Orthopaedic Surgery - Osteochondral Defect of the Talus

Basics

An osteochondral defect of the talus is an injury involving the articular cartilage and underlying subchondral bone of the talar dome within the ankle joint.

The term osteochondral lesion of the talus (OLT) is also commonly used.

The talus is one of the more frequent sites of osteochondral injury, after the:

Knee

and

Elbow.

Lesions most often involve the:

Posteromedial talar dome

or

Anterolateral talar dome.

Historically, approximately 53% have been reported medially and 46% laterally.

Classification

The classic classification is based on the Berndt and Harty system, with later modifications.

Stage I

There is:

Compression or contusion of the subchondral bone

without a clearly separated osteochondral fragment.

Stage II

There is a:

Partially detached osteochondral fragment.

The fragment remains incompletely separated from the talus.

Stage III

The osteochondral fragment is:

Completely detached but remains nondisplaced and stable within the defect.

Stage IV

The fragment is:

Completely detached and displaced.

This may create a loose body within the ankle.

Stage V

A later modification added:

Subchondral cyst formation.

This stage is particularly relevant in chronic lesions.

Prevention

There is no proven method that prevents all talar osteochondral lesions.

Because many lesions are related to ankle trauma, preventive strategies include:

Reducing recurrent ankle sprains

Rehabilitating ligament injuries appropriately

Treating significant chronic ankle instability

Correction of persistent ankle instability may reduce repetitive shear injury to the talar dome.

Epidemiology

Most patients are diagnosed in the:

Second through fourth decades of life.

Historical studies report a mean age of approximately:

27 years.

Men have traditionally represented approximately 65% of affected patients in some series.

Incidence

Osteochondral lesions of the talus are relatively uncommon compared with routine ankle sprains and fractures.

Older reports estimate that they account for approximately:

0.09% of all fractures

and a small proportion of all osteochondral lesions.

Their true frequency is probably underestimated because some lesions are occult on initial radiographs.

Risk Factors

Because most lesions are traumatic, important risk factors include:

Previous ankle fracture

Ankle sprain

Recurrent ankle sprains

Chronic ankle instability

Genetics

There is limited evidence suggesting that genetic factors may influence susceptibility in selected patients, but trauma remains the dominant recognized cause.

Pathophysiology

Osteochondral lesions are produced by combinations of:

Shear forces

Compression

Impact loading

These forces damage the articular cartilage and subchondral bone.

Etiology

The most common cause is trauma.

Acute Trauma

An acute lesion may follow:

Ankle sprain

or

Ankle fracture.

Chronic Trauma

Repeated instability may cause recurrent:

Shear and impact injury to the talar dome, eventually producing cartilage and subchondral bone damage.

Lateral Lesions

Lateral talar lesions are particularly strongly associated with trauma.

Historically, a recognizable traumatic episode has been identified in approximately:

93% of lateral lesions.

They are often more:

Shallow

Wafer-shaped

and

Displaced

than medial lesions.

Medial Lesions

Medial lesions have also been associated with trauma, but less consistently.

Historical data identify a recognized traumatic event in approximately:

61% of medial lesions.

These lesions are often:

Deeper

Cup-shaped

and more likely to become chronic or cystic.

Other Causes

Possible nontraumatic contributors include:

Ischemic injury

Avascular necrosis

Abnormal local bone biology

Associated Conditions

Common associated conditions include:

Ankle fracture

Ankle sprain

Chronic lateral ankle instability

Diagnosis

Diagnosis requires a combination of:

Clinical suspicion

Physical examination

and

Imaging.

History

Important questions include:

Was there a previous ankle injury?

Has the patient had repeated ankle sprains?

Is there a history of ankle instability?

Are there mechanical symptoms such as catching or locking?

Signs and Symptoms

Patients commonly report:

Deep ankle pain

Pain with weight bearing

Swelling

Intermittent stiffness

Catching or locking

Persistent symptoms after an ankle sprain

The pain may be poorly localized.

Mechanical Symptoms

Catching, clicking, or locking suggests:

An unstable fragment, loose body, or irregular articular surface.

Physical Examination

A complete foot and ankle examination should be performed.

Swelling and Effusion

Assess for:

Ankle swelling

Joint effusion

Talar Dome Tenderness

Localized tenderness over the talar dome may be present, although deep lesions can be difficult to palpate directly.

Ankle Instability

Evaluate for ligamentous instability using:

Anterior drawer test

and

Talar tilt test.

Generalized ligamentous laxity should also be assessed.

Range of Motion

Evaluate ankle:

Dorsiflexion

Plantarflexion

and rotational movement.

Look for:

Pain

Crepitus

Catching

Mechanical restriction

Exclusion of Other Causes of Ankle Pain

Other abnormalities that may explain chronic ankle pain should be excluded, including:

Peroneal tendon subluxation

Lateral process fracture of the talus

Fifth metatarsal fracture

Syndesmotic injury

Tarsal coalition

Imaging

Imaging is central to diagnosis.

