Source
*R Adams Cowley Shock Trauma Center, Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD the †Orthopaedic Mechanobiology Laboratory, Department of Bioengineering, University of Maryland, College Park, MD.
Abstract
OBJECTIVE:
: To compare the biomechanical performance of a cephalomedullary nail (CMN), a proximal femoral locking plate, and a 95° angled blade plate in a comminuted subtrochanteric fracture model.
METHODS:
: A comminuted subtrochanteric femoral fracture model was created with a 2-cm gap below the lesser trochanter in 15 pairs of human cadaveric femora confirmed to be nonosteoporotic. The femora were randomized to treatment with one of the previously mentioned 3 devices. Each was tested under incrementally increasing cyclic load up to 90,000 cycles from 50% to 250% of body weight to simulate progressive weight bearing during 3 months of an average 700-N (approximately, 70 kg or 150 lb) person. Force, number of cycles, and total load sustained to reach 10 mm of displacement were compared. Failure modes were also noted.
RESULTS:
: The CMN construct withstood significantly more cycles, failed at a significantly higher force, and withstood a significantly greater load than either of the plate constructs (P < 0.001). Varus collapse was significantly lower in the CMN construct (P < 0.0001). Modes of failure differed among implant-bone constructs with damage to the femoral head through implant cutout in 5 of 10 blade plate specimens and 2 of 10 CMN specimens, whereas no damage to the femoral head bone was observed in any of the locking plate constructs.
CONCLUSIONS:
: The CMN construct was biomechanically superior to either the locking plate or 95° blade plate constructs. The locking plate construct was biomechanically equivalent to the blade plate construct.