Fig. 4
From: Nerve entrapment syndromes of the lower limb: a pictorial review
24-year-old male with posterior impingement secondary to an os trigonum, who underwent os trigonum resection. Preoperative sagittal T1 (a) demonstrates the prominent os trigonum (yellow arrow). Post-surgical MRI was performed due to altered sensation in the plantar forefoot laterally. Post-surgical MRI in the short axis PDFS (b and c) sequences demonstrates extensive muscle oedema and atrophy (circled) involving the lateral lumbricals, abductor digiti minimi, quadratus plantae, adductor hallucis and flexor digiti minimi brevis consistent with lateral plantar nerve impingement. Axial PD (d and e) sequences demonstrate adhesions and granulation tissue formation, extending towards the sural nerve posterolaterally (green arrow) and lateral plantar nerve medially (red arrows), resulting in impingement of the nerves