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 frustum 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 login to view 1 more bullet 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 login to view 2 more bullets Operative arthroscopy with removal of the loose fragment, debridement and marrow stimulation indications login to view 4 more bullets retrograde drilling and/or bone grafting indications login to view 1 more bullet osteochondral grafting (osteochondral autograft transplantation, autologous chondrocyte implantation, bulk allograft) indications login to view 2 more bullets contraindications login to view 3 more bullets 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 login to view 2 more bullets Kirschner wire can be passed using anterior portals, or transmalleolar for central or posterior lesions login to view 2 more bullets 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 login to view 2 more bullets if bone grafting indicated, cannulated drill placed over K wire login to view 2 more bullets 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 login to view 6 more bullets lateral malleolar osteotomy or ATFL/CFL release for lateral lesions login to view 4 more bullets bone work login to view 4 more bullets complications login to view 4 more bullets Autologous chondrocyte implantation approach two-stage procedure consisting of login to view 2 more bullets 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