Discussion
trauma, fracture, dislocation, fractures, bimalleolar fractures, Fractures
SECONDARY
The results show that based on plain X-rays only it was not possible to rule out accompanying PM fractures in tibial shaft fractures with certainty. Although increased awareness led to a significant improvement in sensitivity (0.17 vs. 0.56), it was still not possible to achieve the required reliability for responsible patient treatment.There are several studies indicating high incidences of additional PM fractures in tibial shaft fractures (25–50%) [The figures show an example of the X-ray and CT images of a patient with a tibial shaft spiral fracture type A with fracture of the posterior malleolus. CT images were not available for the examiners. Additional screw osteosynthesis of the posterior malleolus was performed in this patientNo study has dealt with the reliability of X-ray in identifying these fractures and investigated the impact of previous knowledge, awareness, specialization and level of training on diagnostic accuracy. The present study closes this gap in the literature and shows that plain X-ray imaging is not sufficient to ensure a reliable diagnosis of tibia shaft fractures with a high risk of associated PM fractures—regardless of the examiner. Even with advanced awareness of additional PM fractures, 20% (5/25) of the additional PM fractures in tibial shaft spiral fractures—especially in type A fractures [Fractures with a high risk of PM involvement are primarily spiral fractures and fractures in the distal third of the tibia [Bouche et. al. compared the detection rates of PM fractures in bimalleolar fractures on plain X-ray or CT in a retrospective study. In this study, both, the plain X-rays and the CT scans, were evaluated by 2 surgeons for the presence of a PM fracture twice with an interval of 6 weeks. Similar to the present study, significantly fewer PM fractures were detected on X-rays (35/60 in X-ray vs. 53/60 in CT) and the interrater-reliability on plain X-rays was in a comparable range with a kappa of 0.39 (0.292 in our study). These results support the present results of the current study in that PM fractures cannot be excluded with certainty in the plain X-ray. However, compared to the present study, the study refers to ankle fractures and there were fewer examiners (2 vs. 8) [Furthermore, there is further evidence that the size of the fragments in PM fractures cannot be adequately judged on plain X-rays and that there is poor interrater reliability for these fractures (in plain X-rays) [There are no standardized treatment guidelines for fractures of the PM, however, the size of the PM has been a classic indication of internal fixation. Recent studies suggest that other fracture factors may be more important clinically [In the patient population of the present study, in which preoperative CT imaging was available for all patients, all PM fractures large enough for screw osteosynthesis were fixated internally. Of these fractures, there were 2/17 fractures requiring surgical fixation that would not have been recognized preoperatively by all 8 experienced examiners in their daily routine (see Table In addition, the presence of a fracture of the posterior malleolus is essential for surgical planning as the insertion of an intramedullary nail can result in secondary dislocation of the posterior malleolus. To avoid this, it must either be fixed with screw osteosynthesis beforehand or plate osteosynthesis must be used instead of the intramedullary nailing.Despite the known accumulation of PM fractures in tibial shaft spiral fractures type A and distal tibial fractures, the indication and planning of the surgery are usually carried out without CT imaging on the basis of plain X-rays. Therefore it can be assumed that the PM fractures that are overlooked and not treated in everyday care occur even more frequently here than in ankle fractures, where preoperative CT scans are more common. Due to the ongoing trend towards earlier mobilization and weight bearing in recent years, the reliable detection and surgical fixation of additional PM fractures is becoming increasingly important [The present study has some limitations. There are previous publications demonstrating the coincidence of PM fractures in tibial shaft fractures, so the “no awareness” group maybe had some awareness for PM fractures [However, in our opinion, these limitations do not affect the key statement, that plain X-ray imaging is not sufficient for comprehensive diagnosis of accompanying PM fractures in tibial shaft fractures.The strengths of the study are its prospective design, the inclusion of radiologists and trauma surgeons, and the comparison of different levels of training. In conjunction with the incidences of fractures of the posterior malleolus in tibial shaft fractures described in the literature, we recommend preoperative CT imaging for all tibial shaft spiral fractures—especially with a fracture path in the AP X-ray extending from proximal-lateral to distal-medial (type A)—and all tibial fractures in the distal third.