November 2016

Adjacent-joint arthritis after ankle arthrodesis

11OA-iStock_39793176Altered biomechanics after ankle arthro­desis often increase stress on the adjacent joints in the foot, which can cause or exacerbate osteoarthritic degeneration in those joints. Clinicians and researchers are working to better understand this process and how to minimize patients’ risk.

By Cary Groner

People who develop osteoarthritis (OA) of the ankle joint, whether due to traumatic injury or the effects of age, have traditionally faced limited therapeutic options.1 Surgical procedures including ankle fusion (arthrodesis) or replacement (arthroplasty) are typically deployed when less invasive approaches fail, but both have drawbacks.

Fusion limits the multiplanar motions of the ankle joint and leads to deficits in function.2 Moreover, some of that lost motion and its associated stress is transferred to the adjacent joints in the foot, particularly the subtalar joint, and this may cause or exacerbate arthritic changes in those joints.3

Ankle joint replacements, though retaining ankle motion, have implant longevity limitations that make them less practical as an alternative to arthrodesis in younger patients.4 As a result, clinicians and researchers are striving to better understand adjacent-joint OA and discover ways to alleviate it. Surgeons are refining arthrodesis techniques, and medical device companies are working to make ankle joint implants function better and last longer. Eventually, those in the field hope to be able to minimize or eliminate adjacent-joint OA, but there’s much work to be done.

The nature of the beast

A study published in 2001 in the Journal of Bone and Joint Surgery suggested the long-term scope of the problem. Patients who’d had arthrodesis to treat post-traumatic ankle OA were followed for a mean of 22 years.5 The authors reported that OA of the ipsilateral subtalar, talonavicular, calcaneocuboid, naviculocuneiform, tarso­metatarsal, and first metatarsophalangeal joints was consistently more severe than the OA in those joints on the nonarthrodesis side. The leg that received ankle fusion was also significantly worse in terms of activity limitation, pain, and disability.

The foot’s flexible adaptation to a restricted ankle joint allows compensations that make gait more functional, but can also lead to degeneration in other joints over time.

A 2015 paper analyzed the long-term results of two different arthrodesis techniques—isolated tibiotalar fusion and combined tibiotalar and subtalar fusion—and found each had drawbacks.6 The former was associated with severe arthritic degeneration at the subtalar joint, and the latter was associated with arthritis at the talo­navicular and Lisfranc joints.

Another recent article has questioned such results, however. A systematic review analyzed 24 studies and reported that, though most found altered biomechanics in the fused ankle, it remained unclear whether the fusion caused OA in the adjacent joints.7

The literature is one thing, though, and the exam room is another. All of the clinicians LER spoke with for this article were concerned about adjacent-joint OA related to arthrodesis, though they had different ideas about addressing it.

“The fused ankle joint doesn’t move, and the resulting altered gait stresses the adjacent joints,” said David Thordarson, MD, a professor of orthopedics at Cedars Sinai Hospital in Los Angeles. “Twenty years after an ankle fusion, you’ll start to see arthritic changes in the hindfoot joints caused by the altered biomechanics of the foot. This can be particularly exacerbated if the fusion isn’t done in proper alignment.”8

The talonavicular and subtalar joints are the adjacent joints that are most at risk, said Jeffrey Johnson, MD, professor of orthopedic surgery and chief of the Foot and Ankle Service at Barnes Jewish Hospital at Washington University Medical Center in St. Louis, and current president of the American Orthopaedic Foot and Ankle Society.

“After arthrodesis, the ankle joint is constrained, so those adjacent joints need to function as inverters, everters, dorsiflexors, and plantar flexors,” Johnson said. “They are asked to perform functions that they were never designed to do.”

According to Matthew Sorenson, DPM, FACFAS, an attending surgeon at the Weil Foot and Ankle Institute in Des Plaines, IL, when motion is taken away from one joint, the associated forces will inevitably travel somewhere else.

“Ideally we’re not fusing joints if we don’t have to, but it’s important to remember that arthritis in the ankle limits its motion too, and that motion is going to the surrounding joints, which then tend to wear out more quickly,” Sorenson said. “The patients have a subconscious compensation in response to pain, and the global degeneration is the body’s response to the arthritis.”

