[Flexor hallucis longus tendon rupture as an impingement lesion induced by os trigonum instability]

A Flexor hallucis longus tendon lesion induced by an unstable Os trigonum has not been described heretofore. A 39 years old karateka complained increasing load induced pain at the posteromedial ankle. Because of this, he was unable to take part in sports activities. Clinical, X-ray and MRI investigation assumed a Flexor hallucis longus tendon tear induced by an impingeing Os trigonum. At surgery a longitudinal and a partial transverse tendon tear was present. The Flexor hallucis longus tendon pulley was narrowed by a partially unstable Os trigonum. Tendon reconstruction, Os trigonum removal and early functional posttreatment resulted in full ability in sport, leisure-time activities and profession five months later.