CHAPTER 15 Osteochondral Lesions of the Talar Dome

New Horizons in Cartilage Replacement

Stephen P. Abelow, Pedro Guillen, Marta Guillen, Isabel Guillen

Osteochondral lesions of the talar dome larger than 2.5 to 3.0 cm ² pose a special problem in the young and middle-aged population (Figs. 15-1 to 15-3). These lesions affect the articular cartilage of the talar dome and the underlying subchondral bone.¹ If encountered acutely or if a large fragment exists, some of these lesions can be stabilized and internally fixed with metallic or bioabsorbable implants. Success rates of 78% (range, 40% to 100%) have been reported with reduction and fixation of the osteochondral fragments.² Most of the acute lesions suitable for internal fixation are laterally located and are usually anterior on the talar dome, making them relatively easy to access using a small, anterolateral arthrotomy incision or arthroscopic techniques.

FIGURE 15-1 Grade IV lesion of the talar dome.

FIGURE 15-2 Anteroposterior magnetic resonance imaging shows an osteochondral lesion of the medial talus.

FIGURE 15-3 Lateral view of an osteochondral lesion of the talus.

Unfortunately, patients with these lesions represent a small proportion of those who present for treatment of symptomatic osteochondral lesions of the talar dome. Most have chronic, medial lesions, which tend to occur more posteriorly on the talar dome. They are more difficult to access and usually require a medial malleolar osteotomy for open exposure. The posteromedial lesions more commonly manifest as chronic lesions that have greater depth than their lateral counterparts and that demonstrate degenerated articular cartilage with necrotic supporting subchondral bone.

Most chronic lesions of the posteromedial talar dome may be treated with conventional arthroscopic techniques, including débridement of the major fragments of bone and articular cartilage, establishment of a stable articular cartilage margin with perpendicular edges, and some type of marrow stimulation of the bony base, such as abrasion, drilling, or microfracture. This technique can produce good or excellent results in approximately 80% of patients.

Patients who fail conventional treatment or who have lesions known to have a poor prognosis with conventional treatment may be treated with some type of articular cartilage replacement technique. Large lesions (>1.5 to 2 cm in diameter) and lesions associated with large subchondral cysts (stage V lesions) are thought to have a poor prognosis with standard débridement procedures and may be considered for articular cartilage replacement. The indications for surgical cartilage replacement are symptomatic, deep lesions classified by the International Cartilage Repair Society (ICRS) as grade 3 (i.e., greater than 50% cartilage depth and down to but not through subchondral bone) or grade 4 (i.e., subchondral bone exposed, with lesions extending through the subchondral bone plate or deeper into the trabecular bone). There should be no uncorrected malalignment or instability and no significant osteoarthritis.

When considering the appropriate treatment for a talar dome lesion, it is important to separate the short-term from the long-term goals. In the short term, the goal is to eliminate or reduce pain to improve function. In the long term, the goal is to forestall the development of degenerative arthritis in the ankle joint while maintaining pain relief. In evaluating the various types of articular cartilage replacement techniques presented in this and previous chapters discussing autologous osteoarticular transplant techniques and autologous chondrocyte implantation (ACI) techniques, it is important to understand that there has been no level 1 study that has prospectively evaluated a randomized group of patients to compare techniques in the ankle.

Autologous osteochondral implantation techniques using plugs obtained from the knee joint or ACI using cultured chondrocytes implanted beneath a layer of periosteum using open techniques are approved for use in the United States. Orthopedic surgeons in other countries are using various types of articular cartilage implantation techniques that are potentially more amenable to arthroscopic surgery but are not approved for use in the United States. They represent a promising avenue of research for treatment of these lesions and are described in this chapter.

COLLAGEN-COVERED AUTOLOGOUS CHONDROCYTE IMPLANTATION

The technique of harvesting and suturing a periosteal patch in ACI is technically demanding and time consuming. Problems such as periosteal patch quality, symptomatic periosteal hypertrophy, and delamination have stimulated the development of biocompatible and bioabsorbable membranes to cover the chondral defect. A bilayer, absorbable, porcine collagen I/III membrane (Chondro-Gide, Geistlich Biomaterial, Wolhuser, Switzerland) has been used in European studies instead of a periosteal patch. The membrane is degraded by enzymatic division (i.e., collagenase), and the resultant collagen fragments denature at 37° C to gelatin.

In a prospective study presented at the ICRS meeting in 2004, Steinwachs ¹⁷ described 163 patients treated for chondral defects in the knee with ACI using a periosteal flap or the Chondro-Gide membrane instead of the periosteal patch. At approximately 3 years of follow-up, 78% of patients in the periosteal group reported good or excellent results, and 88% of patients in the Chondro-Gide group reported good or excellent results. Statistical significance was not discussed by the investigator. There were no cases of membrane hypertrophy.¹⁷