The Effect of Plaster of Paris on Reliabilities of RUST and mRUST Scoring Systems

PURPOSE OF THE STUDY The aim of our study is to investigate the reliabilities of the radiographic union score for tibial fracture (RUST) and modified RUST scoring systems in the evaluation of fracture healing in adult tibia fractures treated with intramedullary nailing and pediatric tibia fractures treated with closed reduction and cast immobilization and to compare the reliabilities between two groups. MATERIAL AND METHODS Between January 2016 and January 2020, the informations of patients (ages of 4-10) with tibia fractures treated with closed reduction and casting and patients (aged 18-65 years) with tibia fractures treated with intramedullary nailing were analyzed retrospectively. Forty-seven good quality AP and lateral radiographs (represent different healing stages) each for pediatric and adult fracture groups were selected and were included in two PPTs separately. The radiographs were assessed twice with an interval of three weeks by an observer group consisting of four senior orthopedic surgeons and four orthopedic residents, and fractures were evaluated according to the RUST and mRUST scoring systems. RESULTS The inter-observer agreement of RUST and mRUST were 'perfect' in adult tibia fractures and 'substantial' in pediatric tibia fractures in both evaluations. However, in deciding fracture consolidation, inter-observer agreement was found to be 'perfect' in pediatric tibia fractures, while it was 'substantial' in adult fractures in both assessments. The mean intra-observer reliability of RUST system in adult tibia fractures was 0.860 (0.674-0.968) and 0.818 (0.693-0.909) in pediatric tibia fractures, respectively. The mean intra-observer agreement of mRUST system was 0.842(0.745-0.979) in adult fractures and 0.857 (0.756-0.932) in pediatric fractures, respectively. The mean intra-observer reliability of decision on union was 0.842 (0.638-1.000) in adult fractures and 0.785 (0.611-0.977) in pediatric fractures, respectively. DISCUSSION The decision of union in tibia shaft fractures is based on repeated clinical and radiological evaluations but there are no universally accepted guidelines to evaluate radiographic union. It has been shown in previous studies that the RUST and mRUST scoring systems can be used safely in the evaluation of fracture healing in adult patients with tibia fracture treated with intra-medullary nailing. To our knowledge, there are no studies investigating the reliability of RUST and mRUST systems in conservatively treated pediatric tibial fractures. We hypothesized that the plaster of Paris makes it difficult to assess fracture union on direct radiographs and reduce the reliabilities of these scoring systems in pediatric tibial fractures. CONCLUSIONS Our study showed that both RUST and mRUST scoring systems are useful tools that can be used safely assessing fracture healing in both pediatric and adult tibia fractures. The presence of a plaster of Paris on the extremity did not adversely affect the inter-observer and intra-observer agreement of the RUST and mRUST scoring systems. Key words: pediatric tibia fracture, radiographic union score for tibial fracture (RUST), modified RUST, radiographic union, reliability.