What is a trigonal process on the posterior aspect of the talus?
Nov 25, 2022
Source: Cainiu Health
Dr. Lin Yunfei
Introduction
The os trigonum is an accessory bone formed when the posterior ossification center of the talus fails to fuse with the rest of the talus during development. Most os trigonum cases are asymptomatic; however, in individuals engaged in sports activities requiring frequent plantarflexion, the os trigonum may become impinged within the limited space of the posterior ankle, leading to repetitive trauma and injury due to constant irritation.
Posterior talar trigonal accessory bone (os trigonum) results from a secondary ossification center at the posterior margin of the talus that fails to fuse with the rest of the talus during development. Most os trigonum cases are asymptomatic; however, in individuals participating in sports such as football, gymnastics, and dancing—activities involving frequent plantarflexion—the os trigonum may become impinged within the confined space of the posterior ankle. This repeated impingement causes microtrauma, inflammation, pain, and ultimately affects athletic performance.
The primary pathological basis of os trigonum injury involves degeneration of articular cartilage, along with bone proliferation, necrosis, and sometimes fracture. Patients typically have a history of repetitive plantarflexion or ankle sprains, presenting with posterior ankle pain—especially on the posteromedial side—that worsens during plantarflexion, walking, or physical activity and improves with rest.
When conservative treatment fails, surgical intervention is considered. Currently, arthroscopic resection of the os trigonum, combined with debridement of local inflammatory tissue and damaged flexor hallucis longus tendon, has become the preferred surgical approach due to its thorough lesion removal, excellent clinical outcomes, low complication rate, minimal invasiveness, and rapid recovery.
