Osteochondral lesions of the ankle (OsteoChondral Lesions - OCLs) are defects of the subchondral bone and the overlying articular cartilage that commonly affect young and active patients. The main symptoms include chronic ankle pain, recurrent swelling, stiffness, and instability. The ideal treatment for OCLs remains a matter of debate. Various surgical techniques have been proposed, both arthroscopic and open. The choice of treatment depends on several factors, including lesion pathology, patient characteristics, and surgeon preference.

In the presence of subchondral cysts or lesions with intact and stable cartilage surfaces, retrograde drilling is among the most commonly used techniques. This is a reparative, extra-articular procedure that reaches the lesion via a retrograde approach, thereby preventing iatrogenic cartilage damage. The surgical technique involves creating multiple channels in the subchondral bone using a Kirschner wire to stimulate the migration of mesenchymal stem cells, promote revascularization of the lesion site, and induce new bone formation.

Although retrograde drilling has shown good results over the years, concerns remain regarding the regenerative potential of subchondral bone, particularly in the case of large lesions or cysts. For this reason, various biological adjuncts have been combined with drilling in an attempt to improve treatment efficacy, with inconclusive results. Among the proposed modifications is that of Beck et al., who expanded the talar tunnel to allow for improved debridement, subsequently filling it with bone graft.

Another treatment option is subchondroplasty, which has shown promising results; however, few studies are available for the ankle, and significant complications have been reported. Therefore, the management of large subchondral cysts remains controversial.

In cases of large OCLs with cartilage damage, regenerative treatments are generally preferred, and several surgical techniques can be performed. However, these approaches are also controversial, as they are typically performed via an anterograde approach and involve extensive debridement of the overlying damaged cartilage, sometimes removing healthy cartilage as well. Significant improvements in AOFAS scores have been reported for all currently used techniques, but none has emerged as the gold standard. Consequently, clinical research is focused on developing new interventions that demonstrate superiority over traditional techniques.

In this context, subendocondral regenerative treatment has gained interest. This approach involves the application of a bone marrow-derived scaffold combined with retrograde drilling in patients with subchondral cysts and intact cartilage or large OCLs of the ankle. This innovative surgical technique combines several procedures already validated in the literature, aiming to leverage their advantages and enhance overall efficacy.

First, it includes an intra-articular arthroscopic approach to assess cartilage status, remove loose bodies, and treat associated conditions such as synovitis, soft tissue impingement, exostoses, and osteophytes. After confirming the appropriate indication based on arthroscopic findings, a Kirschner wire is inserted retrogradely into the lesion under fluoroscopic guidance. Retrograde drilling is then performed using a dedicated reamer.

The novelty of this procedure lies in the placement of a hyaluronic scaffold enriched with bone marrow-derived cells beneath the cartilage, which is therefore not further disrupted. This fully biodegradable scaffold creates a favorable microenvironment for regeneration by supporting the adhesion of bone marrow-derived stem cells and their three-dimensional organization, thereby facilitating restoration of normal tissue anatomy. Large subchondral cysts have shown limited healing potential due to poor vitality of the subchondral bone and a lack of mesenchymal stem cells needed for lesion repair. Therefore, a cartilage scaffold enriched with bone marrow-derived cells may represent an important source of mesenchymal stem cells and promote cellular interaction and mechanical stability during the regenerative process.

This scaffold has been approved for the repair of chondral or osteochondral lesions; however, clinical and MRI outcomes following its subchondral placement in the presence of intact cartilage have not yet been described.

The aim of this pilot study is to evaluate the clinical and imaging outcomes of this innovative surgical technique for subchondral regenerative treatment, which involves the application of a scaffold enriched with bone marrow-derived cells combined with retrograde drilling in patients with subchondral cysts and intact cartilage or large osteochondral lesions of the talus.

All patients diagnosed with subchondral cysts with intact cartilage or massive osteochondral lesions (OCLs) of the ankle joint treated with retrograde drilling and application of bone marrow aspirate on a scaffold at the First Clinic of the Rizzoli Orthopaedic Institute in Bologna will be included, in accordance with the criteria specified below.

INCLUSION CRITERIA:

Patients with one or more chronic cystic subchondral lesions of the talus (Grade IIA according to the Giannini classification); Patients with one or more chronic subchondral lesions with intact cartilage or large chronic OCLs (Grade IIA according to the Giannini classification); Age ≥ 18 years and ≤ 55 years; Ankle pain with limitation in normal activities of daily living (American Orthopaedic Foot and Ankle Score - AOFAS < 85, Short Form-36 - SF-36 < 86); Patients able to provide written informed consent to participate in the study.

EXCLUSION CRITERIA:

Patients < 18 years or > 55 years of age; Presence of active infections at the time of study inclusion; Positive status for HIV, HBV, or HCV; Pregnancy; Patients with autoimmune or rheumatologic diseases; Disorders of the immune system; Presence of severe malalignment of the tibiotalar joint in the coronal plane, whether supra-, intra-, or infra-articular (distal tibial articular angle < or > 10°, talar tilt > 8°, severe cavus or flatfoot); Any other condition or disease that contraindicates surgical treatment.