DEFINITION

Osteochondral lesions of the talus (OLT) are common conditions that can involve both the cartilage and underlying bone of the talar dome and have the propensity to degrade and lead to osteoarthritis if left untreated.2,10 Cartilage injuries have a poor inherent healing response.

Bone marrow stimulation (BMS), initiating fibrocartilage through microfracture or microdrilling, is a commonly used technique for small, noncystic lesions.

The objective is to create multiple breaches in the subchondral plate to facilitate the flow of marrow with mesenchymal stem cells (MSCs) from the underlying bone.

 

 

ANATOMY

 

The talus articulates with the tibial plafond superiorly as well as the medial and lateral malleoli to form the ankle mortise.

 

Approximately 60% of talar surface is covered by cartilage.

 

It has no muscular attachments and thus its blood supply is derived from branches of the posterior tibial artery (artery of the tarsal canal and deltoid branches), the peroneal artery (artery of the tarsal sinus), and the dorsalis pedis.

 

PATHOGENESIS

 

The etiology is primarily traumatic with an incidence of between 50% and 70% following ankle sprains and fractures.7,11,13

 

Repetitive microtrauma leading to OLTs is often associated with ankle instability.11

 

Impaction, crush, and shearing injuries occur with the location of the OLT dependent on the position of the ankle at time of injury.

 

NATURAL HISTORY

 

Smaller lesions can occasionally heal with nonoperative management, although this is more commonly seen in a pediatric population.19

 

Theoretically, OLTs tend to progress, as highly pressurized fluid invades the subchondral plate through cartilaginous defects and eventually infiltrates subchondral bone.

 

Spontaneous healing is uncommon and there is a propensity for further degeneration.

 

Prevention of disease progression is aimed at repair of the subchondral plate and alignment of the joint.

 

Surgical intervention can be considered as reparative (BMS) or replacement (autologous chondrocyte implantation, autologous osteochondral transplantation, juvenile particulate cartilage).

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

OLTs may be asymptomatic.

 

Patients often, but not always, will recall an acute injury. Activity-related deep anterior ankle pain is the typical complaint.

 

Mechanical symptoms such as clicking or locking of the ankle joint are less common and may indicate a loose fragment.

 

 

Clinical examination may reveal swelling and localized tenderness along the joint line. Chronic cases with associated synovitis and joint effusions can have limited ankle motion.

 

As many cases occur with concomitant pathology, such as ankle instability, detailed clinical examination of the ankle osseous, ligamentous, and tendinous structures is advocated.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Imaging studies are useful to assess lesion location, size, and depth as well as the presence of subchondral cysts preoperatively. This will determine the most appropriate treatment strategy.

 

Standard weight-bearing plain radiographs (anteroposterior [AP], lateral, and mortise views) (FIG 1A)

 

 

 

May miss up to 50% of OLTs, especially if very small or isolated cartilage lesions9 Useful to assess lower limb, ankle, and hindfoot alignment

 

Computed tomography (CT) (FIG 1B,C)

 

 

Permits further evaluation of osseous morphology and dimensions, especially depth

 

Only gives information about the osseous structure; no information regarding overlying chondral loss or damage

 

Magnetic resonance imaging (MRI) (FIG 1D,E)

 

 

Recommended for a definitive diagnosis and evaluation

 

 

Evaluation of articular cartilage and the degree of subchondral involvement/bone edema T2 mapping sequences provide increased sensitivity for cartilage architecture and quality.

Can also assess for concomitant pathology (ligamentous injury, tendinous injury, loose bodies, etc)

DIFFERENTIAL DIAGNOSIS

Anteromedial or anterolateral ankle impingement Chronic ankle instability

Tendinopathy (peroneals, tibialis posterior, tibialis anterior) Early posttraumatic osteoarthritis

Inflammatory arthropathy

 

 

Stress response or fracture

 

 

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FIG 1 • A. AP plain radiograph demonstrating an osteochondral lesion of the medial talar dome. B. Midsagittal CT image of an OLT. C. Midcoronal CT image. D. Midsagittal MRI scan of an OLT. E. Midcoronal MRI scan.

 

NONOPERATIVE MANAGEMENT

 

Indicated for minimally symptomatic, smaller, stable lesions that involve cartilage alone

 

A period of immobilization and restricted weight bearing followed by progressive weight bearing and physical therapy. Range-of-motion exercises are encouraged to preserve cartilage nutrition.

