American athletes are becoming bigger, stronger, and faster. The average male in the United States weighs 195 pounds and has a body mass index of 28.6 kg/m2.
The increases in mass and velocity translate to increased forces on tendons, ligaments, and joints to accommodate changes in direction and impacts from collisions. The ankle joint is at particular risk of injury in athletes, elite and recreational alike. Some ankle sprains, particularly in chronically unstable ankles, can result in cartilage injury (Fig. 1). In fact, it is estimated that as many as 79 percent of severe ankle sprains result in some form of cartilage injury.
Injuries to the talar articular surface of the ankle joint are most commonly referred to as osteochondral defects (OCDs) of the talus (OLTs). However, other uses of the term OCD can lead to some terminology confusion (e.g., osteochondritis dessicans, another type of cartilage injury that is different than the OLTs which orthopaedic surgeons more commonly treat). Therefore, many purists refer to the lesions as OLTs, as this article will do. The International Congress on Cartilage Repair of the Ankle (ICCRA) will convene a consensus meeting on terminology for OLTs and their treatments in 2019.
OLTs can lead to pain and functional deficits, especially in active patients. More severe injuries can worsen with repeated injury, potentially leading to degenerative changes in the ankle joint. For this reason, increasing attention has been given to treatment strategies for OLTs, including significant advances in grafts, biologic scaffolds, and growth factors. As with many musculoskeletal injuries and conditions predisposed to technological solutions, many products have recently emerged designed to treat OLTs and ostensibly improve outcomes. Orthopaedic providers bear the responsibility of implementing best practices in patient care, maintaining awareness of when new strategies demonstrate superior outcomes and cost-effectiveness, and where they may fall short.
Evolution of surgical management of OLTs
Osteochondral lesions of the talar dome were originally described in the late 1970s and early 1980s. However, early descriptions did not differentiate between acute traumatic OLTs, chronic OLTs, and osteochondritis dessicans, which is related to disruption of blood supply to the underlying bone. Arthroscopic débridement was first described in the 1990s, with limited but generally positive outcomes. There is some consensus that asymptomatic OLTs should be treated nonoperatively, but evidence suggests that fewer than 50 percent of symptomatic patients will be treated successfully with nonoperative management. Surgery most often is indicated in such cases, and multiple successful techniques are currently utilized. Herein is a review of those techniques and current indications.
Bone marrow stimulation (BMS)
Arthroscopic débridement with curettage and drilling or microfracture remains the gold standard for smaller lesions, generally those less than 10 mm in greatest diameter. This treatment approach in the ankle closely follows the microfracture technique for the knee developed by the Steadman Hawkins group in the late 1990s. Most studies suggest satisfactory results in more than 85 percent of ankle OLT patients treated with this technique.
Larger lesions tend not to do as favorably with BMS alone. A specific size cutoff is difficult to define due to the complexity of associated factors (e.g., location, depth, minimum versus maximum diameter, chronicity, patient age, ligamentous laxity). A generally accepted diameter of 10 mm is supported by basic science data on edge loading. Clinical series data suggest that the cutoff might be 15 mm in diameter or 150 mm2 in total area. These became the basis for generally accepted criteria. In 2017, a group of thought leaders systematically reviewed the literature and concluded that “BMS may best be reserved for OLT sizes of less than 107.4 mm2 in area and/or 10.2 mm in diameter.” No evidence-based guidelines currently exist to most effectively address larger lesions or failed BMS procedures. However, the reported results of the 2017 ICCRA consensus meeting on OLTs, published in July as a supplement in Foot & Ankle International, provide useful guidelines.
Osteochondral autografts and allografts
Larger and deeper osteochondral lesions can have more significant biomechanical consequences and often require restoration of the subchondral bone surface, in addition to a cartilage surface with structural integrity. Until a few years ago, the most common treatment strategies were osteochondral autograft transfer (OAT), mosaicplasty from the ipsilateral knee, and osteochondral allograft transplantation. OAT and mosaicplasty reportedly have successful results in up to 90 percent of patients with larger lesions, but they are associated with potential donor-site morbidity, curvature mismatch, and fibrocartilage between plugs. Allograft transplantations became popular because they mitigated those issues and can be used in cases with irregular defects. This gives allograft a biomechanical advantage over autograft OAT. However, allograft tali are expensive; require a matching process; and, despite evidence supporting their success, may be denied by insurance carriers, rendering them cost-prohibitive in many cases. An alternative study by Sammarco et al. utilized the talus as the site of osteochondral plug harvest from the medial and/or lateral talar facet. Although the researchers reported good results, the technique produces limited total graft size and is not used consistently.
