Osteochondral Lesions of the Talar Dome: D

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CHAPTER 12 Osteochondral Lesions of the Talar Dome

Débridement, Abrasion, Drilling, and Microfracture

Thomas O. Clanton, Brian Weatherby

Osteochondral lesions of the talus (OLTs) have various names and presentations. After the diagnosis is clear from the history, physical examination, and appropriate imaging studies, the treatment plan can be outlined for the patient. Nonoperative treatment with immobilization and no weight bearing remains a valid alternative, particularly for the patient without evidence of separation of the lesion.

The recommendations in this chapter pertain primarily to the patient who has presented with pain or mechanical symptoms that necessitate intervention or to the patient who has failed prior nonoperative management. In such cases, surgery is indicated, and the most thought-provoking decision for the surgeon and the patient becomes the exact procedure that will produce the best overall outcome for correcting the problem.

Since the introduction of arthroscopy, the most common operative treatments rendered for OLT have been a continuation of what had been performed previously through standard incisions, such as excision of a loose fragment, débridement of the lesion, drilling, or abrasion and curettage. With the addition of the microfracture technique, as originally described for the knee by Steadman ¹ and later modified to the ankle, these forms of treatment for OLTs are collectively known as conventional surgical treatment.

INDICATIONS AND CONTRAINDICATIONS

Several factors must be taken into consideration to select the most appropriate surgical procedure for a symptomatic OLT, including the location, size or depth, and grade or stage of the lesion. Patient-specific characteristics, such as age, body mass index (BMI), degree of ankle instability, ankle alignment, duration of symptoms, and previous surgery, also influence outcomes.²^–⁶

The lesion’s location does not technically limit the ability to perform the conventional surgical treatments discussed in this chapter as it does other restorative procedures, such as osteochondral autograft or allograft transplantation (i.e., osteoarticular transfer system [OATS]) or autologous chondrocyte implantation (ACI), which require greater access to the talar dome.⁷ Schimmer and colleagues⁸ found a trend toward a better prognosis for medial lesions, and Choi and associates⁹ found that anterior lesions had better results than posterior lesions, although this was disputed in a large case series that showed no correlation between outcome and lesion location.²^,¹⁰ The location of the osteochondral lesion should not preclude treatment or greatly affect the outcome of lesions treated with conventional surgical treatment. It does however, have an impact on the use of specific surgical techniques (discussed later).

In contrast to the location of the lesion, size has proved to be an important prognostic indicator of the success of conventional surgical treatment. Good or excellent outcomes have been demonstrated in several studies in which the OLT was intraoperatively measured at less than 1.5 to 2.0 cm ², with later studies advocating a cut-off size of 1.5 cm².²^,⁶^,¹¹^,¹² For lesions larger than 1.5 cm², OATS or ACI have been recommended by several surgeons.¹³^–¹⁵ These transplantation techniques have yielded good or excellent results.¹⁶^–¹⁸ Size may also be a determinant for internal fixation of acute, displaced osteochondral fragments in young patients. DeLee¹⁹ advocated internal fixation for a fragment that is larger than one third of the size of the dome. Alternatively, Stone and coworkers²⁰ recommended that the lesion be at least 7.5 mm in diameter to warrant internal fixation.

Various grading and staging systems exist for the classification of OLTs, and each is driven by its own descriptors. Unfortunately, this has made the interpretation of results difficult for correlation of outcomes with stage or grade.¹² It is widely accepted that a higher stage has a worse prognosis, as seen in a case series that established a relationship between the arthroscopic stage of Ferkel and clinical outcome.¹⁰

The literature on this topic reflects the importance of separating lesions into two distinct categories: those that have a cystic component, reflecting an underlying bony defect, and those that do not.³^,⁴^,⁶^,²¹ Cystic lesions should then be further subdivided into two groups based on the presence or absence of an intact dome of overlying articular cartilage. Cystic lesions usually have poorer outcomes than noncystic lesions when treated with excision and curettage or with excision and drilling.³^,⁴^,⁶ However, successful treatment outcomes for cystic lesions with an intact cartilage cap have been demonstrated with the technique of retrograde drilling from the lateral talar process or sinus tarsi and bone grafting.²¹^,²² This technique avoids violation of the intact talar dome cartilage while stimulating restoration of the underlying void. If a defect in the overlying cartilage is associated with a cystic lesion, it should be débrided and drilled or microfractured, and bone should be grafted to provide structural support for the replacement layer of fibrocartilage and any existing stable cartilage flap.