Patients who restrict activity after arthrodesis rather than finding other ways to maintain function often end up with fewer adjacent-joint issues, noted Smita Rao, PT, PhD, an associate professor of physical therapy at New York University.

“The most mobile joints may be the ones that compensate and end up at risk for OA,” Rao said.

Surgery and its effects

Research has helped clarify the nature of the adjacent joint adaptations. For example, one study compared patients who had undergone ankle arthrodesis to a control group who had not; the former’s cadence and stride length were negatively affected, and there was significantly decreased sagittal, coronal, and transverse range of motion of the hindfoot and midfoot.9 Another study suggested that pressure increases in the talonavicular and calcaneocuboid joints may be responsible for the secondary tarsal joint degeneration associated with ankle arthrodesis.10

One paper reported that arthrodesis tended to relocate force and pressure from the lateral column to the medial column of the foot, significantly increasing force and peak pressure on the talo­navicular joint.11 A 2009 article in Foot & Ankle International (FAI) found a 10.8% combined compensatory increase in motion in the subtalar joint and medial column after arthrodesis—a hypermobility that likely contributes both to functional gait and later development of arthritis.12 Finally, a 2015 paper found that substantial ankle malalignment, primarily varus deformity, is common in ankles with end-stage OA, and that the subtalar joint often compensates for the malaligned ankle in static weightbearing.13

In other words, the foot’s flexible adaptation to a restricted ankle joint—whether due to arthritis or arthrodesis—is a double-edged sword; it allows compensations that make gait more functional but that lead to other degenerative changes over time. And, if a patient’s initial arthritis isn’t limited to the ankle joint, but may already be present to some degree in adjacent foot joints, one question is whether fusion accelerates that arthritic process. Many clinicians suspect that it does, but the situation is complex.

“In late-stage ankle osteoarthritis, the patient often adapts their gait to alleviate pain, and that causes more strain on the surrounding joints, whether the subtalar or the talonavicular,” said Eric Barp, DPM, FACFAS, a foot and ankle surgeon at the Iowa Clinic in West Des Moines. “A correctly aligned ankle fusion should decelerate that adjacent osteoarthritis, but one that’s improperly aligned could cause more problems.”

James DeOrio, MD, a professor of orthopedic surgery and codirector of the Foot and Ankle Fellowship at Duke University in Durham, NC, acknowledged that many patients who present with ankle arthritis already have it in adjacent joints, particularly the subtalar joint.7

“When we do an ankle fusion, we prefer not to do additional fusions because we’d like to allow some motion in the hindfoot,” DeOrio said, adding that the risk of adjacent joint OA after ankle fusion is strongly affected by the patient’s activity level. “If people do too much, they’re headed for subtalar arthrosis for sure. When you walk enough miles you’re going to take off that remaining cartilage.”

DeOrio considers proper surgical technique crucial in ankle arthrodesis, and is bluntly critical of surgeons who remove the fibula as part of the procedure.

“If you have a young patient—say, a rock climber who’s fallen—and you choose arthrodesis over joint replacement because the implant won’t last long enough, it’s imperative to leave the fibula,” he said. “If you don’t, you can’t do an ankle replacement later. I just had a patient that this happened to; his heel was sliding toward the lateral side where the fibula would have blocked and protected it, so I had to put his subtalar joint back together. You need the fibula to support the ankle arthrodesis and to permit the patient to have an ankle replacement later if they need one.”

DeOrio and his colleagues prefer a two-plate fusion technique that, according to their research, is stiffer and improves fusion rate, especially in patients with suboptimal bone quality.14

Of course, when it comes to arthritis, what appears on an x-ray may not be obviously related to what the patient reports. Johnson said that the common disconnect between radiographic findings and arthritis symptoms has influenced his clinical decisions.

“In the old days, if we had a patient with ankle arthritis who already had hindfoot arthritis, we would probably have fused both the ankle and the subtalar joint, because we knew that if we did just the ankle, the subtalar joint would start being painful, and then they’d have two surgeries instead of one,” he explained. “Now we’re more accepting of arthritis at the subtalar joint and the talo­navicular joint unless it’s very painful, or there’s a deformity there we need to correct.”

