Reproducibility of computed tomography to evaluate ankle and hindfoot fusions

Although plain radiographs have been historically used to evaluate the status of arthrodesis in the foot and ankle, computed tomography (CT) has gained popularity for evaluation of fusion status. The degree of fusion identified on CT scan has been correlated with functional outcome, with an arthrodesis area of 25-50% necessary for clinical success. In the clinical setting, orthopaedic surgeons often evaluate CT scans independently. The purpose of this study was to evaluate the interrater reliability of CT scans to assess the status of hindfoot or ankle fusions among orthopaedic foot and ankle surgeons.

Forty-one CT scans were identified retrospectively from the tertiary referral practices of 4 fellowship-trained orthopaedic foot and ankle surgeons. Inclusion criteria were patients with ankle, subtalar, or tibiotalocalcaneal fusions. Fusions with bulk allograft were excluded. All CT scans were completed at the investigating institution. The primary author (RAC) reviewed all CT scans to ensure the adequacy and completeness of the films. Images were blinded of any patient identifiers. All 4 surgeons individually reviewed the blinded scans and determined whether the arthrodesis site was greater than or less than 50% fused. Interrater reliability was completed via kappa analysis.

Based on kappa analysis, there was high interrater reliability in the assessment of subtalar arthrodesis. This was not statistically significant for the evaluation of ankle arthrodesis.

The CT scan has become instrumental in determining the adequacy of arthrodesis in the foot and ankle. The present study demonstrates the reliability of orthopaedic surgeons to ascertain the status of subtalar arthrodesis via CT scan.

Level IV, case series.