37 Arthroscopic Microfractures for Osteochondral Lesions of the Talus Abstract Arthroscopic microfracture is a routine and safe procedure for managing osteochondral lesions of the talus. No special expertise is required to perform this technique and results are satisfactory when good preoperative planning is carried out. The main focus must be put on the size and location of the lesion, with appropriate assessment of imaging features, activity level, and age of the patient. Great attention must also be paid to postoperative rehabilitation, to ensure full healing of the microfracture site, before allowing the patient to load the ankle. Keywords: osteochondral, talus, microfracture, marrow stimulation Osteochondral defects are common in sports medicine practice, involving major joints such as knee, elbow, hip, and ankle. The lesion consists of a full-thickness defect of the cartilage, also with the involvement of the subchondral bone. Osteochondral lesions of the talus (OLTs) are relatively uncommon in the general population, but increasingly common in athletes.1 OLTs are mainly caused by trauma, but can also be subsequent to ischemia, abnormal ossification, genetic predisposition, and severe osteoarthritis.2,3 These lesions cause pain with athletic activities, and also make walking and weight bearing difficult. A number of OLTs are asymptomatic and are revealed by imaging studies carried out for different complaints.4 Therefore, the mere presence of a lesion at imaging can be a chance finding, and does not mandate surgical treatment. • Primary indication for microfractures is a small, largely frayed, noncystic lesion. • However, in all the cases in which advanced cartilage softening, fraying of the cartilage, and instability of the osteochondral fragment are present, microfractures are recommended. • OLTs < 150 mm2 in surface area. • Unstable OLTs recalcitrant to nonoperative modalities. • During sport activities, inversion of the foot, forced dorsiflexion, plantar flexion, and external tibial rotation are the most common injuries causing these lesions.5 About 50% of ankle sprains and about 70% of fractures are associated with osteochondral defects.6 Trabecular bone fractures affect vascularization of the area and, as a consequence, subchondral bone is affected, developing OLT.7 • When isolated OLT occurs, common symptoms include pain, catching, and stiffness of the joint, with effusion and swelling of the ankle. As these symptoms are nonspecific and are commonly reported in ankle trauma and sprain, OLTs are often not diagnosed, and hence not treated. • In general, patients mainly report pain on weight bearing and walking, and the ankle is painless at rest. This is caused by the increase in fluid pressure when the joint is loaded on weight bearing.5 Moreover, ankle sprain pain resolves spontaneously in 4 to 6 weeks, while persisting pain is more commonly associated with osteochondral defects. • Clinical presentation is often nonspecific, with complaints of vague activity-related ankle pain and swelling. Patients may complain of a feeling of instability of the ankle. The location of the patients’ subjective pain often does not correlate with the location of the OLT. • On clinical evaluation, patients will usually have joint-line ankle tenderness, particularly at the location of the lesion. Given most lesions are at the equatorial region of the talus, and not anteriorly, plantarflexion of the ankle during palpation may help deliver the lesion into the clinical field and increase the accuracy of palpation locating the lesion. In most cases, the ankle joint is stable without clinical evidence of ligamentous dysfunction, despite the common symptom of subjective ankle instability. There is, however, a subset of patients with combined ankle instability and an OLT. These patients will have both clinical laxity of their lateral ligaments on anterior drawer testing and pain in the ankle joint—and are best correlated with magnetic resolution imaging (MRI) examination. • Standard three-view weight-bearing radiographs of the ankle are initially performed. The OLT may not be seen in all cases, but may be visualized as a lytic shadowing or as a loose fragment over the affected area of the talar dome. • In most cases, additional studies are required to evaluate the bioactivity and anatomic configuration of the lesion. MRI is the best initial study to confirm the diagnosis in unclear cases of OLTs, or to confirm that a lesion seen on plain radiographs is in fact the cause of the patient’s symptoms. This is demonstrated by the presence of bone marrow edema at the site of the OLT on MRI. An MRI is additionally useful to exclude other commonly associated pathologies such as tears