Tibial and talar trabecular lines in the assessment of ankle alignment

Abstract The measurement of talar alignment in patients with ankle destruction due to arthritis or previous surgery can be difficult when planning surgery. Radiographs were used to determine whether tibial and talar trabecular lianes are a reliable method of assessment. Trabecular orientation within the talus and distal tibia was measured using an electronic goniometer in standard mortise view anteroposterior (AP) ankle radiographs from 25 normal patients. Radiographs of 12 cadaver ankles were taken in AP, and in 15 and 30° of both internal and external rotation and the trabecular orientation similarly measured. Three independent clinicians assessed the radiographs on two separate occasions. In the normal group the mean trabecular angle was 0.5° valgus (95 percentile: 4° varus to 5° valgus). In the cadaver group of mortise AP radiographs the mean trabecular angle was 1.6° valgus (95 percentile: 4° varus to 10° valgus). Positioning cadaver ankles in internal or external rotation had little effect on the mean trabecular angle, but observer variation increased. Normal ankles consistently have a tibio-talar trabecular angle of between 5° varus and 5° valgus on good mortise view AP radiographs. Uncertainty of measurement increased with rotation or plantarflexion of the ankle. These lines can be used to determine the varus/valgus orientation of the talus within the ankle joint, which may be useful when assessing joints destroyed by disease or removed at surgery.