An osteochondral lesion of the talus (OLT) is an area of abnormal, damaged cartilage and bone on the top of the talus bone (the lower bone of the ankle joint). This condition is also known as osteochondritis dissecans (OCD) of the talus or a talar osteochondral lesion (OCL). The common treatment strategies of symptomatic OLTs include nonsurgical treatment with rest, cast immobilization, and use of NSAIDs; surgical treatment includes surgical excision of the lesion, excision, and curettage, excision combined with curettage and micro fracturing, filling of the defect with autogenous cancellous.
Chondral and osteochondral injuries are relatively common in weight-bearing joints of the lower extremity. Osteochondral lesion of the talus (OLT) is a broad term used to describe an injury or abnormality of the talar articular cartilage and adjacent bone. A variety of terms have been used to refer to this clinical entity, including osteochondritis dissecans (OCD), osteochondral fracture, and osteochondral defect.
Pathophysiology
- General
- Definition: combined lesion of subchondral bone and overlying cartilage
- In the foot and ankle, most commonly occur on the talar dome
- The defect is bilateral in about 10% of cases
- Talus
- Vulnerable to OCD due 60% of the surface being articular cartilage with poor regenerative capacity and talaus has poor blood flow
- Most are localized on the anterolateral or posteromedial talar dome
- Lateral: usually shallow oval shaped and are caused by a shear mechanism
- Medial: usually deep, and cup-shaped, indicating a mechanism of torsional impaction and axial loading
- Asymptomatic
- Some osteochondral defects remain asymptomatic and inert
- It is not fully why
- Management is challenging
- Lesions have limited healing potential due to the poor regenerative capacity of articular cartilage, poor blood supply of the talus
- There are no consensus guidelines on appropriate treatment
- Osteochondritis dissecans
- Focal, idiopathic lesion of the subchondral bone with risk for instability and disruption of the adjacent articular cartilage
Causes
- General
- Etiology and pathogenesis are not fully understood
- Dysfunction of the subchondral bone is thought to be vascular in nature
- Osteonecrosis of the subchondral bone contributes to damage to the overlying cartilage
- Single traumatic insult
- Widely accepted as the most important etiology factor
- Talus: described in 93-98% for lateral defects, 61-70% for medial defects
- Atraumatic or repetitive microtrauma
- Ischemia, subsequent necrosis and genetics are thought to play a role in atraumatic cases
- Idiopathic
- Traumatic
- In ankle sprains, the talus twists inside a boxlike housing which can damage the cartilage lining the talus
- Separation can occur at the cartilage or in the subchondral bone
- Fragments may remain partially attached and stable or break off and float loosely in the joint
- They can heal and remain asymptomatic or progress to deep pain on weight-bearing with subchondral bone cyst formation
- Cadaveric studies
- Berndt and Harty reproduced lateral defects by strongly inverting a dorsiflexed ankle leading to compression of the lateral talus against the fibula
- They also reproduced medial lesions by plantarflexing the ankle in combination with slight anterior displacement of the talus on the tibia, inversion and internal rotation of the talus on the tibia
- Lateral Ankle Sprain, Medial Ankle Sprain
- One study reported cases in up to 6.5% of cases
- May occur in up to half of ankle sprains
- Ankle Fracture
- Commonly found after acute ankle fractures
- The reported incidence ranges from 17% to 79%
- Chronic Ankle Instability
- Incidence in patients undergoing surgery ranges from 17% to 63%
Differential Diagnosis
- Fractures & Dislocations
- Distal Tibia Fracture
- Distal Fibular Fracture
- Talus Fracture
- Calcaneus Fracture
- Subtalar Dislocation
- Ankle Fracture (& Dislocation)
- Peroneal Subluxation
- Muscle and Tendon Injuries
- Peroneal Tendon Injuries
- Achilles Tendonitis
- Achilles Tendon Rupture
- Posterior Tibial Tendon Dysfunction
- Flexor Hallucis Longus Tendinopathy
- Ligament Injuries
- Lateral Ankle Sprain
- Medial Ankle Sprain
- Syndesmotic Sprain
- Chronic Ankle Instability
- Intersection Syndrome Foot
- Bursopathies
- Retrocalcaneal Bursitis
- Nerve Injuries
- Peroneal Nerve Injury
- Tarsal Tunnel Syndrome
- Arthropathies
- Osteoarthritis of the Ankle
- Osteochondral Defect Talus
- Pediatrics
- Fifth Metatarsal Apophysitis (Iselin’s Disease)
