Sagittal displacement in patients with end stage ankle arthritis has been described as the tibiotalar ratio (TTR). Yet the incidence, distribution and predictive factors of talolisthesis are unknown.
The radiographs of 470 cases of ankle arthritis were compared with a control group of 49 normal ankles. The TTR was measured for both groups. Additional co-variables included the anterior and lateral distal tibial angles, and talar tilt.
The mean TTR in the arthritis cohort was 34.8+9.12 compared to the normal group of 34.1+2.62. Twenty-eight percent of the ankles had anterior displacement and twenty-eight percent had posterior talolisthesis, while forty-four percent had normal tibiotalar alignment. Multivariate linear regression revealed significant predictors of anterior distal tibial angle (p<0.0001) and talar tilt (p=0.0007) for abnormal TTR.
Sagittal displacement is common in end stage ankle arthritis and is affected by ligamentous laxity and joint morphology.