Diffusion Tensor Imaging Detects Functional and Structural Alterations in Post-Traumatic Distal Tibial Physeal Bars: A Preliminary Study.

BACKGROUND

Conventional advanced imaging for post-traumatic physeal bars of the distal tibia identifies abnormal ossification but provides limited information about the integrity of the remaining physis. This study sought to determine if diffusion tensor imaging (DTI) can noninvasively detect and quantify changes associated with the size of a post-traumatic physeal bar.

METHODS

We conducted a single-center, retrospective, cross-sectional study of 16 pediatric patients (mean age: 11.8±1.5 y) with a radiographically confirmed unilateral post-traumatic physeal bar of the distal tibia. All patients underwent bilateral ankle MRI at 3.0 Tesla (T) with a DTI sequence. The contralateral healthy physis served as an internal control. Physeal bar size was quantified as a percentage of the total physeal cross-sectional area. Spearman correlation was used to assess the relationship between physeal bar size and DTI metrics, including fractional anisotropy (FA), apparent diffusion coefficient (ADC), and tractography-derived parameters.

RESULTS

Physeal bar size demonstrated a strong positive correlation with FA within the region of interest (ρ=+0.71) and a strong negative correlation with ADC (ρ=-0.77) and radial diffusivity (ρ=-0.80). As bar size increased, tract count (ρ=-0.60) and tract volume (ρ=-0.65) on the affected side decreased significantly. Furthermore, physeal bar size strongly correlated with the magnitude of side-to-side asymmetry, particularly for the relative difference in tract volume (ρ=+0.76) and tract count (ρ=+0.74) between the injured and healthy ankles.

CONCLUSIONS

This preliminary study demonstrates that DTI can detect and quantify significant alterations in the distal tibial physis that correlate with the size of the physeal bar noted on conventional imaging. The observed changes in tissue anisotropy and diffusion tract metrics suggest that DTI may serve as a sensitive imaging biomarker for assessing the true extent of the physeal injury. This technique holds promise for enhancing the early diagnosis and monitoring of pediatric growth disturbances.

LEVEL OF EVIDENCE: Level II.