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Update on Osteochondritis of the Ankle

Fragments of bone loose in a joint is a problem called osteochondritis. Improved technology in the area of imaging such as CT scans, MRIs, and arthroscopic exam has brought it to our attention that these osteochondral lesions occur in the ankle more often than we thought. That's why the authors of this article thought it might be time to bring us current information about osteochondral lesions of the talus.

The talus is a bone in the ankle between the calcaneus (heel) and the two bones of the lower leg (tibia and fibula). Sometimes the talus is referred to as the anklebone but really there are many bones that work together to form ankle motion.

Trauma is the main reason why a corner of the talus breaks off and enters the joint space. Other causes may include heredity, hormones, and loss of blood supply to the area. A small number of people seem to develop this problem for no apparent reason. Scientists are still scratching their heads over that and trying to figure out what's really going on.

Chronic ankle pain and loss of ankle motion are the two main symptoms of this problem. Severe ankle pain after trauma (such as an ankle sprain) could be caused by problems other than osteochondritis. There could be a disruption of the blood supply, a fracture, infection, nerve damage, or even an unstable (dislocated) ankle.

The doctor will examine the foot and ankle carefully for any signs that can help point to the correct diagnosis. X-rays, MRIs, and arthroscopic examination of the bone help pinpoint the exact location and amount of damage. MRIs also show the condition of the cartilage and layer of bone just under the cartilage (subchondral bone). Early signs of bone edema and subchondral damage will show up on MRIs when X-rays still look normal.

Once an osteochondral lesion of the talus has been identified as the problem, the physician uses the same diagnostic X-rays to now classify or stage the condition. Staging places the lesion in a category (I through IV) based on the size of the lesion, whether or not it has detached from the talus and/or has been displaced (moved).

All of this information will help guide the surgeon in establishing the best plan of care. Sometimes conservative (nonoperative care) is possible. Small, stable lesions (stages I and II) can be treated with immobilization such as casting or bracing. Even with protected weight-bearing, healing can take a very long time (up to a year).

More severe damage (stages III and IV) or lesions that just don't heal with nonoperative care may require surgery. If surgery is needed, CT scans will help outline the bone shape and structure as well as accurately display the bone lesion.

The surgeon has several techniques at his or her disposal for the treatment of osteochondral lesions of the talus. It may be possible to use glue, wires, pins, or screws to reattach and hold the piece of bone back on the talus. This procedure is called internal fixation.

Sometimes, the surgeon just removes the bone fragment and smoothes down the edges of the talus where it broke off. This type of surgery is called excision and curettage. Drilling into the bone or creating tiny fractures in the bone are two more ways to stimulate healing. The repair cells that show up build a scaffold or matrix upon which bone cells can attach and fill in. This technique is called marrow stimulation. The joint can't restore damaged surface cartilage this way but enough healing occurs to allow for functional weight bearing activities.

Newer surgical techniques such as osteochondral grafting or chondrocyte implantation now allow for restoration of the cartilage. Graft (donor) material can come from a donor bank or can be taken from a place in another one of the patient's joints that is non weight-bearing. Grafting is reserved for large defects in the bone that probably won't heal on their own even with drilling or marrow stimulation.

Implantation of chondrocytes is done by taking some of the patient's own healthy cartilage cells and growing more in a laboratory setting. Then the multiplied cells are placed in the hole created by the defect.

If nothing is done, the lesion will progress to form severe ankle arthritis that will require an ankle fusion or even an ankle replacement. Early identification and treatment is ideal for preventing chronic pain from a chronic problem developing. Restoring motion, full weight-bearing, and a smooth gait (walking) pattern is the focus of treatment.

Kevin S. White, D.O., and Andrew K. Sands. Osteochondral Lesions of the Talus. In Current Orthopaedic Practice. March/April 2009. Vol. 20. No. 2. Pp. 123-128.

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