechanical primary stability of two different side plate fixation devices in an unstable intertrochanteric cadaver model: the Sliding Hip Screw with an additional derotation screw was compared with the Percutaneous Compression Plate.

METHODS

Eight pairs of human cadaver femurs were tested for comparison of the primary stability of the two implants in two modes: (a) cyclic loading up to 200 N, 400 N, 600 N, 800 N, and 1000 N, respectively. In vitro combined axial and bending loads were applied. Angular displacements of the proximal head fragment during loading were recorded in rotational, varus-valgus, and anterior-posterior directions. (b) The load to failure was determined.

FINDINGS

Specimens fixed with the Percutaneous Compression Plate showed higher displacements in the varus during loading up to 200 N (P=0.033), and 400 N (P=0.001), compared to the Sliding Hip Screw. A similar tendency was observed for higher loads. The Percutaneous Compression Plate allowed more external rotation of the proximal fragment only at loads up to 800 N (P=0.019). No statistical difference could be found for the slight migrations in the posterior direction. Load to failure also revealed no statistical difference between the two implants.

INTERPRETATION

The Percutaneous Compression Plate as a double-axis fixation device with a sliding capability allows higher displacements in the varus direction and also in external rotation at 800 N loading compared to the Sliding Hip Screw as a single-axis fixation device combined with an additional derotation screw. While both implants are successful used in clinical practice, this should be considered in treatment of unstable intertrochanteric fractures with inferior comminution in osteoporotic patients.