- Calcaneal Apophysitis (Sever’s Disease)
- Other
- Haglund’s Deformity
- Posterior Ankle Impingement Syndrome
- Sinus Tarsi Syndrome
Diagnosis
- History (Acute)
- In the acute setting, often presents like a lateral ankle sprain and the OCD is missed
- At this time, patients have pain over the ATFL, trouble weight-bearing, and swelling
- Subacutely, pain, swelling, limited range of motion, and trouble weight bearing often persist
- In displaced lesions, patients can report locking or catching
- In 24% of cases, the patient denies any association with acute or repetitive trauma[17]
- History (Chronic)
- Chronic lesions present as deep ankle pain during or after activity[18]
- Range of motion is often normal, pain is not reproducible
- Swelling is absent
- Physical Exam: Physical Exam Ankle
- The effusion may or may not be present
- Tenderness to palpation over the lesion
- Decreased range of motion, pain with dorsiflexion and plantarflexion
- Special Tests
- Anterior Drawer Test Ankle
- Talar Tilt Test
Radiographs
- Standard Radiographs Ankle
- Fireline imaging
- Often normal, especially in acute injuries with nondisplaced lesions
- Sensitivity is low for OCD[19]
- Can not assess articular cartilage or characterize the lesion
- Potential findings
- Displacement
- Osteonecrosis
- Cystic changes
MRI
- The imaging modality of choice
- 96% sensitive, 96% specific[19]
- Staged by Happy Classification
- Good visualization of the articular surface
- Potential findings
- Edema of the bone, cartilage
- Considerations
- May overestimate the size of the lesion
CT
- Not routinely ordered
- 81% sensitive, 99% specific[19]
- Benefits
- May better characterize the subchondral bone, cysts
Arthroscopy
- Diagnostic gold standard
- Most patients will have advanced imaging prior to intervention
- 100% sensitive, 97% specific[19]
Classification
Berndt and Harty Classification
- Radiographic classification using plain films[20]
- I. Subchondral Compression
- II. Partially detached osteochondral fragment
- III. Completely detached fragment without displacement
- IV. Detached and displaced fragment
Ferkel and Sgaglione CT Staging System
- Based on CT[21]
- I. Intact roof/cartilage with an underlying cystic lesion
- III A. Cystic lesion with communication to the surface
- IIB. An open surface lesion with an overlying fragment
- III. Nondisplaced fragment with lucency beneath
- IV. Displaced fragment
Hepple MRI Staging System
- Based on MRI findings[22]
- I. Articular Cartilage injury only
- IIA. Acute cartilage injury with bony fracture
- IIB. Chronic cartilage injury with bony fracture
- III. Detached, nondisplaced bony fragment
- IV. Displaced fragment, uncovered subchondral bone
- V. Subchondral cyst present
Arthroscopic Classification
- A. Smooth and intact but soft
- B. Rough surface
- C. Fibrillation/fissures
- D. Flap present or bone exposed
- E. Loose, non-displaced fragment
- F. Displaced fragment
Treatment
Nonoperative
- Indications
- Asymptomatic lesions found incidentally
- Acute, symptomatic lesions that are nondisplaced (Grade B recommendation)
- Immobilization
- Duration is typically about 6 weeks followed by a slow return to activity
- Either in Short Leg Cast or Tall Walking Boot
- Weight-bearing (WB)
- Strategies vary widely and there is no clear consensus
- Consider non-WB, protected WB or full WB in immobilization
- Physical Therapy
- NSAIDS
Operative
- Indications
- Symptomatic lesions which have failed 3-6 months of nonoperative treatment
- Displaced OCD, acute or chronic
- Technique
- Cartilage repair
- Cartilage replacement
- Regenerative strategies
Retrograde drilling is usually reserved for large OCDs with intact overlying cartilage. This technique is used for stable primary OCDs when there is more or less intact cartilage with a large subchondral cyst or when the defect is hard to reach via the usual anterolateral and anteromedial portals, usually Berndt and Harty types I and II. Drilling is aimed at bringing blood supply to the lesion without disrupting the articular cartilage [10]. It is the treatment of choice when there is a large subchondral cyst with overlying healthy cartilage. For medial lesions, arthroscopic drilling can take place through the sinus tarsi. For lateral lesions, the cyst is approached anteromedially. The aim is to induce subchondral bone revascularisation and stimulate new bone formation. Kono et al. [11] and Taranow et al. [12] reported treatment success in the range of 81–100 %.
