summary Lower Extremity Os are secondary ossification centers that remain separated from the normal bone and may be confused with a fracture. Diagnosis requires plain radiographs of the foot and ankle. Treatment is generally observation as most are completely asymptomatic. In the event of symptoms, treatment depends on location of Os and chronicity of symptoms. Epidemiology Up to 40 accessory ossicles and multiple sesamoids have been described in the foot and ankle Etiology Definition accessory ossicles secondary ossification centers that remain separated from the normal bon sesamoids are bones that are incorporated into tendons and move with normal and abnormal tendon motion Most common ossicles os trigonum accessory navicular (os tibiale externum) os intermetatarseum 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 Classification Accessory Ossicles and Sesamoids of the Foot and Ankle Accessory bone Prevalence Clinical significance Differential Os trigonum 10-25% Posterior ankle impingement, FHL entrapment Shepherd's fracture Type II accessory navicular 2-12% Posterior tibial tendon dysfunction Navicular tuberosity avulsion fx, type I accessory navicular Os subfibulare 2% Painful os subfibulare Lateral malleolus avulsion frx Os peroneum 9-20% Painful os peroneum, fracture, diastases Painful os vesalianum, bipartite os peroneum Os vesalianum 2% Painful os vesalianum Avulsion frx of the 5th metatarsal base Hallux sesamoids ~100% Fracture, stress fracture Bipartite tibial sesamoid Os Trigonum Definition accessory ossicle representing the separated posterolateral tubercle of the talus usually asymptomatic, but can become symptomatic and cause os trigonum syndrome Epidemiology incidence 10-25% of the population have os trigonum commonly symptomatic in ballet dancers due to extreme plantar flexion ("en pointe" toe position) Pathophysiology of os trigonum syndrome repetitive microtrauma (ankle plantarflexion) may present as a stress fracture acute forced plantarflexion may present as an acute fracture Associated conditions FHL tenosynovitis or entrapment Anatomy 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 Presentation 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 radiographs recommended views lateral radiograph with foot in plantar flexion findings shows os trigonum impinged between posterior tibial malleolus and calcaneal tuberosity os trigonum can be round, oval or triangular and of variable size MRI findings shows os trigonum and associated inflammation and edema in FHL tendon Differential diagnosis fracture of the posterior process of the talus (Shepherd's fracture) FHL and posterior tibialis tendinitis produce posterior medial ankle pain and tenderness Treatment nonoperative NSAIDS, rest, immobilization, restricted weightbearing operative surgical excision indications if nonoperative management fails techniques through open lateral approach or posterior ankle arthroscopy Os Tibiale Externum (Accessory navicular) See Accessory Navicular Os Subfibulare Definition small piece of bone adjacent to inferior fibula Epidemiology incidence 1-2% of population Pathoanatomy may represent avulsion fx of ATFL that secondarily ossifies or accessory ossification center Presentation symptoms may be asymptomatic may have ankle pain (symptomatic os subfibulare) may be associated with chronic ankle instability and present with recurrent ankle sprains signs focal tenderness and swelling at the site of the ossicle laxity with anterior drawer and inversion/eversion stress testing Imaging radiographs recommended views standard ankle series (weightbearing AP, lateral, mortise) varus stress view findings accessory ossicle talar tilt on varus stress view suggesting ankle instability increased separation of os fragment from fibula tip Differential diagnosis acute lateral malleolus avulsion fracture (by the ATFL) Treatment nonoperative NSAIDS, rest, immobilization, restricted weightbearing indications initial treatment for symptomatic os subfibulare operative surgical excision indications failed nonoperative management Os Peroneum Definition sesamoid bone found within the peroneus longus tendon near the base of the 5th MT may represent avulsion or rupture of peroneus longus Epidemiology incidence 9-20% of adults bilateral in 60% bipartite in 30% Pathophysiology of injury or fracture direct trauma indirect trauma (sudden inversion and supination) associated with peroneus longus tendon rupture Imaging radiographs findings normal os peroneum acute os peroneum fracture peroneus longus rupture MRI findings normal os peroneum acute os peroneum fracture peroneus longus rupture Differential diagnosis painful os vesalianum bipartite os peroneum Treatment nonoperative NSAIDS, rest, immobilization, restricted weightbearing indications initial treatment for painful os peroneum syndrome minimally displaced os peroneum fractures operative surgical excision indications painful os peroneum syndrome (with minimal tendon involvement) refractory to conservative treatment os peroneum fracture with displaced fragments surgical excision and repair of peroneus longus tendon or tenodesis to peroneus brevis indications os peroneum associated with peroneus longus tendon rupture Hallux Sesamoids See Sesamoid Injuries of the Hallux
QUESTIONS 1 of 6 1 2 3 4 5 6 Previous Next (SBQ18FA.2) A 23-year-old soccer player with a history of multiple ankle sprains presents with posterolateral ankle pain that has been present for the past 3 months. On physical exam, the patient has pain over the posterolateral ankle with plantar flexion, but no pain is elicited with combined passive dorsiflexion and eversion of the ankle. He denies any numbness or tingling in his foot or sensation of ankle instability. The pain has been managed with rest, physical therapy and intra-articular steroid injection with only marginal improvement. A current MRI is shown in Figures 1 and 2. What is the best next step? QID: 211121 FIGURES: A B Type & Select Correct Answer 1 Peroneal brevis tubularization 5% (85/1868) 2 Arthroscopic excision of os trigonum 85% (1584/1868) 3 Flexor hallucis longus (FHL) tendon debridement 4% (69/1868) 4 EMG to evaluate for tarsal tunnel syndrome 2% (29/1868) 5 Subtalar loose body removal 4% (74/1868) L 2 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ11.253) A 17-year-old ballet dancer presents with 5 months of pain in the posterior aspect of the right lower extremity that is exacerbated with the ballet position shown in Figure A. Her symptoms returned with ballet activity following a 1 month course of full rest, nonsteroidal anti-inflammatory medication, and physical therapy. On physical examination she has no tenderness at the insertion of the achilles tendon at the calcaneus. Radiographs are shown in Figure B and a MRI is shown in Figures C-E. Which of the following options is the most appropriate next step in treatment? QID: 3676 FIGURES: A B C D E Type & Select Correct Answer 1 Referral to an orthopaedic oncologist for biopsy and staging 1% (20/3008) 2 Arthroscopic Haglund deformity excision and debridement of achilles tendon 6% (182/3008) 3 Open os naviculare excision 3% (87/3008) 4 Arthroscopic os trigonum excision 88% (2642/3008) 5 Posterior tibial tendon debridement 2% (55/3008) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK
All Videos (3) Podcasts (1) Login to View Community Videos Login to View Community Videos Posterior Ankle Endoscopy (Hindfoot Arthroscopy) Kemal Gokkus Foot & Ankle - Lower Extremity Os C 11/28/2021 70 views 0.0 (0) Login to View Community Videos Login to View Community Videos Os trigonum removed arthroscopically Michael Hughes Foot & Ankle - Lower Extremity Os D 6/14/2012 794 views 2.5 (6) Login to View Community Videos Login to View Community Videos Os trigonum Michael Hughes Foot & Ankle - Lower Extremity Os C 6/14/2012 6205 views 4.4 (8) Foot & Ankle⎪Lower Extremity Os Foot & Ankle - Lower Extremity Os Listen Now 15:55 min 11/5/2020 146 plays 0.0 (0)