Studies On Sciatic Nerve Injury Characters And Imageology Diagnosis In The Early Stage In Swine Inflicted With High-speed Triangular Fragment

Peripheral nerve injury(PNI) is one of the commonest neurological disorders with high morbidity, disability and medical costs. Currently, the diagnosis of PNI mainly relies on the nerve function examinations such as electrophysiology evaluation. A conservative approach can save the patient a needless surgery but it requires following the patient for several months for regeneration/recovery to occur. The major caveat of this approach is that"the fittest window for PNI repairing"may be missed or lost. Therefore, new morphological diagnostic approach for PNI is needed.Peripheral nerve injury by gunshot is a specific type of PNI. It's morbidity above 15% in war. In modern warfare, with the rapid development of high-speed and high-energy explosive weapons, its irregular fragments have higher initial velocity, make more complex wound track, higher instantaneous cavity pressure and energy transfer rate. These can cause an extensive and complex soft-tissue injury. The incidence of remote effect is more higher than traditional weapons, and serious systemic damage maybe occur. There are many new features of PNI causing by high-speed irregular fragments including higher morbidity, more complex injuries, more difficult to quantitate comparing with PNI causing by traditional weapons. Therefore, further study on the characteristics of PNI and investigating new methods for early accurate diagnosis of PNI caused by high-speed small irregular fragments are essential.Objective:Aims of this study were to investigate the characteristics of swine sciatic nerve injuries and systemic body injuries, to explore characteristics of high-resolution CT(HRCT) imaging of sciatic nerve and wound track, to study accuracy and feasibility of early diagnosis with multi-planar reconstruction, three-dimensional reconstruction, CT perfusion(PCT) imaging in sciatic nerve injury and important of PCT on the diagnosis of wound track classification in swine inflicted with high-speed triangular fragment. These maybe get earlier and more effective diagnostic methods for peripheral nerve injuries and soft tissues injuries caused by high-speed fragments.Method:1.Study on the characteristics of swine sciatic nerve injuries caused by high-speed triangular fragments.Direct and indirect sciatic nerve injury models were made steadily by means of aiming at the midpoint of the lateral body surface projection of the sciatic nerve and 2cm from it respectively with a 0.37g triangle fragment at the velocity of 773.1±12.4m/s and the shot-distance of 40cm. Compound Muscle Action Potential and nerve conduction velocity of swine sciatic nerve were determined pre-injured, 1h, 24h and 48h after injured. The hepatica function and renal function, Cardiac zymogram were detected by automatic biochemical analyzer simultaneously. The pathologic changes of nerves were observed 48h after injured by gross anatomy, light and transmission electron microscopy. The gross anatomy and pathological changes of wound tract and viscera were also observed .2. The study on the early diagnosis values of HRCT in the swine sciatic nerve injures caused by high-speed triangular fragments.The swine lower limbs were detected with noncontrast 64-slice Volume CT and perfusion CT(PCT) in the pre-injured and 1h, 24h,48h after injured. The characteristics of MPR and 3D reconstruction of the normal swine sciatic nerves and injured by high-speed triangular fragments were analyzed. CT measurement parameters were compared with macroanatomy. The parameters of CT perfusion imaging include time-density curves (TDC), blood flow (BF), blood volume (BV), mean transit time (TT) and permeability surface (PS) of normal nerve were compared with muscle and adipose tissues. And those parameters were changed after high-speed triangular fragments injuries compared with macroanatomy and microscopy to investigate the relationships between CT findings and pathological changes.3. To investigate the characteristics and values of determination soft tissue of PCT after the swine sciatic nerve injures caused by high-speed triangular fragments.The regions of interest(ROI) of PCT were selected in perpendicular to the original wound tract 0-3mm (A zone), 5-8mm (B zone) and 10-13mm (C zone). The characteristics of TDC, BF, BV, MTT, PS at pre-injured, 1h, 24h and 48h after injured were observed. And these changes were compared with pathological changes in order to find early determination of sensitive and accurate soft tissues activity index.Results and Conclusions:1. A stability direct and indirect sciatic nerve injury model has been successfully established to fit the experiment requirements. The entrance area of wound tract caused by fragments was 30 times than the fragment itself. The local tissue damages of wound tract were severe, and the contusion zones and concussion zones were crisscrossed. Not only local tissues but also distant organs damaged severity. 