Brain-derived neurotrophic factor is up-regulated in severe acute cauda equina syndrome dog model.

To determine the level of brain-derived neurotrophic factor (BDNF) in experimental dog model of severe acute cauda equina syndrome, which was induced by multiple cauda equina constrictions throughout the entire lumbar (L), sacral (S) and coccygeal (Co) spinal cord and their central processes of the dorsal root ganglia neurons. Adult male mongrel dogs were randomly divided into 2 groups. The experiment group (n=4) was subjected to multiple cauda equina constrictions. The control group (n=4) was subjected to cauda equina exposure without constrictions. Level of BDNF in the spinal cord and the dorsal root ganglion cells (L7, S1-S3) was assessed 48 hours after multiple constrictions by immunohistochemical and histopathological analyses. 48 hours after multiple constrictions of cauda equina, up-regulation of BDNF within lumbosacral (L7-S3) spinal cord and dorsal root ganglion was observed in experimental group as compared to control group. Our result suggests that BDNF might play a role in the inflammatory and neuropathic pain as a result of multiple cauda equina constrictions. Regulation of BDNF level could potentially provide a therapy for treating cauda equina syndrome.

[Biomechanical performance of different wires and cable fixation devices in posterior instrumentation for atlantoaxial instability].

OBJECTIVE: To compare the biomechanical performances of different wires and cable fixation devices in posterior instrumentation for atlantoaxial instability, and test the effect of different fixation strengths and fixation approaches on the surgical outcomes. METHODS: Six specimens of the atlantoaxial complex (C0-C3) were used to establish models of the normal complex, unstable complex (type II odontoid fracture) and fixed complex. On the wd-5 mechanical testing machine, the parameters including the strength and rigidity of anti-rotation, change and strength of stress, and stability were measured for the normal complex, atlantoaxial instability complex, the new type titanium cable fixation system, Atlas titanium cable, Songer titanium cable, and stainless wire. RESULTS: The strength and rigidity of anti-rotation, change and strength of stress, stability of flexion, extension and lateral bending of the unstable atlantoaxial complex fixed by the new double locking titanium cable fixation system were superior to those of the Songer or Atlas titanium cable (P<0.05) and medical stainless wire (P<0.05). Simultaneous cable fastening on both sides resulted in better fixation effect than successive cable fastening (P<0.05). Better fixation effect was achieved by fastening the specimen following a rest (P<0.05). CONCLUSIONS: The fixation effects can be enhanced by increased fastening strengths. The new type double locking titanium cable fixation system has better biomechanical performance than the conventional Songer and Atlas titanium cables. Fastening the unstable specimens after a rest following simultaneous fastening of the specimen on both sides produces better fixation effect.

Preparation and biocompatibility evaluation of apatite/wollastonite-derived porous bioactive glass ceramic scaffolds.

An apatite/wollastonite-derived (A/W) porous glass ceramic scaffold with highly interconnected pores was successfully fabricated by adding a plastic porosifier. The morphology, porosity and mechanical strength were characterized. The results showed that the glass ceramic scaffold with controllable pore size and porosity displayed open macropores. In addition, good in vitro bioactivity was found for the scaffold obtained by soaking it in simulated body fluid. Mesenchymal stem cells (MSCs) were cultured, expanded and seeded on the scaffold, and the adhesion and proliferation of MSCs were determined using MTT assay and environmental scanning electron microscopy (ESEM). The results revealed that the scaffold was biocompatible and had no negative effects on the MSCs in vitro. The in vivo biocompatibility and osteogenicity were investigated by implanting both the pure scaffold and the MSC/scaffold construct in rabbit mandibles and studying histologically. The results showed that the glass ceramic scaffold exhibited good biocompatibility and osteoconductivity. Moreover, the introduction of MSCs into the scaffold observably improved the efficiency of new bone formation, especially at the initial stage after implantation. However, the glass ceramic scaffold showed the same good biocompatibility and osteogenicity as the hybrid one at the later stage. These results indicate that porous bioactive scaffolds based on the original apatite-wollastonite glass ceramic fulfil the basic requirements of a bone tissue engineering scaffold.

[Anti-rotation biomechanical study of wire and various cable system in the posterior brooks instrumentation for atlantoaxial instability].

OBJECTIVE: To compare the anti-rotation biomechanical performances of wire and various cable fixation devices currently used in the posterior Brooks instrumentation for atlantoaxial instability. METHODS: In this experiment,six specimens of the atlantoaxial complex (Occipital-C3) were used. The models of the normal complex,unstable complex (type II odontoid fracture) and fixed complex were established. On the WD-5 mechanics experimental machine,the parameters including the strength and rigidity of anti-rotation were quantified for the normal complex (group N),the atlantoaxial instability complex (group M), the new type Titanium cable (group A), Atlas titanium cable (group B), Songer Titanium cable (group C), stainless wire(group D). RESULTS: The max strength of A, B, C, D groups was 12.5, 11.3, 11.52, 11.55 N x m respectively, the max rigidity was 58.81, 53.17, 54.11, 54.35 N x cm/deg respectively. The strength and rigidity of anti-rotation, compare to the unstable atlantoaxial complex which were fixed by the new double locking Titanium cable fixation system were superior to those of normal complex, instability complex, Songer or Atlas Titanium cable (P < 0.05). CONCLUSION: Having been changed the locking method, the anti-rotation biomechanical characteristics of the new type double locking Titanium cable fixation system are superior or similar to the traditional Songer or Atlas Titanium cable.

