Microdialysis of the spinal cord during thoracic aortic cross-clamping in a porcine model

OBJECTIVE: Utilising microdialysis to measure the changes of glucose, lactate, pyruvate and glutamate levels in the spinal cord after cross-clamping of the thoracic aorta in an established porcine model to monitor the degree of ischaemia. DESIGN: Experimental study with a porcine model. SETTING: University Hospital, Trondheim. SUBJECTS: Six pigs. MAIN OUTCOME MEASURE: Lactate, pyruvate and glutamate concentrations in the microdialysis perfusate from the spinal cord. RESULTS: A significant increase of the lactate-pyruvate ratio during the last 30 min of the 1 h clamping period, with a maximum increase of 169% from the basal value the last 10 min before declamping. No evident change in this ratio between the clamping and the reperfusion period. No significant change in glutamate levels during clamping or reperfusion period. CONCLUSION: Microdialysis reflects the ischaemic state of the spinal cord during cross-clamping of the thoracic aorta in pigs, and is well suited to study each phenomena.     

Labor epidural placement in a woman with a cervical spinal cord stimulator

A 37-year-old female, gravida 1 para 0, in active labor at term, with a cervical spinal cord stimulator in situ, presented for epidural analgesia for labor. She had received the cervical spinal cord stimulator some 30 months before, to treat chronic regional pain syndrome I. She was taking no medication, and was thin but otherwise healthy. The cervical spinal cord stimulator electrodes entered the C7-T1 interspace, and their end was in the epidural space at the C3 level. The electrodes were fixed to a cervical spinous process, crossed the midline high in the back and then went down the left side of her back parallel to her spine to the generator, which was in her buttock. The electrode cable could be felt high on the left side of her back, but not in her lumbar region. After consultation, it was felt safe and reasonable to proceed with labor epidural anesthesia. The procedure took place with the patient sitting, using a standard reusable 17-gauge Tuohy needle. Subsequent analgesia was acceptable. The patient also observed about 20 min after receiving the epidural medication that suddenly she could move her right hand more easily and that it felt warm. Her labor and delivery proceeded uneventfully. The spinal cord stimulator continued to function well throughout the entire process. She noticed that the feeling in her right hand returned to baseline after the delivery.     

Intrapleural placement of a thoracic epidural catheter in a patient with spinal stenosis

Due to the close proximity of the thoracic epidural space and parietal pleura, pleural puncture with intrapleural catheter placement is a potential complication of thoracic epidural anesthesia. The authors present a case of an obese patient with a history of spinal stenosis that underwent thoracotomy. Repeated failed attempts at epidural anesthesia were complicated by intrapleural placement of the catheter. The patient subsequently developed clinical signs of pneumothorax and required urgent thoracostomy.     

后路椎旁肌间隙入路治疗胸、腰椎结核

 目的 探讨经后路椎旁肌间隙外科技术治疗胸、腰椎结核的可行性并观察其临床疗效。方法 回顾性分析自2009年6月至2013年6月采用后路椎旁肌间隙外科技术治疗胸、腰椎结核29例：T_8,9结核2例,T_9,10结核6例,L_1,2结核8例,L_2,3结核10例,L_4,5结核3例。男12例,女17例;年龄28~53岁,平均40.78岁。9例患者伴有后凸畸形,Cobb角平均29.67°（19°~39°）,2例患者为结核术后复发,术前Frankel分级为C级。术前所有患者均规范口服异烟肼、利福平、吡嗪酰胺、乙胺丁醇、葡醛内酯2~4周。手术方法均采用经后路椎旁肌间隙入路,一期完成前方病灶清除,后方椎弓根钉内固定。记录手术时间、术中出血量、术后引流量;术后1周及末次随访时疼痛视觉模拟评分（visual analogue scale,VAS）、Cobb角变化,术后红细胞沉降率恢复正常所需时间,神经症状改善情况和植骨融合情况。结果 患者手术过程顺利,手术时间为3~4 h,平均3.3 h;手术出血量为300~600 ml,平均434 ml。手术后引流250~450 ml ,平均340 ml。所有患者均获得随访,平均16.56个月（6~36个月）。 X 线及CT重建复查无内固定松动,植骨融合。患者无窦道形成及结核复发,无内固定失效及相关并发症。术后平均4.22个月红细胞沉降率恢复正常;2例结核复发患者术前Frankel分级为C级,术后1例恢复至D级,1例E级;术后Cobb角平均为10.33°（9°~12°）,末次随访时为12.22°（11°~14°）。结论 经后路椎旁肌间隙入路一期行胸、腰椎结核清除加内固定术是可行、有效的,临床疗效满意。     

Triggered electromyographic threshold for accuracy of thoracic pedicle screw placement in a porcine model.