Weight-Bearing Radiographs

Initial imaging should generally include:

Weight-bearing ankle radiographs.

Plain films are inexpensive and can identify:

Osteochondral fragments

Subchondral cysts

Sclerosis

Arthritis

Other fractures or structural abnormalities

However, talar osteochondral lesions may be difficult to visualize on routine radiographs.

Historical sensitivity has been approximately 70%, with high specificity.

CT

CT provides excellent evaluation of:

Subchondral bone

Lesion dimensions

Cyst formation

Fragment displacement

Osseous architecture

Historically reported sensitivity is approximately 81%, with specificity near 99%.

Role of CT

When a lesion is visible on radiographs, CT is particularly useful for confirming and defining:

Its size, depth, and bony extent.

It is often the best study for accurate characterization of the subchondral component.

MRI

MRI is highly sensitive for detecting osteochondral lesions.

Historical studies report:

Sensitivity around 96%

and

Specificity around 99%.

Role of MRI

MRI is especially useful for identifying:

Bone marrow edema

Cartilage injury

Subchondral cysts

Associated ligament injury

Tendon abnormalities

Synovitis

It is generally the best modality for evaluating associated soft-tissue pathology.

MRI Limitations

MRI may overestimate lesion size because surrounding:

Bone marrow edema

can make the abnormal area appear larger.

Metallic implants can also produce artifact that limits interpretation.

CT Versus MRI

Both CT and MRI are highly useful.

CT is superior for:

Detailed bony architecture

whereas MRI is superior for:

Cartilage, marrow, and soft tissues.

The preferred modality depends on the clinical question.

Bone Scintigraphy

Bone scanning was historically used to identify metabolically active occult lesions.

It is less commonly required now because MRI provides more detailed information.

Arthroscopy

Ankle arthroscopy provides the most direct assessment of the:

Articular cartilage surface.

It also permits simultaneous treatment.

Limitations of Arthroscopy

Arthroscopy is:

Invasive

Operator dependent

and does not fully demonstrate:

Deep subchondral bone pathology.

Pathological Findings

In chronic nondisplaced lesions, an osteochondral fragment may remain attached to the defect by:

Fibrous tissue.

Subchondral Bone Violation

If the subchondral bone is penetrated, healing occurs primarily through formation of:

Fibrous tissue or fibrocartilage.

Intact Subchondral Bone

When the subchondral plate remains intact, intrinsic healing is limited because articular cartilage has poor regenerative capacity.

Displaced Fragments

The cartilage cap of a fragment may remain viable, but the underlying bone can become:

Avascular

with reduced healing potential, particularly in chronic lesions.

Differential Diagnosis

The differential diagnosis includes most causes of chronic ankle pain.

Important alternatives include:

Occult fracture

Fifth metatarsal fracture

Lateral process fracture of the talus

Medial or lateral malleolar fracture

Ankle sprain

Syndesmotic injury

Chronic ankle instability

Peroneal tendon subluxation

Anterior ankle impingement

Tarsal coalition

Ankle or subtalar synovitis

Posterior tibial tendon pathology

Treatment

General Principles

Treatment depends on:

Lesion stage

Size

Location

Stability

Presence of cysts

Duration of symptoms

Patient activity level

Previous treatment

Nonoperative Treatment

Nonoperative management can be attempted for:

Stage I

Stage II

and some

Stable Stage III lesions.

Immobilization

Treatment may include:

Activity modification

Walking boot

Short-leg cast

Temporary non-weight bearing

The exact protocol varies according to symptoms and lesion characteristics.

Success Rate

Historical studies report successful nonoperative treatment in approximately:

50% of patients.

Failure of conservative treatment does not necessarily worsen the results of later surgery.

Pediatric Considerations

Children are believed to have greater healing potential than adults because of:

Greater biological activity and remaining skeletal growth.

Therefore, nonoperative treatment is often favored initially.

However, favorable results are not guaranteed.

One older pediatric series reported good or excellent outcomes in only about:

38% of children treated without surgery.

Activity Modification

Nonoperative recommendations range from:

Avoidance of impact activity

to

Strict non-weight bearing in a cast.

Return to sport should be based on:

Pain resolution

Restoration of motion and strength

Healing or stability of the lesion

Physical Therapy

Rehabilitation may include:

Ankle range-of-motion exercises

Peroneal strengthening

Progressive weight bearing

Proprioceptive training

Balance exercises

Treatment of chronic ankle instability

Surgery

Surgery is considered for:

Unstable lesions

Displaced fragments

Persistent symptoms despite conservative treatment

Large lesions

Cystic lesions

Recurrent lesions after previous surgery

A variety of techniques are available.

Fragment Reduction and Fixation

Large viable osteochondral fragments may be:

Reduced and internally fixed.

This is most appropriate when the fragment:

Is large enough to accept fixation

Has viable bone

Can be anatomically restored

Acute lesions generally have a better healing potential than chronic displaced lesions.

Bone Marrow Stimulation

The most common initial surgical treatment for small lesions includes:

Débridement

Curettage

Microfracture

or

Subchondral drilling.

