Total Ankle Joint Replacement (Arthroplasty)
by Dr. Michael M. Cohen, DPM, FACFAS
Anatomy of the ankle
The human ankle joint acts much like a hinge and is formed by the union of three bones. The ankle bone is known as the talus. The talus fits inside a socket that is formed by the lower end of the tibia which is often called the shin bone and the fibula, a smaller bone on the outside of the lower leg. The bottom of the talus sits on the heel bone and is otherwise known as the calcaneus. The ankle joint is a flexible free-moving joint containing cartilage which allows it to absorb shock. The bones are held together with ligaments which are bands of tough tissue preventing the ankle joint from dislocating. Full function of the ankle joint depends on the successful coordination of many free moving parts. These interrelated structures include bones, muscles, tendons, ligaments, and nerves.
Cartilage is specialized joint tissue that covers bone and allows the bones to move in relationship to each other with minimal friction. Loss of the cartilage will decrease joint function and ultimately result in pain, stiffness, swelling, and warmth. Damaged cartilage causes bones to grind on each other during movement resulting in a condition known as arthritis. There are several types of arthritis in the ankle. The most common type of arthritis is osteoarthritis, a condition which is often a result of previous trauma to the ankle or leg and rheumatoid arthritis. Rheumatoid arthritis is an immune system disease resulting in inflammation of the joint lining and in advanced stages will lead to cartilage bone ligament tendon and muscle damage.
What is in total ankle arthroplasty?
Total ankle arthroplasty- otherwise known as total ankle replacement is considered as an option in patients with advanced arthritic changes of the ankle joint which have failed to respond to conservative treatment. This may have included the use of medical therapy, such as medication and injections, activity modification, physical therapy and bracing.
What type of symptoms may the patient encounter?
Patient's with advanced arthritis may experience pain with bearing weight, walking, and movement of the ankle. They may have limited ankle motion with grinding, locking or catching.
How can ankle replacement help?
There are several ankle replacement systems available to the surgeon. Some total ankle replacement systems require more bone removal in order to obtain the desired result, others are referred to as resurfacing systems which remove less bone and essentially replace the surfaces of the joint. Certain ankle replacement systems are used for revision surgery. Today's Total ankle replacements are essentially anatomic and provide the patient with the ability to reproduce the natural movement of the ankle joint. One of the most advanced systems utilizes the Prophecy technique developed by Wright Medical. The Prophecy technique allows precise implantation of the device by using CT scans before surgery. This allows bioengineers to map out a customized plan for the individual patient thereby enhancing the success of the operation.
The proper ankle replacement will depend on the patient's age, level of disease in the ankle joint, and the level of activity. The success of an ankle replacement is influenced by the condition and quality of the bone, the type and severity of arthritis, the condition of the muscles and tendons around the ankle, the weight, age and overall health of the patient, and finally the patient's commitment to physical therapy and rehabilitation.
Are there any complications?
Today's success rate is very good with ankle replacement. Studies show that patients preferred the outcome of ankle replacement over the fusion which bonds the joint in one position to eliminate all movement. However, there are complications both in the immediate period following surgery as well as long-term complications of total ankle replacement. These may include infection, scarring, nerve damage and loosening or wearing of the implant.
In some cases, the surgeon may perform adjunctive procedures to align the ankle joint prior to inserting the ankle replacement system. Postoperative recovery generally requires four to six weeks in a short leg cast or fracture boot with physical therapy starting at four to six weeks postoperative period this is an added advantage over fusion which requires several months in a cast.
There are several types of ankle replacement prosthetic replacements available. In some cases, the type of ankle may determine which design is better for that individual's condition. Not all patients are candidates for total ankle replacement surgery. There are several factors that must be considered when a replacement may be indicated. Some of the factors are age, medical conditions, the weight of the patient, vascular status and structural position of the ankle joint and associated bones, amongst others.
Below are images of ankle joint replacement surgeries depicting the various implant designs. The first set of images show the ankle before surgery and arthritis can be seen in the joint with narrowing of the joint space and wearing of the bone because of the close apposition of the bones. The shape of the talus has been changed because of the constant wearing of the joint.
The images below are post-surgical films of the ankle replaced with a Salto-Talaris (Tornier) model ankle prosthetic. Because of the altered position of the ankle in varus position (inverted), this required a surgical cut through the calcaneus (heel) bone to slide the bone outward to balance out the foot and fixate it with a surgical screw. The talus that was previously worn down has been reshaped using the prosthesis.
In this case, the individual had a severe ankle fracture many years ago that was surgically repaired and later developed limiting arthritis to the point where they could no longer use their ankle because of pain. There is the absence of joint space at the ankle joint along with remodeling of the bones around the ankle due to degeneration of the joint. The abnormal appearance of the thin bone called the fibula is a result of not fixing this bone when the patient had the original surgery. This is referred to as a malunion.
The following are images after surgical replacement of the ankle joint with a mobile bearing ankle prosthetic called the S.T.A.R. (SBI). This replacement joint will function similarly to a normal anatomical joint, allowing the patient normal function in daily activities, but was not designed to take repetitive use during more intense athletic activity. The joint has a polyethylene spacer between two metal parts that acts as a shock absorber and gliding agent similar to cartilage. There is a physical therapy that is required after surgical joint replacement in order to get the patient back to functional capacity.
Below are pre-surgical images of an individual who had severe post-traumatic arthritis of the ankle. The patient had previous open reduction with internal fixation of an ankle fracture. Then later on because of structural changes, developed severe ankle arthritis with complete obliteration of the ankle joint space and reshaping of the talar dome and the distal tibia.
The following images are postsurgical films of the same ankle with an IN BONE (Wright Medical) ankle prosthesis, which is typically reserved for severe ankle arthritis involving non-optimal bone stock and/or the necessity for more bone removal to accomplish ankle replacement. This type of prosthetic is ideal for this case because of the large tibial stem that could be made bigger or smaller as needed.
Post-traumatic arthritis treated with total ankle replacement.
This is a series of pics of an ankle fusion takedown with replacement with a total ankle implant. The patient was having pain and getting arthritic changes at the talonavicular joint. This is the first ankle fusion takedown with the replacement of a total ankle implant performed in South Florida by one of the surgeons in our practice.
These are pics of the fusion prior to takedown.
These first three pics are the placement of screws in the medial malleolus and distal fibula to aid in stability.
This is a pic of the implant getting mapped out for placement in the distal tibia
This is the guide for the tibial component of the implant
These are pics of the implant being placed in the ankle joint.
These are final pics of the ankle replacement after fusion takedown.
Pre and Post-op Pics of Arthritic Ankle status post Total Ankle Replacement (TAR)
Pre, Intraop and Postop X-rays status post Total Ankle Replacement for Ankle Arthritis