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British Medical Books Health Issues Computerized Tomography

ANATOMY

  • articular cartilage covers 3/5

Head

  • articular facets for navicular (anterior)
  • spring ligament (inferior)
  • sustentaculum tali (post-inferior)
  • deltoid ligament (medially)

Neck

  • narrowed below, laterally and superiorly
    • ligament attachment
    • vascular foramina
    • 15-20 varus

Body

  • trochlear articular surface for ankle joint
  • inferior articular surface - subtalar joint
  • tarsal sinus and canal

Processes

  • posterior (medial + lateral tubercle)
    • attachments of post. deltoid & talofibular ligaments
    • os trigonum
  • lateral

BLOOD SUPPLY

  • DPA + PTA + peroneal artery form anastomotic sling around neck
  • vessels in fascial structures and capsule
  • intraosseous branches in tarsal canal, sinus tarsi

AVN

  • very common - 15-71%
  • mostly affect body & neck
  • related to # neck displacement
    • undisplaced # - intraosseous vessels disrupted
    • displaced # - anastomotic sling disrupted

HEAD FRACTURES

  • rare
  • involves talonavicular joint
  • mech - extreme plantarflexion
    • comminution
    • navicular fractured

X-ray

  • AP, lateral and oblique

Rx

  • Undisplaced
    • ice, elevation + cast (6/52) to preserve longitudinal arch
    • moulded splint for TN jt for 3-8/12
  • Displaced
    • small fragments - excise
    • large fragments - reduce + fixation
  • Prognosis - good or TN arthritis

NECK FRACTURES

  • 30% talar fractures
  • mech - hyper-dorsiflexion injury

Classification - Hawkins

  • type 1
    • undisplaced
    • vertical fracture line
  • type 2
    • displaced
    • subluxed/ disloc. subtalar joint
  • type 3
    • displaced
    • dislocated subtalar + ankle joint
  • type 4 ( Canale + Kelly )
    • head fragment dislocated

Clinical

  • Hx of severe injury ( MVA, bike, fall from height )
  • any age
  • males predominant
  • marked displacement
    • skin necrosis or open #s
    • N/V compromise
  • associated injuries common
    • calcaneus #
    • medial malleolus #

X-rays

  • AP, oblique
  • lateral
    • talar neck fracture line
    • alignment of posterior facet
  • CT scan

Rx

  • Type 1
    • B/K cast 8 - 12/52
    • NWB 4-6/52
  • Type 2
    • closed reduction
      • plantar flexion
      • correct valgus/ varus + POP in equinus
      • 4/52 equinus - NWB 8-12/52
    • open reduction (50%)
      • approach - antero-medial to tib. ant (most authors)
      • NWB 8-12/52
  • type 3 - 4
    • 25% open
    • prognosis depends on degree of displacement
    • neck # & dislocation of body- orthopaedic emergency
      • risk of neurovascular compromise - gangrene + skin slough
    • anatomical reduction
      • can try close
      • open - medial malleolus osteotomy for exposure
      • fixation w/ cannulated screws

Prognosis

  • degree of displacement
  • accuracy of reduction

Complications

  • Skin necrosis and infection
    • reduce dislocation immediately
    • poor response to local debridement - radical debridement
    • often ended up w/ Syme’s amputation
  • Delayed union/ non-union
    • rare - 4%
  • Malunion
    • reduction must be anatomical in frontal & sagittal planes
    • limited ankle dorsiflexion
    • varus deformity
  • Post-traumatic arthritis
    • in ankle or subtalar joints
    • initial damage, AVN & immobilisation
    • Rx
      • conservative – NSAID
      • ankle or/+ subtalar fusion – determine source of pain w/ local injection
  • 5. AVN (osteonecrosis )
    • common of the talar body
      • type 1 – 5-10%
      • type 2 – 50%
      • type 3-4 – 90%
    • radiographic diagnosis
      • » density of body
      • later collapse, fragmentation, narrowing of joint space
    • Hawkins sign
      • indicates viability of body - excludes AVN
      • disuse atrophy along dome of talus when NWB at 6-8/52
    • Tc bone scan or MRI aid diagnosis
    • Rx
      • triple arthrodesis
      • total talectomy w/ tibiocalcaneal fusion
      • talectomy
      • subtalar arthrodesis
      • pantalar arthrodesis
      • tibiotalar arthrodesis (Blair's)
      • excision of talar body
      • sliding cortico-cancellous graft from anterior distal tibia into residual head/neck
      • conservative

FRACTURES of BODY

  • rare
  • Mechanism
    • axial loading b/t plafon and calcaneus
  • Classification
    • # limited to sup. articular surface - no subtalar involvement
    • sagittal/ coronal fractures
    • posterior process fractures
    • lateral process fractures
    • Crush fractures (ankle + subtalar)
  • Rx
    • closed reduction & casting
    • open reduction & fixation
    • high rate of complications
  • FRACTURES of the TALAR PROCESSES
  • lateral or posterior
  • isolated or w/ other ankle/talus injuries
  • rare
  • avulsion or direct compression
  • often undisplaced – B/K cast
  • if large & displaced - ORIF

SUBTALAR DISLOCATION

  • Definition
    • simultaneous dislocation of talonavicular & talocalcaneal joint
    • tibio-talar it not disturbed
  • Incidence
    • 1% of all dislocations
    • 15% of talar injuries
    • 10-40% open
    • N/V injuries rare
  • Medially displaced
    • 85%
    • talus prominent dorso-laterally
  • Lateral dislocation
    • 15%
  • Rx
  • Closed reduction
    • under GA/ spinal
    • flex knee to lessen tension on Achilles tendon
    • cast 4/52
  • Failed closed reduction - open
    • entrapment of capsule, ligaments or EDB
    • medial approach
  • AVN
    • rare

TOTAL TALAR DISLOCATION

  • rare
  • extreme supination or pronation
  • most open
    • 89% infections
    • all need talectomy
    • complications: AVN/ degenerative arthritis
  • Rx
  • debride
  • reduce
    • arthrodesis preferred instead of talectomy (Rockwood)
    • preserving talus - if no infection
    • AVN + arthritis - then tibiotalar or pantalar arthrodesis.
    • closed reduction with calcaneal pin - poor results
  • reduction held with K-wires + cast 6/52
  • if symptomatic - arthrodesis.