OS TRIGONUM SYNDROME

OS TRIGONUM SYNDROME

INTRODUCTION:

v Up to 40 accessory ossicles and multiple sesamoids have been described in the foot and ankle

·       Definition

o   accessory ossicles are secondary ossification centers that remain separated from the normal bone

o   sesamoids are bones that are incorporated into tendons and move with normal and abnormal tendon motion

v Most common ossicles

·       os trigonum

·       accessory navicular (os tibiale externum)

·       os intermetatarseum

v Most common sesamoids

·       os peroneum

·       located in the peroneus longus tendon

·       hallux sesamoids located in the flexor hallucis brevis tendon at the base of the 1st metatarsal head.

ANATOMY:

 DEFINITION:

                                Accessory ossicle representing the separated posterolateral tubercle of the talus usually asymptomatic, but can become symptomatic and cause os trigonum syndrome.

 

 EPIDEMOLOGY:

                                                       Incidence 10-25% of the population have os trigonum commonly symptomatic in ballet dancers due to extreme plantar flexion ("en pointe" toe position)

PATHOPHYSIOLOGY:

                                           Pathophysiology of os trigonum syndrome repetitive microtrauma (ankle plantarflexion) may present as a stress fracture acute forced plantarflexion may present as an acute fracture.

OSTEOLOGY:

             The secondary ossification center forms posterior to the talus between 8-13yrs normally fuses with talus within 1yr if the ossicle fails to fuse, it articulates with the talus through a synchondrosis the os lies lateral to FHL, tibial nerve, PTT, and posterior tibial artery.

SYMPTOMS: 

                            Symptoms pain in "en pointe" position physical exam posterolateral ankle pain with passive ankle plantar flexion differentiate from FHL tendinitis where ankle pain is posteromedial and there may be triggering may have swelling and tenderness over FHL if associated with FHL tendinitis.

IMAGING:

                                         X-Ray:

 MRI:

TREATMENT:

§  Non-operative:

§               NSAIDS, rest, immobilization, restricted weightbearing

§  Operative:

§               Surgical excision:

§                        Indications: if non-operative management fails 

         Techniques: through open lateral approach or posterior ankle arthroscopy.