The first of these factors is patient selection, which begins with a complete and detailed history and physical examination. A history of smoking, diabetes, inflammatory arthritis, vascular disease, neuropathy, immunosuppression, neurologic disease (i.e., spasticity, paralysis), osteoporosis, or poor nutritional intake may be exclusion criteria. The anterior soft tissue envelope of the ankle is relatively thin when compared with those of other joints where arthroplasty is performed. Medical issues that may compromise healing need to be evaluated. Whalen et al.¹ showed that there is a statistically significant increase in the incidence of wound breakdown in TAR patients who had greater than a 12 pack-year history of smoking. Similarly, poorly controlled diabetes and vascular insufficiency are also known to have a deleterious effect on healing postoperative incisions about the foot and ankle. In a retrospective chart review using multivariate regression analysis, Raikin et al.² demonstrated that patients with inflammatory arthritis are 14 times more likely to require a return trip to the operating room to manage wound complications than those without inflammatory arthritis. Immunosuppressive treatments often used for rheumatoid arthritis (RA) increase the risk of not only wound dehiscence but also postoperative joint infection. Neurologic disease can affect implant stability as well as postoperative function. Patients with spasticity who are not able to achieve a plantigrade foot represent a particular challenge, especially if that deformity is combined with a coronal plane deformity. Varus or valgus malalignment of the ankle due to muscle spasticity can lead to edge loading and early failure of the implant. Osteoporotic patients may not have sufficient cortical integrity remaining in the distal tibia or proximal talar body to support the prosthesis and may not achieve adequate bony ingrowth to stabilize the implant.

Age is another important factor in a patient’s long-term outcome following TAR. Unlike the hip and knee, the ankle is more often affected by posttraumatic arthritis, which tends to occur in younger, more active patients. Unlike their healthy counterparts, these patients may already have some soft tissue compromise from their previous injury, surgery, or both. The higher physical demands younger patients will place on the prosthesis may lead to more rapid wear of the prosthesis and a need for multiple revisions through an already compromised soft tissue envelope. At the other end of the spectrum is the elderly patient. Chronologic age is less important than physiologic age, as estimated by his or her health and probable life expectancy. A chronologic 70-year-old with a past medical history significant only for hypertension, who walks 4 miles a day and eats a healthy balanced diet, can be a physiologic 50-yearold. Alternatively the same person with a past medical history of diabetes, hypertension, hypercholesteremia, and chronic obstructive pulmonary disease, who smokes two packs a day and lives a sedentary lifestyle, can be a physiologic 90-year-old. The physiologic 50-year-old is a far better candidate for TAR than the 90-year-old as his body has more reserve and will be able to better compensate for the increased postsurgical demands.

The role of body mass index (BMI) in the outcome of TAR patients remains unclear. In 2009, Baker et al.³ found no association between high BMI (>30) and reduced outcomes or need for secondary surgery following TAR. This was corroborated in 2010 when Barg et al. demonstrated, in a review of 118 obese patients with a mean follow-up of 67 months, that implant survivorship was comparable to results obtained in nonobese patients. They also found significant improvement in preoperative ankle pain and function.⁴ Despite what appears to be a benign relationship between obesity and TAR outcome, Barg et al.⁵ noted that obesity, a previous venous thromboembolic event, and the absence of full postoperative weight bearing are independent risk factors for developing a symptomatic deep vein thrombosis following TAR despite being on low-molecular-weight heparin.

As mentioned earlier, the thin soft tissue envelope around the ankle makes soft tissue management paramount to a successful outcome following TAR. Soft tissue management begins with the initial examination. During the preoperative evaluation, the skin should be inspected for any previous surgical or traumatic scars (Fig. 3.1). Angiosomes are composite anatomic vascular territories of skin and underlying muscles, tendons, nerves, and bones, based on segmental or distributing arteries.⁶ The anterior tibial artery supplies the anterior ankle and then becomes the dorsalis pedis artery, which supplies the dorsum of the foot.⁷ Most TAR designs use an anterior ankle incision, which would be in the middle of the anterior tibial artery angiosome, making it riskier than an incision between angiosomes. The soft tissue between angiosomes has blood supply from both its medial and lateral sides, whereas the blood supply to the soft tissue within an angiosome is primarily unidirectional. Any previous scarring in the area places the skin at even further risk of postoperative breakdown.

Muscle function, tendon excursion, and ankle range of motion should also be assessed. If the patient has had little motion at the tibiotalar joint, tendon excursion may be compromised, leading to atrophy and weakness of the corresponding muscles.

The patient should also be assessed for any associated pathology that may need to be addressed prior to or at the time of surgery. The gastroc-soleus complex can often be contracted because of the decreased dorsiflexion in the arthritic ankle. Preoperative assessment will determine whether a concomitant procedure such as a percutaneous tendoachilles lengthening or gastrocnemius recession is necessary at the time of TAR. Patients with advanced posterior tibial tendon dysfunction (PTTD) may present with excessive hindfoot valgus, which can lead to laxity of the medial ankle ligament complex. Conversely, if the peroneals are dysfunctional, it may lead to excessive hindfoot varus and place the lateral ligament complex at risk. Ligament stability should also be evaluated to determine whether any concomitant soft tissue procedures will be required to stabilize the ankle (i.e., lateral ligament reconstruction such as a Brostrom for stability).