Summary

This study demonstrates the importance of clinical examination of the knee, and that failure of tibial internal rotation to control anterior draw is indicative of a secondary peripheral ligamentous deficiency, and that ALC deficiency should be considered as should its augmentation.

Abstract

Background

It has become increasingly recognised that the augmentation of the Antero-Lateral Complex (ALC) by way of either Extra-articular tenodesis or Antero-Lateral ligament (ALL) reconstruction, may be required in conjunction with an Anterior Cruciate Ligament (ACL) reconstruction. It is equally recognized, that not all ACL deficient knees require ALC augmentation.

There remains some debate surrounding the indication for ALC augmentation. Indications include the Hyper-mobile patient, a knee with an ‘Explosive Pivot shift’, and the revision ACL reconstruction. In the case of the first two indications, these can be somewhat subjective and would not include a significant proportion of ACL deficient knees with significant and concomitant ALC instability.

Purpose

To compare the kinematic effects of ALC deficiency upon anterior draw in neutral (Drawer test) and tibial internal rotation (Slocum’s test), in the ACL deficient knee. With the aim of informing decision making as to whether or not to perform an ALC augmentation.

Study design: Controlled laboratory study.

Methods

Eighteen cadaveric knees were tested in a 6-degree of freedom mechanical rig using an optical tracking system. The tracking system recorded kinematic data with the knee flexed at 90 degrees with an applied neutral anterior drawer, internal rotation alone and a combined anterior drawer and internal rotation forces. Testing was done in intact knee, ACL deficient and Combined ACL plus ALC deficient states. Anterior translation loads of 90N and internal rotation torque of 5Nm were applied. Statistical analysis using paired student t-tests were performed using SPSS software.

Results

The difference in anterior translation upon Drawer test in the intact knees (2.59mm) compared to the ACL deficient knees (7.56mm) was statistically significant (p<0.01). The difference in the Drawer test comparing the ACL deficient (7.26) and combined ACL/ALC deficient knees (9.26) was not statistically significant p=0.19.
The difference in Slocum’s test in the intact knees (1.34mm) compared to the ACL deficient knees (2.46mm) was not statistically significant (p=0.129) compared to combined deficiencies (3.10mm) which was statistically significant (p<0.001).
In the ACL deficient group, the mean tibial translation on Slocum’s test was significantly less than on Drawer test (5mm, p<0.05).
Comparing Drawer and Slocum’s test, in ACL and combined ACL/ALC deficient knees showed a significantly increased laxity on Slocum’s test in the combined deficiency group 1.1mm (p<0.05).

Conclusion

Persistent laxity upon performing Slocum’s test in the ACL deficient knee, suggests ALC insufficiency and ALC augmentation should be considered to restore native knee kinematics.