A measurement device for anterior laxity of the ankle joint complex

Background. Evaluation of anterior ankle joint laxity remains an intriguing clinical problem. Manual examination is of subjective nature. The aim of the present in-vitro and in-vivo study was to develop a tester for quantitative measurement of anterior ankle joint laxity. Methods. The tester was evaluated on 7 cadaver specimens and on 24 individuals, 14 with prior ligament injury and 10 without. Subsequently, a post hoc analysis was performed on 6 individuals without ligament injury. Findings. In the cadaver tests, mean increase in anterior displacement was 2.0 mm (SD 1.6) with cut anterior talofibular ligament, 2.7 mm (SD 2.7) with cut anterior talofibular and calcaneofibular ligaments and 3.3 mm (SD 3.3) with cut anterior talofibular, calcaneofibular and posterior talofibular ligaments. In the normal subjects, mean displacement was 23 mm (SD 6.6) for left and 25 mm (SD 7.5) for right ankles. In the group of subjects with prior ankle ligament injuries but no instability symptoms, there was no detectable laxity difference between injured and non-injured. The intra-observer reliability for the tester was 0.94. Post-hoc analysis showed a device-related systematic error of < 1 mm. Interpretation. The displacement values present the motion between the anterior aspect of the distal tibia and the posterior aspect of the heel, not solely motion in the ankle joint but in the entire ankle joint complex. The test principle has the potential to provide an objective value for anterior displacement values of the ankle joint. The test apparatus in its present form is not suitable for use in clinical practice.