A new knee arthrometer demonstrated to be reliable and accurate to assess anterior tibial translation in comparison with stress radiographs

Introduction: For several years, many arthrometers have been developed to assess anterior knee laxity. The aim of our study was to evaluate the validity of a new practical and handy testing device with the hypothesis that the new arthrometer had good validity in terms of reliability and accuracy. Methods: Lachman test was performed on five fresh frozen cadaveric knees by five examiners. Anterior tibial translation (ATT) was measured with a new arthrometer (BLU-DAT) and on lateral stress radiographs. Data on ATT were obtained under 7 kg (69 N), 9 kg (88 N), and maximum manual traction (MMT). Tests were performed on the same specimens before and after arthroscopic ACL excision. Inter-rater reliability of the BLU-DAT measures was assessed with the intraclass correlation coefficient (ICC) for single and average measurements. The Bland–Altman method was used to estimate agreement between the BLU-DAT and stress radiographs. Results: ICC values for single measurements were 0.62, 0.54 and 0.58 for 7-kg, 9-kg and MMT assessment, respectively. Overall reliability was good (ICC = 0.63). ICC values for average measurements were 0.89, 0.85 and 0.88 for 7-kg, 9-kg and MMT assessment, respectively. Overall reliability was very good (ICC = 0.90) SEM ranged from 1.4 mm to 1.6 mm for single measurements and was below 1 mm at each testing condition for average measurements. Analysis of agreement between BLU-DAT and radiographic measurements showed a mean difference equal to 0.83 mm ± 2.1 mm (95% CI: 0.55–1.11). Upper LOA was equal to 4.9 mm (95% CI: 5.39–4.41). Lower LOA was equal to − 3.2 mm (95% CI: − 2.71 to − 3.69). Conclusion: Measurement of anterior knee laxity with the BLU-DAT testing device has a good to very good inter-rater reliability and good agreement with a gold standard such as stress radiographs. Cadaveric Diagnostic Study, Level of Evidence IV.