Straight antegrade humeral nailing and risk of iatrogenic injury of supraspinatus tendon footprint: An MRI study.

Background: Straight antegrade humeral nailing (SAHN) is associated with excellent clinical results in proximal humerus fractures. The optimal entry point is the top of the humeral head. However, the anatomy is variable, and the entry point can affect supraspinatus tendon footprint (SSP-F) or fracture reduction. The aim of this study was to analyze the relationship between the SSP-F and SAHN entry point by analyzing magnetic resonance imaging (MRI) studies of the humerus. Methods: In total 58 MRI studies of entire humerus were reviewed. The mean age was 51.6 ± 12.4 years, with 40 female patients. The distance between the SSP-F and the SAHN insertion point (critical distance: CD), the width of the footprint, and the neck-shaft angle (NSA) were measured. Univariate and multivariate analysis were performed. Results: The mean CD was 7.51 mm ± 2.81 (0-12.9 mm) with 51.7% of proximal humerus "critical type" (CD <8 mm). The CD was found to be lower in females, with no difference found with varying age (62.5% "critical type"). CD correlated with NSA (linear regression). "Critical type" correlated with female gender and NSA (logistic regression). Discussion: More than half of the humerus are "critical types" as to SAHN and may, therefore, be at risk for procedure-related complications.