Distal femoral fixation: a laboratory comparison of the 95 degrees plate, antegrade and retrograde inserted reamed intramedullary nails.

Overview

A biomechanical cadaver study was performed to compare the stability of three standard distal femoral fixation techniques. Eighteen mildly osteoporotic femurs were selected, based on a dual-energy x-ray absorption scanning bone density of 0.3-0.5 g/cm2 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 fixation: (a) six-hole 95 degrees supracondylar plate, (b) retrograde inserted statically locked supracondylar intramedullary nail, and (c) antegrade inserted statically locked Russell-Taylor nail. The instrumented femurs were mechanically tested, a 1-cm gap created, and the femurs retested. 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 both a compressed transverse and gap distal femoral osteotomy model. The Russell-Taylor nail provided the least rigid fixation. The 95 degrees plate and Russell-Taylor nail had statistically significant greater loads to failure than the supracondylar intramedullary nail. These results support the use of a 95 degrees plate when maximum rigidity of fixation or maximum compression is desired.