64.2% of lungs were suffered which much higher than that caused by the standard bullet and steel ball. Although other organs had no obvious gross pathological injuries, the concentration of serum ALT, AST, CREA, Urea, CK and LDH were increased significantly at 1h after injured and the changes lasted for 48h after primary lower limb high-velocity triangular fragments injuries. Therefore, we should not simply judge the nerve damage if or not by point of impact in the surface projection of nerves. We should also pay more attention to internal organs function in order to prevention and cure complications.2. High disrupt rate,severe and wide extent lesion,intensive inflammatory reaction, earlier Wallerian degeneration and lower potentiality of independence renovation than others were the main characteristics of direct injuries in the swine's sciatic nerves caused by high-speed triangular fragments. Proximal CMAP and MCV decreased seriously or couldn't measured. The indirect injuries could induced pathologic and functional changes too. The lesion degrees were related to the distance between nerves and primary wound tract. The distal nerve CMAP decline appeared earlier. The changes of proximal CMAP were consistent with the pathological damages. The distal amplitude early changes reflected the rate and extent of Wallerian degeneration. Thus, the characteristics of electrophysiological changes at the early period are very specific. Electrophysiology is an available diagnostic tool for the early detection of nerve lesions by high-speed triangular fragments. But it could not discern the type of pathological lesion exactly.3. From piriformis to tibiofibular bifurcation of wine sciatic nerve can be clearly displayed on the same slice and its relationship with the surrounding tissues adjacent by multiplanar reconstruction. The three-dimensional reconstruction could display the spatial location relationship between the nerve and femoral or other important structures. The sciatic nerve parameters such as transverse diameter, anteroposterior diameter and cross-sectional area measured by CT were consistent with the gross anatomy (P>0.05). This study break the traditional view of CT could not be used for neural imaging and as the basis of diagnosis of neuropathy. Comprehensive use of HRCT three-dimensional reconstruction and MPR and other post-processing technology can provide multi-planar, multi-faceted and integrated nerve imaging, showing position relationship between nerves and wound tract, nerves transection, edema, adhesions, as well as nerve and adjacent tissue damage characteristics. It can provide richer information on firearms caused nerve damages, and improve the diagnostic accuracy rate, the choice of treatment for clinical reference.4. In normal swine sciatic nerves perfusion, TDC were low and flat or gently rising curves, mean CT value was -21.17±5.71HU, significantly higher than adipose and lower than muscle (P<0.01); BF value 2.54±1.24 ml/min/100g, significantly lower than muscle and adipose (P <0.01); BV value 0.88±0.25 ml/100g, significantly higher than adipose (P <0.01); MTT value 23.46±0.30S, much slower than muscle and adipose (P <0.01); PS value 1.71±0.52 ml/min/100g, significantly higher than adipose (P<0.01). The BF, BV, MTT and PS values were significantly different with the adipose and muscle tissues, which set the foundation of the neural recognition. At different time points after injured by high-speed triangular fragments, the TDC, BV, BF and PS value increased and MTT decreased in different degrees than pre-injured. The changes in magnitude were consistent with and the degree of pathological damage. The early specific changes of perfusion index of sciatic nerve after injured may be the basis of imaging category of nerve damages. The changes from the perspective of neural microcirculation reflect neuropathological damage. It provides a novel approach for the clinical diagnosis of nerve injuries.5. The characteristics of wound tract PCT imaging after swine hind leg injuries caused by high-speed triangular fragments were those: The TDC of the A, B and C zone vertical axis value all decreased sharply compared with pre-injured. A zone decreased most significantly which significant differences between the groups. The BF, BV, PS values of A zone declined significantly than pre-injured when B and C zone were increased significantly. This changes tips the capillary volume and flow decreased and function was reduced in A zone. MTT reduced significantly in all groups, without significant difference between them. Pathologically confirmed A, B, and C were corresponding contusion zone, coexistence zone and concussion zone. Muscles microcirculation changes alongside the wound tract after high-speed triangle fragments swine hind leg injury occurs early and sensitive. PCT can earlier monitor the soft tissue's activity through micro-perfusion situation, which prompted the degree of soft tissue activity. TDC, BF, BV, PS were important indexes in early discriminate soft tissue's activity.