Structural integrity of the distal femoral growth plate following radial pressure wave exposure in immature Wistar rats

Extracorporeal mechanical wave therapies are widely used for musculoskeletal disorders, but their effects on immature skeletal structures, particularly the growth plate, remain insufficiently understood. This study evaluated the histological and structural effects of repeated radial pressure wave exposure on the distal femoral growth plate of immature Wistar rats. Twelve immature male Wistar rats were studied using a controlled intra-animal design. Radial pressure waves were applied to the right distal femoral region, with the contralateral limb serving as an internal control. Animals underwent three weekly sessions of 2,500 impulses at 4.0 bar and 10 Hz. Seven days after the final session, distal femurs were harvested for hematoxylin-eosin and Gomori trichrome staining. Growth plate thickness was independently measured by three blinded raters and averaged for morphometric analysis. Inter-rater reliability was assessed using Friedman test, repeated-measures ANOVA, and intraclass correlation coefficients. Morphometric analyses included paired Student’s t-test, Wilcoxon signed-rank test, Bland–Altman analysis, TOST equivalence testing, and Pitman–Morgan paired dispersion testing. Gomori scores were analyzed using Wilcoxon, McNemar–Bowker, and Cohen’s kappa tests. No necrosis, inflammation, or structural disruption was observed. Growth plate architecture, zonal organization, and chondrocyte morphology remained preserved, with excellent inter-rater reliability. Mean growth plate thickness was 150.11 ± 1.43 μm in treated limbs and 149.76 ± 1.25 μm in controls, with a mean paired difference of 0.35 μm (95% CI, − 0.14 to 0.84). No significant difference was detected by paired Student’s t-test ( p = 0.1428) or Wilcoxon test ( p = 0.1763), and equivalence was not demonstrated by TOST. Dispersion did not differ between limbs (Pitman–Morgan p = 0.4285), and Bland–Altman analysis showed no evident magnitude-dependent pattern. Gomori scores were identical between limbs, with perfect agreement (Cohen’s kappa = 1.00; McNemar–Bowker p = 1.000). Only superficial, transient local reactions were observed. Under these experimental conditions, repeated radial pressure wave exposure was not associated with detectable histological, morphometric, or semiquantitative alterations in the distal femoral growth plate of immature Wistar rats. These findings indicate short-term structural preservation, while longer-term and functional studies remain warranted.