Performance of modified anatomic plates is comparable to proximal femoral nail, dynamic hip screw and anatomic plates: finite element and biomechanical testing.

Abstract

To establish whether the modified anatomic plate (MAP) performs as well as the anatomic plate (AP), dynamic hip screw (DHS) and proximal femoral nail (PFN) from a biomechanical perspective. The, AP, MAP, DHS and PFN were assessed using finite element (FE) methods and biomechanical tests. A solid model was created based on the fracture lines and results were assessed using analyses of variance. Independent variables were the implants (n=4) and axial loads: 0-1000 Newton (N) in 100 N increments. Dependent variables were loads at the intertrochanteric fracture line as measured by load cells. Axial loads ≤400 N generated significantly (p<0.05) greater stress at the fracture line in both the FE model and biomechanical settings: the PFN generated the highest forces at the fracture line followed by the AP, MAP and DHS. For axial loads ≥400 N, the AP and DHS generated nonsignificant (p>0.5) lower forces (almost 50% less) compared with the MAP and PFN. At 1000 N, the DHS generated the highest (p<0.05) load at the fracture line. The biomechanical features of the MAP were similar to those of the PFN. The MAP generated optimal loads at both the fracture site and the proximal femur. FE methods and biomechanical tests revealed that the MAP is associated with both intra- and extra-medullary fixation features, even though the load was applied as an extramedullary stimulus.