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Updated: Sep 12 2023

Osteochondral Lesions of the Talus

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  • summary
    • Osteochondral Lesions of the Talus are focal injuries to the talar dome with variable involvement of the subchondral bone and cartilage which may be caused by a traumatic event or repetitive microtrauma.
    • Diagnosis can be made with plain ankle radiographs. MRI studies are helpful in determining the size of the lesion, the extent of bony edema, and identify unstable lesions.
    • Treatment can be nonoperative or operative depending on patient age, patient activity demands, lesion size, and stability of lesion. 
  • Epidemiology
    • Incidence
      • 69% of ankle fractures
      • 70% of ankle sprains
      • 10% are bilateral
      • medial talar dome lesions more common
    • Anatomic location
      • medial talar dome
        • usually no history of trauma
        • more posterior
        • larger and deeper than lateral lesions
      • lateral talar dome
        • usually have a traumatic history
        • more superficial and smaller
        • more central or anterior
        • lower incidence of spontaneous healing
        • more often displaced and symptomatic
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • ankle inversion and dorsiflexion during axial load creates shearing of lateral talar dome and lateral OLT
        • ankle inversion, external rotation, and plantarflexion during axial load creates shearing of medial talar dome and medial OLT
      • pathophysiology
        • possible repeitive microtrauma creates ischemic environment and loss of integrity of subchondral bone
        • leads to softening and disruption of overlying cartilage
    • Associated conditions
      • cavus hindfoot alignment
  • Anatomy
    • Osteology
      • talus geometrically complex structure
      • resembles a frustrum
      • anterior portion broader than posterior
      • no muscular attachments
    • Cartilage
      • covers 70% of talus
      • among the thickest in the body (implications for osteochondral autografting)
      • maintains tensile strength longer than femoral head with aging process
    • Blood supply
      • relies on extra-osseous blood supply
      • deltoid artery supplies majority of talar body and dome
    • Biomechanics
      • ankle is a highly congruent mortise joint, oriented 15 degrees externally from midsagittal line of ankle
      • talus articulates with the medial malleolus medially, tibial plafond superiorly, posterior malleolus posteriorly, and fibula laterally
  • Classification
      • Berndt and Harty Radiographic Classification
      • Stage 1
      • Small area of subchondral compression
      • Stage 2
      • Partial fragment detachment
      • Stage 3
      • Complete fragment detachment but not displaced
      • Stage 4
      • Displaced fragment
      • Ferkel and Sgaglione CT Staging System
      • Stage 1
      • Cystic lesion within dome of talus with an intact roof on all view
      • Stage 2a
      • Cystic lesion communication to talar dome surface
      • Stage 2b
      • Open articular surface lesion with the overlying nondisplaced fragment
      • Stage 3
      • Nondisplaced lesion with lucency
      • Stage 4
      • Displaced fragment
      • Hepple MRI Staging System
      • Stage 1
      • Articular cartilage edema
      • Stage 2a
      • Cartilage injury with underlying fracture and surrounding bony edema
      • Stage 2b
      • Stage 2a without surrounding bone edema
      • Stage 3
      • Detached but nondisplaced fragment
      • Stage 4
      • Displaced fragment
      • Stage 5
      • Subchondral cyst formation
  • Presentation
    • History
      • inversion ankle sprain
    • Symptoms
      • pain centered over ankle joint line
      • joint effusion
      • mechanical symptoms such as catching or locking
    • Physical exam
      • inspection
        • joint effusion
        • palpation rarely reproduces pain
        • cavus hindfoot alignment
      • motion
        • often limited secondary to pain or effusion
      • provocative tests
        • evaluate for ligamentous laxity or insufficiency
  • Imaging
    • Radiographs
      • recommended views
        • standard weightbearing ankle series
      • findings
        • often normal
        • subtle lucency or bone fragmentation
    • Bone scan
      • indications
        • suspicion for OLT in setting of equivocal radiographs
      • sensitivity and specificity
        • 94% sensitive and 96% specific for OLT
    • CT
      • findings
        • helpful in evaluating subchondral bone and cysts
        • less reliable in purely cartilaginous lesions of nondisplaced OLTs
        • provides fine detail of lesions for pre-operative planning
    • MRI
      • indications
        • persistent pain following injury, ankle sprains that do not heal with time
      • findings
        • variable edema patterns, may overestimate degree of injury
        • unstable lesions show fluid deep to subchondral bone
      • sensitivity and specificity
        • predicts stability of lesion with 92% sensitivity
  • Treatment
    • Nonoperative
      • immobilization and non-weight bearing
        • indications
          • acute injury
          • nondisplaced fragment with incomplete fracture
    • Operative
      • arthroscopy with removal of the loose fragment, debridement and marrow stimulation
        • indications
          • chronic lesions
          • displaced smaller fragment with minimal bone on the osteochondral fragment (poor healing potential)
      • retrograde drilling and/or bone grafting
        • indications
          • size > 1 cm with intact cartilage cap