Accumulated experience in treating OLTs has taught us that factors associated with the individual patient can have a tremendous impact on the result of conventional surgical treatment.²^–⁶ Several case series with relatively long-term follow-up have suggested that acute lesions have significantly better clinical outcome scores than chronic lesions.²^–⁶ The threshold offered in most studies that delineates the two categories is a 12-month duration of symptoms. More controversy surrounds the influence of patient age on the outcome of OLT treatment. Three separate case series with a total of 386 patients revealed no significant correlation between patient age and outcome.³^,⁶^,⁹ In contrast, two case series with a total of 122 patients revealed a significant association between patient age and outcome, with success more often seen in patients younger than 30 to 35 years and failure seen in patients 45 to 50 years old.²^,⁴

With regard to patient weight (i.e., BMI), two small case series addressing OLTs failed to establish any relationship with outcomes.³^,²³ The opposite viewpoint is supported by a large case series evaluating OLTs² and another large, prospective cohort study analyzing osteochondral lesions of the knee,²⁴ which showed a BMI grater than 28 to 30 to be a significant variable in predicting successful conventional surgical treatment.

Ankle instability has been an accepted cause of OLT, and surgically correcting ankle instability in the setting of a talar OLT should correlate with outcome. This has been clearly demonstrated by two independent studies,²^,⁸ and it is recommended that any patient with mechanical ankle instability undergo some type of anatomic ligament reconstruction at the time OLT is surgically addressed. Although it seems that the immobilization required after ligament reconstruction may impair the healing process stimulated by conventional surgical treatment and promoted by early passive motion and no weight bearing, this approach has not been confirmed.

Another patient-specific factor to take into consideration is prior conventional surgical treatment. Existing literature on this topic has exhibited inconsistent findings and led to controversy on the topic. Schuman and colleagues ²⁵ showed that revision curettage and drilling had a poorer outcome (75% good or excellent results) compared with that of primary curettage and drilling (86%), and a case series² of 105 patients found that 17 patients who underwent repeat débridement and microfracture did not meet the criteria for a successful result, although they did improve their American Orthopaedic Foot and Ankle Society (AOFAS) scores by a mean of 17.2 points postoperatively. A different case series of 12 patients treated with repeat arthroscopic débridement and curettage reported overwhelmingly successful results.²⁶ Based on these findings, it is reasonable to recommend repeat conventional surgical treatment to address persistently symptomatic OLTs after a primary procedure, with the exception of cystic lesions.³

After processing all of the aforementioned factors, operative intervention using conventional options can be chosen as a valid treatment for an OLT. It is therefore helpful to compartmentalize the information presented into more concrete categories: indications, contraindications, and relative contraindications (Table 12-1). Conventional surgical treatment encompasses several different surgical techniques. In the treatment of noncystic lesions, arthroscopic excision of loose fragments and débridement of the lesion are consistent approaches. Variability is introduced in the selection of drilling, abrasion and curettage, or microfracture as the additional maneuver. The medical literature shows no significant differences in outcome for these approaches. This has been demonstrated in studies directly comparing these surgical options ¹¹^,²⁷ and by numerous other studies that show successful outcomes with each individual technique.^{2,5,9,10,12,23} In the treatment of a lesion with a cystic component, the surgical technique directly impacts the outcome, and retrograde drilling with bone grafting should be performed when possible.²¹^,²²

TABLE 12-1

Indications	Contraindications	Relative Contraindications
Failure of nonoperative treatment Displaced fragments Small cystic and noncystic lesions Size < 15 mm ² Age < 50 years BMI < 30 Presence of ankle instability

Size > 15 mm ²

Two prior CSTs

Large cystic lesion

Inadequate nonoperative treatment if indicated

Acute lesion with attached subchondral bone > 7.5 mm diameter

One prior CST

Age > 50

BMI > 30

Kissing lesion on the tibia

BMI, body mass index; CST, conventional surgical treatment.

