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.