Experimental validation of the GNRB® for measuring anterior tibial translation.

ABSTRACT

INTRODUCTION: The objective of this study was to validate the technique used to measure anterior tibial translation in cadaver knees using the GNRB® device by comparing it with the gold standard, the OrthoPilot® navigation system. HYPOTHESIS: Simultaneous measurement of anterior tibial translation by the GNRB® and the OrthoPilot® in the chosen experimental conditions will result in significant differences between devices. MATERIAL AND METHODS: Five fresh frozen cadavers were used. The knee was placed in 20° flexion. Four calibrated posterior-anterior forces (134N to 250N) were applied. For each applied force, the anterior tibial translation was measured simultaneously by both devices. Two conditions were analyzed anterior cruciate ligament (ACL) intact and ACL transected. The primary criterion was anterior tibial translation at 250N. The measurements were compared using a paired Student's t-test and the correlation coefficient was calculated. Agreement between the two methods was determined using Bland-Altman plots. Consistency of the measurements was determined by calculating the intraclass correlation coefficient. RESULTS: For all applied forces and ligament conditions, the mean difference between the GNRB® and the navigation system was 0.1±1.7mm (n.s). Out of the 80 measurements taken, the difference between devices was less than ±2mm in 66 cases (82%). There was a strong correlation, good agreement and high consistency between the two measurement methods. DISCUSSION: The differences between the measurements taken by the GNRB® and the navigation system were small and likely have no clinical impact. We recommend using the GNRB® to evaluate anterior knee laxity. LEVEL OF EVIDENCE II controlled laboratory study.