[Treatment of bilateral cervical facet dislocation by reduction through anterior distraction].

OBJECTIVE: To investigate the effect of reduction through anterior distraction in treatment of bilateral cervical facet dislocation. METHODS: Twenty-one patients with bilateral cervical facet dislocation underwent leverage reduction through anterior distraction, interbody fusion, and internal fixation. Follow-up lasted 16 months (4 months to 5 years). RESULTS: All of the 21 patients got reduction of cervical facet dislocation and bony fusion. The neurological deficiency in 4 of the 21 patients improved. CONCLUSION: Simple and safe, reduction through anterior distraction is effective in treatment of bilateral cervical facet dislocation with reliable fusion.

[The biomechanical study of craniovertebral junction fixation with posterior transarticular screw].

OBJECTIVE: To evaluate the stability of biomechanics of occipitoatlantoaxial reconstruction with transarticular screw fixation. METHODS: Twelve fresh human cadaveric occipitocervical spine specimens were mounted in a custom-designed, spine-testing machine that applied pure moments while recording the three-dimensional angular movement at occiput (Oc)-C(1) and C(1 - 2) segments. The specimens were tested under seven different conditions: the intact (intact group), the occipitoatlantoaxial instability (Destabilized group), fixation with Ti-cable plus bone graft group (cable + graf group), fixation with the transarticular fixation (CTS group), fixation with SUMMIT occitocervical spinal fixation system (SUMMIT group), fixation with transarticular screw plus bone graft (CTS + graf group), and fixation with SMMIT system and plus graft group (SUMMIT + graf group). The data obtained were statistically analyzed. RESULTS: The CTS group reduced motion to well within the normal rang. In the Oc-C(1) segment, The CTS group and SUMMIT group allowed a very small rang of motion (ROM) and neutral zone (NZ) during lateral bending and axial rotation. The ROM and NZ during flexion and extension of the SUMMIT group, were significantly smaller than those of cable + graf group and CTS group (6.64 degrees +/- 0.59 degrees, 2.49 degrees +/- 0.26 degrees, 0.50 degrees +/- 0.03 degrees, 0.21 degrees +/- 0.01 degrees, 0.27 degrees +/- 0.07 degrees, 0.13 degrees +/- 0.01 degrees vs 10.01 degrees +/- 1.26 degrees, 3.80 degrees +/- 0.79 degrees, 7.93 degrees +/- 1.34 degrees, 3.18 degrees +/- 0.95 degrees, 9.54 degrees +/- 0.87 degrees, 5.93 degrees +/- 0.74 degrees, P < 0.05). In the C(1 - 2) segment, ROM and NZ in all directions of CTS group were smaller in rotation than SUMMIT group (1.64 degrees +/- 0.39 degrees, 0.61 degrees +/- 0.15 degrees, 0.14 degrees +/- 0.05 degrees, 0.02 degrees +/- 0.01 degrees, 0.32 degrees +/- 0.04 degrees, 0.08 degrees +/- 0.01 degrees, vs 0.21 degrees +/- 0.04 degrees, 0.07 degrees +/- 0.03 degrees, 0.21 degrees +/- 0.12 degrees, 0.10 degrees +/- 0.02 degrees, 2.92 degrees +/- 0.28 degrees, 1.27 degrees +/- 0.11 degrees, all P < 0.05). There was no significant difference in ROM and NZ in all directions between CTS + graf group and SUMMIT + Graf group (P > 0.05). CONCLUSION: In vivo biomechanics studies show that posterior occipitocervical transarticular fixation has unique features in reconstructing dynamic stability of the occipitoatlantoaxis, especially in controlling stability of rotation and lateral flexion, thus ensuring successful fusion of the implanted bone and allowing for clinical use of the technique.

[Changes of motor evoked potentials after spinal cord injuries in rats].

AIM: Study on the relationship between the degraded spinal cord injuries and the changes of the motor evoked potentials (MEP) to prove the diagnosis and prognosis value of MEP. METHODS: After injury at T8-T9 cord using modified Allen's weight-drop method, 27 male SD rats were divided randomly into control group (n = 5), group A (50 gcf, n = 8), group B (70 gcf, n = 8) and group C (100 gcf, n = 6). MEPs elicited by monopolar transcortical stimulation were recorded continuously before injury, just after injury, 15 minutes, 1 hour, 3 hours and 6 hours after injury. The rate of the size of the bleeding or necrosis area to the total cord was also calculated. RESULTS: MEP had no significant change in the control group. The amplitude of MEP's early components in group A or group B decreased or even obliterated after SCI, and then partially recovered, while the late components were lost without any recovery signals. All animals in group C showed no MEP waves excepting 2 rats had recovery signals. The size of the cord injuries area increased according to the dropping force and was correlated significantly with the amplitude of the largest peaks of scMEP 1 hour after SCI (r = -0.821). CONCLUSION: The scMEP changes after SCI are correlated with the injury forces and the pathological changes in the cord, which indicates that scMEP can be used as an objective index for the cord functional monitoring.