Management of Osteochondral Lesions of the Talus

Abstract

Key Words

Osteochondral defect, allograft, autograft, talus, cartilage, OATS

Surgical Approaches to Osteochondral Lesions of the Talus

With osteochondral lesions of the talus (OCLT), surgery is performed only in symptomatic cases because the lesions do not show any marked tendency for progression and typically do not lead to osteoarthritis. These lesions are a very slowly progressive condition, so there should never be any sense of urgency to treat the lesion in the absence of symptoms that warrant intervention. Surgical treatment options include debridement and bone marrow stimulation, autologous osteochondral transfers, autologous chondrocyte implantation, fresh osteochondral allograft transplantation, the use of articular cartilage allograft products, and the adjunctive use of concentrated bone marrow aspirate. There have been no randomized-controlled trials comparing these methods, and the treatment algorithm for OCLT is controversial. Multiple factors including defect size, location, patient age and prior surgeries must be considered. We generally initiate treatment with arthroscopic debridement and microfracture for smaller lesions (<1.5 cm ²). The results with arthroscopic treatment of OCLT are good to excellent in approximately 85% of patients at initial presentation. The results with repeat arthroscopy are also fairly good, depending on the extent of the lesion, and there is no requirement to perform a more aggressive treatment with allograft or autograft if the lesions remain small (<1.5 cm ²). Recently, the advent of cartilage allograft products such as Biocartilage (Arthrex, Naples, United States) in combination with bone marrow aspirate has altered our current practice. Although there is limited data, we have prospectively reviewed the outcomes of our first 20 patients with excellent clinical results in the short term. The long-term efficacy of this technique is yet to be determined. If the lesion is very large, if previous operations have failed, or if the lesion is cystic, then osteochondral autograft or allograft procedures are preferable.

Once a decision has been made to proceed with surgical treatment, several factors should be considered in selecting a particular surgical approach: the size and depth of the lesion, the exact location of the lesion (medial versus lateral, anterior versus posterior), a history of previous surgical treatment, the stage of the disease, and the viability of the articular cartilage. Whenever possible, we treat the lesion either using arthroscopy or through anterior or posterior arthrotomy. To this end, flexion-extension lateral radiographs are useful to show the location of the lesion and its accessibility by arthrotomy as opposed to osteotomy, which is associated with far greater potential morbidity. We believe that an osteotomy should be avoided if at all possible, as we have seen cartilage death at the site of the osteotomy, significantly compromising the function of the patient. The use of Biocartilage with concentrated bone marrow aspirate can be used to treat almost any defect smaller than 3 cm ², with the use of a pin distractor to allow access to the joint without an osteotomy.

We traditionally initiated treatment arthroscopically, with abrasion, drilling, and microfracture ( Fig. 26.1 ). For lesions that are large and those that have not responded to arthroscopic treatment, use of a cartilage restoration technique, such as cartilage allograft or osteochondral autograft/allograft, should be considered. Moderate-size defects can be filled with several small osteochondral autografts from the ipsilateral knee. Larger defects, particularly those involving the medial or lateral talar wall, may require an allograft. These marginal sidewall lesions are difficult to treat with an osteochondral autograft because the graft must be inserted perpendicular to the axis of the talar dome. With these marginal defects, a medial or lateral malleolar osteotomy must be performed. We have found that the use of cartilage allograft has allowed us to treat marginal defects as the material can be placed at any angle, and allowed the treatment of lesions that would have required an osteochondral allograft given the location at the shoulder.

Most anterior lesions are accessible for debridement and grafting with arthrotomy. However, if the lesion remains covered by the articular margin of the tibia, then creation of a small window in the anterior tibia is needed for further exposure. If extended visualization is required, this approach may be extended with an osteotomy of the anterior tibia, followed by replacement of the bone fragment and screw fixation.

