The Use of Single-Photon-Emission Computed Tomography (SPECT) for the Evaluation of Painful Ankle Arthroplasties

CATEGORY: Ankle; Ankle Arthritis INTRODUCTION/PURPOSE: The evaluation of the painful ankle arthroplasty remains challenging. Clinical and radiographic examination are the mainstay of surveillance. The use of CT is also widespread. In our series using CT we were however unable to reliably differentiate between prosthetic and other causes of pain. We do not therefore recommend the use of CT in evaluating this patient group. Since 2017 we have evaluated all cases of painful ankle replacement with single-photon-emission computed tomography (SPECT). The aim of this study was to review the use of SPECT in our patient cohort. METHODS: A retrospective analysis of all ankle arthroplasties evaluated by SPECT was performed. Case notes, plain radiographic imaging and SPECT imaging were reviewed and tabulated for analysis. RESULTS: 29 painful ankle arthroplasties were identified and included in this study. Implants included 14 BOX, 11 Mobility, 3 Salto xt and 1 Zenith. The mean time from index surgery was 5 years (1 -11 years). Plain radiographs demonstrated no obvious abnormality in 18 out of 29 patients. Of these SPECT demonstrated abnormal periprosthetic uptake suggestive of loosening in 12 out of 18, in the remaining 6 no loosening / ankle pathology was identified. Of these 6 patients SPECT identified an area of extra- articular high uptake suggestive of a pain source in 3 cases (1 talonavicular joint, 1 subtalar joint and 1 syndesmosis). In the 11 patients with a demonstrable abnormality suggestive of loosening on plain imaging, SPECT confirmed the diagnosis in all 11 cases. CONCLUSION: SPECT is a useful tool in the evaluation of the painful ankle arthroplasty. SPECT provided confirmatory information where plain radiographs were positive but also helped elucidate potential causes of pain where plain radiographs were negative. We would no longer recommend the routine use of CT but rather would recommend the use of SPECT in the evaluation of all painful ankle arthroplasties.