Radiological Assessment for Distal Fibular Length

Purpose: This study was performed to reevaluate the radiological parameters for assessing the length of the distal fibula in the mortise view of the ankle and to introduce a more reliable method to lessen measurement error. Materials and Methods: Mortise view radiographs of 36 normal ankles from 18 healthy volunteers were obtained. The talocrural angle and bimalleolar angle were measured two times and compared bilaterally by two independent observers. Also, The lateral malleolar angle, newly devised in our department was measured and compared bilaterally. Results: The average of the talocrural angle, bimalleolar angle, and lateral malleolar angle was 78.4 degrees (range 74 to 83), 78.3 degrees (range 73 to 86), and 36.7 degrees (range 30 to 41), respectively. The difference of the talocrural angle, bimalleolar angle, and lateral malleolar angle between right and left was 2.1 degrees, 3.0 degrees, and 1.2 degrees (95% confidence limit), respectively. Intraobsever difference of the talocrural angle, bimalleolar angle, and lateral malleolar angle was 1.5 degrees, 1.6 degrees, and 0.4 degrees, respectively. Interobsever difference of the talocrural angle, bimalleolar angle, and lateral malleolar angle was 1.3 degrees, 2.4 degrees, and 1.0 degrees, respectively. Conclusion: When using various measurement methods to judge the length of the distal fibula, the measurement error should be considered. The proposed method, lateral malleolar angle, would be a good method for assessing the length of distal fibula in the mortise view of ankle.