The crevice sign: a new indicator of meniscal instability in ACL reconstructions.

<bold>Purpose: </bold>Meniscus preservation is key in knee surgery. The newly documented crevice sign indicates instability of the medial meniscus in ACL-deficient knees. Once the sign is visualised, it is imperative that the stability of the medial meniscus is assessed and potentially treated. It was hypothesized that there would be a strong correlation between the presence of an unstable medial meniscal tear in patients with the crevice sign in ACL-deficient knees.<bold>Methods: </bold>This was a multicenter prospective study carried out to evaluate the incidence of medial meniscal tears in patients with ACL-deficient knees and their correlation with a crevice sign. All patients (128) who had undergone ACL reconstruction between May 2020 and November 2020 were assessed arthroscopically for meniscal stability and divided in to two groups: stable (n = 84) and unstable (n = 44). Thereafter, the presence of the crevice sign was determined in each case.<bold>Results: </bold>The populations were comparable in terms of sex and age (Table 1). Fisher's exact test showed a significant association between the presence of the crevice sign and the instability of the medial meniscus (p < 0.001). Descriptive statistics suggest that the presence of crevice sign was associated more frequently to MM instability (38.6% vs 1.2%; p < 0.001). The specificity of this test was 98.8% and its sensitivity was 38.6%. The positive predictive value (PPV) was 94.4% and the negative predictive value (NPV) was 75.5%. Table 1 Descriptions and comparisons of internal meniscus instability of patients by presence of crevice sign Internal meniscus instability (N = 44) Internal meniscus stability (N = 84) Total (N = 128) Gender  N 44 84 128   Male 33 (75.0) 58 (69.0) 91 (71.1)   Female 11 (25.0) 26 (31.0) 37 (28.9) Fisher's exact test (n.s.) Age (years)  N 44 84 128   Mean (ET) 28.6 (9.4) 30.1 (10.2) 29.6 (9.9)   Median (IIQ) 26.5 (22.0;34.5) 27.0 (22.5;37.0) 27.0 (22.0;36.0)   [Min-Max] [14-54] [14-52] [14-54] Wilcoxon test bilateral (n.s.) Crevice sign  N 44 84 128   Absent 27 (61.4) 83 (98.8) 110 (85.9)   Present 17 (38.6) 1 (1.2) 18 (14.1) Fisher's exact test p < 0.001 CONCLUSION: The hypothesis was confirmed since medial meniscal instability was strongly correlated with the existence of the crevice sign and showed high specificity and PPV.<bold>Level Of Evidence: </bold>III. [ABSTRACT FROM AUTHOR]