DEFINITION

The terminology of osteochondral lesions is not uniform: Transchondral fractures, osteochondral fractures, flake fractures, and osteochondritis dissecans (OCD) are used to describe the same entity. Most recently, “osteochondral lesions of the talus (OLT)” has emerged as the most common term used to describe these lesions.

OLTs are characterized by aseptic separation of a fragment of articular cartilage, with or without attached subchondral bone.

The causes for OLTs remain controversial. The most important distinction to make is if the lesion is acute or chronic.

 

 

ANATOMY

 

The talar body is trapezoidal. The anterior surface is on average 2.5 mm wider than the posterior surface. The dome is covered by the articular surface, which articulates with the tibial plafond. The medial and lateral facets articulate with the medial and lateral malleoli.

 

 

About 60% of the talar surface is covered by articular cartilage.

 

Most of the blood supply enters through the neck of the talus via the sinus tarsi.

 

Biomechanical studies have shown that the talar cartilage is softest at the posteromedial part, whereas the maximum thickness is found at the posterolateral corner.

 

 

The tibial cartilage is 18% to 37% stiffer than the corresponding sites on the talus.2

 

PATHOGENESIS

 

Lateral lesions are most frequently caused by acute trauma, with a common mechanism being a dorsiflexed ankle forced into inversion. This results in impaction of the talus on the fibula.

 

 

In our experience, lateral lesions are often located in the anterior part of the talar dome. They tend to be shallower than medial lesions.

 

Medial lesions are mostly associated with a single or repetitive supination trauma (microtrauma).

 

 

Impaction of the medial talus on the tibia with a plantarflexed ankle forced to hindfoot inversion combined with external rotation is regarded as the causative mechanism.

 

Medial lesions are more common (inversion ankle sprains are the most common sports injury) than lateral lesions and occur mostly in the middle or posterior third of the talus. These lesions appear cup-shaped and deeper than lateral lesions.

 

Injury to the talar dome associated with supination trauma to the ankle generally exhibits one of two trends in recovery:

 

 

In most, swelling and pain resolve expediently.

 

Occasionally, swelling and pain persist. In these cases, our investigations using magnetic resonance imaging (MRI) suggest that 20% of these ankles with persistent pain and swelling have an identifiable bone bruise on the medial talar dome.

 

The question is the long-term effect of an episode of subchondral effusion (hemorrhage?) on the cartilage layers: minor trauma on the tide zone with a prolonged separation?

 

In our experience, chronic ankle instability creates a medial talar dome lesion with an abrasive character that suggests a repetitive insult. Unlike the classic OCD with a subchondral origin of the pathology, these deteriorations of the cartilage derive from a classic mechanical overload. The long-term damage is a full-thickness cartilage lesion at the medial talus and tibia plafond with varus hindfoot alignment. Medial lesions may be detected bilaterally, mostly with coincidence of bilateral ankle sprains.

 

In contrast to chronic osteochondral lesions occurring as a result of repetitive trauma, acute osteochondral injuries result in an acute separation of an osteochondral fragment. Other reported causes for OLTs are genetic predisposition and endogenous factors. These causes lack meaningful evidence-based support and represent little more than theories.

 

NATURAL HISTORY

 

Initially, the patient experiences ankle pain with impact activities such as jogging and sports that subsides immediately with rest.

 

With time, increasing ankle pain generally forces the patient to stop impact sports activities. The time frame varies from patient to patient based on the patient's pain threshold and age.

 

Some cases have an identifiable traumatic incident (ie, ankle sprain) where an initially inapparent lesion is detected and the patient never returns to a pain-free state. (For us, this is an interesting phenomenon: Does the lesion cause the pain or is there a psychosomatic influence once the lesion is detected on the imaging study?)

 

Some OLTs are incidentally discovered with screening imaging studies (radiographs or MRI scans). For instance, an imaging study is obtained for an acute ankle sprain and an obviously nonacute OLT is noted. These patients have an anticipated normal healing course of the ankle injury with complete subsidence of pain and swelling and should never be treated for the asymptomatic OLT.

