2015 ISAKOS Biennial Congress ePoster #1355

Patients with Non-Contact Anterior Cruciate Ligament Injuries Have Higher Anterior and Rotational Physiological Knee Laxity in their Healthy Knee in Comparison to Controls

Caroline Mouton, PhD, Luxembourg LUXEMBOURG
Daniel Theisen, MSc, PhD, Luxembourg LUXEMBOURG
Hélène Agostinis, MSc, Luxembourg LUXEMBOURG
Christian Nührenbörger, MD, Luxembourg LUXEMBOURG
Dietrich Pape, MD, PhD, Luxembourg LUXEMBOURG
Romain Seil, MD, Prof., Luxembourg LUXEMBOURG

Sports Medicine Research Laboratory, Public Research Center for Heatlh , Luxembourg, LUXEMBOURG

FDA Status Not Applicable

Summary: Anterior and rotational knee laxity are recognized as risk factors for non-contact ACL injuries and inferior reconstruction outcomes. Our study shows that patients with non-contact ACL injuries have higher static anterior and internal rotational knee laxity profiles in their contralateral knee than controls. Subjects identified with higher laxity thus might benefit from adapted prevention programs

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Abstract:

Introduction

Excessive physiological anterior and rotational knee laxity are recognized as risk factors for non-contact ACL injuries and for inferior outcomes after ACL reconstruction. However, absolute measurements should be evaluated with caution since they may be influenced by personal characteristics (i.e. gender, body mass). Our purpose was (1) to determine if the healthy contralateral knee of ACL-injured patients have higher knee laxity profiles than a healthy control group using corrected scores (2) to establish a threshold to distinguish physiological knee laxity between both groups to target the group of healthy subjects that might benefit from specific prevention programs.

Material And Methods

One hundred and seventy-one contralateral healthy knees of non-contact ACL-injured patients and 104 healthy knees of control participants were tested for anterior and rotational laxity (internal and external rotation) following a standardised protocol. Linear regression model including gender and body mass was established using data of the control group for each laxity. Based on this model, standardised laxity scores were calculated as follows: (observed value – predicted value from the model) / standard deviation of the differences. The control group (reference) was thus characterised by an average laxity score of 0 and a standard deviation of 1. Laxity scores lead to classify knees as hypolax (score <-1), normolax (between -1 and 1) or hyperlax (>1). Proportions of subjects in each group were compared using a chi-square test. ROC curves were computed to establish a threshold to discriminate laxity between groups and odds ratios were calculated to determine the probability of being in the injured group when having an increased laxity.

Results

Contralateral knees of ACL-injured patients had greater laxity scores for anterior displacement and internal rotation (p<0.05). The healthy contralateral knees of patients were less likely to have a normolax anterior displacement/hypolax internal rotation (p=0.02) and more likely to have a normolax internal rotation/hyperlax anterior displacement (p<0.01) profile than controls. The threshold for laxity score was 0.75 for anterior laxity and -0.55 for internal rotation. Forty percent of contralateral knees of ACL-injured patients had both scores above thresholds versus 17% of controls (p<0.01). An individual was 3.18-fold more likely to be in the injured group if both laxity scores were above the defined thresholds (95% CI: 1.74-5.83).

Discussion

The combination of static anterior and rotational laxity measurements may provide a better description of knee laxity envelope and function and a potential new insight in risk factor analysis for non-contact ACL injuries.

Conclusion

The 17% of healthy subjects identified with higher anterior and rotational knee laxity might benefit from specific prevention programs.