DISTAL FEMORAL FIXATION - A BIOMECHANICAL COMPARISON OF THE STANDARD CONDYLAR BUTTRESS PLATE, A LOCKED BUTTRESS PLATE, AND THE 95-DEGREE BLADE PLATE

Objectives: This biomechanical cadaver study was performed to compare the fixation stability of a standard lateral condylar buttress plate w ith a similar condylar buttress plate with the distal screws locked to the plate. Then the study was repeated with six additional matched fe moral pairs to compare the locked plate with a standard 95-degree blad e plate. Design: Six matched pairs of mildly osteopenic femurs were se lected, and each side was assigned randomly to fixation with either a standard lateral condylar buttress plate or a modified lateral condyla r buttress plate with locked distal screws. The experiment was repeate d with six additional matched pairs of femurs instrumented with either a modified lateral condylar buttress plate with locked distal screws or a standard 95-degree blade plate. Intervention: The femurs were ins trumented, and a gap osteotomy was created at the distal femoral metap hysis. The instrumented femurs were then mechanically tested in axial compression and bending/torsional loading to determine fixation stabil ity; then they were loaded at 1,000 newtons for 10(5) cycles and retes ted for stability. Main Outcome Measurement: The displacement across t he osteotomy gap at 100-newton and 1,000-newton axial loads was measur ed directly for each specimen before and after cycling. In addition, r esistance to displacement in bending/torsional loading (newtons/centim eter) was determined from load/displacement curves, before and after c ycling. Results: The locked buttress plate provided significantly grea ter fixation stability than the standard plate both before and after c ycling in axial loading. The locked buttress plate also proved signifi cantly more stable in axial loading than the blade plate both before a nd after cycling. Conclusion: A condylar buttress plate with locked sc rews is a valid concept for improving fixation stability.