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 untreated lateral ligamentous insufficiency at time of osteochondral defect repair increases failure rates 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 size < 1 cm 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