Biomechanical evaluation of simulated feline patella fracture repairs

Objective: To investigate four techniques for stabilisation of feline patellar fracture. Methods: Feline cadaveric stifles with simulated patellar fracture were stabilised with one of four techniques: Group A-circumferential wire, group B-figure eight wire, group C-combined figure eight and circumferential wire, group D-pin and tension band wire. All repairs were subjected to a period of cyclic loading prior to load to failure testing. Experiments were recorded by video capture to determine load at failure and failure mode. Failure was defined as an opening of the fracture gap of 3mm. Results: Mean fracture gap opening (±SD) during peak loading after 1000 cycles was: group A-1.66mm (± 0.69), group B-1.01mm (± 0.45), group C-0.81mm (± 0.58), group D-0.65mm (± 0.54). Groups C and D had statistically lower mean fracture gap opening after 1000 cycles when compared to group A (p<0.05).Mean loads (+/-SD) at failure were: group A–171.4 (+/-62.2)N, group B–208.7 (+/-20.7)N, group C–288.2 (+/-62.5)N and group D–219.5 (+/-48.0)N. Group C had statistically higher mean load to failure than all other groups (p<0.05). There was no difference between other groups. In groups A, B and C the principle mode of failure was wire elongation and tearing of sutures through the retinaculae and periarticular soft tissues. In group D the principle mode of failure was the pin pulling through the bone of the distal fragment. Conclusions: Combined figure 8 and circumferential wires may be useful for treatment of transverse feline patellar fracture repair