The STAR and Inbone Total Ankle Replacements: Which is best for Ankle Arthritis Cases
With the advent of new technology and an improved biomechanic understanding of ankle function, the treatment of ankle arthritis has broadly changed in the past decade. Ankle replacement is rapidly becoming a comparable option to ankle fusion in the treatment of ankle arthritis. The new generation of ankle replacements have provided an excellent option in the treatment of ankle arthritis and have proven to be a better option to ankle fusion in the proper situations. The purpose of this article is to provide the current options for ankle replacement and also to educate the reader about the benefits and current thinking for the use of the different ankle replacements available on the market today. It is important to remember that for the best potential outcome, patient selection and proper placement of the implant is key to an ideal outcome.
Ankle Replacement Patient Selection:
Ankle replacement procedures are outstanding as long as the proper implant is placed in the proper patient. Furthermore, proper patient selection for replacement versus fusion procedures is essential for the best outcome. In general, ankle fusion is reserved at our institute for younger, very active patients, who require a great deal of strength and stability from their ankle. Ankle fusions are also preferred for cases of severe angular deformities which may not be correctable with ankle replacement. If the ankle is not well aligned and will not become well aligned with boney or soft tissue procedures prior to placement of the ankle replacement implant, an ankle fusion is often performed. Ankle replacement is reserved for patients who do not perform heavy manual labor, are over the age of 45, and preferably over the age of 55, and have little to no ankle deformity. Although some level of ankle deformity may be corrected with soft tissue or bone realignment procedures, the ankle replacement patient of choice is one with an arthritic ankle that is well aligned. Of interest is the fact that patients who have arthritic midfoot and hindfoot joints about the ankle seem to do better with an ankle replacement, rather than an ankle fusion. This is due to the fact that an ankle fusion places greater stress on the surrounding joints which may lead to further arthritic changes of the hindfoot joints, while an ankle replacement allows motion at the ankle resulting in less strain at the surrounding joints.
Ankle Replacement Pre-operative Planning:
Patients will often present to our offices with a pre-conceived notion of what procedure is best for them. This is important to address early in the relationship between the patient and the doctor. It is important to explain the risks and benefits of replacement verus fusion to the patient and to also explain the two procedures in detail. A complete examination of the vascular and neurologic status are undertaken. If the circulation of the patient is poor, an ankle replacement is not selected at the anterior incision and soft tissue complications associated with ankle replacement may not be in the patient’s best interest. Furthermore, a neuropathic patient with lack of sensation to the foot is not a good ankle replacement candidate and such cases have shown an increased rate of failure. The dermatolic work-up require adequate check of the skin for breakdown and quality. If the skin is of poor quality, a skin graft or flap has been placed on the anterior ankle or if there are severe varicocities noted, a possible contraindication to ankle replacement may be noted. Finally, the function of the muscles, ligaments, tendons and bones of the foot and leg must be checked prior to consideration for an ankle replacement. Laxity about the ankle from previous ligament injury must be addressed prior to ankle replacement to build a solid platform for the replacement. A non functioning tendon must also be considered to make sure the pull about the ankle is ideal. Finally, alignment of the bones must be ideal or be corrected prior to ankle replacement. In most cases, standard radiographs are enough to address a potential ankle replacement. Alignment and bone stock is checked as is the level of arthritis at the ankle and surrounding joints. If there is a potential for cystic changes in the talus or tibia or signs of avascular necrosis, an MRI or CT scan may be ordered to further assess the ankle joint. In the case of avascular necrosis, as long as the majority of the talus is okay, an ankle replacement may be undertaken but if the talus is very damaged, an ankle fusion may be a better option. If there is severe arthritic changes of the joints surrounding the ankle, a potential hindfoot fusion and ankle replacement may need to be performed.
The STAR Mobile Bearing Versus The Inbone Fixed Ankle Replacement Options:
Currently, our institute utilizes two different ankle replacement options. The InBone total ankle replacement (Wright Medical) is a fixed ankle replacement while the STAR total ankle replacement (Small Bone Innovations) is a mobile bearing option. Both have shown excellent results and both have pros and cons. The main difference between a fixed and a mobile bearing ankle replacement is that in the mobile bearing option, the plastic spacer material is not attached to the talar or tibial component and floats in between the two. This allows for some varus and valgus tilt and it is suggested that there is less stress during movement on the metal-bone attachment point of the implant resulting in less loosening. The fixed option has a plastic spacer that is attached to the tibial component which does not allow varus or valgus tilt but allows for a long stem insertion into the tibia which has been suggested to add strength and prevent subsidence. The choice of implant is a difficult one to make. The STAR implant is very low profile and has an excellent potential for conversion to either a fusion or larger ankle replacement in the case of a problem. On the other hand, the InBone option has an excellent implantation guidance system and the long tibial stem allows for excellent tibial stabilization. Both systems have had excellent results and are fairly easy to insert after a learning curve is mastered.
In our institute, we have began to use the STAR ankle replacement in stable and simple ankle replacement cases which require minimal soft tissue or boney procedures. The Star also has a more stable talar component which we prefer in cases of severe talus arthritic changes or severe medial and lateral gutter arthritis. It is still unclear if there is a major benefit to a three piece mobile bearing implant. On the other hand, if there is any cystic changes in the tibia or if there is previous distal tibial fracture and the bone is not ideal, we prefer the InBone ankle replacement as it has a far more stable tibial component. Also, the InBone ankle replacement has a better surgical guidance system which allows better positioning in more difficult ankles. Finally, in the case of a previously failed ankle replacement that requires revision, the InBone is our preferred system.
Ankle Arthritis Treatment Options Conclusions:
In conclusion, patient selection and proper surgical procedure are essential for ideal outcomes with ankle replacements. With the continued advancements in ankle replacement options, further clarifications will be made to which procedure and replacement material is best for each type of patient. In general, we prefer the mobile bearing ankle in straight forward cases or cases with severe talar damage or medial/lateral gutter arthritis. We prefer the more stable fixed bearing option for tibial cystic changes, deformed tibias, revision cases or more difficult alignment cases. Both replacement have worked very well and have proven to be an excellent addition to our practice with many happy patients.
The University Foot and Ankle Institute Advantage:
University Foot and Ankle Institute is proud to have established a comprehensive ankle arthritis treatment center. From conservative injection therapy and bracing to the most complicated ankle replacement and fusion options, there is no procedure to small or large to handle. Our 9 podiatric foot and ankle surgeons work in a team setting to deal with ankle arthritis cases in a timely and advanced manner utilizing the latest proven technology.
Our patients are our number one priority and we consider them, along with our own families and our dedicated staff, to be our greatest assets.
We are driven to get our patients back to their normal activities with the highest level of function, in the least amount of time, using the least invasive treatments possible. From start to finish, we are with you every step of the way.
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