Rapid prototyping fracture models used in the diagnosis and classification of calcaneal fractures

Abstract

Objective To explore the guiding role of rapid prototyping (RP) models in the diagnosis and classification of calcaneal fractures. Methods From January 2010 through January 2013, RP technique was used to fabricate fracture models preoperatively for 38 patients with calcaneal fracture (41 calcanei). Three patients had bilateral calcaneal fractures. There were 27 male patients (30 calcanei) and 11 female patients (11 calcanei). Their age ranged from 21 to 76 years (average, 34.4 years). Of them, 7 were injured from falling, 23 from falling from a great height and 8 from traffic incident. All patients took axial and lateral X-rays and three-dimensional CT scanning of the calcaneus. The CT data were transformed into STL files that could be read by a RP machine before RP models of calcaneal fracture with a ratio of 1: 1 were produced. Fracture classifications based on the RP models were compared with those based on conventional CT scans. Results According to CT scans, 14 cases were type Ⅱ, 16 cases type Ⅲ and 8 cases type Ⅳ by Sanders classification. The posterior joint surface was not involved in 3 cases which were classified into Essen-Lopresti type Ⅰ. According to the RP fracture models, 12 cases were classified into type Ⅱ, 15 type Ⅲand 11 type Ⅳ by Sanders'classification. The classifications determined according to RP fracture models were more severe than those determined according to CT scans. Conclusion RP fracture models can provide detailed three-dimensional information of severe calcaneal fractures which helps surgeons to visualize much more clearly the fracture in understanding the mechanism, diagnosing, making operative plan and judging the prognosis of the fracture. Key words: Calcaneus; Fracture; Models, anatomic; Rapid prototyping