Validity of GNRB® arthrometer compared to Telos™ in the assessment of partial anterior cruciate ligament tears

Purpose The main goal of this study was to compare the results of the GNRB ® arthrometer to those of Telos™ in the diagnosis of partial thickness tears of the anterior cruciate ligament (ACL). Methods A prospective study performed January–December 2011 included all patients presenting with a partial or full-thickness ACL tears without ACL reconstruction and with a healthy contralateral knee. Anterior laxity was measured in all patients by the Telos™ and GNRB ® devices. This series included 139 patients, mean age 30.7 ± 9.3 years. Arthroscopic reconstruction was performed in 109 patients, 97 for complete tears and 12 single bundle reconstructions for partial thickness tears. Conservative treatment was proposed in 30 patients with a partial thickness tear. The correlation between the two devices was evaluated by the Spearman coefficient. The optimal laxity thresholds were determined with ROC curves, and the diagnostic value of the tests was assessed by the area under the curve (AUC). Results The differential laxities of full and partial thickness tears were significantly different with the two tests. The correlation between the results of laxity measurement with the two devices was fair, with the strongest correlation between Telos™ 250 N and GNRB ® 250 N ( r = 0.46, p = 0.00001). Evaluation of the AUC showed that the informative value of all tests was fair with the best results with the GNRB ® 250 N: AUC = 0.89 [95 % CI 0.83–0.94]. The optimal differential laxity threshold with the GNRB ® 250 N was 2.5 mm (Se = 84 %, Sp = 81 %). Conclusion The diagnostic value of GNRB ® was better than Telos™ for ACL partial thickness tears. Level of evidence Diagnostic study, Level II.