Diagnostic Evaluation of Mechanical Ankle Instability by Comparing Injured and Uninjured Contralateral Ankles Using Arthrometry

Context: Individuals with mechanical ankle instability (MAI) have obvious lateral ligament laxity and excessive ankle joint motion beyond the physiological range. Arthrometry has been introduced to quantitatively measure the laxity of the ankle joint. However, the diagnostic accuracy of arthrometry in MAI is still debatable. Objectives: To (1) evaluate the difference in laxity between bilateral ankles in patients with and those without MAI and (2) calculate the diagnostic accuracy of ankle arthrometry using bilateral comparisons. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: A total of 38 individuals with unilateral MAI (age = 31.24 +/- 7.90 years, height = 168.93 7.69 cm, mass = 65.72 +/- 10.47 kg) and 38 individuals without MAI (control group; age = 32.10 +/- 7.10 years, height = 166.59 7.89 cm, mass = 62.93 +/- 10.72 kg). Main Outcome Measure(s): Bilateral ankle laxity in each participant was quantitatively measured by performing the arthrometric anterior drawer test. Continuous data of loading force and joint dis- placement were recorded. Data from both ankles were compared for the ankle joint displacement at a loading force of 75 N (D75) and load-displacement ratio from 10 to 40 N (LDR 10-40). Results: The D75 between injured and uninjured ankles patients with MAI was different (t37 = 9.78, P < .001). The mean LDR 10-40 in injured ankles was higher than that in uninjured ankles (t37 = 9.80, P < .001). In the control group, no differences were found between the left and right ankles. The MAI group had larger bilateral differences than the control group (t37 range 7.33-8.18; P < .001). When LDR 10-40 was used to diagnose MAI, the arthrometer showed sensitivity and specificity of 0.900 and 0.933, respectively, with a cutoff value of 0.0351 mm/N. Conclusions: An ankle arthrometer can be used to quantitatively measure the difference in bilateral ankle laxity in patients with MAI. Arthrometer-measured LDR 10-40 can be used to diagnose MAI with high diagnostic accuracy.