Fig 1.
Experimental design and grouping of SETS models.
Five experimental groups were established: (1) Control: the tibial nerve remained intact, and only the peroneal nerve was transected; (2) Mild-SETS(–): a 10 mm decellularized nerve graft (DNG) was inserted without SETS; (3) Mild-SETS(+): a 10 mm DNG was inserted, followed by SETS; (4) Severe-SETS(–): a 20 mm DNG was inserted without SETS; and (5) Severe-SETS(+): a 20 mm DNG was inserted, followed by SETS. In the SETS procedure, epineurial and perineurial windows were created in the tibial nerve (yellow) approximately 5 mm distal to the distal DNG suture site (blue), and the proximal stump of the peroneal nerve (green) was coapted to the tibial nerve using 10−0 nylon sutures. The schematic diagram (left) and intraoperative photograph (right) illustrate the surgical configuration in the Severe-SETS(+) group. Black arrows indicate the proximal and distal graft anastomoses, as well as the end-to-side coaptation site.
Fig 2.
Functional recovery assessed by the Sciatic Functional Index (SFI).
SFI scores at 4, 8, 12 and 16 weeks postoperatively. The SFI formula is calibrated such that a score of 0 reflects normal sciatic nerve function, whereas –100 corresponds to complete functional loss. *p < 0.05; **p < 0.01; ***p < 0.001 (one-way ANOVA followed by Tukey’s post hoc multiple comparisons test).
Table 1.
Recovery rates of CMAP detection at 8 and 16 weeks.
Fig 3.
Electrophysiological evaluation of compound muscle action potentials (CMAPs).
CMAPs of the gastrocnemius muscle were evaluated at 8 and 16 weeks postoperatively. The CMAP latency ratio was calculated as the latency on the experimental side relative to the contralateral side. The peak amplitude ratio was defined as the peak amplitude on the experimental side relative to the maximal amplitude on the contralateral side. Statistically significant differences were determined by one-way ANOVA followed by Tukey’s post hoc multiple comparisons test; asterisks indicate only the differences between SETS(–) and SETS(+) groups within the same severity category. *p < 0.05.
Fig 4.
Evaluation of gastrocnemius muscle recovery.
(A) Gastrocnemius muscle weight ratios at 8 and 16 weeks postoperatively. The ratio was calculated as the weight of the muscle on the operated (ipsilateral) side divided by that on the unoperated (contralateral) side. *p < 0.05; ***p < 0.001 (one-way ANOVA with Tukey’s post hoc test). (B) Representative photographs of gastrocnemius muscles at 16 weeks. Upper panels: Severe-SETS(–) group; lower panels: Severe-SETS(+) group. The operated (ipsilateral) limb is on the left, and the unoperated (contralateral) limb on the right.
Table 2.
Immunohistochemical evaluation of NF-positive axon counts and S100β-positive Schwann cell counts in three regions surrounding the coaptation site.
Fig 5.
Immunohistochemical evaluation of axonal regeneration.
Representative immunofluorescence images from three anatomical sites at 16 weeks postoperatively. All sections were obtained in the axial plane and stained for neurofilament (NF, axons; red) and S100β (Schwann cells; green). Images were acquired at 400 × magnification. Scale bar = 100 μm.