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

Background: 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.

Methods: 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.

Results: 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) (P < .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) (P = .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 P < .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%, P = .29; LEP Tib-F 28.80% vs LEP Tal-F 25.91%, P = .16).

Conclusion: 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.

Clinical relevance: 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.