Quantitative Bone SPECT/CT in Varus-Type Ankle Osteoarthritis: Association With Radiographic Stage and Preoperative Pain.

BACKGROUND

To evaluate the potential clinical relevance of quantitative bone single-photon emission computed tomography combined with computed tomography (SPECT/CT) in patients with ankle osteoarthritis (AOA), focusing on the relationship between radiotracer uptake and disease severity, as well as its correlation with preoperative subjective pain levels.

METHODS

We retrospectively analyzed 44 patients with varus-type AOA who underwent preoperative bone SPECT/CT between July 2018 and October 2024. All patients were classified according to the Takakura-Tanaka classification: stage 2 (n = 5), stage 3a (n = 15), stage 3b (n = 13), and stage 4 (n = 11). Quantitative parameters included the maximum standardized uptake value (SUVmax), SUVpeak, and total bone uptake (TBU), calculated at thresholds of 20% and 40% of SUVmax. Pain severity was assessed using the visual analog scale (VAS) within 1 month of imaging. Group comparisons were performed using the Kruskal-Wallis test with Dunn post hoc analysis. Pearson correlation coefficient was used to assess associations between uptake values and VAS scores.

RESULTS

Both SUV and TBU values showed a general increase in accordance with advancing radiographic stage. In post hoc comparisons with Bonferroni correction, SUVmax and SUVpeak showed significant differences between stages 2 and 3b, stages 2 and 4, and stages 3a and 4 (all P < .0125), whereas 20%TBU and 40%TBU showed significant differences between stages 2 and 4 and stages 3a and 4 (all P < .0125). All 4 quantitative parameters demonstrated moderate correlations with preoperative VAS scores (r = 0.49-0.55, P < .0125), suggesting that both tracer uptake intensity and extent were associated with the patient's perceived pain levels.

CONCLUSION

Quantitative bone SPECT/CT parameters were associated with radiographic severity in patients with varus-type ankle osteoarthritis. Exploratory analyses suggested moderate associations between radiotracer uptake parameters and preoperative pain, although these findings should be interpreted cautiously because VAS data were available only in a subset of patients. These results support further investigation of quantitative SPECT/CT as a complement to conventional radiographic evaluation in AOA.

LEVEL OF EVIDENCE: Level IV, retrospective case series.