 

 

Pharmacotherapy (oral nonsteroidal anti-inflammatory drugs [NSAIDs] and intra-articular steroid injection) Nonoperative management has traditionally shown high failure rates.5,15,21

 

The role of biologic adjuncts such as platelet-rich plasma (PRP), concentrated bone marrow aspirate (CBMA),

and hyaluronic acid (HA) are under investigation.

 

SURGICAL MANAGEMENT

 

Microfracture was first described by Steadman et al17 and has gained widespread popularity, as it is marginally technically demanding, minimally invasive with minimal postoperative pain, is low cost, and is associated with low complication rates.

 

Indications

 

 

 

Primary noncystic lesions3,4 that are less than 15 mm in diameter or have an area less than 150 mm2 Failed conservative management

 

Consider retrograde drilling for subchondral bone lesions where the overlying cartilage is intact.

 

Absolute contraindications include severe degenerative joint disease and infection. Caution is recommended in the setting of active inflammatory arthropathy, especially if the patient is on long-term oral steroids.

 

Preoperative Planning

 

Based on clinical examination and preoperative imaging outlined earlier

 

The lesion location will determine surgical approach, whereas lesion size determines the technique.

 

Anterior arthroscopy is used for most lesions through standard anteromedial and anterolateral portals. Accessory posteromedial portals are also employed on occasion.

 

In our experience, approximately 75% of the ankle joint is accessible with the anterior approach.

 

Posterior arthroscopy is used for the most posterior of lesions. The original two-portal technique is safe and provides access not only to an OLT but other hindfoot, posterior ankle, subtalar joint, and extra-articular

pathologies.16

 

Retrograde drilling is used for lesions in which the overlying cartilage is preserved and is performed under fluoroscopic navigation.12

 

If concomitant ankle stabilization is to be performed, we evaluate the ankle while the patient is anesthetized to help determine the corrective procedure of choice.

 

If necessary, additional corrective osteotomies to address mechanical deformity should be performed concurrently.

 

Positioning

 

Preoperatively, we identify and initial the correct limb.

 

The procedure is typically performed under regional anesthesia (combined spinal anesthesia and popliteal block), although a general anesthesia can be performed if preferred.

 

For anterior arthroscopy, the patient is positioned supine on a standard operating table with a well-padded thigh tourniquet. A towel roll (“bump”) is placed under the ipsilateral

 

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buttock to improve lower limb orientation with the foot perpendicular to the floor (FIG 2A).

 

 

 

FIG 2 • A. The patient is positioned supine on a standard operating table with a well-padded thigh tourniquet. A towel roll (bump) is placed under the ipsilateral buttock to improve lower limb orientation with the foot perpendicular to the floor. B. A noninvasive ankle distractor is fastened to the operating table and secured to the ankle with the ankle joint in plantarflexion. C. Posterior ankle arthroscopy positioning with the patients foot overhanging the edge of operating table.

 

 

A padded thigh holder is placed proximal to the popliteal fossa so that the hip is flexed at 60 degrees and the knee can be easily positioned at 90 degrees with gentle traction.

 

Standard prepping and draping of the limb is performed.

 

A noninvasive ankle distractor is fastened to the operating table and secured to the ankle with the ankle joint in plantarflexion (FIG 2B). Approximately 15 pounds of distraction force is appropriate for most cases to expand the joint and improve access.

 

If a posterior approach is selected, the patient is placed prone with the ankle overhanging the end of the operating table (FIG 2C).

 

 

Alternatively, a triangular cushion can be placed under the distal tibia.

 

Approach

 

Anterior arthroscopic procedures typically use anterolateral and anteromedial portals.

 

 

Inject 10 mL of saline into the ankle from an anteromedial direction. There should be easy insufflation of fluid with correct intra-articular placement with bulging of the anterolateral joint capsule noted.

 

The anteromedial portal is placed 5 mm distal to the joint line and just medial to the tibialis anterior tendon. We recommend incising only the skin and carefully form a path through the subcutaneous tissue by gently spreading a mosquito forceps. Outflow of saline confirms the capsule has been breached and a blunt trocar inserted (2.7-mm arthroscopic instrumentation).

 

The anterolateral portal is created in a similar fashion, also at a level of 5 mm below the joint line. The approach is just lateral to peroneus tertius tendon with care taken to avoid the superficial peroneal nerve that we identify and mark preoperatively where possible.

 

For posterior ankle arthroscopy, standard posteromedial and posterolateral portals are used (FIG 3).

 

 

A line is drawn from the tip of the medial malleolus to the tip of the lateral malleolus parallel to the sole of the

foot.