Use of Cartilage Allograft Without Osteotomy

Cartilage allografts are an effective treatment for OCLT that bridge the gap between simple microfracture and osteoarticular transfer system/Allograft reconstruction. Lesions with a large cystic component that lead to an uncontained defect cannot be treated with this technique, and allograft is superior in those cases. Although the data is limited with regards to this treatment method, the early results are promising and have allowed us to treat patients with larger lesions and shoulder lesions without the need for an osteotomy. We have transitioned to treating all osteochondral defects with this technique regardless of size, despite the added costs of this procedure. The significant reduction in the subchondral edema and the isointense signal on magnetic resonance imaging noted at 6 months in conjunction with the clinical resolution of pain has been quite impressive ( Fig. 26.2 ).

The approach to the lesion can be done arthroscopically; however, placement of the graft can be difficult, as it must be contoured to the remaining native talar cartilage and the bed must be dry during application. In patients with central or shoulder osteochondral defects, this can become difficult arthroscopically. Anterior-based lesions are more amenable to an arthroscopic approach. Our preference is to perform an ankle arthrotomy to reconstruct the OCLT given the reproducibility of the cartilage restoration and ability to mechanically distract the joint. Although, initially we noted that a 1-cm plafond-plasty was required to adequately visualize centrally based defects, with the use of a large pin distractor, we have minimized the size of the plafond-plasty to a few millimeters and eliminated its use in many cases ( Fig. 26.3 ). For patients with lesions in the posterior one-third of the talus, we use a posteromedial or posterolateral approach based on lesion location.

Following visualization of the defect, the use of a small curette to remove the loose and nonviable cartilage is very effective. We use the backside of the curette to determine if the cartilage is no longer securely attached to the subchondral bone. If the cartilage is loose, the curette is then rotated and the cutting edge taken from superficial to deep and angulated toward the center of the lesion to avoid iatrogenic damage to the intact cartilage. Following debridement of the nonviable cartilage, any cystic lesions are curetted out to healthy vascular bone. Although this can be disconcerting, creating a cavitary defect, the avascular bone must be removed to encounter bone that is viable for healing. A microfracture awl or burr is used to prepare the subchondral bone to create a raw bleeding surface and to ensure there are vascular channels to the remaining healthy talus.

Bone marrow aspiration from the pelvis is performed in standard fashion, which is then concentrated to maximize the number of colony-forming units (CFUs) per milliliter ( Fig. 26.4 ). Unconcentrated bone marrow with insufficient CFU/cc has not demonstrated efficacy, and therefore concentration is critical. This concentrated bone marrow aspirate (BMA) is then mixed with 1 cc of Biocartilage to create a putty ( Fig. 26.5 ). In the setting of a cystic defect, local calcaneal autograft or allograft is used to impact the defect until it is 1 mm beneath the subchondral bone. We prefer to mix the concentrated BMA with the graft when filling the cystic defect. The mixture of the BMA with Biocartilage is then applied to the defect with the goal of filling it to level of the native articular surface. A freer elevator is very useful in smoothing down the surface and removing the excess graft. A key element during placement of this graft is that the bed must be dry. Therefore a tourniquet can be useful in these cases during this step. We prefer to inflate the tourniquet only after we are satisfied that healthy bleeding subchondral bone has been created.

Upon completion of contouring the cartilage allograft mixture on the defect, it must be sealed with fibrin glue. The fibrin glue will hold the graft in place and prevent synovial fluid from penetrating the subchondral bone, which may be important in preventing further subchondral damage. The glue should be allowed to set for 3–5 minutes, followed by removal of the pin distractor if used ( Figs. 26.6 and 26.7 ). The ankle is then reduced and gentle range of motion can be performed to ensure stability of the graft. With the ankle held in dorsiflexion to prevent washing out of the graft, the ankle is irrigated and then closed in standard fashion. Following closure, the remaining concentrated BMA is then injected into the ankle given the antimicrobial and antiapoptic effects. Although there is recent data to suggest that weight bearing at 2 weeks does not compromise the results from microfracture, we prefer to keep these cartilage allograft patients non–weight bearing for 6 weeks total. Two weeks are undertaken in a splint immediately postoperative, with a further 4 weeks non–weight bearing in a boot with gentle range of motion to encourage cartilage health. Transition to weight bearing at 6 weeks in a boot, and laceup ankle brace at 3 months. Impact activity, including running, is discouraged until 6 months’ postoperatively.