Single-photon-emission computed tomography in painful total ankle replacements

The use of single-photon-emission computed tomography (SPECT) in identifying unexplained pain in the foot and ankle has been described, where other imaging modalities have failed. The investigation of a painful total ankle replacement (TAR) is difficult, often not delineating a definitive cause. Our aim in this study was to investigate the use of SPECT-CT imaging in painful TARs.

We performed a retrospective analysis of SPECT imaging performed for painful TARs in our department between October 2010 and December 2014. There were 14 patients identified who had undergone SPECT-CT imaging for a painful TAR. The mean age was 63.1 years, with a male/female sex ratio of 2:3 and a minimum time from surgery to imaging of 18 months.

Of the 14 patients, 13 were positive for increased osteoblastic activity in relation to the periprosthetic area consistent with implant loosening. The most common finding was tracer activity in relation to the talar component in 13 cases. There was additional tracer activity localized to the tibial component in 5 of these cases. In 10 of the 13 cases with prosthetic loosening/failure of bony ongrowth, there was no evidence of loosening on the plain radiographs. Infection was ruled out by using joint aspiration as clinically indicated.

In our series, SPECT-CT imaging revealed a high incidence of medial sided talar prosthesis activity consistent with loosening. The finding of a high incidence of talar nonintegration illustrates the limitations of conventional radiology in follow-up of total ankle replacements, as this was not apparent on plain radiographs. We therefore conclude that there should be a high index of suspicion for talar prosthesis nonintegration in patients with otherwise unexplained ongoing medial pain in total ankle replacements.

Level IV, retrospective case series.