TREATMENT

Conservative Management

In the evolution of treatment for osteochondral lesions, the nonoperative approach with protection from weight-bearing stresses began with the adolescent knee.²⁸^–³¹ This approach was extended to the ankle until the classic study by Berndt and Harty, which included a careful analysis of 24 cases of OLT and a systematic review of the literature that included 191 lesions in 183 patients.³² Their study found a 75% rate of poor results for the conservatively treated patients, and it confirmed that the results in children were no better than in adults. Over the ensuing 50 years, the nonoperative treatment of limited weight bearing and cast immobilization has continued to be the recommended treatment for Berndt and Harty stage 1 and 2 lesions, which are nondisplaced fragments that remain at least partially attached.³³^–³⁵ Because there are no adverse affects on the final outcome if surgery is delayed for up to 12 months, a trial of nonoperative treatment of these lesions is warranted.³⁵^–³⁷

Another consideration in the nonoperative management of OLT, viscosupplementation, has gained attention. Viscosupplementation has been used as an approved treatment for arthritis of the knee for some time, and although it remains controversial, several studies have shown its effectiveness for use in the treatment of ankle arthritis.³⁸^–⁴⁰ This experience has been extrapolated to sporadic use for OLTs, and a prospective study has shown promising results. Mei-Dan and colleagues⁴¹ demonstrated statistically significant decreases in pain and stiffness, with increases in functional scores over a 26-week follow-up period. In a patient who is adamantly averse to surgical intervention, viscosupplementation can be introduced as a potentially viable treatment option.

Unfortunately, the correlation between the radiographic grade and the actual condition of the articular cartilage is not very accurate, making it difficult to recommend treatment guidelines based solely on radiographic or CT images.⁴² Magnetic resonance imaging (MRI) has become the standard for evaluation of the articular cartilage in osteochondral lesions, and findings correlate well with arthroscopic findings.⁴³ MRI studies should be obtained for all symptomatic lesions requiring treatment. The articular cartilage can then be analyzed to determine whether it remains contiguous at some point, allowing creation of a flap, or there is complete disruption of continuity, signaling an unstable pattern and warranting surgical intervention.

Arthroscopic Technique

The arthroscopic approach is the gold standard for treatment of OLTs. This technique facilitates visualization of the entire joint and avoids the morbidity associated with an open procedure. Advances in arthroscopic technology have provided small, fiberoptic, 2.7-mm arthroscopes with options of 30-degree and 70-degree viewing angles; more effective constructs to adequately distract the joint; and smaller versions of arthroscopic instruments. Not every OLT is directly accessible, and even the seasoned arthroscopic surgeon may have significant technical difficulty in addressing certain posterior lesions.

After standard visualization and working portals have been established, the joint is thoroughly visualized and photographed. Loose bodies within the joint should be identified and removed. In most circumstances, this means the arthroscope is in the anteromedial portal to begin the case. A probe can then be introduced through the anterolateral portal to locate and outline the lesion and to determine the integrity of the articular cartilage and underlying subchondral bone. Depending on the medial or lateral location and extent of the lesion, the arthroscope may be moved to the opposite portal to facilitate visualization and access. If at this point the lesion is seen to be too posterior to allow adequate evaluation, the posterolateral portal should be established without hesitation. The posteromedial portal is an option for posterior lesions, but extreme caution must be used in this area because of the potential for injury to the neurovascular bundle.

After the OLT is evaluated and proper access is obtained, the specific treatment is based on the type of lesion. At this stage, it is essential to have the necessary instrumentation and any special equipment potentially required to address unexpected situations (Box 12-1). This is best confirmed in the preoperative setting to ensure an unhindered operation.

The technique for most osteochondral lesions (i.e., those without underlying cystic lesions) is straightforward. Any loose, unstable articular cartilage or osteochondral fragments must be débrided by shaving or curettage (Fig. 12-1) or by extracting the loose fragments from the joint with a grasper (Fig. 12-2). This leaves a defect in the articular surface with irregular margins that can be reformed into trephined edges with a small ring or regular curette (Fig. 12-3). Debris is removed from the joint with the shaver or a grasper, or both. If the basal layer of articular cartilage remains atop the defect, it is abraded or “scratched up” with a curette (Fig. 12-4). The surgeon can stop at this point or proceed with drilling or microfracture of the lesion to further expose marrow elements to create a “super clot” (Fig. 12-5).

FIGURE 12-1 A, The arthroscopic image of an unstable osteochondral lesion on talar dome that is being débrided with a shaver. B, Drawing of arthroscopic débridement shows the scope in the anterolateral portal and the shaver in the anteromedial portal.

