In the surgical management of ankle fractures, post-traumatic arthritis is the outcome that practitioners and patients would most like to avoid. But given the sensitivity of joint cartilage to even the slightest malalignment or pressure shift, that can be easier said than done.

By Cary Groner

Breaking an ankle is bad enough, but it turns out that even when a patient appears to be healed, she may not be. Clinicians are increasingly alert to the risk of post-traumatic arthritis (PTA) following ankle fractures, a vexing problem because the etiology remains poorly defined and treatments aren’t very effective.

Whereas OA is relatively rare in ankles—it occurs in less than 1% of people—it is usually associated with previous injury, unlike OA in other joints.^1,2 PTA onset, moreover, may not occur for decades after the initial trauma. One study reported an average latency between injury and end-stage ankle OA of roughly 21 years, though the time lag was affected by fracture severity and type, complications during healing, and other factors, including patient age.³ That statistic may be misleading, however, because there’s a big difference between end-stage OA and the amount of pain it takes to severely cramp the lifestyle of an average person.

“Eighty percent of the people I see with ankle OA are post-traumatic,” said James DeOrio, MD, a consultant in orthopedic surgery at Duke University Medical Center in Durham, NC. “The other twenty percent have inflammatory arthropathy due to rheumatoid arthritis, gout, or hematochromatsosis—diseases that destroy cartilage.”

Cartilage

The clinical focus on ankle fractures has long centered on surgical reduction—restoring the damaged joint as closely as possible to its original alignment—and ideally this will prevent PTA. The picture is complicated, however. Articular fractures deliver blunt trauma to the cartilage and disrupt the articular surface and subchondral bone. Cartilage damage—specifically, lesions on the anterior and lateral talus and on the medial malleolus—have been reported to predict PTA.⁴

Still, you’ve got to start somewhere.

“Restoration of the articular joint surfaces is necessary to optimize outcomes,” said Eric Bluman, MD, PhD, an assistant professor of orthopedics at Harvard Medical School and research director of the Brigham Foot and Ankle Center at Brigham and Women’s Hospital in Boston. “If you have a step-off or incongruity of the joint, and part of the joint is rubbing against that, it’s like a cheese grater; the cartilage will get shredded off of the joint.”

If PTA arises, it can occur due to the initial injury, during the surgery to fix it, or later, if the joint morphology wasn’t adequately restored. Once the patient has damaged cartilage, he may be out of luck, because cartilage is at once astonishingly tough and desperately fragile. The tissue is avascular, nourished by synovial fluid rather than blood, and it heals slowly and poorly if it heals at all. Damage may be difficult to detect during surgery because there’s no telltale bleeding, and trauma frequently results in apoptosis—programmed cell death—that destroys the cartilage cells over time even if they survive the initial insult.

“The chondrocytes die off and the cartilage goes bad, and you can develop post-traumatic arthritis even with a perfectly congruent joint,” Bluman said.

Because the problem is difficult to detect, surgeons can be deceived about prognosis until symptoms prove them wrong.

“We can go in and put the joint back together, and it looks like we’ve restored normal anatomy on x-ray,” DeOrio said. “Then the patient comes back in pain a year later, and there’s severe narrowing of the joint space. All those fat, plump cartilage cells have died, and the resulting friction has initiated an inflammatory process.”

A 2006 paper in the Journal of Orthopedic Trauma described the many factors that may influence the destruction of cartilage.⁵ The abnormal mechanical environment following injury may place uneven loads on the tissue, damaging or killing it. Initial damage may lead to fissures that broaden and deepen as time goes on, eventually exposing bone. Apoptosis, as noted, typically plays a role, as does inflammation. Genetic factors may increase risk, as well.

Overall, it’s a treacherous environment once a trauma launches this cascade. But some traumas, it turns out, are worse than others.

The breaks

Most ankle fractures are rotational injuries, occurring as a result of sudden direction changes—say, from playing soccer or falling while wearing high heels.

“Those are lower-energy injuries,” said David Thordarson, MD, a professor of orthopedic surgery at the University of Southern California in Los Angeles. “They’re pretty straightforward to fix, and it’s uncommon to get arthritis as a result.”

By far the most damaging break is a tibial plafond fracture, also called a pilon fracture. These devastating injuries, typically associated with car accidents or falls from high places, can shatter the ankle with a direct axial load and are notoriously difficult to repair.

“Pilon fractures have poor outcomes because the force goes right through the joint surface and breaks the weight-bearing surface to pieces,” Thordarson said. “When we operate, sometimes we just can’t get it back perfectly, and people will start developing arthritis as early as a year or two later.”

Alignment issues

Even though PTA is rarer in lower-energy injuries, such as rotational fractures, it still occurs, usually due to malalignment of the bones that affect the cartilage over time.

