INTERNAL-FIXATION OF SUPRACONDYLAR FEMORAL FRACTURES - COMPARATIVE BIOMECHANICAL PERFORMANCE OF THE 95-DEGREE BLADE PLATE AND 2 RETROGRADE NAILS

Objective: The biomechanical stability of supracondylar femoral fractu res fixed with a condylar blade plate (plate), a Green Seligson Henry nail (GSHN), or a new retrograde unreamed supracondylar femoral nail ( new nail) based on the AO unreamed femoral nail were compared. Design: A standardized simulated comminuted supracondylar femoral fracture (s egmental defect) in fresh frozen paired cadaveric femora was stabilize d with one of the implants. The inter-fragmentary fracture site stiffn ess in three directions and axial strength of the fixator-bone constru ct were compared (painwise). Results: The plate versus the new nail wa s (a) axially 10 percent as stiff and 50 percent as strong (ultimate s trength), (b) as stiff in A/P bending, and (c) five times more stiff i n torsion. Varus angle at failure under axial load was significantly g reater for the plate than for the new nail. There were no statistical differences in axial stiffness and ultimate strength between the new n ail and the GSHN, but the new nail was 50 percent and 30 percent as st iff in A/P bending and torsion, respectively. The magnitude of deforma tion at failure under axial loading was similar. Conclusions: In fixat ion of extraarticular comminuted supracondylar distal femur fractures, results indicate that (a) the new nail provides equal or greater stab ility than does the plate, except when large torsional loads are antic ipated, and (b) the new nail provides stability equal to the GSHN for axial loading and lesser stability against off-axis loads. As is evide nt in this and other studies, intramedullary implants are less torsion ally stiff than are plates. The torsional stiffness of the new nail is expected to be sufficient because it is comparable to many available nails, and low torsional moments are expected for healing femoral supr acondylar fractures.