STUDY DESIGN: A porcine model of thoracic pedicle screw insertion was used to determine the effect of screw position on triggered electromyographic response. OBJECTIVE: To develop a model of intraoperative detection of misplaced thoracic pedicle screws. SUMMARY OF BACKGROUND DATA: Triggered electromyographic stimulation has been a valuable aid in determining appropriate placement of lumbar pedicle screws. The use of pedicle screws is increasing in the thoracic spine. Misplaced thoracic pedicle screws may have significant implications if the spinal cord is injured. This study was an attempt to determine whether the established lumbar model can be used for thoracic pedicle screws. METHODS: Five 120- to 150-lb domestic pigs had 85 pedicle screws placed bilaterally in the thoracic spine at each level from T6 to T15. Screws were inserted entirely in the pedicle (Group A). After removal of the medial pedicle wall, the screws were reinserted in the pedicle with no neural contact (Group B). The screws were then placed with purposeful contact with the neural elements (Group C). The screws were stimulated, eliciting an electromyographic response in the intercostal muscles for each instrumented level. The type of response noted was classified as either primary (response from appropriate nerve root), secondary (response at different root) or no response (response at different root, no response at appropriate root). RESULTS: Two hundred fifty responses were recorded. A primary response was noted in 72% of recordings. There was a relatively consistent decrease in the triggered electromyographic response from Group A (mean 4.15 +/- 1.80 mA) to Group C (mean 3.02 +/- 2.53 mA) screws (P = 0.0003). There was little difference in the response obtained from Group A to Group B (mean 4.37 +/- 2.48 mA) screws (P > 0.05). When a primary response was recorded, the mean threshold electromyographic response recorded was significantly lower than recordings with secondary and no response recordings (P < 0.05). CONCLUSION: Even though there was a consistent decrease between the A and C screws that was more definitively separated when a primary response was elicited, it was not possible to determine a cutoff trigger electromyographic level that would consistently differentiate intraosseous from epidural pedicle screw placement. Furthermore, this method could not differentiate screws clearly in the pedicle from screws with medial pedicle wall breakthrough. A more direct method of spinal cord monitoring must be established to provide the surgeon with early warning of the potential of neural injury in the placement of thoracic pedicle screws.     

Expandable cage placement via a posterolateral approach in lumbar spine reconstructions. Technical note

The authors describe a technique for inserting an expandable cage via a posterior extracavitary approach while protecting the segmental nerves. The advent of expandable cages has allowed the use of a less invasive anterior access to the spine, thereby decreasing the surgery-induced insult to the patient. In an attempt to minimize this trauma, the authors have used a posterolateral approach that has allowed them to perform neural decompression, anterior reconstruction with an expandable cage, and posterior stabilization with posterior pedicle screws. The authors describe their surgical technique of posterior circumferential decompression, which entails the use of an expandable cage that is inserted at 90 degrees, rotated in place where the corpectomy has been performed, and then expanded with special custom-made tools, thus respecting the segmental nerves of the lumbar spine. One case example is provided to illustrate the technique.     

