Aim; Cast index (CI) is widely used to assess risk of loss of reduction in pediatric patients for conservative treatment of forearm fractures, but its convenience in adults has not been investigated. We aimed to evaluate the success of CI in predicting risk of loss of reduction in conservative treatment of adult distal radius fractures.

Method; Ninety-six adult patients with distal radius fractures followed conservatively were evaluated retrospectively in terms of demographic data, AO/OTA classification and CI in two groups according to follow-up data: Non-displaced (n =58) and displaced (n =38). Also inter- and intra-observer reliability was assessed.

Results; No statistically significant difference was found in terms of CI between two groups. In logistic regression analysis, only AO/OTA classification was found to have an effect on displacement. There was strong inter- and intra-observer reliability for CI measurements.

Conclusion; CI was unsuccessful in assessing risk of displacement of distal radius fractures in adults despite having high inter- and intra-observer reliability.