Assessment of the GNRB Arthrometer: High Inter-Rater Reliability Alone Does Not Support Replacement of the KT1000 in Anterior Cruciate Ligament Reconstruction Patients.

PURPOSE: To evaluate the inter-rater reliability and sensitivity of the GNRB arthrometer compared with the KT1000 and clinical examination with the Lachman test for patients with an anterior cruciate ligament (ACL) injury. METHODS: Patients with ACL injury were examined preoperatively and postoperatively by 2 examiners. One examiner also performed a clinical examination and an examination with the KT1000. Side-to-side difference of ≥3 mm was classified as an ACL injury for both the GNRB and the KT1000. The interclass correlation was used to evaluate inter-reliability, and a paired t-test was used to identify differences between examiners. The sensitivity was calculated preoperatively. RESULTS: A total of 20 patients underwent preoperative assessment with the GNRB, whereas 17 were available postoperatively. The GNRB diagnosed 12/20 and 13/20 for the 2 examiners, respectively, as having ACL injuries preoperatively, whereas the KT1000 diagnosed 19/20. Postoperatively, 5/17 and 4/17, respectively, had a side-to-side difference of ≥3 mm with the GNRB versus 7/17 for the KT1000, hence indicating an ACL injury or insufficient reconstruction. Clinical examination concluded that 15/17 had a manual Lachman of ≤+1. The interclass correlations between examiners were 0.80 for the involved side preoperatively and 0.84 postoperatively, considered moderate to good. Sensitivity for the GNRB was 60% and 65% for examiners 1 and 2, respectively. For the KT1000, it was 95%. CONCLUSIONS: In this study, the GNRB had a high inter-rater reliability, even with limited experience with the device. However, it was inferior to the KT1000 in correctly identifying ACL deficiency preoperatively in patients with ACL injury. LEVEL OF EVIDENCE: Level III, prospective comparative study.