Learning objectives
Recognize the most common accessory ossicles in the spine and upper extremities
Differentiate accessory ossicles from their most common misdiagnoses
Recognize the different presentations of accessory ossicles through various imaging modalities
Background
Accessory ossicles are unfused secondary ossification centers,
separate from the adjacent bone.
Unlike sesamoid bones,
which function as friction reducers to protect tendons from injury,
accessory ossicles are thought to be supernumerary bones without definite function.
Most accessory ossicles are congenital,
normal variants,
yet some may arise after trauma or local degenerative disease.
Normally,
accessory ossicles are clinically insignificant and incidental.
Nonetheless,
they may sometimes be misdiagnosed as fractures,
loose bodies or infectious processes,
leading to unnecessary workup and management.
Findings and procedure details
1.
SPINE
Diagrammatic overview
See Fig. 1 and Fig. 2 for an overview of spine ossicles
Pictorial review
Nuchal ligament sesamoid ossicles
Prevalence: Overall 7.4%,
with male predilection (11.3% males,
3.5% females)
Location: Varies,
with 80% occurring either at C5/C6 or C6/C7 levels
Overview: An anatomical variant that is typically asymptomatic and may be misdiagnosed as an avulsion fracture or myositis ossificans.
[1]
Radiographic characteristics: Seen usually as a single,
well-defined and corticated,
round or ovoid opacity on lateral plain films,
and as cortical bone...
Conclusion
Accessory ossicles are secondary ossification centers separate from adjacent bone that may be clinically insignificant anatomical variants and vary in prevalence depending on the area of the body in which they are found.
Familiarization with the most commonly encountered accessory ossicles in the spine and upper extremities is key in distinguishing an incidental,
clinically insignificant,
osseous structure from a more sinister misdiagnosis,
which could entail unnecessary workup.
Personal information
Alexandra Pérez Pérez,
MD
San Juan City Hospital,
Transitional Yeard Department
e-mail:
[email protected]
***Special thanks to Dr.Javier Pérez-Andreu,
Dr.
Elizabeth Trullenque (Department of Veteran Affairs,
MSK Radiology) and Dr.Vidal-Fontfor their help in making this project possible.***
References
[1] George K.
Paraskevas,
A.
R.
(2011).
Sesamoid ossicles within the nuchal ligament: a report of two cases and review of the literature.
Journal of Radiological Case Reports ,
5 (8),
22-29.
[2] Theodore E.
Keats,
M.
(1967,
December).
THE INFERIOR ACCESSORY OSSICLE OF THE ANTERIOR ARCH OF THE ATLAS.
American Journal of Radiology ,
834-836.
[3] R.
Shane Tubbs,
M.
M.
(2016).
Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. John Wiley & Sons.Dens variants
[4] Perdikakis E,
Skoulikaris N.
The odontoid process: various configuration...