 

Over the past 20 years, our clinical experience (H.T.) in treating OLTs suggests that there is no evidence to support that the natural history of untreated OLTs is the development of osteoarthritis of the ankle. We thus view surgical management of OLTs as one of pain relief and not as a salvage procedure to prevent osteoarthritis of the ankle joint.

 

 

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McCullough and Venugopal18 found that in five of six patients treated conservatively for OLTs, radiologic assessment at a mean follow-up of nearly 16 years (range 7 to 28 years) showed that the lesions had failed to heal and that in each instance the ankle joint was relatively asymptomatic, without evidence of diffuse degenerative changes.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Acute OLTs must be ruled out after traumatic events when an OLT or osteochondral fracture is suspected.

 

In most cases, patients complain of chronic ankle pain with or after sports activities. Swelling and stiffness are accompanied in advanced cases with more constant pain. Occasionally, but not always, mechanical symptoms are present, including catching, locking, and giving way.

 

 

The severity of symptoms may not correlate with the severity of the lesion. Physical examination is relatively nonspecific in OLTs.

 

By having the patient plantarflex the foot and ankle, the anterior aspects of the talar dome can be palpated at the anteromedial and anterolateral joint space. Tenderness in the specific area may indicate an osteochondral lesion.

 

Tenderness behind the medial malleolus by having the patient dorsiflex the ankle may indicate a posteromedial lesion.

 

Range of motion of the ankle is tested with the knee flexed to eliminate restriction by shortened gastrocnemius muscles. Range of motion is limited only in case of ankle synovitis and effusion.

 

The examination should also include evaluation of associated pathology, taking into account the differential diagnosis.

 

 

Bony structures, tendons, ligaments, and soft tissue structures should be palpated and tested against resistance to discern tenderness of the specific anatomic part.

 

Ligamentous instability or laxity is assessed with the anterior drawer test and passive varus or valgus stress test.

 

Pushing the ankle against resistance helps identify inflammation or partial tears of tendons of the contracted muscles.

 

Palpation of pulses and neurologic assessment should be part of every examination.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Standard ankle plain film radiographs should include anteroposterior (AP), lateral, and mortise views.

However, only 50% to 66% of osteochondral defects can be visualized by plain film radiographs alone.15 The radiologic signs vary from a small area of compression of subchondral bone to a detached osteochondral fragment.

 

The four-stage classification system by Berndt and Harty6 is still the gold standard based on radiologic appearance:

 

 

 

Stage I: compression lesion, no visible fragment Stage II: fragment attached

 

 

Stage III: nondisplaced fragment without attachment (FIG 1) Stage IV: displaced fragment

 

Stress view radiographs are frequently recommended if instability is suspected. However, a thorough clinical examination is more important and in most cases is sufficient for assessment.

 

A computed tomography (CT) scan offers more accurate staging and characterization of the lesion, with clear definition of the exact dimensions of the osseous portion of the lesion, but subjects the patient to relatively

high radiation. We recommend and use limited CT studies with minimal radiation exposure to the patient and sufficient characterization of the OLT.

 

 

 

 

FIG 1 • Osteochondral lesion stage III as per Berndt and Harty's classification.

 

 

MRI is an ideal screening tool and, in our opinion, the method of choice for all patients with suspected OLTs. MRI defines occult injuries of the subchondral bone and cartilage that may not be detected with routine radiographs. Furthermore, the MRI is accurate in diagnosing associated stress fractures and stress reactions

—for example, in the medial malleolus. Although MRI may demonstrate associated edema in the talar body, in our hands, accurate sizing of the OLT is feasible.

 

Dipaola et al9 developed an MRI classification system based on Berndt and Harty's original radiographic system.

