Lower extremity ossicles Flashcards Preview

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Flashcards in Lower extremity ossicles Deck (32):

Define accessory ossicles?

  • Secondary ossification centres that remain separated from the normal bone 


Define sesmoids?

  • Bones that are incorporated into tendons and move with normal and abnormal tendons


Name the most common ossicles?

  • Os trigonum
  • Accessory navicular ( os tibiale externum)
  • Os intermetatarseum


Name most common sesmoids?

  • Os peroneum- in peroneus longus
  • Hallux sesmoids- located in flexor hallucis brevis


What is this?

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  • OS trigonium
  • Semoid bone representing the separated POSTERIOR TUBERCLE OF TALUS
  • Usually asymptomatic but symptomatic -> os trigonium syndrome



Describe the epidemiology of Os trigonum?

  • 10-25 % of population have os trigonium
  • Commonly symptomatic in BALLET dancers due to EXTREME PLANTAR FLEXION


Describe the pathophysiology of OS trigonium?

  • Repetitive microfracture- may present as Stress FRACTURE
  • Acute forced plantarflexion may present as acute fracture- downhill running, kicking or dancing

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Name associated conditions of OS trigonium?

  • FHL Tenosynovitis or entrapement


Describe the osteology of os trigonium?

  • Secondary ossification centre forms posterior to talus between 8-13 years
  • Normally fuses with talus within 1 year
  • If ossicles fail to fuse, it articulates with talus thru synchondrosis
  • Os lies LATERAL to FHL, TIBIAL nerve, PTT, POST tibial artery


Describe the symptoms of os trigonium?


  • Pain en pointe position


  • Posterior lateral ankle pain with passive ankle flexion
  • may have swelling & tenderness over FHL is associated with FHL tendonitis


What investigations are useful in Os trigonium?

  • Xrays
    • lateral with foot in planar flexion
    • show os trogonium impinging between posterior malleolus and calcaneal tuberosity
  • MRI
    • show os trigonium adn associated inflammationadn oedema in FHL tendon

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What is the Differential dx of Os trigonium ?

  • Posterior process of talus fracture - Shepherd's fracture- see pic
  • FHL & Post tibial tendonitis- produce medial ankle pain and tenderness.

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What is the Tx of Os trigonium?

  • Non operative
    • NSAIDS, rest, immobilisation, restricted WB
  • Operative
    • Surgical excision
    • if non op fails
    • through an OPEN LATERAL APPROACH or POST ANKLE ARTHROSCOPY- 80% gd to excellent results at 2-5 yr mark

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What is this?

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  • Os Subfibulare
  • small piece of bone adjacent to inferior fibula


What is the epidemiology and pathoanatomy of Os Subfibulare?


  • 1-2% of population
  • May represent Avulsion fx of ATFL that secondarily ossifies
  • Accessory ossification centre


What are the symptoms and signs of Os Subfibulare?



  • May be asyptomatic
  • Ankle pain ( symptomatic os subfibulare)
  • Assoc with chronic ankle instability- present with recurrent ankle sprains


  • Focal tendermess & swelling at site of ossicle
  • Laxity with anterior draw & inversion/eversion stress test


What imaging is helpful in Os Subfibulare?


  • xrays
    • standard ankle series- WB AP, Lateral , Mortise
    • varus stress view
    • See accessory ossicle
    • Talar tilt on varus stress view- see pic
      • suggest ankle instability
      • increased separation of os fragment from fibular tip

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What is DDX of Os Subfibulare?


  • Acute lateral malleolus avulsion fracture ( by ATFL)

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What is the Tx of Os Subfibulare?


  • Non operative
    • NSAIDs, Rest, Immobilisation, restricted WB
    • intial tx for symptomatic os fibulare
  • Operative
    • Surgical exicision
    • failed non operative treatment


What is this?

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  • Os Peroneum
  • Sesmoid bone found within PERONEUS LONGUS tendon near the base of the 5th MT
  • May represent avulsion/rupture of peroneus longus


What is the epidemiology of Os peroneum?

  • Incidence 9-20%
  • Bilateral 60%
  • Bipartite 30%

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Describe the pathophysiology of injury/fracture?

  • Direct Trauma
  • Indirect Trauma- Sudden inversion/eversion
    • assoc with peroneus longus tendon rupture

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What investigations are useful in DDx of Os peroneum?

  • Xrays
    • normal os peroneum
    • acute os peroneum fracture
    • peroneus longus rupture
  • MRI
    • Normal os peroneum
    • Acute os peroneum fracture
    • peroneus longus rupture- see pic

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What is the DDX of Os peroneum?

  • Painful os Vesalianum- see pic
  • Biparite os peroneum

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Describe the Tx of OS peroneum?

  • Non operative
    • NSAIDS, Rest, immobilisation, restricted weightbearing
    • inital Tx for painful os peroneum syndrome
    • minimally displaced os peroneum fractures
  • Operative
    • Surgical Excision
      • Painful os peroneum syndrome w consx tx
      • os peroneum fracture w displaced fragments
    • Surgical excision w repair of Peroneus Longus Tendon or tenodesis to Peroneus Brevis


What is this?

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  • Accessory NAVICULAR
  • Normal variant in 12% population
  • Majority pts are asymptomatic
  • More common in females


What is the pathoanatomy of accessory navicular?

  • Occurs as a PLANTAR ENLARGEMENT of navicular bone
  • Navicular ossifies at age 3 in girls, 5 in boys
  • Accessory navicular doesn't ossify until 8 years
  • exists as secondary bone or complete ossified extension to navicular


What is the classification ot the accessory navicular?

  • Radiograph
    • TYPE 1= Sesmoid bone in substance of TIBIALIS POST tendon- see pic
    • TYPE 2= Separate accessory bone attached to native navicular via synchondrosis
    • Type 3= Complete bony enlargement

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What are the symptoms and signs of accessory navicular?

  • Symptoms
    • Medial Arch pain is worse w OVERUSE
    • due to repetitive microfracture at the synchondrosis or from inflammation of the posterior tibialis tendon insertion
  • O/E
    • Tender at medial and plantar aspect of navicular bone


Describe the imaging useful for Dx?

  • Xrays
    • Ap, Lat, obliques
    • best seen on EXTERNAL OBLIQUE
    • bony enlargement or accessory bone
  • ​MRI
    • ​Helps delinate insertion of tibialis posterior tendon

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What is the TX of accessory navicular?

  • Non operative
    • Activity restriction, shoe modification and non- narcotic analgesia
    • use of arch supports/pads over bony prominences
    • UCBL orthosis may invert heel during walking and decrease symptoms
    • nearly all children & adolsecents who have symptomatic accessory tarsal navicular bone become asymptomatic when they reach skeletal maturity
    • Short period pf cast immobilisation
  • Operative
    • Excision of accesory navicular
    • failed consc tx


Describe the technique for surgical excision of accessory navicular?

  • Bone needs to be resected flush with MEDIAL CUNEIFORM
    • most common cause of persistent symtpoms post surgery is INADEQUATE BONE RESECTION
    • other pts may have persistent pain from SCAR TISSUE or other causes
  • May need to SPLIT the posterior tibialis tendon in order to excise the navicular
  • Re- routing the posterior tibialis will NOT CORRECT FLAT FOOT DEFORMITY
  • CALCANEUS OSTEOTOMY if flatfoot correction is needed.