How to do calcaneal fracture classification

Sanders classification was used to classify the fractures into four types: type Ⅰ for intraarticular fractures without obvious displacement; type Ⅱ for fractures with displacement>2mm on the posterior articular surface of the calcaneus; type Ⅲ for fractures with two fracture lines on the posterior articular surface of the calcaneus; type Ⅳ for fractures with displacement of four or more parts on the posterior articular surface of the calcaneus.