Biomechanical cadaver testing of a fixed-angle plate in comparison to tension wiring and screw fixation in transverse patella fractures.

INTRODUCTION: Operative treatment of patella fractures is frequently associated with implant failure and secondary dislocation which can be attributed to the employed hardware. Therefore, a 2.7 mm fixed-angle plate designed for the treatment of patella fractures was tested biomechanically against the currently preferred methods of fixation. It was hypothesized that under simulated cyclic loading fixed-angle plating would be superior to modified anterior tension wiring or cannulated lag screws with anterior tension wiring.
MATERIALS AND METHODS: Eighteen human cadaver knees, matched by bone mineral density and age, were divided into three groups of six. After setting a transverse patella fracture each group received one of the osteosyntheses mentioned above. Repetitive testing over 100 cycles was performed at non-destructive loads by simulating knee motion from 90° flexion to full extension.
RESULTS: Anterior tension wiring as well as lag screws with tension wiring showed significant fracture displacement after the initial cycle already. Both constructs, lag screws plus wiring (3.7 ± 2.7 mm) as well as tension wiring alone (7.1 ± 2.2 mm) displayed fracture displacement of >2 mm which is clinically regarded as failure. Those patellae stabilized with fixed-angle plates showed no significant fracture gap widening after completion of 100 cycles (0.7 ± 0.5 mm). The differences between the fixed-angle plate group and the other two groups were statistically significant (p<0.05).
CONCLUSION: In contrast to modified anterior tension wiring and cannulated lag screws with anterior tension wiring the bilateral fixed-angle plate was the only fixation device to stabilize transverse patella fractures securely and sustainably.