      • osteochondral grafting (osteochondral autograft transplantation, autologous chondrocyte implantation, bulk allograft)
        • indications
          • size > 1 cm and displaced lesions, shoulder lesions
          • salvage for failed marrow stimulation or drilling
        • contraindications
          • diffuse ankle arthritis
          • bipolar kissing lesions
          • advanced osteonecrosis of the talar done
  • Techniques
    • Immobilization and non-weight bearing
      • period of immobilization in cast or boot for 6 weeks, followed by progressive weight bearing with physical therapy emphasizing peroneal strengthening, range of motion, and proprioceptive training
      • outcomes
        • 45% good-excellent outcomes
    • Arthroscopy with marrow stimulation (microfracture or antegrade drilling)
      • approach
        • standard arthroscopic approach to ankle
      • instrumentation
        • debridement of unstable cartilage flaps to create stable and contained defect using curettes or shaver
        • loose bodies and cartilage removed using shaver or grasper
      • bony work
        • microfracture awl placed perpendicular to surface and tapped into subchondral bone 2-4 mm deep
          • holes spaced 2-3 mm from each other
          • inflow stopped to allow fat or blood to emanate from holes, indicating adequate penetration
        • Kirschner wire can be passed using anterior portals, or transmalleolar for central or posterior lesions
          • commercial targeting guides available
          • talus dorsiflexed and plantar flex to necessitate only 1 transosseous passing of wire
      • complications
        • articular cartilage delamination and graft failure
      • outcomes
        • 85% pain improvement
        • 65-90% improvement in patient reported outcomes
        • fibrocartilage formation at site of lesion in 60% of patients on second-look arthroscopy, no correlation noted with patient outcomes
    • Arthroscopy with retrograde drilling and bone grafting
      • approach
        • standard arthroscopic approach to ankle
      • instrumentation
        • evaluate cartilaginous surface for softening, dimpling with probe seen
        • confirm integrity of cartilaginous cap
      • bony work
        • Kirschner wire drilled from sinus tarsi into defect
          • commercial targeting guides available
          • fluoroscopy often helpful to confirm location
        • if bone grafting indicated, cannulated drill placed over K wire
          • curette out cystic material
          • graft harvested and placed
      • complications
        • violation of intact cartilage cap
    • Osteochondral autograft and allograft transplant
      • approach
        • dictated by location of OLT and concomitant procedures required (i.e. Brostrum)
        • medial malleolar osteotomy for medial and posterior lesions
          • longitudinal incision centered over medial malleolus
          • anterior arthrotomy to expose joint line
          • flexor retinaculum released posteriorly; PTT retracted posteriorly
          • osteotomy guided based of 2 parallelly placed K-wires, with goal to enter plafond at lateral extent of OLT
          • prior to osteotomy, 2 drill holes placed to aid in reduction following procedure
          • sagittal saw and osteotome used to complete osteotomy, care taken not to cause thermal necrosis to bone or damage cartilage
        • lateral malleolar osteotomy or ATFL/CFL release for lateral lesions
          • longitudinal incision centered over lateral malleolus
          • oblique osteotomy planned, with predrilling of small fragment screws holes to aid in reduction following procedure
          • alternatively, if lateral ligament reconstruction is planned, extensor retinaculum may be released
          • peroneal tendons retracted posteriorly and ATFL and CFL released, ankle inverted and plantarflexed to expose talar dome
        • bone work
          • OLT debrided and measured using sizing guide
          • appropriately sized autograft may be harvested from knee and placed into OLT, impacted gently into defect
          • OATs harvested from the knee have a cartilage thickness less than the native talus
            • this will cause immediate post-operative xrays to show a prominent graft despite the cartilage surface being flush
        • complications
          • osteotomy site delayed- or non-union
            • do not release deltoid ligament as may jeopardize deltoid artery blood supply
          • ankle impingement if graft plug left proud
          • autograft harvest site morbidity
    • Autologous chondrocyte implantation
      • approach
        • two-stage procedure consisting of
          • arthroscopic harvest of chondrocytes (from ankle or alternatively from knee) are sent for cultured growth
          • open approach via osteotomy for implantation
      • instrumentation
        • debridement of lesion to create stable cartilage rim, subchondral bone exposed
        • bone graft may be placed if underlying cyst and bone loss
        • periosteum from tibia taken and fitted to defect
        • this is sutured into place this small caliber suture, omitting one area to leave access to underlying defect
        • water-tight seal confirmed, cultured chondrocytes placed under flap and suture placed, fibrin glue placed over defect
      • outcomes
        • newer technique of matrix-based chondrocyte implantation (MACI) shown equivalent outcomes to ACI and may obviate need for osteotomy
  • Complications
    • Graft failure
      • complication of all grafting procedures
    • Persistent pain
      • small percentage of patients do not achieve pain relief regardless of treatment
  • Prognosis
    • Lesions may progress to involve entire ankle joint
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