 

 

Stage I: thickening of articular cartilage and low signal changes

 

Stage II: articular cartilage breached, low signal rim behind fragment indicating fibrous attachment

 

Stage III: articular cartilage breached, high signal changes behind fragment indicating synovial fluid between fragment and underlying subchondral bone (FIG 2A,B)

 

Stage IV: loose body

DIFFERENTIAL DIAGNOSIS

Degenerative joint disease (any origin)

Soft tissue or bony impingement on the ankle joint

 

Ankle or subtalar instability

Subtalar joint pathologies (ie, chondral lesion, subtalar impingement lesion)

Tendinitis or partial rupture of the tibialis posterior, tibialis anterior, or peroneal tendons Tarsal coalition (talocalcaneal)

Stress fracture (medial or lateral malleolus, talus)

 

 

NONOPERATIVE MANAGEMENT

 

The approach and objectives in nonoperative treatment of OLTs vary from those of surgical management.

 

 

In children and adolescents, the goal is to reverse the cartilage separation and to treat the pain. Partial weight bearing (not unloading) of about 15 kg for 2 to 3 months and nonsteroidal anti-inflammatory agents (NSAIDs) at

 

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appropriate doses adjusted for age and weight for 1 to 2 months to relieve the patient's pain are important from physical and psychological standpoints. Given the advantages shown in clinical and experimental trials, we recommend use of the combination of chondroitin and glucosamine sulfate for at least 6 months. We also encourage the daily use of moist heat to enhance vascularity to the ankle and talus. In select cases of extensive talar body edema, we have observed, based on anecdotal experience, that hyperbaric oxygen (HBO) therapy (20 dives, 20 minutes each) results in resolution of edema and pain. We favor low-impact exercise such as biking and swimming for about 1 year. Regardless of MRI findings, the young patient should gradually return to age-appropriate activities once she or he is pain-free. We recommend yearly serial MRI and clinical examinations to monitor talar body status.

 

 

 

 

FIG 2 • A. Coronal MRI (T1-SE-540/20) showing an osteochondral lesion stage III. B. Sagittal MRI (T2-SE-2000/90) showing an osteochondral lesion stage III.

 

 

Although osteochondral transfer systems and autologous chondrocyte implantation (ACI) are accepted salvage procedures, to date, we lack an optimal reconstruction of an OLT. Nonoperative treatment for OLTs is the treatment of choice if the adult patient has minor complaints. The goal of nonoperative treatment is not to ameliorate the cartilage lesion but to make the ankle pain-free and resilient. We recommend NSAIDs, physiotherapy, ice or moist heat applications, well-cushioned shoes, biking, swimming, and cross-training

for 6 months.

 

We allow our adult patients with OLTs activity to tolerance. Immobilization with partial weight bearing has healing potential only for fresh traumatic osteochondral lesions. In an area with little perfusion, some contact pressure is necessary to create a healing response.

 

 

We rarely use cast or walker boot immobilization because we believe that ankle motion is important. The occasional cast or boot is applied for only brief periods (2 weeks) to reduce pain and patient insecurity. Cast immobilization is associated with inferior results compared with restricting the activity of the patient by

partial weight bearing.24 Flick and Gould10 concluded that therapy of 4 to 6 weeks with cast immobilization is inadequate immobilization, resulting in poor results for most transchondral fractures.

 

In summary, nonoperative treatment is applied for every patient who is opposed to surgical intervention. There is no time frame when a lesion has to be operated on to prevent deterioration. Pain is the benchmark, not the radiographic or MRI findings. In our opinion, an OLT that is primarily cystic and has an intact cartilage surface suggested on MRI (if detectable) should prompt nonoperative rather than operative management.

 

If deterioration or no improvement is evident after a period defined by the patient, the optimal means of determining the status of the articular cartilage is arthroscopic probing of the OLT, which is useful in determining the appropriate surgical procedure.

 

SURGICAL MANAGEMENT

 

In our opinion, asymptomatic OLTs should not be treated. Many incidentally discovered OLTs do not become symptomatic and are unrelated to the trauma that prompted the imaging study that led to the detection of the OLT. When, however, the OLT is the most likely source of pain and nonoperative treatment has failed, we recommend arthroscopic surgery for evaluation and treatment of the OLT.

