Summary

A lateral norch sign greater than 2 mm is indicative of high grade pivot shift.

Abstract

Background

The lateral femoral notch sign (LNS) is a bony impression on the lateral femoral condyle correlated with anterior cruciate ligament (ACL) injury. Its presence is associated with lateral meniscus injury and higher cartilage degradation on the lateral femoral condyle.

Hypothesis/Purpose: The present study aimed to investigate the effect and magnitude of LNS on rotatory instability. The hypothesis was that a positive LNS was correlated with a high-grade pivot shift (PS).

Study design: Cross-Sectional Study; Level of evidence, 3

Methods

90 consecutive patients with complete ACL tears from 2013 to 2017 underwent intraoperative kinematic evaluation with the surgical navigation system, and were included in the present study. The same surgeon performed a standardized PS under anesthesia. The PS was quantified through the acceleration of the lateral compartment during tibial reduction (PS ACC) and the internal-external rotation (PS IE). LNS presence and depth were evaluated on sagittal MRI images (1.5 Tesla).

Results

In 47 patients, the LNS was absent. In 33, the LNS depth was between 1mm and 2mm, and in 10 patients, it was higher than 2mm. Patients with a notch deeper than 2 mm showed increase PS ACC and PS IE compared with the group without the LNS. However, no significative differences were present between the group with a notch between and 1 and 2mm and the patients without LNS.

Conclusion

The presence of a lateral LNS deeper than 2mm could be used to preoperatively identify patients with a high risk of increased rotatory instability. Clinical Relevance: The LNS could be useful in the clinical setting to set patient’s expectations and probably modify the surgical planning in terms of graft choice and additional lateral extra-articular procedures.