Transmalleolar antegrade drilling is considered in cases of OLTs that are difficult to approach because of their location on the talar dome. In this technique, a K wire is inserted about three centimetres proximal to the tip of the medial malleolus and directed across the medial malleolus into the lesion through the intact cartilage. Kono et al. [11] and Robinson et al. [13] described the results of this technique, which was reported to be successful in 63 % of cases.
Surgical treatment includes: excision, in which the partially detached fragment is excised and the defect itself is left untreated; excision and debridement, in which after excision of the loose body, the surrounding necrotic subchondral tissue is curetted using either an open or arthroscopic technique; excision, debridement and bone marrow stimulation (BMS), in which after excision and curettage, multiple openings into the subchondral bone are created by drilling or by microfracturing. This way, intraosseous blood vessels are disrupted and the release of growth factors leads to formation of a fibrin clot. The formation of local new blood vessels is stimulated, bone marrow cells are introduced into the osteochondral defect and fibrocartilaginous tissue is formed. Van Dijk et al. [14], in a review of the literature, noted a success rate of 54 % with the excision technique when performed for superficial cartilaginous lesions with mainly intact underlying subchondral bone. Respectively, excision and curettage had a reported success rate of 77 %, where most patients had a Berndt and Harty stage III or IV lesion, although stage II lesions occurred. Finally, excision, debridement and BMS had the best reported rate of success (85 %), where most patients often had a Berndt and Harty stage III or IV lesion, although stage I and II lesions occurred; lesion diameter usually did not exceed 1.5 cm. Kouvalchouk et al. [15] studied defect filling with an autogenous bone graft. In this technique, the remaining defect after excision and debridement of OLTs of the talar dome with partial necrosis is filled with autogenous cancellous bone with the aim of restoring mechanical properties of the talus. Indications for such treatment were large, often medial, lesions greater than 1.5 cm in diameter.
Larger lesions that fail to improve six months after arthroscopy should be considered for osteochondral grafting or autologous chondrocyte implantation. The concept of using restorative cartilage treatment with autograft and allograft is reported in the literature [16, 17]. The results of osteochondral autograft transplantation are reported at intermediate follow-up with good results. Two related procedures have been developed: mosaicplasty and OATS. Both are reconstructive bone grafting techniques that use one or more cylindrical osteochondral grafts from the less weightbearing periphery of the ipsilateral knee, which are then transplanted into the prepared defect site on the talus. The aim of this technique is to restore mechanical, structural and biochemical properties of the original hyaline articular cartilage. It is carried out either using an open approach or an arthroscopic procedure. Indications involve large, often medial, lesions, sometimes with a cyst underneath. Osteochondral grafting of defects yielded 90–94 % good to excellent results, with Scranton et al. [18] noting 90 % satisfaction in 50 patients at a 36-month follow-up and Hangody et al. [19] reporting 94 % good to excellent results in 36 patients at an average of 4.2 years.
Autologous chondrocyte implantation attempts to regenerate tissue with a high percentage of hyaline-like cartilage. The ACI technique involves placing cultured chondrocytes under a periosteal patch that covers the lesion. It is done for lesions larger than one square centimetre in the absence of generalised osteoarthritic changes. Harvesting is first accomplished from either the knee or ankle from the region on the perimeter of the talus lesion. A second procedure is performed after the cells have been cultured for six to eight weeks. An osteotomy of the medial malleolus can be performed for medial defects. The damaged articular surface is curetted to a stable border, and a periosteal patch is harvested from the tibia. The patch is sutured to the defect and sealed with fibrin glue. Finally, cultured chondrocytes are injected under the patch. Whittaker et al. [20] reported their results with ACI on ten patients with a four-year follow-up: 90 % of patients were pleased with the results at 24 months, with no change at 48 months.
