Transverse patellar fracture fixation with wagon wheel construct versus anterior tension banding: A biomechanical cadaveric study

Abstract

Introduction: Despite advancements in surgical technique, patellar fractures remain challenging to manage. Internal fixation of simple transverse patellar fractures is commonly performed using tension band wiring techniques, such as cannulated screw anterior tension band wiring (CATB). However, CATB is associated with high rates of symptomatic hardware, fixation failure, and reoperation. The wagon wheel (WW) construct is a novel transtendinous/transligamentous technique that involves circumferential mini-fragment plating with radially directed screws. A previously published case series demonstrated that the WW construct was associated with decreased rates of reoperation, symptomatic hardware, time to union, and gait aid dependences compared with CATB. However, no biomechanical study has compared these fixation strategies. The goal of this study was to evaluate the biomechanical performance of the WW construct compared to CATB for fixation of simple patella fractures.

Materials and methods: Seven paired fresh-frozen human cadaveric lower extremities (n=14 knees) were utilized. All patellae were fractured using an oscillating saw to simulate two-part simple transverse AO/OTA 34-C1 patella fractures. Matched pairs of knees underwent randomization to the WW and CATB constructs. All surgically fixed specimens underwent cyclic loading testing through 1000 cycles, as well as subsequent load-to-failure testing. Failure was defined as fracture displacement ≥ 2 mm. High-resolution optical motion tracking system recorded fracture displacement in three dimensions throughout testing.

Results: The WW construct demonstrated less mean fracture displacement on the first flexion cycle (WW: 0.09 vs. CATB: 0.32 mm; p=0.11) and after 1000 cycles of flexion (WW: 0.31 vs. CATB: 1.0 mm; p=0.017), equating to 69% less mean fracture displacement than CATB. The mean force required to cause construct failure was more than double for knees fixed with the WW construct compared with CATB (900 vs. 434 N; p=0.025) DISCUSSION: In the first human cadaveric biomechanical study to compare the novel WW construct to CATB, the WW construct demonstrated superior fixation stability and 69% less fracture displacement after 1000 cycles of flexion. The findings of this study provide biomechanical validation for previously reported clinical advantages of the peripheral plate-based WW construct, compared to CATB, demonstrating that the WW may offer superior fracture fixation stability through cyclic loading.

Keywords: Biomechanical study; Cadaveric study; Fracture displacement; Motion tracking; Simple patella fracture; Tension band wiring; Wagon wheel.