Johnson acknowledged that it’s challenging to predict which patients will have problems with adjacent-joint OA, but he particularly worries about those with hypermobility in the joints.

“Those joints go through a much greater range of motion than they normally should, and it stretches out the capsules and wears them out,” he said.

Some research suggests subtalar fusion is more likely to fail in patients who’ve had a previous ankle arthrodesis; if the foot is relying on the subtalar joint for much of its flexibility, after all, that joint will experience more of the forces that can undo a fusion attempt. For example, a 2015 study in FAI reported that in subtalar fusions without previous ankle arthrodesis, 91.3% were successful; by contrast, in patients who’d had ankle arthrodesis, subtalar fusions succeeded only 61.5% of the time.15

Replacement vs fusion

For a long time, most surgeons considered total ankle replacement (TAR) a poor stepchild to arthrodesis.16 There were good reasons for this, and some of those reasons remain valid.

“How confident do you feel that you can perform a successful arthroplasty in a given patient, considering their bone stock, their expectations, whether there is deformity?” asked Johnson. “If I have a patient who says he wants just one operation and never wants to address this again, I have a hard time ignoring the literature that says that the average patient that has an ankle replacement is going to have more operations in the coming years than the one who has arthrodesis.”

One such study, for example, reported TAR survival rates of 81% at 10 years;4 this contrasts with a reported fusion success rate of 91%.3 Another paper found that 11% of patients who had arthrodesis required major revision surgery within five years, versus 23% of those with a TAR. (Ankle replacement, however, was associated with a reduced risk of subsequent subtalar joint fusion—.7% vs 2.8%, respectively).17

“Knees and hips are classic joint replacements that now last twenty-plus years,” said David Thordarson. “Those are bigger bones [than in the foot and ankle], so it’s easier to dissipate the stress, and with a bigger prosthesis there’s more bearing surface, so it takes longer for them to wear out. The alternative—a knee or hip fusion—is a god-awful operation that drastically affects your ability to walk. But on the other hand, if all you have is an isolated ankle fusion, six months afterward ninety percent of patients can walk in a regular flat shoe with no detectable limp. Fusion is a good operation, and ankle arthritis is much rarer than hip or knee arthritis,18 so ankle arthroplasty will probably never be done in the same numbers as knees and hips. Even so, five or six years ago I was doing three fusions for every replacement, and now I’m doing two replacements for every fusion.”

Improvements in replacement devices and surgical techniques are influencing many clinicians’ decisions, as it happens. Thordarson said patient profiling is a crucial part of the process.

“If someone is age fifty or fifty-five, they’re too young, the replacement will fail, and then it’s going to be a much bigger problem to fuse,” he said. “For people over fifty-five without significant varus or valgus deformity, I’ll discuss it.”

But in certain cases, younger patients may be candidates for TAR, according to Thordarson.

“If somebody already has significant pre-existing arthritis in the foot, or has already had other foot joints fused, to fuse the ankle joint is a very different beast,” he said. “They’ll walk with a limp for the rest of their life, so in a case like that, an ankle replacement, even in a relatively young person, may be a good idea. You may get only ten or twenty years out of the replacement, but at least you postpone throwing their gait off.”

Surgical technique, as always, plays an important role.

“The current consensus,” Rao said, “is that anatomic alignment is critical to the longevity of ankle arthroplasty.19 I could see it being a choice in a younger patient of maybe fifty, with good alignment—someone who has ankle OA secondary to a post-traumatic intra-articular mechanism, with no deformity or residual instability.”

According to Johnson, postreplacement revisions, including fusion, still present challenges.

“That isn’t an easy fusion because there’s bone loss related to the arthroplasty,” he said. “I may have to fuse both the ankle and the subtalar joint, and once you do that, the patient has a tibiotalocalcaneal fusion, which is much more rigid and less functional than an isolated ankle fusion.”

Johnson also pointed out that surgeons shouldn’t be cavalier about subjecting their patients to repeated procedures.

“Your skin envelope is not a zipper,” he said. “When you go in a second time, there’s scar tissue, and things become more problematic.”

