Radiography of Sesamoid Bones

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Introduction

Apart from patellar radiography, specific radiography of sesamoid bones is uncommon. This page considers all aspects of radiography of sesamoid bones.

What is a sesamoid Bone?

A sesamoid bone is a bone embedded within a tendon. Sesamoid bones are found in locations where a tendon passes over a joint, such as the hand, knee, and foot. Functionally, they act to protect the tendon and to increase its mechanical effect. The presence of the sesamoid bone holds the tendon slightly farther away from the center of the joint and thus increases its moment arm. Sesamoid bones also prevent the tendon from flattening into the joint as tension increases and therefore also maintain a more consistent moment arm through a variety of possible tendon loads. <a class="external" href="http://en.wikipedia.org/wiki/Sesamoid_bone" rel="nofollow" target="_blank">http://en.wikipedia.org/wiki/Sesamoid_bone</a> The largest and most commonly imaged sesamoid bone is the patella.

Sesamoid Bone Pathology

Sesamoiditis and sesamoid fracture are the most common pathologies involving sesamoid bones. Other sesamoid bone pathologies include arthritis and osteochondritis.

Radiography of Sesamoid Bones

Sesamoid Bones	Tendon	Anatomy	Radiography
Patella	Quadricepts tendon		Skyline View Sunrise View Merchant's View
1st MP Joint Foot	Flexor Hallicus Longus	Plantar View

PA vs AP Patella

AP

PA

It is theoretically better technique to perform PA rather than AP patellar radiography. The PA projection places the anatomy of interest (the patella) closer to the IR.

This is the same knee imaged in a PA position using the same CR system. Although this comparison lacks scientific rigour, the differences in the quality of demonstration of the patella are not obvious- this is despite the relative underexposure of the AP image. It could be argued that the costs in terms of putting the patient through the discomfort of lying in the PA position with an injured knee outweigh the benefits of theoretically improved imaging of the patella.