DISTAL FEMORAL FIXATION - A LABORATORY COMPARISON OF THE 95-DEGREES PLATE, ANTEGRADE AND RETROGRADE INSERTED REAMED INTRAMEDULLARY NAILS

A biomechanical cadaver study was performed to compare the stability o f three standard distal femoral fixation techniques. Eighteen mildly o steoporotic femurs were selected, based on a dual-energy x-ray absorpt ion scanning bone density of 0.3-0.5 g/cm(2) and a Singh index of III- IV. After initial mechanical characterization of these intact femurs, a distal femoral osteotomy was created, reduced, and stabilized under compression using random assignment to one of three methods of fixatio n: (a) six-hole 95 degrees supracondylar plate, (b) retrograde inserte d statically locked supracondylar intramedullary nail, and (c) antegra de inserted statically locked Russell-Taylor nail. The instrumented fe murs were mechanically tested, a 1-cm gap created, and the femurs rete sted. The specimens were finally loaded to failure in A-P three-point bending. The 95 degrees plate provided significantly stiffer fixation than the supracondylar intramedullary nail or Russell-Taylor nail in b oth a compressed transverse and gap distal femoral osteotomy model. Th e Russell-Taylor nail provided the least rigid fixation. The 95 degree s plate and Russell-Taylor nail had statistically significant greater loads to failure than the supracondylar intramedullary nail. These res ults support the use of a 95 degrees plate when maximum rigidity of fi xation or maximum compression is desired.