Review Question - QID 212922

The patient is presenting with a painful total ankle arthroplasty (TAA) that is likely due to aseptic loosening. The most appropriate step in treatment would be to obtain a CT scan with artifact-reducing protocol to determine the extent of osteolysis.

Total ankle arthroplasty is an effective treatment for symptomatic arthritis of the tibiotalar joint. Studies have shown that outcomes are best when utilized for primary osteoarthritis, with worse outcomes being associated with post-traumatic arthritis and inflammatory arthritis. It is speculated that previous ankle surgery and increased tissue laxity is attributable to this finding. Overall, pain relief after TAA is equivalent to arthrodesis; however, functional outcomes after TAA are better due to preserved ankle range of motion. Persistent pain after TAA can occur, with concern for osteolysis leading to implant subsidence. Persistent pain after TAA should, therefore, be thoroughly evaluated with a metal artifact-reducing protocol CT scan of the ankle.

Easley et al. reviewed the literature regarding outcomes and survival of TAA implants. They found that studies comparing TAA and arthrodesis have demonstrated equivalent pain relief, with TAA having greater functional outcomes. Implant survival ranged from 70-98% at 3-6 years, and 80-95% at 8-12 years. Most studied reported a high reoperation rate to address impingement, polyethylene exchange, addressing instability, or bone grafting cystic lesions with retention of the tibial and talar components.

Hsu et al. reviewed the treatment and management of painful TAA. The initial workup of a painful prosthesis should include infection evaluation, consisting of ESR, CRP, and CBC. Persistent pain after a successful arthroplasty is common and can include impingement and arthrofibrosis. Evaluation with flexion and extension radiographs as well as physical examination of the gutters can assist in determining the etiology of pain. Loosening can occur through bone cyst formation and subsequent subsidence, and is best evaluated with a CT scan with metal artifact-reducing protocols. Ballooning osteolysis, a cyst > 2mm, and rapid cyst progression is concerning for progression to implant loosening and should be addressed with curettage and bone grafting.

Figures A and B are AP and lateral radiographs of the right ankle with a TAA prosthesis, osteolysis present surrounding the tibial component, and subsidence of the talar component.

Incorrect Answers:
Answer 1: Bone scans can be performed to evaluate for infection or aseptic loosening, but the study itself cannot differentiate between the two and is therefore not the next best step. Further, there are high false-negative and false-positive rates with this imaging study.
Answer 3: Given the physical examination, serum analysis, and previous aspiration results suggesting a lack of infection, a repeat aspiration would not provide further diagnostic information, as the concern for infection is low in this patient.
Answer 4: The patient has radiographic features of aseptic loosening and osteolysis that need to be addressed. Routine follow-up would predispose the patient to worsen implant subsidence and make revision surgery more difficult in the future.
Answer 5: The patient currently does not have any evidence of infection so a two-stage revision is not indicated at this time.