Chapter 11

### INTRODUCTION

A sign is a mark carrying a conventional meaning and used in place of words to convey a complex notion. In medicine, a sign is an objective evidence of disease specially observed and interpreted by a physician. Multiple signs are described in the radiology literature. The recognition of these signs allows the radiologist and the clinician to make a specific diagnosis or give a brief differential diagnosis. We have compiled a collage of easily recognizable signs in musculoskeletal radiology. Familiarity with these signs can direct the radiologist toward an accurate diagnosis, timely intervention, and astute management. These signs are illustrated with radiographs to help elucidate direct or indirect evidence of the pathology and mechanism of injury. Findings are best appreciated on different imaging modalities; for example, an axial computed tomography (CT) image of the spine will confirm spondylolisthesis suspected on a radiograph.

The adage, a picture is worth a thousand words, is true in this context. However, pattern recognition requires practice. Familiarization with these signs helps build a mental archive for image recall.

### ABSENT BOW TIE SIGN1

Introduction and Anatomical Context: Normal menisci can be seen as a series of hypointense classic bow ties on sagittal magnetic resonance imaging (MRI). The knee joint is cushioned by fibrocartilaginous medial and lateral menisci. The menisci lie along the margin of proximal tibial articular surface. Menisci act as shock absorbers and allow smooth movement of joint surfaces over each other.

Etiology: Post-traumatic. Medial meniscus is more commonly injured than lateral meniscus. Most common cause of lateral meniscus injury is a discoid meniscus (Figure 11-1).

###### Figure 11-1.

Absent bow tie. Two consecutive sagittal cuts of proton density MRIs of the peripheral medial meniscus of the knee.

Radiological Findings: The second image reveals loss of the normal bow tie appearance of the meniscus. The “absent bow tie” is a good sign of a bucket handle tear of the meniscus. The absence of the normal bow tie is secondary to the displaced fragment that makes up the “handle” of the bucket. The absent bow tie sign mandates that at least two adjacent sagittal images with a normal meniscal body segment appearance are not present. A word of caution is dependent on the cuts; sometimes one of the two bow ties may be absent without a real bucket handle tear. Therefore, correlation with the coronal and axial images can be helpful.

Diagnosis: Bucket handle tear of menisci.

Imaging Modality: MRI.

PEARLS

• Absent bow tie sign is present when two adjacent sagittal MRIs exhibit a discontinuous body of the meniscus.

### ANTEATER NOSE2

Introduction and Anatomical Context: Anteater nose is a direct sign of calcaneonavicular coalition. Most common clinical ...

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