Fig 1.
Flowchart of the study process in the two groups.
Fig 2.
Normal nerve and muscle before surgical intervention.
On the oblique coronal (A-C) and axial (D) fat-suppressed T2-weighted images, the expected locations of the left sciatic nerve are indicated by the arrows. However, the structures are not clearly distinguished from the intermuscular fascia. The calf muscles are isointense to the adjacent muscles.
Fig 3.
MR images of a rat with a crush injury three days after the surgery.
In the oblique coronal fat-suppressed T2-weighted images (A, B), the suture and surrounding edema can be observed at the injury site (empty arrows). The injured nerve is not clearly visible, and the nerve change is considered to be grade 1. In the axial fat-suppressed T2-weighted images (C, D), the calf muscles show slight hyperintensity compared with the surrounding muscles (thick arrows), suggesting grade 2 muscle change.
Fig 4.
MR images of a rat with a compression injury three days after the surgery.
In the oblique coronal (A, B), axial (C, D) fat-suppressed T2-weighted images and MIP image (E), the injured sciatic nerve is diffusely thickened and distinctly hyperintense. Therefore, the nerve change is classified as grade 3, which is apparent at the proximal (dashed arrows) and distal (arrows) portions of the compression site (empty arrows), revealing the suture. The calf muscles show distinct hyperintensity (thick arrows) compared with the surrounding muscles, and the muscle change is considered to be grade 3.
Fig 5.
MR images of the rat with crush injury 10 days after the surgery.
In the oblique coronal (A, B) and axial (C, D) fat-suppressed T2-weighted images, the injured nerve (arrows) is observed as a thick hyperintense structure, suggesting grade 3 nerve change. However, the nerve change is more prominent distal to the injury and subtle proximal (dashed arrows) to the injury. The calf muscles are distinctly hyperintense (thick arrows) compared to the surrounding muscles, suggesting grade 3 muscle change.
Fig 6.
MR images of a rat with compression injury 10 days after the surgery.
In the oblique coronal (A, B) and axial (C, D) fat-suppressed T2-weighted images, the injured nerve is diffusely thickened and distinctly hyperintense, suggesting grade 3 change. This change in the nerve is obvious at the proximal (dashed arrows) and distal (arrows) portions of the compression site (open arrow), showing the suture. The calf muscles show distinct hyperintensities (thick arrows) compared with the surrounding muscles, and the muscle changes are consistent with grade 3.
Table 1.
Differences in the nerve and muscle changes in the two groups.
Fig 7.
Histological staining of the nerve three days after the surgery.
(A) Double staining of neurofilament (NF) and p75NTR (scale bar, 50μm). Neurofilament staining shows compact dot and tubular structures in the normal peripheral nerve (arrows in the upper row, the far-right image). Neurofilament is markedly decreased in the compression injury group (lower row) compared with the crush injury group (upper row). In the compression injury group, the decrease in the levels and morphological changes of the neurofilament is pronounced proximal to the injury. Both groups stained positive for p75NTR (arrowhead). Compared with the crush injury group, severe morphological changes in p75NTR were detected in the compression injury group. A comparison of the intensity of neurofilament between the two groups (the rightmost graph in the lower row) showed that the amount of neurofilament expression was significantly decreased in all portions of the compression injury group compared with the crush injury group (p < 0.001). (B) Double staining of MBP and p75NTR (scale bar, 50μm). MBP staining shows ring-like structures in the normal peripheral nerve (arrows in the upper row, the far-right image). MBP is markedly decreased in the compression injury group (lower row) compared with the crush injury group (upper row). In the compression injury group, the decrease in the levels and morphological changes of MBP are pronounced proximal to the injury. p75NTR staining (arrowhead) shows a pattern similar to that shown in Fig 7A. A comparison of the intensity of MBP between the two groups (the rightmost graph in the lower row) shows that the amount of MBP expression at the injury site was significantly reduced in the compression injury group compared with the crush injury group (p < 0.05).
Fig 8.
Western blot analysis of the nerve tissue at the distal portion of the injury three days after the surgery.
The expression of neurofilament in the crush injury group was similar to that of the normal control group and decreased in the compression injury group. MBP expression was decreased in the compression injury group. Increased expression of p75NTR and c-jun was more pronounced in the crush injury group than in the compression injury group.
Fig 9.
Illustration of fat-suppressed T2-weighted MR neurography in rats with normal sciatic nerve (A), acute crush injury (B), and acute compression injury (C) of the sciatic nerve. Normal sciatic nerve (A) shows intermediate to high signal intensity on fat-suppressed T2-weighted images. When an acute injury occurs, the injured nerve shows increased caliber and signal intensity. The injured nerve shows marked changes in acute compression injury (C) compared with acute crush injury (B). In acute compression injury (C), the injured nerve shows a long tubular structure, including both the proximal and distal portions of the injury. Denervation edema of the calf muscles (arrows) is similar in the two types of injury (arrowheads: injury site).