Classification of intraarticular calcaneal fractures: comparison of two classification systems

Accurately classifying displaced intraarticular calcaneal fractures (DIACFs) is essential for orthopedic surgeons to choose optimal treatment methods and provide results evaluation and communication. Many authors studying used Sanders classification reported moderate intra- and interobserver reliability. Taking the software opportunity of 3D virtual exarticulation, Goldzak updated French tri-dimensional Utheza classification, providing an alternative framework for classifying DIACFs. The aim of this study was to compare the intra- and interobserver reliability of Sanders versus Goldzak classification systems.

The CT scans of 30 patients with displaced intraarticular calcaneal fractures, treated in the same trauma center between 2014-2018, were analyzed by 16 medical doctors (specialists and residents in orthopedic surgery, specialists and residents in radiology), and classified according to Sanders and Goldzak classifications. The same images were sent on two separate sessions, in a randomized order. Interobserver reliability and intraobserver reproducibility were assessed using Kappa statistics and Gwet's AC1 coefficient.

Interobserver reliability using Gwet reported a value of 0.36 for Goldzak classification and 0.30 for Sanders classification (corresponding to "fair assessment" in both cases). In absence of subclasses, "substantial assessment" was reported for Goldzak classification (Gwet of 0.61) and "moderate assessment" for Sanders classification (Gwet of 0.46). Goldzak system had a greater interobserver reliability in the group of radiology residents. Intraobserver reliability coefficient was 0.60 for Goldzak classification and 0.69 for Sanders classification, indicating a substantial agreement for both classifications.

Despite the better view of the fracture lines provided by 3D reconstructions, this study failed to prove the superiority of Goldzak classification compared to Sanders classification for DIACFs.