 

The posterolateral portal is created 5 mm anterior to the lateral border of the Achilles tendon immediately proximal to the aforementioned line. Care is required to avoid the sural nerve when creating the subcutaneous tunnel.

 

The posteromedial portal is also created 5 mm anterior to the medial border of the Achilles tendon and just proximal to the drawn line. The medial neurovascular bundle is at risk, so great care must also be employed when creating a path through the soft tissues.

 

 

 

 

FIG 3 • Posterior ankle arthroscopy with standard posteromedial and posterolateral portals.

 

 

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TECHNIQUES

• Anterior Ankle Arthroscopy

Once the anteromedial portal has been created, standard 2.7-mm arthroscopic instrumentation is used with a 30-degree arthroscope. A water pump with inflow and outflow is attached to the arthroscopic port with a pressure of 40 mm Hg adequate for most cases.

Full evaluation of the ankle joint is necessary; in pathologic joints, débridement of scar tissue and diseased hypertrophic synovium is frequently required for adequate visualization (TECH FIG 1A).

A limited resection of the anterior tibial margin may also be required with the use of an arthroscopic burr (TECH FIG 1B).

All concomitant intra-articular pathology such as synovectomy and loose body retrieval should be addressed prior to microfracture so that the induced marrow clot will not be disrupted.

A systematic approach should be employed in all cases to ensure all aspects of the joint are formally evaluated (medial and lateral gutters; talar dome and tibial plafond). We advocate the 21-point systematic

 

Ferkel evaluation.6

 

 

 

TECH FIG 1 • A. Débridement of scar tissue and diseased hypertrophic synovium is often required for complete visualization of the ankle joint. B. A limited resection of the anterior tibial margin may be necessary for which we use an arthroscopic burr.

• Identification, Evaluation, and Preparation of the Osteochondral Lesion of the Talus

   

  The location of the lesion should be localized and identified based on preoperative imaging studies.

   

  Careful probing of the cartilage is performed and softened pathologic areas of cartilage should be identified in ankles where no loose cartilaginous flaps exist (TECH FIG 2A).

   

  A curette is used to remove pathologic cartilage until a smooth rim of stable healthy cartilage is created (TECH FIG 2B).

   

   

   

  TECH FIG 2 • A. Careful probing of the articular cartilage is performed to identify softened pathologic lesions or unstable cartilaginous flaps. B. A curette is used to remove pathologic cartilage until a smooth rim of stable healthy cartilage is created. C. A shaver is used to remove additional small loose fragments of cartilage and bone.

   

   

  A shaver is used to help remove loose fragments (TECH FIG 2C).

   

  All delaminated cartilage should also be removed, as the cartilage lesion can extend beyond the margins indicated by preoperative imaging.

   

   

  Where a subchondral cyst is present, the associated pathologic bone and cystic lining must be removed. The calcified cartilage layer is removed with careful curettage to facilitate clot adhesion and repair.

   

  Additional manual plantarflexion from an assistant may be required to obtain adequate exposure of the OLT.

   

   

  The exact dimensions can be determined using a graduated probe to establish both transverse dimensions and lesion depth.

   

• Bone Marrow Stimulation/Microfracture Technique

   

  Microfracture is performed only when complete removal of the OLT has been achieved, leaving a smooth, perpendicular rim of stable, healthy, and native cartilage.

   

  12

   

  Commonly used techniques include drilling with a Kirschner wire or breaching the subchondral bone with a microfracture awl

   

  Awls with various angulations are available and should be used judiciously depending on the location of the lesion to ensure the subchondral bone is penetrated perpendicular to the OLT base.

   

  The subchondral bone is breached to a depth of 2 to 4 mm, with the depth usually indicated on the awl (TECH FIG 3A,B).

   

   

   

  TECH FIG 3 • A,B. The subchondral bone is breached to a depth of 2 to 4 mm with the depth usually indicated on the awl. C. Fat droplets emerging from the cancellous bone indicate adequate penetration through the subchondral plate. D. Turning off the water pump allows marrow blood to emerge from each BMS breach.

   

   

  The emergence of fat droplets indicates adequate penetration has been achieved for subsequent subchondral bleeding and recruitment of MSCs from the marrow (TECH FIG 3C).

   

  Each microfracture should be separated by 3 to 4 mm.

   

   

  Ensure that BMS is also performed at the periphery of the OLT to improve fibrocartilage integration. Final evaluation and lavage of the joint are performed and all loose bodies are removed.

   

  The water pump is turned off, and if a tourniquet is used, it can be deflated to confirm the presence of fat droplets and blood emerging from each BMS breach.

