Presentation
15 year male with great toe pain after motor vehicle accident
Patient Data
Dorsal dislocation of the great toe distal phalanx is present.
Associated capsular distention and joint effusion are seen.
Abnormal intrasubstance increased fluid signal is present at flexor hallucis longus tendon near to insertion site on to great toe distal phalanx is related to tendinosis.
Subluxation of subhallucal interphalangeal sesamoid bone into joint space with abnormal bone marrow signal(low on T1 and high on PD/STIR) is suggestive for sesamoiditis is noted.
Sesamoid bone contusion/fracture, as well as avascular necrosis, are in the differential diagnosis.
Case Discussion
Osteonecrosis (avascular necrosis) show features of bone marrow edema in the early stages with sclerosis predominantly in late stages. Thus in early stage they are mildly hypointense on T1W and hyperintense on STIR images, but they appear hypointense on all sequences in later stages due to sclerosis.
Regarding the same imaging features of bone marrow edema at both early stage of osteonecrosis and sesamoiditis, MRI cannot reliably differentiate between this two conditions. However, CT can differentiate between them by demonstrating increased sclerosis in osteonecrosis, compared to the normal density of sesamoiditis.
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