 

Retrograde drilling is suggested for a symptomatic subchondral cyst with an overlying intact cartilage surface. High levels of evidence or grades of recommendation for retrograde drilling do not exist. Our theory for the mechanical pain from OLTs is an irreversible separation in the cartilage's tide zone. Drilling may decompress edema but may create heat necrosis and cystic degeneration. Moreover, without three-dimensional (3-D) CT or navigation, drilling may miss the smaller to intermediate lesions. If the chondral surface is found to be softened and is easily detachable, unstable cartilage and fibrous tissue have to be débrided.

 

Our preferred surgical management for stage II to IV OLTs is microfracture to stimulate fibrocartilage formation. After débridement of unstable cartilage in the OLT, microfracture awls designed for small joints are penetrated into the subchondral bone to open the zone of vascularization. Blood from within the talus escapes through the subchondral bone and leads to clot formation in the lesion. This clot contains pluripotent, marrow-derived mesenchymal stem cells that typically produce a fibrocartilage repair with varying amounts of type II collagen

content.13,22

 

 

The microfracture technique using dedicated small joint awls avoids the risk of thermal necrosis associated

with other marrow stimulation techniques such as abrasion or drilling.17 Moreover, all lesions may be accessed without

 

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more invasive steps such as transtibial drilling or osteotomy of the medial malleolus.

 

 

Because several studies indicate that a defect size greater than 1.5 cm2 results in inferior defect fill and inferior clinical findings after microfracture alone,7,8,14 covering the microfractured area with commercially available acellular matrix (autologous matrix-induced chondrogenesis [AMIC] technique) may improve

stabilizing the blood clot induced by the microfracture of the subchondral bone and improve the results compared to microfracture alone in larger defects.25

 

If the microfracture technique failed to relieve symptoms, repeat microfracture has been shown to be effective

in select cases.21 However, in our hands, particularly if we performed the index microfracture procedure, we recommend salvage with an AMIC or, in select cases of adolescents, a matrix-based autologous chondrocyte implantation (MACI).

 

 

Based on first-generation results after injecting the cultured cells under a periosteal flap, this appeared to be a viable alternative when treating osteochondral or chondral lesions of the talus.3,16

 

MACI with cultured cells in scaffolds seems to be more promising and technically less demanding, with good and excellent short-term results.23

 

However, costs for the procedure are high, the approach is more invasive, and longer term results remain to be evaluated to prove superiority over microfracture technique. Moreover, in the United States, MACI lacks Food and Drug Administration (FDA) approval.

 

The AMIC technique implies certain advantages over ACI. It is one single surgery and cartilage culturing after initial chondrocyte harvesting and a second-stage reimplantation is not needed. The matrix used with the described arthroscopic technique is a readily available “off-the-shelf” item.

 

Osteochondral autograft transfer (OATS) or mosaicplasty is an option in the repair of severe osteochondral lesions with a significant lack of subchondral bone or in cystic lesions.1,12 The osteochondral plugs can be harvested by either open arthrotomy or arthroscopy of the knee. The option of local osteochondral grafting

has also been reported.20 Major problems with these techniques include the different characteristics of knee (donor) and ankle (recipient) cartilage (different thicknesses and radii of curvature), which may lead to edge loading and graft deterioration. Donor site morbidity can be significant, resulting in a decline of knee function

and problems in performing activities of daily living.19

 

 

 

FIG 3 • A. Positioning of the patient for ankle arthroscopy. B. Positioning of the patient if a posterolateral approach is necessary. C. Atraumatic distraction of the ankle with bandages.

 

Preoperative Planning

 

Review of all imaging studies, especially MRIs, is in our opinion most important for preoperative planning. The OLT size, location, topical geography, and depth must be identified to determine the correct approach and technique.

 

Ankles must be inspected for severe swelling, warmth, or erythema. We consider elevated blood sample

parameters that indicate an acute inflammatory process a contraindication to surgical intervention for OLT management. In our experience, any OLT in any location within the ankle can be treated arthroscopically through standard portals.

