Summary
Evaluation of AMRL using the Feagin-Thomas Examination
Abstract
Background
Anteromedial rotatory laxity (AMRL) can contribute to instability in ACL-injured knees. However, it is often under diagnosed. The Feagin –Thomas examination technique for assessing AMRL has been previously presented at the ACL Study group in St Kitts 2023. This study evaluates the efficacy of the Feagin-Thomas test in quantifying AMRL using 3D optical motion capture.
Methods
Using a refined protocol, AMRL was quantified in 58 uninjured legs (Including contralateral legs of injured participants) and 22 ACL-injured legs (sub-classified by MCL involvement) via anterior medial rotary displacement during the Feagin-Thomas test. Measures included absolute AMRL (mm) and interlimb ratios (MaxMaxNorm and MeanMeanNorm). ANOVA and Games-Howell post hoc analyses assessed between-group differences.
Results
ACL-injured participants demonstrated higher AMRL than controls (9.96 mm ± 3.09). The ACL-only group showed the greatest mean AMRL (13.46 mm ± 4.19), with ACL + deep MCL injuries reaching MaxMaxNorm and MeanMeanNorm ratios of 1.62 ± 0.42 and 1.57 ± 0.36, respectively. Statistically significant differences in AMRL were found between uninjured and deep MCL-involved groups (p = 0.047 and p = 0.023). Large effect sizes (?² = 0.332–0.357) confirmed the relationship between medial compartment involvement and increased AMRL.
Conclusion
This study is the first to validate the Feagin-Thomas test for AMRL quantification in vivo. Findings suggest the test is sensitive to rotational instability in ACL-MCL injuries, especially involving deep MCL fibres. These results support its clinical utility in identifying complex knee laxity patterns and my help in planning type of ACL reconstruction required