CHAPTER 12 Osteochondral Lesions of the Talar Dome
Débridement, Abrasion, Drilling, and Microfracture
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 Steadman1 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 cm2, 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 colleagues25 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 options11,27 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
BMI, body mass index; CST, conventional surgical treatment.
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.