Inside Insights On Ankle Replacement Surgery
Ankle arthritis has been the subject of much research and researchers have made a great deal of progress in this area in the past 50 years. In the past, physicians primarily treated post-traumatic arthritis, which accounts for much of the cause of ankle arthritis, with casting. This often caused malalignment and poor articular position, resulting in rapid arthritis of the hindfoot and ankle.
With the advent of internal fixation and external fixation advances, proper anatomic alignment of the hindfoot and ankle has resulted in a dramatic decrease in the rate of post-traumatic arthritis. This being said, the aging population and the resulting baby boomer generation being healthier and more active has resulted in more cases of degenerative age-related arthritis. The numbers of patients with osteoarthritis of the ankle will likely continue to grow as patients live longer and want to be active for a longer period of their lives.
The main options for ankle arthritis have been: lubrication injections and bracing for conservative care; spur removal and joint clean-up for early cases of arthritis; cartilage replacement in minor arthritis cases; and fusion or ankle replacement in severe cases. The idea of ankle replacement has been low on the consideration ladder for severe cases due to the poor outcome of replacement cases in the mid-‘70s and the need for extensive numbers of revision cases in those early ankle replacements.
In the past 15 years, the need for more research and the prospective market for a good ankle replacement system have produced several replacement options with excellent overall outcomes. Each replacement option has positive and negative factors. I will try to provide a guide with regard to three replacement options that I use in my practice.
Keys To Proper Patient Selection
Initially, one needs to consider proper patient selection for ankle replacement. The patient needs to be relatively healthy for surgery and not be morbidly obese. Patients need to have good circulation and no peripheral neuropathy. The patient should also have a well positioned ankle with no major deformity.
Ideally, these patients should be over the age of 55, have a sedentary lifestyle/job and only participate in recreational activity that is not considered high impact activity. However, with the improvements in ankle replacement in the past 15 years, the envelope for the ideal patient has changed. A gray area now exists. One can now consider ankle replacement in certain cases for patients younger than 55. While we have no age cutoff in our practice, we do require a sedentary lifestyle and low-impact exercise. We also warn younger patients of the potential for fusion or revision replacement in the future.
The level of deformity has also been challenged. We often see post-traumatic patients with severe angular deformity who require correction of the angular deformity prior to being eligible for ankle replacement surgery. Often, we also have to realign the foot under the ankle to allow for proper function of the ankle replacement. This may require one surgery at the time of the replacement or there may need to be a two-part surgery.
We also try not to operate on morbidly obese patients due to the increased stress on the ankle but there is no true weight limit for ankle replacement consideration at this time.
I believe the best tactic is to consider all of the situations as a whole. One should pick those patients who understand the risks and rewards of replacement versus fusion, and feel that the added value of motion outweighs the single treatment benefit and dramatic decrease in pain resulting from a fusion.
What You Should Know About The New Implants
The type of implant one uses is just as critical as emphasizing proper patient selection. Although surgeons may choose from many implants, I have been educated on three implants that I find work well for our institute. These are the Inbone Total Ankle (Inbone Technologies), the Salto Talaris Total Ankle (Tornier) and the Agility Total Ankle (Depuy/Johnson and Johnson). All three of these implants have been used extensively with good outcomes and are all well tested.
The Salto Talaris is the implant of choice in my hands for patients who have limited arthritis to the tibia and talar surfaces only, and no angular deformity. This implant is fairly easy to insert. It does not require hindfoot or tibiofibular syndesmosis fusion, and has a very low profile. It has simple instrumentation. The downside is very poor deformity correction and no resurfacing of the medial or lateral malleolar region. The implant is also not the most sturdy of the lot and one should reserve it for good quality bone without avascular necrosis or osteoporosis.
If there is extensive arthritis of the ankle joint including the medial and lateral gutters to the point that resurfacing of these areas is required, the implant of choice is the Agility implant.
This implant has coverage of the medial and lateral gutters and maleollar regions. It is also the most extensively studied and used implant. It does have excellent components and the company does provide one of a kind implants for revolutionary uses and unique needs. The implant also has a revision system that is now being required in certain cases that were inserted over 15 years ago or failed cases. As use of this implant has increased, surgeons are attempting more angular corrections and the envelope for its use has increased.
The downside of this system is that it is the most difficult of the lot to insert from a technical standpoint and requires a very well trained surgeon. The implant also relies on a syndesmosis fusion as it crosses the tibiofibular joint. This is not as easy a procedure as you may think. Although the implant does line the gutters, it also weakens the medial and lateral malleoli, resulting in a higher risk of stress fractures. Accordingly, most surgeons use a medial and/or lateral plate for added stability but there is added surgical time and more incisions about the ankle.
The implant is ideal for mild deformity angular corrections, patients with no avascular necrosis or osteoporosis, and those patients with severe arthritis involving the entire joint.
The newest and most exciting of the ankle replacements on the market is the Inbone system. This implant is very different from the others in that it is locking far better into the bone than the other systems. It is ideal for ankles with no medial or lateral gutter arthritis and a well-aligned ankle.
However, I feel with time that this implant will become the best implant in all but the most simple of cases, including revision cases and angular correction cases. The equipment is well conceived and the implant design is exceptional and very customizable. The downside is that the implant is somewhat difficult to insert. One has to perform the procedure through the plantar aspect of the foot and calcaneus although a subtalar fusion is not required or necessary.
Overall, I believe that the simple cases and ideal patients do well with the Salto Talaris device. In cases of severe arthritis in ideal patients and those with abnormal implant requirements who need special implants, these patients do well with the Agility implant. The remaining groups, including those with weaker bone, potential avascular necrosis, mild angular deformity or heavier patients, do best with the Inbone system.
With time, ankle replacement surgery is progressing toward standard treatment for ankle arthritis. With the aging population requiring more of their bodies for longer active lives, ankle replacement surgery is here to stay.
I do not believe we will see the problems that surgeons saw with ankle replacement in the ‘70s. I urge doctors and patients to find surgeons who perform more than one type of ankle replacement procedure as this is not a one-size-fits-all job. When one emphasizes proper patient and device consideration, ankle replacement can be a fruitful and promising undertaking.
Dr. Baravarian is an Assistant Clinical Professor at UCLA School of Medicine. He is the Chief of Foot and Ankle Surgery at Santa Monica UCLA Medical Center and Orthopedic Hospital, and is the Director of the University Foot and Ankle Institute in Los Angeles.
Editor’s note: For a related article, see “Are Ankle Implants Worth Another Look?” in the April 2003 issue of Podiatry Today.