Evolution of spinal cord injury in a porcine model of prolonged aortic occlusion

BACKGROUND: Spinal cord injury and subsequent paraplegia remains an unpredictable and devastating complication of thoracoabdominal aortic surgery. The aim of this study was to investigate spinal cord injury due to prolonged thoracoabdominal aortic occlusion. MATERIALS AND METHODS: We used a highly reproducible porcine model of 45-min thoracoabdominal aortic occlusion, which was accomplished by two balloon occlusion catheters. Neurological evaluation after the end of experiment was performed by an independent observer according to the Tarlov scale. The lower thoracic and lumbar spinal cords were harvested at 10, 48, and 120 h (n = 6 animals per time point) and examined histologically with hematoxylin and eosin (H&E) stain and TUNEL method. Tarlov scores, number of neurons, and the grade of inflammation were analyzed. RESULTS: H&E staining revealed reduction in the number of motor neurons which occurred in two phases (between 0 and 10 h and between 48 and 120 h of reperfusion), as well as development of inflammation in spinal cord sections during the reperfusion period, reaching a peak at 48 h. TUNEL reaction was negative for apoptotic neurons at any time point. CONCLUSIONS: In this porcine model, we demonstrated that, after 45 min of thoracoabdominal aortic occlusion, motor neuron death seems to occur in two phases (immediate and delayed). Inflammation was a subsequent event of transient prolonged spinal cord ischemia and possibly a major contributor of delayed neuronal death. Using TUNEL straining we found no evidence of neuronal apoptosis at any time point of reperfusion.     

单侧入路显微内镜椎管减压术治疗腰椎管狭窄症

目的采用前瞻性对比研究评价单侧入路显微内镜椎管减压术治疗腰椎管狭窄症的安全性及疗效。方法 2006年5月-2009年6月,收治79例椎管狭窄症患者,随机分为两组:A组37例采用常规后路开窗减压术,B组42例采用单侧入路显微内镜椎管减压术治疗。两组患者性别、年龄、病程、狭窄节段等一般资料比较差异无统计学意义(P>0.05),具有可比性。采用疼痛视觉模拟评分(VAS)及Oswestry功能障碍指数(ODI)比较两组患者术后症状缓解情况,使用ODI改善率评定手术临床疗效,并对两组手术时间、术中出血量以及围手术期并发症进行对比。结果两组均顺利完成手术,A组手术时间(75.0±25.7)min,术中出血量(140.3±54.8)mL,术后引流量(46.5±19.7)mL;B组分别为(50.4±18.2)min、(80.2±35.7)mL、(12.7±5.3)mL;两组比较差异均有统计学意义(P<0.05)。两组患者切口均Ⅰ期愈合。79例均获随访,随访时间12～39个月,平均16个月。A组5例发生并发症,1例为椎间隙感染,经保守治疗后痊愈;4例为术后腰椎不稳,经腰椎间融合联合脊柱内固定治愈。B组2例发生并发症,均为镜下硬膜小孔样撕裂脑脊液漏,行相应处理后治愈;随访时未发现腰椎不稳。两组术前VAS评分及ODI比较差异均无统计学意义(P>0.05);术后早期及末次随访时较术前均有明显改善(P<0.05)。B组术后24 h的VAS评分及术后1个月的ODI均较A组降低(P<0.05),末次随访时两组间差异无统计学意义(P>0.05)。末次随访时根据ODI改善率得出的手术临床效果,A组优良率为89.2%,B组为92.9%,两组比较差异无统计学意义(χ2=0.896,P=0.827)。结论相比后路开放手术,单侧入路显微内镜椎管减压术手术损伤小、术后恢复好,具有更好的早期临床效果,是治疗腰椎管狭窄的有效方法之一。     

Transdural herniation of the thoracic spinal cord: untethering via a posterolateral transpedicular approach. Report of three cases

Anterior spinal cord herniation is a well-documented condition in which the thoracic cord becomes tethered within a defect in the anterior dura mater. Typical procedures have involved a posterior approach with direct manipulation of the thoracic cord to expose and blindly release its point of tethering. The authors report three cases in which a novel approach for the treatment of anterior thoracic cord herniation was performed, cord manipulation and traction are minimized, and direct dural repair of the defect is performed.     

An animal model of epidural compression of the spinal cord

A new model of subacute compression of the spinal cord is described. Using an expanding epidural mass, a gradual, progressive, and highly reproducible neurological deficit was induced in rats over a 7-day period, resulting in paraplegia. Studies of spinal cord edema, disruption of the blood-spinal cord barrier, and somatosensory evoked responses, as well as histopathological and microangiographical studies, revealed a marked similarity to changes produced in other spinal compression models and in humans. The model may serve to answer some fundamental questions regarding the pathophysiology and efficacy of various treatment modalities of spinal cord compression.