Autologous Osteochondral Transplantation of the Talus Partially Restores Contact Mechanics of the Ankle Joint

Background: Autologous osteochondral transplantation procedures provide hyaline cartilage to the site of cartilage repair. It remains unknown whether these procedures restore native contact mechanics of the ankle joint. Purpose: This study was undertaken to characterize the regional and local contact mechanics after autologous osteochondral transplantation of the talus. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen cadaveric lower limb specimens were used for this study. Specimens were loaded using a 6 degrees of freedom robotic arm with 4.5 N center dot m of inversion and a 300-N axial compressive load in a neutral plantar/dorsiflexion. An osteochondral defect was created at the centromedial aspect of the talar dome and an autologous osteochondral graft from the ipsilateral knee was subsequently transplanted to the defect site. Regional contact mechanics were analyzed across the talar dome as a function of the defect and repair conditions and compared with those in the intact ankle. Local contact mechanics at the peripheral rim of the defect and at the graft site were also analyzed and compared with the intact condition. A 3-dimensional laser scanning system was used to determine the graft height differences relative to the native talus. Results: The creation of an osteochondral defect caused a significant decrease in force, mean pressure, and peak pressure on the medial region of the talus (P = .037). Implanting an osteochondral graft restored the force, mean pressure, and peak pressure on the medial region of the talus to intact levels (P = .05). The anterior portion of the graft carried less force, while mean and peak pressures were decreased relative to intact (P = .05). The mean difference in graft height relative to the surrounding host cartilage for the overall population was -0.2 +/- 0.3 mm (range, -1.00 to 0.40 mm). Under these conditions, there was no correlation between height and pressure when the graft was sunken, flush, or proud. Conclusion/Clinical Relevance: Placement of the osteochondral graft in the most congruent position possible partially restored contact mechanics of the ankle joint. Persistent deficits in contact mechanics may be due to additional factors besides graft congruence, including structural differences in the donor cartilage when compared with the native tissue.