   

  The wounds are closed with 3-0 nylon and a sterile dressing applied.

• Posterior Ankle Arthroscopic Microfracture

 

A systematic four-quadrant approach is used to address associated hindfoot pathologies16 (TECH FIG 4).

 

 

Adequate visualization of the posterior OLT can be achieved with manual ankle dorsiflexion. BMS is subsequently performed as outlined earlier.

 

 

 

TECH FIG 4 • A systematic four-quadrant approach to posterior ankle arthroscopy is used to address associated hindfoot pathologies.

 

 

 

 

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PEARLS AND PITFALLS
	Neurovascular ▪ Avoid overzealous distraction and take great care when creating arthroscopic injury portals. Always use a blunt trocar when switching between portal sites. Ensure the thigh holder is proximal to the popliteal fossa.     Incomplete ▪ Fully evaluate the rim for loose flaps or delaminated cartilage. This is débridement particularly important for anterior margins which may not be easily visualized.     Loose body ▪ Always perform a thorough evaluation and lavage of the entire ankle joint at the fragments end of débridement.

 

	“Kissing” tibial ▪ Coexisting lesions of the tibia should be evaluated and we recommend lesions concomitant management where appropriate.     Perpendicular ▪ Be prepared to use awls with different angles and have a full selection ready orientation of preoperatively. It is advisable to have an assistant stabilize the ankle if controlled BMS application of force is required to breach the subchondral bone and prevent technique iatrogenic injury to native, intact cartilage. Maximal plantarflexion of the ankle, again with the use of an assistant can increase the exposure.     Proper size ▪ It is important that the correct awl size is used. Compression of subchondral awl bone caused by a large awl can lead to closing of trabecular channels and creates a pore size too small to allow neovascularization.

 

 

POSTOPERATIVE CARE

 

A well-padded soft dressing is applied for 14 days.

 

Ankle pump exercises commence at 72 hours postoperatively and are continued for 4 weeks. Controlled ankle plantarflexion and dorsiflexion is performed for 20 minutes each day to prevent adhesion formation and stiffness and through diffusion will facilitate nutrition of the cartilage from the synovial fluid.

 

At 2 weeks postoperatively, the sutures are removed and the patient progressed to a controlled ankle movement (CAM) boot.

 

At 4 weeks postoperatively, weight bearing commences starting at 10% of their body weight and commencing by 10% each day so that full weight bearing is achieved by 6 weeks postoperatively.

 

At 6 weeks postoperatively, we commence formal physical therapy rehabilitation focusing on reestablishing balance, proprioception, and stabilization.

 

At 10 weeks postoperatively, rehabilitation focuses on strengthening and sport-specific training. Return to full contact sport must be evaluated continuously as the patients' symptoms improve.

 

OUTCOMES

The aim of BMS is for pluripotent MSCs within the marrow to coagulate and form a fibrin clot in the defect. An inflammatory cascade should ensue with the ultimate outcome being stimulation of tissue healing.

Although it is hoped that differentiation from MSCs into a chondrocyte-like cells occurs with the ability to synthesize a cartilaginous matrix including type II collagen, there is evidence that formation of

fibrocartilage occurs.14 This is of concern as fibrocartilage has inferior mechanical and biologic properties compared to hyaline cartilage.

Nonetheless, the clinical results of BMS are generally good in the short to medium term with a recent systematic review citing an overall success rate of 85%.20

One study has analyzed 12-year clinical outcomes in 50 patients reporting a median American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score of 88 and overall 78% good to excellent Ogilvie-Harris scores. Twothirds had no radiologic progression of arthritis, whereas the

 

remainder decreased by only one grade.18

There is a lack of additional long-term high-level data to evaluate clinical outcomes of BMS. Concern exists regarding the long-term quality of fibrocartilage to sustain mechanical load.

Fibrocartilage deterioration at 5 years using MRI evaluation and a lack of integration with native cartilage seen arthroscopically has been reported.1,8

In recent years, there has been growing interest in the use of biologic adjuncts such as HA, CBMA, and PRP as well as the use of scaffolds/BioCartilage to augment repair.

 

 

COMPLICATIONS

The overall complication rate after anterior ankle arthroscopic microfracture is as low as 3.5% with noninvasive distraction when great care is taken.22 The rate after posterior arthroscopy is also low at 2.3%.22

Nerve injury is the most commonly reported complication, although most resolve within 6 months. Vascular injury

Infection Synovial fistula Loose bodies

Arthrofibrosis, stiffness Iatrogenic cartilage injury Chronic regional pain syndrome

 

 

REFERENCES

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