Chondral grafts and cartilage scaffolds
For larger lesions not accompanied by significant loss of bone or large cysts, cartilage auto- and allografts are available and have increasing evidence of efficacy. Even some larger, contained lesions with cysts and bone loss can be treated with bone grafting to fill the defect, followed by the addition of a chondral graft, making these appealing and perhaps more cost-effective strategies. In many cases, the procedures can be performed arthroscopically, which minimizes postoperative pain and swelling.
Autologous chondrocyte implantation (ACI) was introduced in the early 2000s, with positive results at up to 10-year follow-up. Matrix-induced ACI recently received clearance from the Food and Drug Administration and has longer-term outcomes data compared to other cartilage options. However, it is a more expensive and technically demanding procedure.
More recently, allograft cartilage scaffold techniques, including micronized cartilage matrix (BioCartilage, Arthrex, Naples, Fla.) and juvenile cartilage fragments (DeNovo, Zimmer, Warsaw, Ind.), have emerged and demonstrated good early results (Fig. 2). Because the one-step procedures are less invasive and less expensive than many of the other strategies, they tend to be met with less resistance from insurance carriers. A primary purported advantage of all cartilage scaffold techniques over BMS alone is the quality of hyaline cartilage. If chondral grafting techniques can be proven to result in higher-quality hyaline cartilage, reducing long-term recurrence or early degenerative changes, they are likely worth the additional cost. Only carefully conducted studies can confirm whether theoretical long-term benefits occur consistently.
The high cost of some of the previously mentioned strategies and products, combined with an improved understanding of in vivo cartilage growth, has led to the development of autograft transfer procedures using structural bone with periosteum. A study presented at the 2018 AAOS Annual Meeting by Kim et al. described a series of 44 patients who underwent osteochondral autograft transfer with a periosteal plug harvested from the anterior distal tibia. The researchers reported a very high level of patient satisfaction and good intermediate outcomes. A study presented at the 2018 European Society of Sports Traumatology, Knee Surgery, and Arthroscopy Annual Meeting by Kerkhoffs et al. reported on intermediate-term results of the talar osteoperiosteal grafting from the iliac crest (also known as TOPIC) procedure, a novel approach for large OLTs and revision cases. Although these solutions lack long-term outcome data or substantive biologic evidence of hyaline cartilage growth, they are less expensive, are technically feasible, do not violate joints other than the ankle, and may be a useful long-term strategy for larger defects.
PRP and bone marrow-derived cells
Platelet-rich plasma (PRP) and bone marrow aspirate concentrate (BMAC) are autologous concentrates of growth factors that can be used to create a favorable biochemical environment for cartilage healing as an adjuvant to BMS techniques. BMAC has been used to augment BMS procedures, with growing and positive evidence of safety and efficacy. A study by Guney et al. described similar results comparing BMS alone to BMS plus PRP.
A study by Giannini et al. reported on the efficacy of arthroscopic transplantation of bone marrow–derived cells in a series of studies, demonstrating new tissue formation at the lesion site on MRI two years postoperatively and “normal appearing” cartilage on second-look arthroscopy in most patients. The techniques are minimally invasive and relatively inexpensive. Their role in the treatment algorithm for OLTs will be further elucidated as additional outcome data become available.
Treating OLTs in your practice
At all times, orthopaedic providers must follow best practices during treatment and shared decision-making processes. Good evidence supports BMS techniques for smaller OLTs and perhaps provides some hope that biologic techniques will improve outcomes in the long term. Treatment of larger lesions remains complex and multifactorial and is without clear evidence-based guidelines. However, many available strategies provide good efficacy and outcomes when performed technically well and for the right indications.
It is important that orthopaedic practitioners follow a comprehensive algorithm as part of a complete treatment arsenal when approaching patients, while maintaining technical expertise and knowledge of outcome data, particularly for newer treatment strategies. The ICCRA consensus group continues to create guidelines that inform well-controlled studies of these treatment strategies. This ultimately will equip the orthopaedic community with outcome data to support treatment approaches and advocate for patients with insurance carriers and hospital utilization committees.
Kenneth J. Hunt, MD, is associate professor of orthopaedics and chief of foot and ankle surgery at the University of Colorado, Denver.