Bone SPECT/CT in the Evaluation of Painful Total Ankle Replacement: Validation of Localization Scheme and Preliminary Evaluation of Diagnostic Patterns.

Abstract

Third-generation total ankle replacement (TAR) is an increasingly popular and effective treatment for end-stage osteoarthritis, yet identifying causes of failure remains challenging. We evaluated integrated bone SPECT/CT in recurrent pain after TAR by validating a standardized reporting scheme, identifying uptake patterns, and assessing diagnostic performance and impact on clinical management. A total of 24 TARs in 16 patients with persistent or recurrent pain received integrated bone SPECT/CT using diagnostic CT settings. Images were retrospectively reviewed, and a novel localization scheme was validated by assessing interrater agreement. Distinct uptake patterns were identified, and diagnostic test characteristics were estimated. Reference standard consisted of clinical follow-up, laboratory findings, and subsequent procedures, including revision surgery. Standardized scoring of bone SPECT/CT uptake was highly reproducible (intraclass correlation coefficient, 0.79; 95% confidence interval [CI], 0.75-0.82). The final diagnoses were gutter impingement (n = 12), periprosthetic (stress) fracture (n = 5), loosening (n = 5), tarsal arthritis (n = 1), and erysipelas (n = 1). Overall, the diagnostic test characteristics of bone SPECT/CT were as follows: sensitivity of 100% (95% CI, 82%-100%), specificity of 80% (95% CI, 28%-99%), and accuracy of 96% (95% CI, 79%-100%). Gutter impingement, periprosthetic fracture, and loosening were correctly identified in all cases revealing distinct uptake patterns. Importantly, persistent diffuse uptake was frequently observed, warranting cautious interpretation. Bone SPECT/CT impacted clinical management in 86%, with symptomatic improvement in 83% of patients. Integrated bone SPECT/CT of painful TARs may benefit from standardized localization to reveal distinct uptake patterns representing common complications after TAR. Initial results show highly promising diagnostic value with potentially important impact on clinical management.