A study published in the Journal of Bone and Joint Surgery (JBJS) in 1976 revealed that in 23 dissected tibiotalar articulations, in which the talus was laterally displaced just 1 mm, the contact area decreased 42%.⁶ Reduced contact area, in turn, can increase joint stress—a risk factor for cartilage damage.

“Even with rotational injuries, very subtle shifts in the bone can lead to significant changes  in contact pressures,” Thordarson said.

His own related study, which simulated ligamentous injury in cadaver lower legs and was published in JBJS in 1997,  reported that the highest pressures were associated with maximum shortening of the fibula along with various combinations of lateral shift and external rotation.⁷

Another paper, published in 2008, found that intact ankles had lower peak contact stress exposures that were relatively uniform and centrally located, whereas fractured ankles had peak stresses about 38% higher, less area with low contact stress, and more area with high stress.⁸

“That’s one of the big arguments for surgery when the fibula is fractured and the deltoid ligament is disrupted,” Bluman said. “You have a talar shift, and if you allow the patient to heal in that position there are going to be greatly increased contact stresses in the joint. It’s not too hard to make the leap that if there are greater contact stresses, there’s going to be greater cartilage wear and more post-traumatic arthritis.”

Ryan Scott, DPM, a junior partner at Orthopedic Foot and Ankle Center in Westerville, OH, concurred.

“Even a little displacement leads to changes in biomechanics and gait, to increased pressure on either the medial or lateral aspect of the talus,” he said. “That’s going to erode the cartilage faster, and once that cartilage is gone, you’ll have a significant increase in arthritis.”

Surgery and outcomes

Different surgical approaches treat various types and severities of ankle fracture, and some address PTA when joints haven’t healed well. Research has begun to focus on outcomes so surgeons have a better idea of which technique to choose in different circumstances.

For example, in a 2006 retrospective review, researchers studied 76 patients with 79 tibial plafond fractures to see if the type of surgical approach affected later outcomes, including arthritis incidence. Thirty-one (39%) of the fractures developed PTA. Patients with open reduction and internal fixation (ORIF, n=63) generally had fewer complications and lower PTA rates than subjects who received wire ring external fixation (EF), though the authors noted that this could reflect a selection bias for open injuries and more severely comminuted fractures managed with EF.⁹

Another study of pilon fractures, conducted in Taiwan, reported that open reduction and plate fixation was associated with better outcomes and lower PTA rates than pin fixation or closed reduction.¹⁰

And a 2010 paper  in JBJS reported outcomes in 69 patients who underwent surgery to treat subtalar PTA following displaced intra-articular calcaneal fractures.¹¹ Group A (n=34) was initially managed with open reduction and internal fixation and subsequently underwent in situ subtalar fusion for PTA; group B (n=35) was initially managed nonoperatively and later had subtalar distraction arthrodesis for PTA. Group A generally had better functional outcomes five years later.

“The relationship of the ankle and foot is like a Rubik’s Cube,” said Judith Baumhauer, MD, MPH, the associate chair of academic affairs in the Department of Orthopaedic Surgery at the University of Rochester School of Medicine and Dentistry in Rochester, NY, and president of the American Orthopaedic Foot and Ankle Society. “If one of the cubes is irregular, the row doesn’t move; and if there is ankle malalignment, the foot articulations don’t function correctly.  Malalignment will also lead to an excessive load on part of the cartilage, which increases wear and arthritis risk.”

Baumhauer noted that wear and load are only two of several factors that may elevate the risk of arthritis. For example, she noted that an open repair of a comminuted articular fracture might take several hours—during which time the cartilage cells are exposed to the toxic effects of oxygen, which may adversely affect outcomes.

“This is why we continue to seek less invasive biologic solutions to fracture care such as external fixation, computer navigation, and limited internal fixation techniques,” she explained.

Realignment and reconstruction

Because of the destructive effects on cartilage exerted by uneven bone surfaces and changes in pressure distribution, malalignment is a big issue after ankle fractures. In this context, malalignment may refer either to the articular surfaces of the fractured bone, to the alignment of bones surrounding the fractured one, or both; surgeons deal with all such problems.

A study published in 2009, for example, found that a varus deformity of the ankle secondary to a distal tibial fracture can lead to functional ankle impairment and OA.² The same study noted that malleolar fractures may also lead to a varus alignment—a common finding in chronic ankle instability—and that lateral ligamentous injuries often lead to abnormal pronation and other disturbed biomechanics associated with increased rotary shear forces, which can damage ankle cartilage and support the onset of ankle OA.

Several factors may lead to postsurgical malalignment of the fractured joint, according to Eric Bluman.

“First, the surgery may not be done properly, so the joint isn’t perfectly aligned,” he said. “Second, the joint may be aligned, but the surgeon may make not use a strong enough stabilizing implant. Third, the surgery and implant may be perfect, but the patient may start walking too soon and throw things off.”

