Comparison of the neural recovery effects of extracorporeal shockwave therapy according to administration time in sciatic nerve-injured rats

Extracorporeal shockwave therapy (ESWT) has been reported to promote peripheral nerve regeneration but whether its efficacy is maintained when treatment is initiated after the acute phase remains unclear. This study compared the neuroregenerative effects of immediate and delayed ESWT in a rat sciatic nerve crush model. Sixty rats were assigned to immediate treatment ([IT]; ESWT immediately after injury), delayed treatment ([DT]; ESWT 7 days postinjury), control, and sham groups. Extracorporeal shockwave therapy was delivered at an energy flux density of 0.19 mJ mm−². Molecular, structural, and functional outcomes were evaluated for 9 weeks. Both IT and DT groups showed higher expression of glial fibrillary acidic protein, S100β, brain-derived neurotrophic factor, growth-associated protein 43, and NF200 than the control group. Histomorphometric analysis showed comparable improvements in axonal area and remyelination. At 9 weeks, G-ratios were lower in the IT (0.59 ± 0.04) and DT (0.60 ± 0.02) groups than in the control group (0.69 ± 0.02; both P < .05), with no difference between the treatment groups. Compound muscle action potentials [CMAP] amplitudes at week 9 were higher in the IT (39.5 ± 2.6 mV) and DT (40.1 ± 3.0 mV) groups than the control group (33.3 ± 2.5 mV; both P < .05). Immediate and delayed ESWT were associated with improved nerve regeneration, supporting the biological efficacy of ESWT initiated 7 days postinjury in this sciatic nerve crush model.