Category: Orthopedics
Keywords: Foot injury, bipartate (PubMed Search)
Posted: 7/10/2016 by Brian Corwell, MD
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Sesamoid Injuries
Unlike other bones in the human body that are connected to each other at joints, sesamoid bones are only connected via tendons (or are imbedded in muscle).
The largest sesamoid bone is the patella.
2 small sesamoid bones lie on the plantar foot near the great toe
Sesamoid bones can fracture and the surrounding tendons can become inflamed (sesamoiditis)
Traumatic injury is usually due to hyperextension and axial loading
Sx: Pain located under the great toe on the ball of the foot (Gradual with sesamoiditis and acutely with a fracture).
There may be associated swelling and bruising. Pain with palpation, flexion and extension.
The medial/tibial sesamoid is larger, has great weight bearing status and is more commonly injured that its lateral counterpart.
In many people (10 - 25%) the medial sesamoid of the foot has two parts (bipartite). This finding is bilateral in 25% of people.
This may confuse some providers as it may appear to be a fracture
Look for a smooth contour to the bones and clinically correlate (bruising, soft tissue swelling, etc.) if it is an incidental finding.
Other radiographic clues include
1) The fractured sesamoid is usually slightly larger than the lateral sesamoid while the bipartite sesamoid has a much larger medial sesamoid than lateral sesamoid
2) The fractured sesamoid shows a sharp, radiolucent, uncorticated line between the two fragments while the bipartite sesamoid has two corticated components
3) The fractured sesamoid fragments often fit together like pieces of a puzzle while the bipartite sesamoid has two components that do not fit together snugly
4) Other means to differentiate the two involve MRI and bone scanning
Treatment involves a stiff-soled shoe or applying a cushioning pad or J-shaped pad around the area to relieve pressure.
It may take months for the pain to subside.
http://www.apfmj-archive.com/afm5_3/afm50.htm#F1
Chu and Resnick, MRI Web Clinic June 2014.