Thordarson agreed, particularly in the context of replacing a TAR with another one.

“When the polyethylene in the prosthesis wears, the body does not like it,” he said. “Histocytes and macrophages attack the adjacent bone, then the metal–bone interface loosens and you have cystic changes.20 In patients with well-fixed metal components, you can just go in and replace the plastic parts, but there are not many of those patients so far. You could say that we’ll fuse the ankle ten years down the line, but when you do a primary fusion you’ve got two well-matched, well-vascularized surfaces. When you have a failed ankle replacement, you’ve got a big hole that you’ve got to fill with graft, and that vastly increases the complexity of the operation.”

James DeOrio believes the evolution of components has never­theless made replacement a more attractive option. He now takes a computed tomography (CT) scan of the patient’s ankle and sends it to the component manufacturers. They use the scan to fabricate plastic molds that facilitate alignment and streamline the surgical process. The technique has been described in the literature by others,21 and DeOrio and his colleagues plan to publish a paper about it this fall. He and his team also have a new ankle replacement coming out that they’ve designed themselves.

As for outcomes, research suggests that TAR and arthrodesis are associated with roughly equivalent levels of postsurgical sports participation.22 Some research supports the position that patient satisfaction scores are similar for both procedures, though TAR more often meets patient expectations.23 And in 2015, Idaho clinicians presented a paper at the annual meeting of the American Academy of Orthopaedic Surgeons indicating that TAR patients do better than arthrodesis patients in activities where more natural-feeling ankle motion is important, such as walking on uneven surfaces such as hills or stairs.24

Bracing and footwear

Of course, not everyone wants surgery or is a candidate for it. According to the clinicians LER spoke with, patients with high body mass indices, diabetes, neuropathy, or other conditions likely to inhibit healing or overstress implants may be better served by arthrodesis than arthroplasty. They may also benefit from more conservative approaches such as foot orthoses, bracing, or specialized footwear before electing either procedure.

“We want to do everything we can conservatively before we choose surgery,” said Eric Barp. “If the patient has had longstanding ankle arthritis—particularly if it’s also in the talonavicular or subtalar joints—an ankle foot orthosis [AFO] can limit the motion, which limits the pain.”

Jeffrey Johnson, too, encourages patients to buy time with bracing.

“AFOs can affect arthritis by limiting joint motion, which may let patients delay their index ankle arthroplasty to later in life, so they only need to have one,” he explained.

Such interventions may also be helpful postsurgically.

“You can put a patient with an ankle fusion in a shoe with a rocker sole, which makes it easier to roll over the stiff foot,” added David Thordarson. “That may also help if they’ve had their hindfoot fused.”

If the patient has a residual deformity after surgery, or a foot fused in poor alignment, he added, an in-shoe orthosis can better distribute the stress across the foot and help alleviate symptoms.

Research supports these positions. One study concluded that rocker-bottom shoes significantly improved the total motion of ankle arthrodesis patients, versus walking barefoot.25 Another reported that interventions including shoe adjustment and orthoses may help reduce forces across the midfoot and prevent ankle arthritis, particularly in patients who already have midfoot arthritis.26

A recent study from the San Antonio Military Medical Center in Texas looked at the effect of a custom orthosis and rehabilitation program on outcomes following ankle and subtalar fusions in soldiers whose ankles had been damaged by traumatic battlefield injuries.27 Patients did rehab in two phases; four weeks without a brace, then four in an Intrepid Dynamic Exoskeleton Orthosis (IDEO). One group had ankle fusions alone or with subtalar fusions; the other had subtalar fusions only. Neither group saw significant improvements until the IDEO was added; then both groups had significant improvements in physical performance, and those with subtalar fusions alone also demonstrated improvements in patient-derived outcome measures.

Down the road

Although orthotic and bracing strategies, alone or in combination with arthrodesis, continue to address ankle and foot arthritis in many patients, trends suggest that as ankle replacements become more durable they will eventually be the treatment of choice—not only for preserving more natural motion but for sparing the adjacent joints from the additional stresses associated with ankle fusion. How soon that future will arrive isn’t certain, but it’s clearly on the way.

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

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