Osteochondral lesions
Osteochondral lesions are injuries affecting both the cartilage and the underlying subchondral bone at the joint level. In the ankle, they are most commonly located on the talus, where they are referred to as "osteochondral lesions of the talar dome" (OLT), but can also involve the tibial plafond.
In the foot, these lesions primarily affect the metatarsophalangeal joints, particularly at the level of the hallux and the second ray, as seen in Freiberg's disease.
What is an osteochondral lesion?
An osteochondral lesion is an injury that must be treated as a bone injury. Cartilage involvement is rarely isolated and reflects the quality of the underlying bone.
There are several types of osteochondral lesions:
- Fracture-type lesions
- Geodic or cystic lesions
- Lesions called “osteochondritis”
These lesions can be painful for at least 2 reasons:
- The presence of a mobile cartilaginous flap can cause painful joint blockages. Cartilage is not innervated, so it is not painful in itself. The pain comes from traction forces on the hinge of the cartilaginous flap at the level of the subchondral bone.
- The osteochondral lesion is painful because it is located in a so-called weight-bearing joint area, which supports the body's weight. This lesion consists of bone of lower quality, and no longer serves as support on the surface outlined by the lesion.
The pain is thus due to the fact that the weight is not evenly distributed over the bone but is concentrated on the periphery of the lesion, which has become non-weight-bearing or insufficiently weight-bearing.
What are the causes?
Post-traumatic osteochondral lesions
These lesions are generally small and mainly cartilaginous. Post-traumatic osteochondral lesions can be secondary to an ankle sprain or a sprain of the big toe, as in the specific case of Turf Toe.
Geodic or cystic osteochondral lesions
The exact origin of these lesions is not known, however the mechanism of evolution of these lesions, whose problem is mainly bony, is known. The articular cartilage becomes less watertight and the joint fluid infiltrates through the pores of the cartilage. The passage of fluid from the joint through the cartilaginous pores leads to an acceleration in the speed of fluid circulation, responsible for a phenomenon of erosion of the subchondral bone. This erosion can continue to degrade the underlying bone and create cystic cavities, the volume of which can increase regularly. These lesions can also present as ankle cysts, whose volume can increase regularly and create cystic cavities that cause pain. It is this loss of bone quality that is responsible for the pain. However, we do not know why, at the same size, some of these lesions are painful and others asymptomatic.
Lesions called "osteochondritis"
These lesions may be due to a fusion defect of ossification centers in a bone during growth. A temporary defect in arterial perfusion is also suggested for this type of lesion. Usually, these lesions are not very progressive, and a fragment of lower quality bone becomes trapped in a fibrocartilaginous shell.
Asymptomatic osteochondral lesions
Not every osteochondral lesion necessarily has clinical manifestations. It is not uncommon to see osteochondral lesions of the talar dome, or LODA, in the medial position during the radiographic assessment of a flatfoot valgus.
Which treatments?
The diagnosis of osteochondral lesion is suggested during history taking in the clinical examination. Patients describe deep intra-articular pain that may change location, is difficult to pinpoint, and can move around. Some patients report episodes of intra-articular cracking or pseudo-joint locking.
However, not all osteochondral lesions are necessarily symptomatic; they may be detected during additional tests such as X-rays, CT scans, MRI, or bone scans. In the case of pain possibly associated with episodes of locking, several treatment options may be proposed.
Rehabilitation
For osteochondral lesions of the LODA type, osteochondral lesions of the talar dome, following an ankle sprain for example, rehabilitation can make these osteochondral lesions asymptomatic.
If the osteochondral lesion is isolated and not post-traumatic, rehabilitation may help improve the painful symptoms but will not result in a pain-free joint.
Cortisone injections
A cortisone injection has an anti-inflammatory effect; it reduces intra-articular inflammatory phenomena and thus reduces pain. Cortisone injections usually provide temporary pain relief but in no way treat an osteochondral lesion. A cortisone injection can sometimes be considered in the case of a very painful inflammatory flare-up but should not be regarded as a treatment for these lesions.
Hyaluronic acid injections
A hyaluronic acid injection helps hydrate the joint cartilage. It does not enable healing of a cartilage flap in post-traumatic cases and has no effect on underlying bone injuries. It is therefore not indicated for osteochondral lesions, but it will be useful in case of extensive cartilage damage in an arthritic joint.
PRP injections (platelet-rich plasma)
Contrary to popular belief, PRP does not regenerate articular cartilage. PRP is a concentrate of platelet-derived growth factors, active in a joint for about 10 to 15 days. PRP therefore does not promote healing of a cartilage flap in a post-traumatic lesion, and has no effect whatsoever on damaged underlying bone. PRP injections therefore have limited effectiveness in the therapeutic management of osteochondral lesions.
Surgical treatment
Any symptomatic osteochondral lesion can be treated surgically. Surgical treatment makes sense as it provides a mechanical solution to a mechanical bone problem. There are two types of surgical treatments: microfractures and osteochondral grafts (mosaicplasty).
Microfractures
The microfracture surgical technique involves removing the damaged cartilage, curetting the poor-quality underlying bone, and perforating the healthy bone around the lesion to make it bleed and promote bone reconstruction. These microfractures can be performed with arthroscopy. Microfractures can be supplemented with synthetic collagen membranes, which help trap bone cells and thus promote bone reconstruction.
This microfracture technique is generally intended for small lesions. For example, concerning osteochondral lesions of the talar dome, microfractures are indicated for lesions up to 10 mm along the long axis or 5 mm deep at present.
Mosaicplasty
Mosaicplasty involves a graft of bone and cartilage taken from the same patient. The goal is to completely clean out the osteochondral lesion so that only healthy bone remains around the edges. The lesion is then measured to determine the size of the osteochondral graft needed. The graft is generally taken from the ipsilateral knee when surgically treating osteochondral lesions of the talar dome that are over 10 mm in long axis or more than 5 mm deep.
Conclusion
Not all osteochondral lesions are symptomatic, and asymptomatic lesions should not be treated. When symptoms do occur, the underlying problem is primarily mechanical and osseous, resulting in inadequate load-bearing support within the affected joint.
In symptomatic cases, surgical intervention is indicated, with options ranging from cartilage debridement combined with microfractures to osteochondral grafting, depending on the extent of the lesion.