of the lateral ankle ligaments, and peroneal or posterior tibial tendon pathology. • MRI, however, is inaccurate at determining the exact size of the lesion because of the presence of bone marrow edema. When the size of the lesion may influence treatment choice, a fine-cut computed tomographic (CT) scan should be added to confirm that anatomy, size, location, and the presence of microcysts adjacent to the OLT. • Conservative management includes immobilization, antalgic therapy with nonsteroidal anti-inflammatory drugs, oral supplementation of cartilage components (chondroitin and glucosamine), intra-articular injections of hyaluronic acid or platelet-rich plasma, physical therapy, and strengthening of the calf muscles. • However, these treatments do not address the structural lesion, and, when pain persists or intra-articular loose bodies are detected, arthroscopic surgery is indicated. Ferkel et al8 proposed a CT-scan–based classification of the lesions (Fig. 37.1), composed of four grades of lesion severity (Table 37.1). Each of the different grades has a different prognosis and treatment. For grade 1 lesions, conservative treatment may reduce symptoms and restore function, although the defect is not filled. Grade 2 to 4 lesions are usually treated by surgery. The Bristol classification is comparable with Ferkel’s classification, although bone cysts are considered as a grade 5. At MRI,9 there is a greater frequency of medial lesions (62%), compared with lateral lesions (34%). The center of the talus was also frequently involved (80%), while involvement of the anterior and posterior edges was less common (6 and 14%, respectively). Concerning location, there is a statistically significant association of medial lesion with poorer prognosis.10 Moreover, lesions greater than 150 mm2 have been associated with poorer prognosis.11 In addition, the prognosis is also influenced by the age of development of the OLT. Lesions developed during childhood and adolescence have a significantly better prognosis when compared to those occurring during adulthood or in the elderly.12 • Diffuse ankle arthritis. • Large cystic type 5 OLTs. • Surface area >150 mm2 (relative contraindication). • Septic arthritis/infection of the ankle. • Recurrent OLTs/failed previous microfracture surgery. Microfracture is a bone marrow stimulation technique, performed to induce bleeding of the subchondral bone and promote fibrocartilage formation. As the cartilage is avascular, spontaneous regeneration cannot be expected. The stimulation of the osteochondral bone to release growth factors contained in the marrow and marrow blood promotes cartilage repair through the formation of an initial cloth, which organizes into fibrocartilage. This is also achieved by migration of bone marrow mesenchymal stem cells, which are mainly responsible for tissue growth at the site of lesion. The average time for fibrocartilage to mature is about 6 weeks, although complete maturation occurs in 12 to 24 weeks. Two major phases can be distinguished, with an initial inflammatory phase (weeks 1–2) with fibrin cloth formation and growth factors release, and a subsequent remodeling phase (weeks 3–12) with proliferation of mesenchymal stem cells and tissue architecture organization.13 However, fibrocartilage does not have the physical, biochemical, and biomechanical properties of native articular cartilage, because of its lower content in collagen type II, and higher content in collagen type I. Therefore, the site of lesion will remain a locus minoris resistentiae of the joint. To improve tissue regeneration, some authors advocate the use of intraoperative platelet-rich plasma or fibrin glue for further delivery of growth factor concentrates at the microfracture site.5 Given the cartilage environment is detrimental to the outcome of the surgery, in cases of chondromalacia, stability of the osteochondral fragment, minimal fraying of the surrounding cartilage, and microfractures should be avoided, and simple debridement or radiofrequency ablation is recommended.7 In addition, microfractures are preferred to other marrow stimulation techniques with radiofrequencies or drilling, to avoid thermal necrosis of the surrounding tissues. Table 37.1 Ferkel’s classification of OLT
37.1 Introduction
37.2 Indications
37.2.1 Pathology
37.2.2 Clinical Evaluation
37.2.3 Radiographic Evaluation
37.2.4 Nonoperative Options
37.2.5 Classification of OLTs
37.2.6 Contraindications
37.3 Goals of Surgical Procedure
Grade | CT scan findings |
1 | Cystic lesion with intact walls |
2a | Cystic lesion in communication with talar dome |
2b | Full-thickness lesion with overlaying fragment |
3 | Undisplaced lesion with lucency |
4 | Free loose fragment |
