Fig. 11
From: Sesamoids and accessory ossicles of the foot: anatomical variability and related pathology
Osteonecrosis. a Short-axis and sagittal CT images depict a fragmented medial hallucal sesamoid (black arrows), with increased density of the fragments (white arrows) which suggests post-traumatic osteonecrosis. b Short-axis and sagittal T2-weighted fat-saturated MRIs, and sagittal T1-weighted MRI obtained 1 month later show a pattern of severe bone marrow oedema (white arrows) with T1 hypointensity (black arrow) isolated to the medial hallucal sesamoid, and further collapse of the medial hallucal sesamoid, consistent with progression of osteonecrosis. Note normal marrow signal in the first metatarsal head (asterisks)