Two Types of Osteochondral Lesions of the Ankle Described
Sprains, strains, fractures, and other trauma to the ankle can result in a condition known as osteochondral lesions of the talus or OLT. The talus is the bone located below the tibia (lower leg bone) and above the calcaneus (heel). The lesion or defect can affect just the cartilage lining the bone (called a chondral lesion) or the hole can go all the way down to the bone (an osteochondral defect).
Surgeons from South Korea compared a large group of patients (almost 300 people) with osteochondral lesions of the talus and described them in this article. These two basic types of lesions (chondral and osteochondral) have some differences that might be important clinically.
The authors focused on comparing patient demographics (age, sex, trauma, body size), characteristics of the lesions (size, location, number of lesions), and patient outcomes (pain, motion, function). They reported that two-thirds of the patients had chondral (cartilage) lesions and the remaining one-third had the full osteochondral (including cartilage and bone) type.
It is important to know what type of lesion is present. Patients with osteochondral lesions have a better chance of self-healing compared with those who have the chondral type. This is because bone marrow cells (inside the bone) can move or migrate from inside the bone to the defect and stimulate healing. Chondral lesions don't have that direct connection to bone marrow cells and must rely on far fewer bone marrow cells reaching the lesion. The cells come from the joint synovial membrane (lining around the joint containing fluid).
And as it turned out, osteochondral lesions were more common in the younger (more active) patients (in their 20s) who might have better healing capabilities as well. Chondral (cartilage only) lesions were present more often in older, heavier adults (50 year old and older with higher body mass index or BMI). Trauma was a key feature for most of the patients in both groups. Symptoms lasted longer in patients with the chondral type of lesions -- possibly because of the delayed healing with reduced self-healing associated with this type of injury.
There wasn't a lot of difference in lesion characteristics between chondral and osteochondral defects. Size and location of the lesions were very similar between the two groups. Chondral lesions in patients without a history of trauma were more likely to form cysts just under the cartilage. Older patients were more likely to experience impingement (pinching) of the soft tissues during ankle motion with the chondral type of lesions. Patients in both groups had equally improved symptoms (decreased pain and increased function) after surgery for either kind of lesion.
In summary, although there are differences in age, duration of symptoms, and body-mass index (BMI), clinical results were very similar for these two types of osteochondral lesions of the talus. Other studies have shown that the most important factor predicting success or failure of treatment is the size of the lesion (larger sizes are less likely to respond well). This study showed that the type of lesion (chondral versus osteochondral) is not as significant a factor in predicting patient outcomes.
Gi Won Choi, MD, et al. Osteochondral Lesions of the Talus. In The American Journal of Sports Medicine. March 2013. Vol. 41. No. 3. Pp.504-510.