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Acute Osteochondral Injuries - Strategies for Management

Acute osteochondral fractures or lesions in the ankle can occur as isolated injuries. More commonly, they are associated with sprains or fractures of the ankle. Arthroscopic studies show that cartilage damage was noted in 25% to 66% of ankles with lateral ligament injuries and 98% of ankles with deltoid ligament injuries.1,2 Others2-4 have shown a high incidence of chondral or osteochondral injuries in ankle fractures, with cartilage lesions seen in 61% to 79% of acute ankle fractures, and the frequency and severity increasing from type-B to type-C fractures.

It remains unclear whether these intra-articular injuries should change our clinical management. In a prospective randomized trial of operative treatment for ankle fractures with or without concomitant ankle arthroscopy, there were no differences in lower extremity scores in the short term between these two groups, despite a high incidence of talar dome cartilage damage.5 A recently published long-term follow-up study, however, shows that initial cartilage damage seen arthroscopically after an ankle fracture is an independent predictor of the development of post-traumatic osteoarthritis.6

Imaging

Because many osteochondral lesions of the talus (OLT) are not visible on plain radiographs, a high index of suspicion is required to make the diagnosis. Acutely, in the setting of an ankle sprain or fracture where one suspects an intra-articular loose body on radiographs, a CT scan is helpful in determining the origin, the size, and the location of the fragment.

In a subacute setting where there is locking or significant persistent pain after an ankle sprain or fracture, an MRI is used to help determine the origin of the pain; it can also delineate the extent of an osteochondral lesion and associated injuries.

In an acute, stable (seen on MRI only) osteochondral defect of the talus, a trial of immobilization and protected weight-bearing can be tried.

Arthroscopy

The mainstay of treatment of persistently symptomatic or unstable osteochondral fractures in the ankle is arthroscopic surgery. A recent systematic review concluded that there is fair evidence-based literature (grade B) to support the use of ankle arthroscopy in the treatment of ankle osteochondral defects.7

Ankle arthroscopy with a small joint (2.7 or 2.9 mm) 30 degree scope allows for a complete assessment of the joint, including the cartilaginous surfaces, ligamentous laxity, syndesmotic stability and the presence of soft tissue contractures or lesions. In the presence of an osteochondral injury, careful examination of the loose fragment and the defect will guide the treatment. It should be probed to determine the condition of the cartilage, the thickness and condition of bone attached to the cartilage, and whether it can be anatomically reduced into the defect. The treatment options and algorithm depend on these characteristics.

In the rare case where there is a substantial piece of healthy bone attached to the viable cartilage, fixation of the fragment can be performed if it can be anatomically reduced. Depending on the location of the fracture, and given the proximity of neurovascular structures in the ankle, further exposure such as mini-arthrotomy by extending one of the anterior scope portals, or if required, medial or lateral malleolar osteotomy, is often necessary. Fibrous tissue should be debrided off the fragment and the base, and the defect can be microfractured to ensure a healthy, bleeding base. Once reduced, the fragment can be temporarily secured with small k-wires, and a small (3.0 mm or smaller) headless metal or bioabsorbable compression screw can be used to fix the piece, taking care to sink the screw well under the cartilaginous surface.

Typically, the bone underlying the cartilage of the fragment is thin, avascular and crumbling, precluding satisfactory internal fixation. In this case, complete arthroscopic debridement of the fragment and the defect, with microfracture or drilling of the base, is standard treatment. For far posterior lesions, a small articulated aiming guide can be useful for transmalleolar drilling. An osteochondral autologous transplant (OATS) from the knee can be performed in acute cases where there is a substantial talar defect, although it is usually reserved for massive chronic OLTs or failed previous debridement. If the articular cartilage is largely intact but there is a large cystic cavity in the talus, usually an indication of a chronic lesion, retrograde drilling and grafting through the sinus tarsi can be done.

At the time of surgery, along with arthroscopy to address intra-articular lesions, concomitant pathology such as lateral ankle instability or malalignment should be addressed. Combination arthroscopy and ankle fracture fixation can be performed if it is indicated, although it is technically challenging.

Newer technologies using minimally invasive techniques for implanting cell-based scaffolds and tissue engineering for articular cartilage repair are showing promising results, and are poised to become a mainstay of treatment of chondral and osteochondral lesions of the ankle in the near future.

References

1. Komenda G.A., Ferkel R.D.: Arthroscopic findings associated with the unstable ankle. Foot Ankle Int 20:708-713, 1999.
2. Hintermann B., Regazzoni P., Lampert C., Stutz G., Gachter A.: Arthroscopic findings in acute fractures of the ankle. J Bone Joint Surg 82B:345-351, 2000.
3. Aktas S., Kocaoglu B., Gereli A., et al.: Incidence of chondral lesions of talar dome in ankle fracture types. Foot Ankle Int 29:287-292, 2008.
4. Loren G.J., Ferkel, R.D.: Arthroscopic assessment of occult intraarticular injury in acute ankle fractures. Arthroscopy 18:412-421, 2002.
5. Thordarson D.B., Bains R., Shepherd L.E.: The role of ankle arthroscopy on the surgical management of ankle fractures. Foot Ankle Int 22:123-125, 2001.
6. Stufkens S.A., Knupp M., Horisberger M., Lampert C., Hintermann B.: Cartilage lesions and the development of osteoarthritis after internal fixation of ankle fractures: a prospective study. J Bone Joint Surg Am 92A:279-286, 2010.
7. Glazebrook M.A., Ganapathy V., Bridge M.A., Stone J.W., Allard J.P: Evidence-based indications for ankle arthroscopy. Arthroscopy 25:1478-1490, 2009.

Reprinted with permission from the Spring 2010 issue of COA Bulletin

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