The radiographic union scale in tibial (RUST) fractures: Reliability of the outcome measure at an independent centre

Abstract

Objectives: The radiographic union score for tibial (RUST) fractures was developed by Whelan et al to assess the healing of tibial fractures following intramedullary nailing. In the current study, the repeatability and reliability of the RUST score was evaluated in an independent centre (a) using the original description, (b) after further interpretation of the description of the score, and (c) with the immediate post-operative radiograph available for comparison.

Methods: A total of 15 radiographs of tibial shaft fractures treated by intramedullary nailing (IM) were scored by three observers using the RUST system. Following discussion on how the criteria of the RUST system should be implemented, 45 sets (i.e. AP and lateral) of radiographs of IM nailed tibial fractures were scored by five observers. Finally, these 45 sets of radiographs were rescored with the baseline post-operative radiograph available for comparison.

Results: The initial intraclass correlation (ICC) on the first 15 sets of radiographs was 0.67 (95% CI 0.63 to 0.71). However, the original description was being interpreted in different ways. After agreeing on the interpretation, the ICC on the second cohort improved to 0.75. The ICC improved even further to 0.79, when the baseline post-operative radiographs were available for comparison.

Conclusion: This study demonstrates that the RUST scoring system is a reliable and repeatable outcome measure for assessing tibial fracture healing. Further improvement in the reliability of the scoring system can be obtained if the radiographs are compared with the baseline post-operative radiographs.Cite this article: Mr J.M. Leow. The radiographic union scale in tibial (RUST) fractures: Reliability of the outcome measure at an independent centre. Bone Joint Res 2016;5:116-121. DOI: 10.1302/2046-3758.54.2000628.

Keywords: interobserver reliability; intramedullary fixation; radiographic union; score; tibial fractures.

Anteroposterior radiographs a) and b) of the tibia and fibula which show bridging callus, yet fracture lines can still be seen between the original cortices.

Diagrams showing a) a fracture with a fracture line and no callus formation; this would be assigned a radiographic union scale in tibial (RUST) fracture score of 1; b) a fracture with callus formation and a fracture line; this is scored as 2; c) a fracture with bridging callus, but the fracture line is still visible across both cortices; this is scored as 3 and d) complete bridging of the callus with no evidence of fracture line and is scored as 3.

Fig. 3

Graph showing the percentage of radiographic union scale in tibial (RUST) fractures scores of radiographs

Fig. 4

This anteroposterior radiograph of the tibia and fibula may seem to have formation of callus around the lateral cortex despite being taken immediately post-operation. The appearance of bridging bone is due to the spiral pattern and slight displacement, where in fact no callus has yet to form.

Fig. 5

Anteroposterior radiograph showing the tibia and fibula. It was taken immediately after operation and shows barely visible fracture lines, but no callus.