Porcine Pilon Fractures Result in Significant Chondrocyte Cell Death on Both Sides of the Tibiotalar Joint.

Abstract

The development of posttraumatic osteoarthritis after intra-articular fracture (IAF) of the tibial plafond is multifactorial and complex. The purpose of this study was to evaluate chondrocyte cell death at various areas of the ankle plafond in a high-energy and low-energy porcine pilon fracture model. Fifteen pilon ankle fractures were created in porcine hindlimbs using a validated large-animal IAF model. Three groups were tested: control pigs (CP), low-energy fracture pigs (LEP), and high-energy fracture pigs (HEP). Chondral samples were taken from the plafond adjacent to fracture (Tib-F), plafond at 5 mm away from the fracture (Tib-C), talus near the fracture (Tal-F), and talus 5 mm away from the fracture (Tal-C). At 48 hours, the samples were stained for live and dead cell labeling and confocal microscopy-evaluated cell death. Cell death was significantly greater for the HEP when compared to the LEP. HEP Tib-F fractional cell death was 41.92% (SD 3.5) compared with LEP Tib-F 28.8% (SD 4.32) (<i>P</i> < .0001) and HEP Tal-F fractional cell death was 40.41% (SD 4.1) compared with LEP Tal-F cell death of 25.91% (SD 4.28) (<i>P</i> = .0018). Similarly, the fractional cell death of chondral samples near the fracture was significantly greater than the cell death 5 mm away from the fracture in both the LEP and HEP (all <i>P</i> < .0001). Finally, despite no visible fractures of the talar dome, the chondrocyte cell death was not significantly different between the tibia and the talus (HEP Tib-F 41.92% vs HEP Tal-F 40.41%, <i>P</i> = .29; LEP Tib-F 28.80% vs LEP Tal-F 25.91%, <i>P</i> = .16). Chondrocyte cell death was greatest at the fracture margin and in high-energy fractures. Interestingly, across both high- and low-energy IAF models, the chondrocyte cell injury rate was similar for both the talar dome and tibial plafond. Future research should focus on mitigating chondrocyte demise after injury. The rate of posttraumatic osteoarthritis after tibial plafond injuries in humans is exceedingly high despite advances in operative treatment. This study uses a clinically relevant, large-animal pilon fracture model to evaluate rates of chondrocyte cell death after 48 hours. This study confirms that cartilage cell death is associated with proximity to the fracture lines, higher-energy injury, and that pilon injuries impact cartilage on both the tibia and talus.