These procedures are often performed arthroscopically.

Surgical Technique

The surgeon removes:

Loose bodies

Fibrous tissue

Unstable cartilage

The underlying subchondral bone is then penetrated to allow:

Bleeding and clot formation.

Mechanism of Healing

The resulting fibrin clot contains marrow-derived cells, including:

Mesenchymal progenitor cells.

These cells form repair tissue that is primarily:

Fibrocartilage.

Fibrocartilage

Fibrocartilage is mechanically inferior to normal:

Hyaline articular cartilage

but can provide satisfactory symptom relief in appropriately selected small lesions.

Lesion Size

Bone marrow stimulation tends to perform best for relatively small defects.

Historically, lesions with a surface area under approximately:

1 cm²

have had more favorable outcomes than larger lesions.

Postoperative Management After Microfracture

Following microfracture or drilling, patients are commonly kept:

Non-weight bearing for approximately 4–6 weeks.

Early ankle range of motion is often encouraged.

Osteochondral Autograft Transfer

Osteochondral autograft transfer, also called:

OATS or mosaicplasty, transfers plugs containing viable hyaline cartilage and subchondral bone into the talar defect.

Donor Site

Grafts are usually harvested from a:

Low-load region of the ipsilateral knee.

Advantages and Limitations of OATS

Advantages include restoration of:

Hyaline cartilage and subchondral bone.

Limitations include:

Donor-site morbidity

Limited graft availability

Need for more extensive surgical exposure

Osteotomy for Access

Large medial or posterior lesions may require:

Medial malleolar osteotomy

or another osteotomy to expose the talar dome.

Patients remain non-weight bearing until the osteotomy heals.

This commonly requires approximately:

4–8 weeks.

Range of Motion After Osteotomy

Ankle motion is generally started within:

2–6 weeks, depending on fixation stability and healing.

Osteochondral Allograft Transfer

Fresh osteochondral allograft can be used to reconstruct:

Large or deep defects.

The graft is harvested from donor talar tissue and transplanted into the lesion.

Indications for Allograft

This technique is particularly useful for:

Large defects

Cystic lesions

Failed previous surgery

Lesions too large for practical autograft harvest

Historically, allograft transplantation has been considered for defects larger than approximately:

3 cm².

Autologous Chondrocyte Implantation

Autologous chondrocyte implantation is a cartilage restoration technique in which:

Cartilage cells are harvested, expanded in culture, and implanted into the defect.

Earlier Generations

First- and second-generation techniques used:

Cell suspension placed beneath a periosteal flap or collagen membrane.

Newer Generations

Later techniques use:

Three-dimensional scaffolds or matrices

to deliver and retain chondrocytes.

Limitations of Chondrocyte Techniques

Although clinical outcomes may be favorable, repair tissue may not consistently reproduce normal:

Hyaline cartilage architecture.

Some biopsy studies demonstrate mixed cartilage or fibrocartilage.

Future Directions

Emerging approaches include:

Improved biologic scaffolds

Growth factors

Mesenchymal stem-cell strategies

Tissue-engineered cartilage

The goal is to reproduce the structure and mechanical properties of native articular cartilage more closely.

Chronic Ankle Instability

When an osteochondral lesion coexists with chronic ligamentous instability, the instability should also be addressed.

This may require:

Ligament repair or reconstruction.

Failure to correct instability may expose the repaired cartilage to continued abnormal loading.

Follow-Up

Patients should be reassessed regularly after treatment.

Monitoring focuses on:

Pain

Swelling

Range of motion

Mechanical symptoms

Return of strength

Weight-bearing tolerance

Osteotomy Follow-Up

When an osteotomy has been performed, serial radiographs are used to confirm:

Progressive union before unrestricted weight bearing.

Prognosis

With appropriate treatment, the overall prognosis is generally good.

Outcomes are influenced by:

Lesion size

Chronicity

Location

Cystic change

Cartilage stability

Associated ankle instability

Previous surgery

Complications

Potential complications include:

Persistent pain

Ankle stiffness

Failure of cartilage repair

Malunion of an osteotomy

Nonunion of an osteotomy

Progressive ankle arthritis

Post-Traumatic Arthritis

Large, chronic, or inadequately treated lesions can cause progressive cartilage loss and eventually lead to:

Degenerative ankle arthritis.

Patient Monitoring

Follow-up should continue until the patient demonstrates:

Clinical improvement

Restored ankle motion

Adequate strength

Healing of any osteotomy

Resolution or acceptable control of symptoms

Return to running and sport should be gradual.

Key Principle

An osteochondral lesion of the talus is a combined injury of the talar articular cartilage and subchondral bone, most commonly related to ankle trauma.

Management is determined primarily by:

Lesion size, stability, chronicity, cyst formation, and patient symptoms.

Small stable lesions may be treated nonoperatively or with arthroscopic marrow stimulation, whereas larger, displaced, cystic, or recurrent lesions may require:

Fragment fixation, osteochondral grafting, cartilage restoration, and correction of associated ankle instability.