Effects of repeated crush injuries on motor functional recovery of the sciatic nerve

What are the risk factors for complications after combined injury of the pelvic ring and acetabulum?

PURPOSE

Combined acetabular and pelvic ring injuries represent a unique subset of pelvic trauma and little is known regarding their complications and outcomes. We sought to further evaluate these injury patterns and quantify their outcomes.

METHODS

A retrospective review at a single level 1 trauma center was performed on all patients with operatively treated combined ring and acetabulum injuries during a seven-year period. Main outcome measurements include all-cause complication including residual neurologic deficit, deep infection, conversion to total hip arthroplasty, deep venous thrombosis and mortality.

RESULTS

Seventy operatively treated combined ring and acetabulum patients with one-year follow-up were reviewed. The overall complication rate was 44%. Hip dislocation occurred in 40% of the cohort and was significantly associated with residual neurologic deficit and all-cause complication. Angiography with embolization was not associated with an increased rate of deep infection. Open acetabular approaches had a significantly higher complication rate compared to percutaneous procedures. Delay to definitive fixation greater than 36 h trended toward but did not reach association with all complications.

CONCLUSION

Combined injuries to the acetabulum and pelvic ring have high rates of complications. No individual fracture patterns were identified as risk factors, but hip dislocation was associated with an increased rate of complications. When possible, percutaneous reduction and fixation of acetabular fractures and early definitive fracture fixation lead to lower rates of complications. Use of angiography with embolization appears to be safe and does not increase the risk of infection or other complications.

Exosomes from LPS-preconditioned bone marrow MSCs accelerated peripheral nerve regeneration via M2 macrophage polarization: Involvement of TSG-6/NF-κB/NLRP3 signaling pathway

Lipopolysaccharide (LPS)-preconditioned mesenchymal stem cells (MSCs) possessed strong immunomodulatory and anti-inflammatory functions by secreting exosomes as major paracrine effectors. However, the specific effect of exosomes from LPS pre-MSCs (LPS pre-Exos) on peripheral nerve regeneration has yet to be documented. Here, we established a sciatic nerve injury model in rats and an inflammatory model in RAW264.7 cells to explore the potential mechanism between LPS pre-Exos and peripheral nerve repair. The local injection of LPS pre-Exos into the nerve injury site resulted in an accelerated functional recovery, axon regeneration and remyelination, and an enhanced M2 Macrophage polarization. Consistent with the data in vivo, LPS pre-Exos were able to shift the pro-inflammation macrophage into a pro-regeneration macrophage. Notably, TNF stimulated gene-6 (TSG-6) was found to be highly enriched in LPS pre-Exos. We obtained si TSG-6 Exo by the knockdown of TSG-6 in LPS pre-Exos to demonstrate the role of TSG-6 in macrophage polarization, and found that TSG-6 served as a critical mediator in LPS pre-Exos-induced regulatory effects through the inhibition of NF-ΚΒ and NOD-like receptor protein 3 (NLRP3). In conclusion, our findings suggested that LPS pre-Exos promoted macrophage polarization toward an M2 phenotype by shuttling TSG-6 to inactivate the NF-ΚΒ/NLRP3 signaling axis, and could provide a potential therapeutic avenue for peripheral nerve repair.

Effects of exercise on muscle reinnervation and plasticity of spinal circuits in rat sciatic nerve crush injury models with different numbers of crushes

INTRODUCTION/AIMS

Motor function recovery is frequently poor after peripheral nerve injury. The effect of different numbers of nerve crushes and exercise on motor function recovery is unknown. We aimed to examine how different numbers of crushes of the rat sciatic nerve affects muscle reinnervation and plasticity of spinal circuits and the effect of exercise intervention.

METHODS

Single and multiple sciatic nerve crush models with different numbers of crushes were created in rats. Treadmill exercise was performed at 10 m/min for 60 min, five times a week. Muscle reinnervation and synaptic changes in L4-5 motor neurons were examined by immunofluorescence staining. Behavioral tests were the sciatic functional index (SFI) and the pinprick tests.

RESULTS

The percentage of soleus muscle reinnervation was not significantly increased by the presence of exercise in single or multiple crushes. Exercise after a single crush increased the contact of motor neurons with VGLUT1-containing structures (Exercised vs. Unexercised, 12.9% vs. 8.7%; P < 0.01), but after multiple crushes, it decreased with or without exercise (8.1% vs. 8.6%). Exercise after a single crush significantly improved SFI values from 14 to 24 days, and exercise after multiple crushes from 21 to 35 days (all P < 0.05). The pinprick test showed no difference in recovery depending on the number of crushes or whether or not exercised.

DISCUSSION

Different numbers of sciatic nerve crushes affect muscle reinnervation and motor neuron synaptic changes differently, but motor function recovery may improve with exercise regardless of the number of crushes. This article is protected by copyright. All rights reserved.

Effects of repeated transection and coaptation of peripheral nerves on axonal regeneration and motoneuron survival

BACKGROUND AND PURPOSE

Salvage procedures for facial reanimation can involve a second neurorrhaphy operation. It remains unclear whether reuse of the original donor nerve in the salvage procedure remains likely to produce successful outcome. This study aimed to investigate the effect of repeated transection and coaptation of a nerve on axonal regrowth and motoneuron survival.

