How To Diagnose And Treat Osteochondral Lesions Of The Talus

     The past several “Treatment Dilemmas” columns have dealt with the treatment of chronic ankle pain subsequent to an ankle sprain (see page 92, July issue and page 88, September issue). We have dealt with the actual ligament injury and its repair, treatment of peroneal tendon injuries and also conservative care of ankle injuries. We will now discuss the final common problem, which involves the treatment options for osteochondral lesions of the talus.      An osteochondral lesion is an injury or small fracture of the cartilage surface of the talus. There are three types of common lesion formation. The first is injury to the cartilage surface with an actual loss of part of the chondral surface and underlying subchondral bone. This is the most common type of injury that will require care. The second most common type is an injury to the superficial cartilage surface with a crush cartilage injury or shear tear of the cartilage surface. Finally, there is a subchondral cyst type injury with a cyst formation deep to the cartilage surface but an intact overlying cartilage and bone surface. This type of injury is fairly rare.      Each type of injury will have different treatment options and require a different type of workup. In order to treat the problem properly, one must diagnose the cause, the amount of injury and the residual problem present. Furthermore, the location of the lesion will also dictate treatment options.

A Closer Look At Osteochondral Lesions

Osteochondral lesions of the talus occur for several reasons. The most common cause is from a crush or injury to the surface of the bone during the abnormal motion of the ankle in a sprain. With an inversion or eversion stress on the ankle, the talus and tibia and/or fibula will contact each other with a massive stress, resulting in a compression or shear stress on the surface of the talus and underlying injury.      Often, the problem is not diagnosed at the initial time of injury either because clinicians did not obtain radiographs or the radiographs do not show a clear lesion. If radiographs show an osteochondral injury at the initial visit for an ankle sprain, treatment will require either casting of the ankle to allow the fracture site to heal or pinning and open reduction of the fracture in cases of a loose lesion. However, the majority of osteochondral lesions do not show themselves at the initial time of injury.      Over a period of time, ankle pain will resolve and the patient will begin to increase his or her level of activity. In cases of osteochondral lesion, the patient will begin to experience swelling and pain in the ankle with this increased activity. It is at this point that the patient will present for further consultation. Pain often occurs with an increase in activities such as sports and is not present with rest. Patients will note a dull ache of the joint and may also describe mild to moderate locking or clicking.      One should physically examine the ankle to check for instability and tendon or ligament injury. Diagnosing an osteochondral lesion is very difficult on a physical exam and one rarely diagnoses this without further testing. Often, performing an injection of local anesthetic into the involved joint will reduce pain but clinicians should not rule out other problems such as loose bodies, synovitis and ligament injury. One may use radiographs to check for a cyst formation or cartilage damage but this imaging rarely shows definitive involvement.      There is a great deal of debate as to which adjunct testing is best for diagnosing an osteochondral lesion. The prevailing thinking is that magnetic resonance imaging (MRI) is better in cases of pure cartilage damage or for superficial lesions while computerized tomography (CT) is better for cystic lesions and lesions that involve both cartilage and bone injury. In our hands, we will get an MRI as our primary diagnostic test as it gives us information on the ligament, tendon and synovial regions as well as the osteochondral lesion. If the MRI shows a cystic lesion and we are concerned about the overlying cartilage and bone seal, and if there is a small fracture in the overlying subchondral bone region, we will often get a CT scan after the MRI. However, in most cases, the MRI gives us enough information.      Conservative care of osteochondral lesions is difficult. Often, it is difficult to reduce pain permanently with bracing or casting. We will often try a period of casting for osteochondral lesions with a small fracture fragment but have found poor outcomes with healing in such cases with conservative care.

