Emphasizing Proper Patient Selection
Similar to any elective surgery, ensuring proper patient selection is key. One must obtain a thorough history and physical examination, and generally exhaust all methods of non-operative treatment. To date, there are no specific parameters to designate candidates for an ankle replacement. The literature does reveal, however, generalized characteristics of the ideal patient population. Patients typically present with: older age, low body mass, minimal osseous deformity and a lifestyle with a low physical demand.10
Although these indications are generalized, absolute contraindications do exist. These contraindications include: peripheral neuropathy and/or Charcot neuroarthropathy; active infection; peripheral arterial disease; significant osseous malalignment or deformity (greater than 15 degrees varus/valgus); extensive avascular necrosis; severe soft tissue or bone quality compromise (previous incisions, flaps, or bone cysts); skeletal immaturity; and high physical demands (laborer, running, jumping).10,16
Keys To Appropriate Preoperative Planning
When it comes to initial radiographs of the ankle, surgeons should evaluate these for degenerative arthritis, quality of bone and osseous alignment. This evaluation must include weightbearing anteroposterior, lateral and mortise ankle views. If proximal deformities are a concern, surgeons should obtain tibio-fibular and long leg axial views to assess overall alignment. One should also consider concerns about knee and hip pathology or malalignment before proceeding with an ankle replacement.
A computed tomography (CT) scan is recommended prior to surgery to evaluate the quality of bone, paying specific attention to any extent of cystic lesions within the tibia or talus as well as adjacent joints. Experience has shown that although the extent of arthritis and subchondral cysts may seem minimal on two-dimensional radiographs, they are often magnified on a CT scan, which can alter surgical planning. If concomitant hindfoot arthrosis is present, an arthrodesis may be beneficial to first provide a stable, plantigrade foot.
Furthermore, one must test soft tissue and ligamentous structures to ensure their competence to constrain the implant. Otherwise, surgery may result in a poor outcome. A Telos stress ankle exam (Austin & Associates, Inc., Telos Medical) of both the lateral collateral and deltoid ankle ligaments often serves this purpose.
It is routine to obtain non-invasive arterial Doppler studies to evaluate arterial perfusion. We typically order ankle-brachial indices, pulsed volume recordings, toe pressures and transcutaneous oximetry. If these are abnormal, surgery is contraindicated.
One must assess the medical condition of the patient prior to surgery. Before surgery, address any major medical issues, such as cardiopulmonary conditions, and smoking. We also consult with infectious disease specialists to treat any underlying infections — such as a urinary tract infection or respiratory infection — that may place the patient at risk for possible implant infection.16