MATERIALS AND METHODS

The sciatic nerves of Sprague Dawley rats were transected and microsutured once (the one-time group) or repeatedly at eight-week intervals (the repeated group), and the animals remained alive for eight weeks before sacrifice. The gastrocnemius muscle was weighed, and muscle fiber diameter was measured with hematoxylin-eosin staining. Axonal count of the distal nerve stump was calculated by toluidine blue staining. Myelin thickness and axonal diameter were analyzed by transmission electronic microscopy. Finally, motoneurons were retrogradely traced to the spinal cord using Fluoro-Gold.

RESULTS

Repeated coaptation of nerves resulted in significant decreases of the wet weight ratio of gastrocnemius and muscle fiber diameter. The axonal counts and myelin thicknesses of the distal stumps were comparable between the groups, whereas axonal diameter was significantly smaller after repeated injury. Additionally, retrograde tracing demonstrated significantly less motoneurons in the L4-L6 spinal segments of the repeatedly injured animals than that of the one-time group.

CONCLUSIONS

Compared with one-time nerve injury, repetitive transection and coaptation of nerves resulted in compromised axonal regeneration, motoneuron survival, and target muscle recovery. It is possible that the final functional outcome could also be compromised, and the patients should be counseled accordingly.

Effects of repeated nerve injuries at different time intervals on functional recovery and nerve innervation

Effects of repeated nerve injuries on functional recovery and nerve innervation were examined in rodents. Crush injuries of the sciatic nerve were inflicted on adult rats and repeated twice or thrice at different time intervals of 1, 2, 3, and 4 weeks. Motor function was assessed by the static sciatic index at 1, 7, 14, 21, 28, 35, 42, 49, and 56 days after the final crush. The rates of nerve innervation of the tibialis anterior muscle, a main muscle innervated by the common peroneal nerve, were evaluated by the quantification of βIII-tubulin-positive nerve terminals and α-bungarotoxin-positive acetylcholine receptors 21 and 56 days after the final crush of triple nerve injuries at 1-, 2-, 3-, and 4-week intervals. Compared with single nerve crush injury, delayed recovery of motor function was observed in repeated crush injuries. In addition, recoveries in the triple crush groups were slower than those in the double crush groups. The rates of reinnervation were lower in the triple crush groups than in the single crush groups, both at 21 days (single: 59.7%; triple: 54.1%-56.1%) and 56 days (single: 88.8%; triple: 72.5%-83.0%) after the final crush, except in the groups with 1-week (triple: 73.8%) and 2-week (triple: 70.5%) intervals at 21 days after the final crush. We concluded that the recovery of motor function was delayed according to the number of repetitions of crush injuries, and that the rates of nerve innervation were still low in the triple crush groups 8 weeks after the final crush.

Effect of graded nerve pressure injuries on motor function

OBJECT

The purpose of this study was to determine the minimum amount of nerve fibers required to maintain normal motor function after nerve injury in rats.

METHODS

The authors first confirmed that a common peroneal nerve injury caused more aggravating effects on lower limb motor function than tibial nerve injury, as assessed by the static sciatic index (SSI). Thereafter, rats were subjected to varying degrees of crush injury to the common peroneal nerve. At 48 hours after the injury, motor function was assessed using the SSI and slope-walking ability (with slope angles of 30° and 45°). The tibialis anterior muscle, a main muscle innervated by the common peroneal nerve, was removed. Muscle sections were co-labeled with neuronal class III β-tubulin polyclonal antibody to identify the presence of axons and Alexa Fluor 488-conjugated α-bungarotoxin to identify the presence of motor endplates.

RESULTS

The evaluation of neuromuscular innervation showed a correlation between SSI scores and ratios of residual axons (rs = 0.68, p < 0.01), and there was a statistically significant difference between slope-walking ability and ratios of residual axons (p < 0.01). Moreover, the ratios of residual axons in the nerve-crushed rats with normal motor function (SSI above -20) ranged from 36.5% to 88.7%, and those ratios in the success group with slope-walking angles of 30° and 45° ranged from 14.7% to 88.7% and from 39.8% to 88.7%, respectively.

CONCLUSIONS

In this study of rodents, less than half of the motor axons were sufficient to maintain normal motor function of the lower limb.

Correlation between motor function and axonal morphology in neonatally sciatic nerve-injured rats

The present study was conducted to investigate the correlation between motor function and axonal morphology in neonatally sciatic nerve-injured rats. The left sciatic nerve of newborn rats was transected or crushed, and functionality of the sciatic nerve was assessed by the static sciatic index after 8 weeks. After functional assessment, the common peroneal nerves in the control, nerve-transected, and nerve-crushed rats were removed and prepared for morphometric examinations. The cross-sectional area of the nerve, total number of myelinated axons, and size of each myelinated axon were analyzed for each group. The control rats showed normal motor function, whereas the nerve-transected rats showed severe motor dysfunction. The cross-sectional area of the nerve and total number of myelinated axons were reduced after nerve transection. Moreover, the percentage per size class of myelinated axons was almost uniform in the control rats, while the distribution was shifted to the left in the nerve-transected rats. Furthermore, no large myelinated axons were observed in the nerve-transected rats. The nerve-crushed rats showed various gait functions with various distribution patterns of axonal size, and the rats were divided into two groups with and without uninjured residual large axons. The results showed that the importance of regenerated medium-sized axons in cases without large axons and of residual large axons in cases with large axons in motor function. It was revealed that motor function was related closely to axonal size in neonatally nerve-injured rats.