Incidence and risk factors of (Occult) posterior malleolar fractures in patients with spiral distal tibial fractures: Reexamination and analysis

To evaluate the incidence and risk factors for posterior malleolar fractures (PMFs) in patients with spiral distal tibial fractures (SDTFs).In a retrospective study, 248 adults with SDTFs who underwent treatment were enrolled between November 2017 and May 2020. In a prospective study, we recruited 113 consecutive, skeletally mature patients with SDTFs who were identified from the trauma clinic of our hospital between June 2020 and May 2021. Radiographs and CT scans of the ankle region on the affected side were obtained to determine the presence of PMFs. If the CT scan was negative, additional MRI examination of the ankle was performed as a supplementary protocol in the prospective study. Univariate analysis and multivariate analysis were conducted to analyze the risk factors.In the retrospective study, the incidence of PMFs associated with simple SDTFs was 74.0% (105/142), which was significantly lower than 90.8% (69/76) in the prospective study. Independent predictors of PMFs in patients with simple SDTFs identified by multivariate analysis in the retrospective study were age (OR = 1.07; P = 0.001) and external rotation of the proximal tibia (OR = 3.36; P = 0.027) and those in the prospective study were osteoporosis (OR = 0.04; P = 0.007) and spiral fibula fractures (OR = 16.05; P = 0.046).This study reexamined the high incidence of concurrent PMFs. Additionally, ankle radiographs and CT scans were recommended for all simple SDTF patients. For simple SDTF patients with negative CT scans, especially those caused by external rotation of the proximal tibia, combined with nonosteoporotic or spiral fibula fractures, additional MRI examinations are recommended.