Background
Arthrometers have become increasingly popular for objective assessments of anterior knee laxity. A broad variety of knee arthrometers is available, however their reliability is still controversial. The purpose of the present study was to evaluate the intra and inter-rater reliability of a new arthrometer (BLU-DAT, FGP, Dossobuono, Verona, Italy) for the measurement of anterior tibial translation (ATT) in outpatient setting.
Methods
A reliability study was conducted. All patients affected by an anterior cruciate ligament (ACL) injury confirmed by magnetic resonance imaging (MRI) were included. Exclusion criteria were: bilateral ACL injuries and/or previous contralateral ACL reconstructions. Three examiners (one orthopedic surgeon fellowship trained in knee surgery and two orthopedic residents) performed a Lachman test by using a new testing device (BLUDAT; FGP srl, Dossobuono, VR, Italy) to measure ATT. Each examiner applied three different loads: 7 Kg (69 N), 9 Kg (88 N) and maximum manual traction (MMT) on the affected and contralateral knee. Every test was repeated three times by each examiner. Mean side-to-side difference in ATT was calculated. A second set of measures was repeated after 2 weeks by one examiner to assess intra-rater reliability. Intraclass Correlation Coefficients (ICCs) were calculated using a two-way random effect model and evaluation of absolute agreement. Confidence intervals (CI) were calculated at 95% confidence level for reliability coefficients. Reliability values range from 0 (no agreement) to 1 (maximum agreement).
Results
The study included 39 patients. Inter-observer reliability showed a good agreement only for MMT (ICC=0.75, 95% CI = 0.57 – 0.86); while intra-observer reliability showed a good agreement for 7 kg (ICC=0.75, 95% CI = 0.52–0.87) and MMT (ICC=0.78, 95% CI = 0.58 – 0.88). All other measurements showed only a moderate agreement.
Conclusion
The BLU-DAT testing device has a good inter-rater and intra-rater reliability at MMT.