When repairs don’t take for any of these reasons, revision surgery is often the answer. For example, in a 2010 paper in JBJS, researchers reported that in 57 malunited ankle fractures, reconstructive osteotomy improved ankle function and delayed the progression of arthritic changes 85% of the time—effects that lasted up to 27 years after initial surgery.¹²

“With an interarticular malalignment, corrective surgery is frequently the best option,” Bluman said. “But that decision is going to depend on how long the malalignment has been present and how well you can actually correct it. If you have an ankle injury that doesn’t directly involve the joint, surgery might be indicated but assistive devices may be a reasonable option too.”

In the case of ligamentous interarticular malalignment, for example, when the bones and cartilage are in the right place but lax or damaged ligaments can’t hold the joint stable, clinicians may choose to try noninvasive approaches such as orthoses, bracing, gait retraining, physical therapy, or some combination of these, Bluman explained.

Ryan Scott agreed.

“If the initial surgery was grossly negligent, then surgical realignment of the ankle joint is absolutely required,” he said. “In other cases, I may treat with a brace or orthosis. It’s important to address any extra inversion or eversion, which can cause excessive wear on the talus and tibia, to reduce arthritis risk.”

Stability and alignment

Stability is an important aspect of postsurgical alignment considerations because of cartilage’s sensitivity to uneven weight distribution.

A study from the U.K. published in 2010, for example, looked at the relative incidence of arthritis in rotational ankle fractures treated operatively or nonoperatively. Of 213 stable fractures treated nonoperatively, just 2.8% eventually developed arthritis. But in unstable fractures the picture was very different. Of 420 treated operatively, arthritis developed in 20.9% at 5.5 years, whereas of 137 cases treated nonoperatively, a stunning 65.5% developed arthritis.¹³

“If you have an unstable ankle fracture that’s treated nonoperatively, it’s more likely to develop incongruity and post-traumatic arthritis,” Bluman said. “If you stabilize the fracture with fixation you overcome that.”

He expressed concern, however, about the therapeutic approaches reported in the study.

“You have to wonder why some of those unstable fractures were treated nonoperatively,” he said. “Did surgeons decide not to operate in some cases because they knew the patients would be noncompliant? And were their arthritis rates higher because they were older? I don’t know.”

David Thordarson voiced similar concerns.

“The vast majority of time malalignment develops, especially after rotational injuries, people just didn’t get proper treatment,” he said. “They were put in a cast instead of treated surgically, and there’s a significantly higher chance that they won’t have perfect congruity in their joint surface, which will lead to abnormal stresses.”

Even if radiography shows that the good alignment of a broken bone allows for casting rather than surgery, patients must be followed closely, he pointed out. If they come back a week later and the bone has shifted, he’ll operate. If the patient disappears for a few weeks—and surprisingly, some do—then returns with a malalignment, the surgeon may have to rebreak the ankle and realign it.

Thordarson pointed out, however, that postfracture instability is relatively uncommon.

“Usually the problem is excessive stiffness, because in addition to breaking the bone they tear a bunch of ligaments,” he said. “It’s a balancing act, because we want them immobilized so their skin and their fracture heal, but we don’t want them immobilized so long that they get stiff.”

To address this, Thordarson and his colleagues often switch patients to a removable fracture boot four weeks after surgery.

“I tell them they still can’t walk on it, but they should take the brace off a couple of times a day and move their ankle up and down to minimize stiffness,” he said.

Judith Baumhauer reiterated the importance of moderation in such cases, suggesting that excessive motion can cause shear forces that increase the risk of cartilage damage.

“Normally we want to mobilize joints after they’re injured so we can get nutrition to the cartilage,” she said. “However, too much mobility can cause additional damage. Everything has to be in good balance for the cartilage to be happy and avoid arthritis after trauma.”

After the fact

Once an ankle has developed arthritis, realignment surgery is proving a viable alternative to joint replacement—or stoic suffering.

In a 2007 study from Switzerland, researchers determined that in 35 patients with post-traumatic ankle arthritis, realignment surgery significantly decreased pain, increased ankle range of motion, and improved walking ability.¹⁴ A subsequent paper by the same team reported that the surgeries had also increased sports frequency and ability to perform activities without symptoms.¹⁵ And researchers in the Netherlands found that medial malleolar lengthening osteotomy corrected varus malalignment in patients with arthritic ankles.¹⁶

Ideally, of course, surgeons would be able to replace cartilage or coax it to regenerate after being damaged.

“They’re working with growth factors and stem cells to make that possible,” Thordarson said. “It’s going to be a while before we can completely resurface a joint, but I believe it will eventually come. That’s what the future holds.”

Cary Groner is a freelance writer in the San Francisco Bay Area.

References

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