How accurate is preoperative MRI in assessing scaphoid vascularity in patients with scaphoid nonunion? A systematic review and meta-analysis.

Background: Scaphoid fractures are a prevalent and complex issue in orthopedic practice, particularly when they lead to complications, such as nonunion and avascular necrosis (AVN), especially in proximal pole fractures. Preoperative assessment of scaphoid vascularity using magnetic resonance imaging (MRI) has become increasingly important for guiding surgical interventions, including deciding on using avascular bone grafting or vascular grafting procedures. However, there is ongoing debate regarding the diagnostic accuracy of various MRI techniques in evaluating scaphoid vascularity. This study aims to analyze existing literature on the diagnostic efficacy of different preoperative MRI methods in assessing scaphoid viability in patients with nonunion.

Materials and methods: This systematic review was designed based on the structure of the Preferred Checklist for Systematic Reviews and Meta-Analyses (PRISMA). The search strategy employed a combination of keywords and MeSH terms related to scaphoid nonunion, preoperative MRI, and vascularity assessment.

Results: Across three databases yielded 431 articles, of which 14 were selected for meta-analysis. The diagnostic performance of these MRI techniques was evaluated, revealing pooled sensitivity and specificity values of 0.702 and 0.85, respectively. Specifically, unenhanced MRI demonstrated a pooled sensitivity of 0.63 and a specificity of 0.85, while enhanced MRI showed improved sensitivity and specificity at 0.77 and 0.87, respectively, with an area under the curve (AUC) of 0.83 (P < 0.0001).

Conclusions: This meta-analysis indicates that contrast-enhanced preoperative MRI provides superior sensitivity, specificity and AUC to unenhanced MRI for detecting scaphoid vascularity. In addition, the study highlights that the detection of hypointensity is a more reliable predictor of AVN, whereas isointensity may not accurately reflect scaphoid viability. Given the significant heterogeneity among studies and the lack of large, randomized trials, further well-designed studies with adequate sample sizes are necessary to confirm the effectiveness of different MRI methods in preoperatively assessing scaphoid vascularity.

Level of evidence:  I.