Arthrometric curve-shape variables to assess anterior cruciate ligament deficiency.
BACKGROUND
Instrumented measurement of asymmetry in anterior-posterior knee laxity is commonly used to assess anterior cruciate ligament integrity. Significant advances in arthrometric technology and data visualization have occurred since first generation arthrometers. However, little has changed with regard to diagnostic criteria employed. To our knowledge, no investigations have assessed the shape of laxity curves to diagnose anterior cruciate ligament (ACL) deficiency. We hypothesized that linear stiffness and compliance after positive curve inflection would be more sensitive and specific to anterior cruciate ligament injury than current measures and would require data from the involved limb only.


METHODS
Laxity curves were obtained from 130 knees on 65 subjects (Anterior Cruciate Injured n=15, Controls n=50) using a CompuKT Knee Ligament Arthrometer. Traditional diagnostic variables and novel descriptive curve-shape variables [(1) inflection point, (2) pre- and post-inflection linear stiffness and (3) a modified compliance index based on the post-inflection linear stiffness] were assessed for sensitivity to anterior cruciate ligament deficiency. Statistical interactions were evaluated using 2-by-2 ANOVA.


RESULTS
Significant interactions (P<0.001) were identified for laxity symmetry, stiffness, compliance index and modified compliance index. Modified compliance index predicted anterior cruciate ligament deficiency with the highest sensitivity (93%) and specificity (100%). For a test performed on a single limb, modified compliance index demonstrated 98% sensitivity and 80% specificity.


CONCLUSIONS
The modified compliance index is a highly sensitive and specific measure to diagnose anterior cruciate ligament deficiency, and may serve as a simple and accurate diagnostic tool for individuals without a healthy contralateral limb.
The Ohio State University, Department of Biomedical Engineering, Columbus, OH, USA.
Samuel C
SC
Wordeman
Mark V
MV
Paterno
Carmen E
CE
Quatman
Nathaniel A
NA
Bates
Timothy E
TE
Hewett
D000293:Adolescent; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007717:Knee / Q000033:anatomy & histology; D007719:Knee Joint / Q000033:anatomy & histology; D008297:Male; D008953:Models, Anatomic; D015233:Models, Statistical; D009985:Orthopedics / Q000379:methods; D012372:ROC Curve; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D013314:Stress, Mechanical