FIGURE 12-2 A, The arthroscopic image shows a loose osteochondral fragment being removed with a grasper. B, The drawing shows removal of an osteochondral fragment with a grasper.

FIGURE 12-3 A, The arthroscopic image shows a ring curette pushing up a loose osteochondral fragment in preparation for trephining the edges. B, The drawing shows curettage of the osteochondral lesion to calcified cartilage layer with trephination of edge.

FIGURE 12-4 A, The arthroscopic image shows an osteochondral lesion at completion of curettage with removal of the calcified cartilage. B, The drawing shows curettage of the osteochondral lesion to remove the layer of calcified cartilage.

FIGURE 12-5 A, The arthroscopic image of microfracture being performed with a 90-degree awl. B, The drawing shows microfracture technique 1.

We use a 0.0625-inch Kirschner wire when drilling and standard or small microfracture awls for the microfracture technique. An assortment of angled awls is useful for penetrating the subchondral bone in a vertical orientation to the degree possible. The punctures are made to a depth of 2 mm and begin at the junction of normal cartilage with the osteochondral de fect. After the perimeter of the lesion is microfractured, the pattern continues into the center of the lesion while keeping the holes 3 to 4 mm apart (Fig. 12-6). The shaver is again introduced to clean up the joint, and if used, the tourniquet is then released and the pump pressure reduced to confirm bleeding in the lesion (Fig. 12-7).

FIGURE 12-6 A, The arthroscopic image shows the osteochondral lesion after microfracture. B, The drawing shows of microfracture technique 2.

FIGURE 12-7 A, The arthroscopic image shows bleeding in the osteochondral lesion after microfracture. B, The drawing shows a mesenchymal clot formed in the osteochondral lesion after microfracture.

(A, From Ferkel RD, Zanotti RM, Komenda GA, et al. Arthroscopic treatment of chronic osteochondral lesions of the talus: long-term results. Am J Sports Med. 2008;36:7150-1761.)

Technical aspects of antegrade drilling of OLTs depend on the location of the lesion. Anterolateral lesions are amenable to drilling through the anterolateral portal or through a separate anterior puncture in the capsule. The Kirschner wire can be introduced directly through the portal or placed through a guide, such as one of the meniscal repair cannulas used for inside-out repairs (Fig. 12-8). Plantar flexion of the ankle improves access to more posterior lesions. As in the microfracture technique described, drill holes should be placed at 3- to 4-mm intervals, beginning at the periphery of the lesion and working toward the center. Care is taken when drilling vertical walls not to perforate viable bone close to the overlying, intact subchondral plate and therefore create a stress riser that may lead to further collapse. Drilling of posteromedial lesions may be facilitated by using a commercially available drill guide with a transmalleolar approach. The aiming guide arm is introduced into the joint with the tip placed into the center of the lesion under direct arthroscopic visualization. A percutaneous incision is made over the area of the medial malleolus as indicated by the location of the external trocar, and the trocar is then advanced down to bone. A 0.062-inch Kirschner wire is drilled through the trocar in a transmalleolar fashion and visualized entering the joint (Fig. 12-9). The ankle can be dorsiflexed and plantar flexed to drill multiple holes in the lesion through the same medial malleolar drill hole.

FIGURE 12-8 A, The arthroscopic image shows a 0.062-inch Kirschner wire placed through a meniscal guide to drill an osteochondral lesion. B, The arthroscope is placed in the anteromedial portal with a meniscal guide, and a Kirschner wire is placed through the anterolateral portal.

FIGURE 12-9 A, The arthroscopic image shows drilling through the medial malleolus, with the drill guide entering anteromedially for a posteromedial osteochondral lesion. B, The drawing shows a drill guide being used for transmalleolar drilling of an osteochondral lesion of a left ankle shoulder lesion.

(A, From Ferkel RD, Zanotti RM, Komenda GA, et al. Arthroscopic treatment of chronic osteochondral lesions of the talus: long-term results. Am J Sports Med. 2008;36:7150-1761).