 

 

In some cases, an accessory posterolateral portal facilitates access to posterior OLTs in relatively tight ankles.

 

Examination under anesthesia allows for better assessment of coexisting ankle instability.

 

 

In case of lateral ligamentous instability, lateral ligament stabilization should be performed along with OLT management. Ankle instability may increase the contact forces and shear stresses on the OLT.

 

Positioning

 

The procedure is performed under general anesthesia with a tourniquet placed at the thigh.

 

The patient is preferably positioned with a leg holder that allows the gastrocnemius-soleus complex to be fully relaxed (FIG 3A).

 

We recommend that the patient be positioned in the lateral position if a posterolateral approach may need to be performed (FIG 3B).

 

Noninvasive ankle distraction may be performed using bandages (FIG 3C).

 

 

However, in our experience, most OLTs may be safely performed without distraction.

 

 

 

Approach

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We use standard anteromedial and anterolateral arthroscopic portals. The anteromedial portal enters the ankle between the medial malleolus and the talar dome 0.5 to 1 cm distal to the joint line and just medial to the anterior tibial tendon. The anterolateral portal enters the joint between the fibula and talus at the same level as the medial portal, lateral to the common extensor tendon.

 

If necessary, the posterolateral portal is placed adjacent to the Achilles tendon and behind the peroneal tendon, slightly below the level of the joint line. A Kirschner wire can be directed under vision of the arthroscope from the anteromedial portal posteriorly to find the same location (Wissinger rod technique). The patient must be fully relaxed and the joint adequately distracted and distended.

 

In addition, a superomedial portal located 1 cm above the joint line, medial to the tibialis anterior tendon, might be helpful to achieve more perpendicular angles for microfracturing (FIG 4).

 

 

 

FIG 4 • Superomedial portal for better angles for microfracturing.

 

TECHNIQUES

• Arthroscopy

Fill the joint with 20 mL saline solution through the anteromedial portal (TECH FIG 1A).

We recommend using a 2.5- or 2.7-mm arthroscope, with 25- to 30-degree and 70-degree angled lenses, needed to assess and treat defects in all areas of the joint (TECH FIG 1B).

 

 

 

 

TECH FIG 1 • A. Filling the joint with 20 mL saline solution. B. 2.5-and 2.7-mm arthroscopes for ankle arthroscopy.

 

 

Perform a limited synovectomy in all cases. This enhances visibility during the procedure and allows the surgeon to remove inflamed synovium that may contribute to ankle pain and swelling.

 

 

Systematically inspect the ankle and document all pathology. Remove loose bodies, if present.

 

We assess and probe all articular surfaces of the ankle, including the talar dome, medial and lateral gutters, and the tibial plafond.

• Preparation of the Lesion

   

  Identify the lesion with a probe (TECH FIG 2A).

   

  Address all unstable cartilage and fibrous tissue of the OLT and the cartilage that lies immediately adjacent to the defect with débridement and curettage (TECH FIG 2B).

   

   

  Create sharp, perpendicular margins to optimize conditions for the attachment of the marrow clot. Completely remove the calcified cartilage layer with a burr.

   

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  TECH FIG 2 • A. Probing of the lesion. B. Débridement and curettage.

• Microfracture with Optional Coverage of an Acellular Matrix

 

The microfracture technique is performed if the subchondral bone layer is healthy and intact.

 

Arthroscopic awls of different angles permit appropriate perpendicular access to all areas of the prepared OLT. Place the microfractures about 3 to 4 mm apart and 2 to 4 mm deep; fat droplets indicate that the subchondral bone has been adequately penetrated.

 

We ensure that the awl is always placed perpendicular to the surface and that penetration of subchondral bone is performed judiciously to maintain the subchondral bone plate integrity and architecture (TECH FIG 3A).

 

Before removing the arthroscope from the ankle, we release the tourniquet and stop the flow of saline through the ankle to confirm that blood is indeed escaping from the talus into the talar defect (TECH FIG 3B).

