Tangent Sign

Original Editor - Essam Ahmed Top Contributors - Lucinda hampton and Essam Ahmed

Introduction

Positive tangent sign

Negative tangent sign[1]

The tangent sign is a practical way to quantify supraspinatus muscle belly fatty atrophy - a positive sign implicated in a worse outcomes after supraspinatus tendon tear repair. The tangent sign, is simple, reproducible, and easily implemented during a busy clinic day.

Method

To evaluate for a positive tangent sign the sagittal T2-weighted MRI images are used. The most lateral image in which the scapular spine and coracoid process are in contact with the body of the scapula is used. The tangent line is made by drawing a line from the superior border of the scapular spine to the superior margin of the coracoid process.

Interpretation

Findings:

1. In a normal supraspinatus muscle, the muscle content should cross superior to the tangent line and is a negative tangent sign.
2. When the muscle atrophies, the supraspinatus falls below the tangent line and is a positive tangent sign.

Past studies have suggested strong correlation between occupation ratio, tangent sign, and improved strength and mobility.