The Methodology and Interpretation of Radiographic Measures for Malunion in Proximal Humerus Fractures: A Systematic Review

Radiographic imaging is an essential tool for surgeons in classifying injury, guiding treatment decision making and assessing for adequate intraoperative reduction. However, the heterogeneity in radiographic outcome measures utilized in clinical studies evaluating proximal humerus fracture treatment has made it difficult for surgeons to interpret and analyze the available evidence, leading to continued controversy in the optimal management of these injuries. The aims of this systematic review are to 1) examine the literature to describe the methods for measuring and interpreting radiographic outcomes for malunion and 2) identify studies that have correlated functional outcome measures and radiographic outcome measures. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, a systematic review of the literature was performed using EMBASE, MEDLINE and the Cochrane Database of Systematic Reviews from inception to January 30, 2024. Outcomes of interest included radiographic outcome measures and functional outcome measures including pain assessment and range of motion measurements. A total of 36 studies that used radiographic measures of alignment following treatment and union of proximal humerus fractures were identified. The most common measure was the head-shaft angle, utilized in 33 studies (92%). Tuberosity position was reported in 22 studies (61%). Only 21 studies (58%) provided a clear and reproducible technique for obtaining radiographic measures. The interpretation for radiographic malunion varied between studies. Varus malunion, using head-shaft angle measures, was defined as under 105 degrees to under 130 degrees in different studies. Although there is known variation between patients, only three studies utilized the imaging from the contralateral shoulder to define patient specific measures for malunion. Twenty-two studies assessed for an association between head-shaft angle malunion and patient functional outcome measures. Given the broad and inconsistent definition of malunion used between the included studies, there remains a lack of clear threshold for radiographic measures of alignment that surgeons can use in their clinical decision making for proximal humerus fractures. Based on the evidence available, we propose a consistent definition of head-shaft angle measurement drawn from specified radiographic views, with varus malunion defined as <125 degrees, and valgus malunion >140 degrees. To optimize the management and outcome of these fractures, radiographic outcomes must be standardized and correlated with function.