ASYMPTOMATIC OSTEOCHONDRAL LESIONS may not require any treatment, as they may be chronic but stable. Patients may not even know that they have these injuries and they are an incidental finding on an MRI or CT scan. Patients may have had these injuries for many years without receiving prior care because the ankle joint was never painful.
- BONE MARROW EDEMA can cause a significant amount of pain to the ankle joint. These injuries may also be suggestive of subtle overlying cartilage injuries. If there is a significant amount of edema in the bone and the foot/ankle is difficult to walk on, it is best to immobilize these injuries with a boot and crutches to minimize pressure to the bone and prevent a bone collapse. Six weeks of nonweightbearing is best but the timeframe would depend on the area of bone that is swollen, the amount of swelling and the age of the patient.
- ACUTE NONDISPLACED FRACTURES should be treated with a period of immobilization for 6-12 weeks. This gives the bone and cartilage an opportunity to heal anatomically and prevent the fracture from displacing. This period of immobilization should be in a cast in most cases. X-ray evaluation is performed. However, a CT scan may be best after the immobilized period to further evaluate the degree of healing that has taken place.
- ACUTE SMALL OSTEOCHONDRAL LESIONS that are displaced can be easily excised arthroscopically. Following the removal of the small fracture, the joint surface can be lightly abraded with a shaver or a small microfracture pick could be introduced to cause marrow stimulation. This would cause the subchondral bone to bleed around the surface of the bone to develop fibrocartilage. A period of nonweightbearing for six weeks may be needed. However, during that time the patient starts early range of motion exercises.
- ACUTE MODERATE TO LARGE OSTEOCHONDRAL LESIONS are best treated with an open or arthroscopic reduction and internal fixation. It is always best to place the bone and cartilage injury into its anatomic position to preserve the native cartilage in the joint. Small pins or screws may be necessary to re-establish the normal joint surface. Nonweightbearing for 6-12 weeks would be necessary to allow the bone cartilage to heal. Lesions on the outside of the ankle may require an incision into the ankle joint with the probability of incising the anterior talofibular ligament (ATFL). The ligament would be repaired after the procedure is finished. Lesions on the inside of the ankle may require an osteotomy (bone cut) of the tibia to help access the lesion. This would give the best opportunity to have an anatomic repair. A period of nonweightbearing for 6-12 weeks would be necessary to allow the talus and tibia to heal best.
- CHRONIC SMALL TO MODERATE SIZE (less than 150 mm squared) OSTEOCHONDRAL LESIONS are best treated with debridement or removal of the bone and cartilage that is injured and performing a microfracture. This microfracture is performed by putting small holes in the bone to cause the bone surface to bleed. This bleeding has cells (mesenchymal stem cells) that have the capacity to differentiate into fibrocartilage. This is not real cartilage but it helps to resurface the bone.
- In some cases, we will use juvenile cartilage in the defect to help form new cartilage. This cartilage is from a cadaver. The postoperative course includes a period of nonweightbearing for 6-8 weeks. During that time the joint is mobilized (moved). The prognosis is very good for small lesions (less than 100 mm squared) but as a lesion gets bigger (towards 150 mm squared or more), the prognosis is guarded.
- SMALL CARTILAGE FLAPS without bone involvement may be treated by simply removing the damaged cartilage and the surrounding inflammation (synovitis). If the injury is small, a period of nonweightbearing for 1-2 weeks may be needed postoperatively with early range of motion exercises and physical therapy to get the patient/athlete back in their sport. Larger lesions may be associated with underlying bone injury and should be addressed at the same time.
- CARTILAGE DELAMINATION typically occurs when there is a small breach in the cartilage that may not be seen and fluid leaks between the cartilage and bone interface. This is a difficult problem because cartilage has a poor blood supply and the ability to get the cartilage to reattach itself to the bone is very difficult at best. When we see these injuries we also look for inflammation (synovitis) that may be the primary source of pain more so than the cartilage delamination. In these cases, we remove the surrounding inflammation and leave the cartilage alone. If the soft cartilage is removed, it often becomes a difficult problem because as soft cartilage is removed the lesion gets bigger during the debridement process and the underlying bone gets exposed. A microfracture can also be performed at that point if needed. The size of the lesion is a primary prognosticator of the end result.
We prefer to just remove the inflamed tissue in most cases and leave the cartilage alone. If there is continued pain a second look arthroscopy may be necessary to address the cartilage concerns by different methods (antegrade or retrograde drilling). None of these methods are perfect but do help to lessen or eliminate the pain and improve function.
- OSTEOCHONDRAL LESIONS WITH BONE CYST FORMATION are very difficult injuries to treat. Once the cartilage and bone surface has been injured or breached, the fluid goes below the bone and forms a cyst. Although some cysts that are small may not be painful, others can cause pain walking or during exercise.
An OATS (osteochondral autograft transfer system may be necessary in some cases. During this procedure, the damaged cartilage and dead/damaged bone are replaced with cartilage/bone plugs from the same knee. One or more cylinders may be necessary to plug the defect. In some cases, pain may be relieved by simply decreasing the pressure within the bone. Once the transplanted bone and cartilage has been integrated into the existing bone the hope is to obtain a pain-free functioning joint. The larger the lesion the more difficulty there is in getting an optimal result.
There are many cases where there is the poor integration of the cartilage to cartilage interface. During the transfer, there may be a small degree of cell death at the graft’s margins. Over time graft degeneration may be present as well as underlying bone cysts. Not all cysts are symptomatic. The greater the age of the patient, the greater the likelihood is of cyst formation.
There are other factors to be aware of in doing this procedure including a failure of the bone to integrate with the surrounding bone. There also may be a mild mismatch of the cartilage surface of the knee relative to the cartilage surface of the talus. This is because of the difference in joint surface contour and the thickness of the cartilage in the knee relative to the ankle. Donor site morbidity (knee pain) may also be a factor.