Pertinent Pearls For Performing An Arthroscopy

Surgical options differ according to the size, depth and amount of damage associated with an osteochondral lesion. A second point to consider is the level of activity the patient would like to return to. For example, an elite athlete with a large cystic lesion will not do well with drilling of the lesion and may require a grafting of the site. Yet a more sedentary patient with the same lesion may do well with drilling.      The most common surgical procedure for an osteochondral lesion is an arthroscopic exploration and treatment. One would use a non-invasive ankle distractor to distract the joint and check the lesion. Remove the lesion and all non-viable articular cartilage. This is easy to identify since the region of damaged cartilage will feel soft and a probe will easily penetrate the cartilage during arthroscopic examination.      After removing all non-viable cartilage, the surgeon should fenestrate the subchondral bone with either a K-wire or a chondral pick. Our preferred technique is to use a 0.62 K-wire and drill lesions in the posterior medial region that cannot be reached with a chondral pic through a medial incision approach. In order to protect the soft tissues, one should drill through the medial malleolus with the use of a microvector guide. This is very simple to perform and one would make several drill holes into the lesion to allow for bleeding and fibrocartilage formation. Have the patient emphasize non-weightbearing for a period of four to six weeks and immediately start using a passive range of motion machine.      As the size of the lesion and, more importantly, the depth of the lesion increase, drilling and removal of the lesion show less than perfect outcomes. In general, our guideline for a cutoff for drilling options is a lesion less than 1 cm in diameter and a lesion less than 0.5 cm in depth. In certain cases, we will try drilling as a first-line treatment option in a more sedentary patient and give complete information to the patient about the possible need for further treatment.      However, in most cases with larger lesions, the surgeon should completely excise the lesion and use osteochondral grafting. There is a great deal of debate as to whether you should use autograft, fresh allograft or graft substitutes. We have found equally good outcomes with the use of autograft and fresh allograft, and therefore use the fresh allograft as our primary option. One can use two allograft regions that mimic the normal makeup of talar cartilage. The best option is a fresh allograft talus. If this is not available, the second option is a femoral head fresh allograft.      With medial lesions, one must osteotomize the medial malleolus to access the joint. Use the OATS system to remove the plug of damaged cartilage and bone to a depth of 1 cm or so, and utilize a replacement graft. If a lesion is a corner lesion involving both the dorsum and lateral wall of the talus, remove the entire lesion with a saw and use a square block to replace the defect. Use a cast to allow for healing of the lesion for six to eight weeks. Employ CT scanning to check for a solid repair at the six- to eight-week point.

What Are The Options For Treating Subchondral Cystic Lesions?

The final and most difficult type of lesion to treat is the subchondral cystic lesion with intact overlying cartilage and bone. In this type of lesion, the pain is from the constant compression of the cyst with activity but there is no overlying damage to the cartilage and bone. There is also a problem with mild sclerosis of the walls of the cyst that one must treat. In certain cases, an OATS allograft option is the best option. This type of treatment is best in large lesions with a major defect of over 1 cm with extensive depth. We try to avoid drilling of these lesions as the superficial cartilage and bone are intact and stable.      The newest and most complicated treatment option is the use of retrograde drilling of the lesion. One would perform an arthroscopy of the joint and identify the lesion. Then using a microvector guide, the surgeon would drill a tunnel from the sinus tarsi region into the cystic lesion with a guide pin. Clean out the lesion with a small curette and debride the sclerotic walls. Then you fill the region with either allograft or autograft. We prefer the use of autograft and often harvest the material from either the calcaneus or distal tibia. It is important to pack the lesion fully to avoid further cyst formation. After performing this procedure, one should emphasize non-weightbearing for six to eight weeks and again use a CT scan to check healing.

Final Thoughts

With proper procedure selection, the options for osteochondral lesion treatment are improving and have great outcomes. As always, it is essential to check for ligament laxity and tendon injury, and address both of these issues at the time of surgery if they are problematic. Over the next few years, one may be able to begin treating cartilage lesions with cartilage cell transplants through an injection and with cartilage caps.      I hope the information presented is helpful for your patient care. It is important to understand the principles of arthroscopy and the use of a microvector guide in the treatment of osteochondral lesions. I would recommend starting with the treatment of easy lesions prior to trying the complex and large lesions. Informed consent must include the possible need for further surgery, graft failure/nonunion and the potential need for ankle fusion or replacement.      Dr. Baravarian is the Co-Director of the Foot and Ankle Institute of Santa Monica. He is an Associate Professor at UCLA Medical Center and is the Chief of Podiatric Surgery at Santa Monica/UCLA Medical Center. Dr. Baravarian may be reached at bbaravarian @mednet.ucla.edu. For related articles, check out the archives at www.podiatrytoday.com.