Validation of the classification of surgically treated acetabular fractures in the Swedish Fracture Register.

Objectives: To validate the classification of surgically treated acetabular fractures in the Swedish Fracture Register (SFR) and to investigate the intra- and interrater reliability of the Judet-Letournel / AO/OTA classification systems.

Methods: Surgically treated acetabular fractures were randomly selected from the SFR (n = 132) and 124 fractures were classified independently by three experienced orthopedic pelvic surgeons at two different occasions. A gold standard classification was established for each case after these two sessions or, if necessary, after a discussion session. The gold standard classification was compared to the registered SFR classification to assess the validity of SFR data. Accuracy and intra- and interrater agreement were evaluated using Cohen´s kappa with interpretation according to Landis and Koch.

Results: There was moderate agreement between the established gold standard classification and the SFR (kappa 0.43). The level of agreement differed between classification groups. The intrarater agreement was substantial to almost perfect and interrater agreement was moderate to substantial.

Conclusions: The accuracy of acetabular fracture classifications in the SFR was moderate and comparable to previous validation studies from the SFR on other fracture types. As the accuracy differed between fracture groups, care should be taken when analyzing data from the SFR on specific acetabular fracture groups.