Summary

By using a side-to side ratio of anteroposterior laxity measurements of the knee, this is possible to compare results obtained with the KT-1000®, the GnRB® and the Rolimeter®. The results of the Telos raises the question of its use as a reference technique.

Abstract

Introduction :
Instrumented knee laxity testing devices have been used in both the clinical and research setting to objectively evaluate persons with injuries about the knee.
Several different instrumental laxity devices are used in the literature as gold standard, but are they really comparable in measuring anterior to posterior translation in ACL deficient knees?
The purpose of this study was to compare the reliability and the reproducibility of both the Telos®, the KT-1000®, the GnRB® and the Rolimeter® for measuring anterior knee laxity in patients with an isolated ACL rupture.
The hypothesis was that the laxity measurements are different and not comparable according to the device used.

Material and method :

Forty consecutive patients with isolated ACL lesions were evaluated with the Lachman test, the pivot-shift test, the Telos® (two different measurements at two different times, the KT-1000® (mean of 3 manual max measurements), the GnRB® (mean of 3 measurements at 200N) and the Rolimeter® (mean of 3 manual max measurements) between February and May 2015. The national ethical committee approved this study (N° 2015-A00423-46). Inclusion criteria were: Isolated ACL rupture (no peripheral ligament tear, no meniscus tear on MRI), patients scheduled for surgery due to instability, contralateral knee without history of injury.


Results :

Median age of the patients was 29.5 (16-41). Median BMI was 25,6 (18.6-29.7). There were 24 right knees and 16 left knees. The median time between injury and laxity measurements was 4.5 months (1-72).

Mean injured knee to non-injured knee difference in anterior laxity was 4.3 mm (S.D 2) using KT 1000, 5.9mm (S.D 4.4) using Telos, 4.1 mm (S.D 2.2) using GnRB and 3.1 mm (S.D 1.5) using Rolimeter. This was statistically different (p<0.04).

When introducing a ratio between injured and non-injured knee, mean results were as follows : GnRb = 1.6 (SD 0.4) ; Rolimeter = 1.87 (SD 1.7) ; KT 1000 1.9 (SD 0.4) ; Telos = 3.6 (SD 3). Regression analysis showed significant correlation between measurements (r2= 0.75, p<0.04) performed with GnRb, Rolimeter and KT-1000.
Type of sport, sex, age, BMI, time between injury and laxity measurements did not influence the results.

Discussion/conclusion :
By using a side-to side ratio of anteroposterior laxity measurements of the knee, this is possible to compare results obtained with the KT-1000®, the GnRB® and the Rolimeter®.
The results of the Telos raises the question of its use as a reference technique.