Abstract
BACKGROUND: To describe a dynamic ultrasound modified prone Lachman test to assess total anterior/posterior knee displacement. To evaluate the intra- and inter-rater reliability of the ultrasound measurements obtained during the modified prone Lachman test. METHODS: Participants laid prone on an exam table as the trained researcher and assistant performed a Lachman test on both limbs. Keeping the posterior view of the medial femur, tibia, and overlying semimembranosus tendon in view, images were captured during the maneuver via a five-second video clip. Measurements were taken from the video clips by two examiners (one experienced, one novice) within the same maneuver to assess the posterior, anterior, and total displacement of the tibia in relation to the femur. RESULTS: Thirty-seven limbs (16.0 ± 1.08 years, 165.7 ± 6.4 cm, 60 ± 6.8 kg) were included for analysis. Good intra-rater (ICC: 0.87–0.88) and inter-rater reliability (ICC:0.88–0.89) was demonstrated for anterior and posterior measures in both examiners. For the computed total displacement, the experienced examiner demonstrated excellent intra-rater reliability (ICC: 0.90) while the novice examiner demonstrated poor reliability (ICC: 0.49). Inter-rater reliability for total displacement was moderate (ICC: 0.55). No significant differences were found between raters or between sessions. CONCLUSIONS: While good intra- and inter-rater reliability was found for both posterior and anterior displacement measures, the notably lower intra-rater reliability observed for the novice examiner in total displacement highlights that examiner experience may influence measurement consistency. Using ultrasound while performing the prone Lachman test allows for an objective tibial displacement measurement to assess ACL competency and knee displacement in the presence of an intact ACL. Ultrasound provides direct visualization of femur and tibia displacement, mitigating the limitation of arthrometers in assessing knee displacement.