Any lesion encountered that maintains an intact cartilage roof with a cystic component and stable subchondral bone, although uncommon, is best treated with retrograde drilling and bone grafting ²¹^,²² (Fig. 12-10). This technique involves the use of a transtalar approach accessed through a more distal anterolateral incision in the area of the sinus tarsi. After the additional incision is made and blunt dissection is carried out down to the talus, the arm of a commercially available drill guide is introduced into the ankle joint through the anteromedial or posterolateral portal with the arthroscope in the anterolateral or posterolateral portal. The tip of the aiming guide is directed to rest on top of the lesion’s intact cartilage roof (Fig. 12-11). This can be assisted by the use of intraoperative C-arm fluoroscopy or, in some institutions, by computer-assisted, three-dimensional guidance systems.⁴⁴ When the aiming guide is in place, a trocar is placed through the exterior arm of the drill guide into the sinus tarsi incision and down to talar bone. Using fluoroscopic guidance, a long Kirschner wire is then placed through the trocar and advanced up into the void of the cystic lesion but not through the stable subchondral bone. This position should be confirmed arthroscopically. The appropriate size of cannulated trephine drill is advanced over the Kirschner wire up to the tip, with care taken not to violate the roof. With an established tunnel leading to the lesion, the subchondral cyst can be curetted and bone grafted using autograft from the calcaneus or distal tibia (Fig. 12-12).

FIGURE 12-10 A, Coronal CT shows an osteochondral lesion of the medial talar dome with intact articular cartilage and an underlying cyst. B, Arthroscopic image of same osteochondral lesion shows intact articular cartilage.

FIGURE 12-11 A, Fluoroscopy shows retrograde drilling of a medial osteochondral lesion of the talus (OLT). B, The drawing shows retrograde drilling of a medial OLT with a drill guide.

FIGURE 12-12 Fluoroscopy shows transtalar curettage of a medial osteochondral lesion of the talus.

For a cystic lesion with unstable cartilage, standard or ring curettes are used to remove any loose articular cartilage flaps back to stable cartilage. The base of the lesion is inspected, and any unstable osteochondral fragment; soft, necrotic bone; or fibrous material is removed by curettage or shaving until viable bone is encountered (Fig. 12-13). The lesion must be thoroughly defined and débrided, including any portion that extends onto the vertical surfaces of the talus in the gutter.

FIGURE 12-13 The arthroscopic image shows an osteochondral lesion of the talus after curettage to viable bone.

The remaining defect should be thoroughly inspected. If a hard sclerotic bony base is present that was not easily penetrated with the curettage performed, additional perforation with a microfracture awl or antegrade drilling is recommended to expose marrow elements to the defect (Fig. 12-14). Additional stimulation should be done if there is no punctate bleeding demonstrated after curettage when the inflow pressure is reduced or the tourniquet is released.

FIGURE 12-14 The arthroscopic image shows an osteochondral lesion of the talus after curettage and microfracture with early bleeding.

The cystic lesion may warrant open bone grafting after curettage and débridement have been done. There is no consensus regarding this issue, and no specific lesion size or depth to guide the indication of bone grafting has been established in the literature. Saxena and colleagues ⁴⁵ performed autogenous bone grafting by open arthrotomy on all Hepple stage 5 lesions (i.e., subchondral cyst formation seen on MRI) found in athletes with 90% good or excellent outcomes and a mean time for return to activity of 20 weeks. We prefer to obtain autogenous bone graft from the calcaneus or distal tibia by using 6- or 8-mm bone graft harvester reamers, which are commercially available. The lesion must then be approached in an open fashion by an arthrotomy or osteotomy, depending on the location of the lesion, as described in detail by Muir and associates.⁷ After the lesion is accessed, the bone graft should be tamped into place so that the void is tightly packed and no graft remnants are left prominent.

PEARLS& PITFALLS

PEARLS

• Nonoperative treatment is the recommended option for nondisplaced lesions that remain at least partially attached. Cast immobilization and limited weight bearing do not endanger surgical outcomes, even when surgery delayed up to 12 months.

• Preoperative planning with CT or MRI can guide the optimal portal placement and ensure adequate visualization and access for the working instruments.

• All conventional surgical methods (i.e., curettage, drilling, abrasion, and microfracture) have statistically similar results. The choice should depend on the surgeon’s preference and access to the lesion.

• The surgeon should preplan the approach to the lesion through the sinus tarsi by use of a foot and ankle model and avoid injury to the lateral branch of the superficial peroneal nerve.

• Familiarity with the article by Muir and colleagues ⁷ can guide the surgeon’s approach, particularly in the event that an open approach becomes necessary. It also can help the operator avoid an ill-conceived approach that will not allow access to the lesion.