Comparison of Radiographs and CT Scans in the Prospective Evaluation of the Fusion of Hindfoot Arthrodesis

Abstract

Background: This prospective study compared radiographs and CT scans for the quantitative evaluation of healing of hindfoot arthrodeses. Methods: Patients undergoing subtalar or triple arthrodesis were prospectively evaluated. Serial radiographs and CT scans were obtained after surgery. The percent of fusion of the joints was sequentially measured on all radiographs and CT scans. At 6 and 12 months after surgery, the patients completed American Orthopaedic Foot and Ankle Society (AOFAS) and Short Form-12 (SF-12) instruments and a visual analog scale (VAS). Results: The mean observed fusion of the posterior facet of the subtalar joint ranged from 41% at 6 weeks to 61% at 12 weeks and to 86% at 6 months on the radiographs; the mean fusion of the posterior facet on the CT scans ranged from 23% to 48% to 64% at the same time intervals. The agreement between the two methods was poor. The clinical results based on the AOFAS, VAS and SF-12 scores were compared to the percent of joints fused on the CT scans. Clinical results appeared to be independent of radiographic results. Conclusions: We believe the progress of the fusion cannot be determined accurately from standard radiographs. CT scanning appears to be significantly more reliable. The concept of what constitutes an adequate fusion deserves more extensive study.