Novel techniques demonstrate superior fixation of simple transverse patella fractures - A biomechanical study.

Introduction: Traditional tension band wiring (TBW) remains the gold standard treatment for simple transverse patella fractures. Challenges include appropriately siting and bending Kirschner wires without damaging surrounding soft tissues. Damage to soft tissues and malposition of metalwork can lead to complications. We propose three novel techniques for fixation of simple transverse patella fractures to ease application without additional resources to traditional TBW. We tested their biomechanical integrity against traditional TBW.

Method: Four configurations were tested; two with longitudinal Kirschner Wires (LKW) and two with cross Kirschner Wires (CKW) fixed with either standard figure-of-eight (AO) or side TBW (STBW). An initial proof of concept human cadaveric study was conducted to ensure real world application of the constructs was feasible. The fracture fixations were tested in a biomechanical study using porcine knees. The knees were cyclically loaded in a specially designed test rig through flexion from 90 to 45 degrees. Fracture gap displacement was measured and data blindly analyzed for all tests reaching 100 cycles.

Results: 17/22 specimens reached 100 cycles with peak loading ranging from 75 to 80 N. CKW with STBW performed best with average fracture displacement of 0.43 mm. LKW with STBW performed worst with average fracture displacement of 1.93 mm. The incremental displacement/cycle for both CKW configurations was 0.27 mm compared to 0.41 & 0.60 mm for both LKW constructs showing that the CKW configuration conferred greater fixation stiffness under cyclic loading.

Discussion: Previous studies have compared alternative methods of patella fracture fixation to TBW through biomechanical superiority often requiring new resources. The methods tested here utilize the same resources as those for standard AO TBW. Reorientating the plane of the wires and position of the cerclage TBW may reduce iatrogenic soft tissue injury; reduce operating time and the risk of complications.

Conclusion: This study shows biomechanical superiority for CKW with either AO or STBW compared to LKW.