Summary

We investigated the influence of concomitant lateral meniscus and anterolateral structure on rotatory knee laxity in anterior cruciate ligament (ACL) deficient knee in cadaver using a quantitative triaxial accelerometer. High-grade rotatory knee laxity (pivot shift grade 2 to 3) were the result of these concomitant injuries in ACL deficient knee.

Abstract

Introduction

Although anterior cruciate ligament (ACL) reconstruction is largely thought of as a successful procedure, the meniscus and the anterolateral structure (ALS) as a secondary restraint of patients with ACL injury is currently debated because unrepaired secondary stabilizers may be a cause for reconstruction failure. How their lesions correlate to clinical tests is necessary so that proper diagnosis can be made.
The purpose of this study was to investigate the influence of concomitant lateral meniscus (LM) and ALS injuries on rotatory knee laxity in ACL deficient knee.

Methods

In this study, the role of the ACL and secondary restraints including LM and ALS in controlling knee stability using an analysis system that measures the acceleration of the tibia during the pivot-shift test was evaluated. The rotatory laxity was quantified in different conditions of instability: ACL intact (Control), after dissection of the ACL(A1), ACL+LM(A2) and ACL+LM+ALS(A3). The standardized pivot-shift test was performed and the peak acceleration values during the pivot-shift test were measured with this system in 6 cadaveric knees. The pivot-shift test was also graded subjectively on the scale of 0–3 based on the IKDC criteria. Furthermore, the relationship between quantitative values and grade of the pivot-shift test was evaluated.

Results

The mean acceleration values were 2.1±0.3, 4.6±1.9, 5.2±1.8 and 5.9±1.5 m/s2 in condition of control, A1, A2 and A3, respectively. The A1, A2 and A3 showed significant higher mean acceleration values than the control intact knees.
The pivot shift was undetectable (grade 0) in all knees with control. A1 continued to be minor (grade 1) on the pivot shift with all six knees. A2 continued to be minor (grade 1) in two cases and moderate (grade 2) in four cases. A3 resulted in an increase in the grade of the pivot shift, with a grade 3 pivot shift seen in three cases and a grade 2 in two cases and a grade 1 in only one case. High-grade rotatory knee laxity (pivot shift grade 2 to 3) were 0%, 66% and 83% in the conditions of A1, A2 and A3, respectively.
A moderate correlation between the peak acceleration values and grade of the pivot-shift test was observed (r=0.69, p<0.01), the subjective grading of the pivot-shift test correlated with objective quantification.

Conclusions

The findings of this study demonstrated that an ACL injury associated with LM and ALS may predispose the knee to higher rotatory laxity. Careful assessment and proper treatment of injuries to these secondary stabilizers should be considered, especially in knees with a high grade of the pivot-shift.