 

 

 

TECH FIG 3 • A. Microfracture. B. Release of the tourniquet. Blood enters the joint from the microfractures. C. Insertion of the acellular matrix in the prepared lesion area. D. Shaping the matrix to the lesion with overlapping to the borders of the defect area.

 

 

In lesions greater than 1 to 1.5 cm2, the portal for inserting the acellular matrix (Chondro-Gide, Geistlich Biomaterials, Wolhusen, Switzerland) is enlarged to approximately 1 cm. The fluid is removed from the joint with small suction devices and the defect dried with small swabs.

 

The matrix is inserted by using a mosquito clamp (TECH FIG 3C). The defect should be fully covered with the matrix overlapping all borders to achieve a sealing effect (TECH FIG 3D).

Fibrin glue is inserted and the ankle kept in neutral position for 10 minutes.

We do not routinely use a drain for arthroscopy. Portals are closed in standard fashion.

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• Lesions Associated with Subchondral Cysts (Cancellous Bone Translation Technique)

In OLTs associated with subchondral cysts, we débride the damaged, unhealthy cartilage; perform microfracture; and use the cancellous bone translation technique.

Fenestrate the cortex at the opposite side, and under fluoroscopic visualization, translate the cancellous bone (like a snowplow) with a curved 4-mm AO plunger into the cyst.

In these cases, coverage of the lesions is always performed by sealing it with the acellular matrix.

 

 

PEARLS AND PITFALLS

 

Indications ▪ Take care to address associated pathology. In case of lateral ligament instability, a stabilizing procedure has to be added to guarantee the success of the microfracture.

 

Technique ▪ Use a superomedial portal to achieve perpendicular penetration of the awl. Use a swan neck-shaped awl.

• Posterolateral approach with the Wissinger rod technique: A rod is inserted through the anteromedial portal in a posterolateral direction to identify the optimal entry for the posterolateral portal.

• The calcified cartilage layer must be thoroughly removed by a small abrader to provide optimal amount and attachment of repair tissue.11

• Arthroscopic AMIC technique to achieve a sealing effect of the defect.

• Cancellous bone translation technique

 

 

 

POSTOPERATIVE CARE

 

Compressive bandaging is applied up to the thigh. The ankle is elevated and immediate cryotherapy is applied.

 

 

In case of inserting a matrix, a cast is applied for 3 to 4 days to ensure stabilization of matrix in the defect and prevent delamination.

 

Continuous passive motion (CPM), as tolerated by pain and swelling, is used for 6 to 8 hours per day for 4 to 6 weeks.

 

Partial weight bearing of 15 kg is allowed for the first 6 weeks, 30 kg for the next 2 weeks. If the ankle is pain-free, then weight bearing can be advanced as tolerated.

 

Biking, swimming, and cross-training are permitted after 8 weeks. Impact sports are permitted after 5 to 6 months if the ankle is pain-free with normal activities. Otherwise, we recommend to wait 10 to 12 months after surgery.

 

Dietary supplements (glucosamine and chondroitin sulfate) may have beneficial effects for cartilage regeneration (6 months).

OUTCOMES

The results of prospective studies have shown significant improvement at 2 and 5.8 ± 2.0 years after microfracture of the talus.4,5

Ninety-five percent of the ankles with osteochondral lesions had excellent or good results. Early results were maintained in a minimum of 5-year follow-up.4

Outcomes did not differ significantly between patients older than 50 years versus younger patients.

Location and grade of the defect showed no statistically significant impact on the results.

MRI studies showed regeneration of tissue in the microfractured area. Subchondral signal changes were observed in almost all postoperative images.4,5

No distinct correlation between clinical and imaging results was detected.4,5

 

 

COMPLICATIONS

Development of ossifications at the anterior tibia with subsequent restriction in dorsiflexion Damage to the deep peroneal nerve with subsequent hyposensitivity in the distribution area Infection

Deep vein thrombosis Arthrofibrosis

 

 

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