Experimental Study Of Chronic Spinal Cord Injury And Surgical Treatment Of Thoracic Spinal Stenosis Using A Modified Transfacet Approach

Part1Experimental Study of Chronic Spinal Cord InjuryObjective:To produce an animal model of chronic spinal cord compress due to investigate the histopathological changes of the spinal cord and its mechanism.Methods:32rabbits which received choral hydrate5ml/Kg intraperitoneal injection anesthesia were randomly and blindly divided into three groups. The first group (the test group n=15) received the operation and the membranous sac was placed in Iumbar2epidural space, then the piston was gradually pushed to compress the spinal cord forward. The second group (the control group n=15) received the operation at the same site, but the piston wasn’t pushed to compress the spinal cord. The third group (normal group n=2) received the shame operation. The spinal cord blocks were cut in cross section10μm thick and stained with Nissl stain. TUNEL technique was used to mark the Apoptosis cells. The histopathological changes and the apoptosis cells were observed with Light microscope.We studied four enzymes by histochemistry and microphotometric determinations. The change of the activities of enzymes was observed under light microscope.Results:After5-7weeks, the first group animal’s low limb muscle strength was Ⅳ±grade according to the open field walking standard (OFW), hypesthesia following. Histopathological changes in the compressed blocks were observed as foliows.The T10cord block was crushed out of shape. Neuron atrophy,declined in the gray matter. The changes in the adjoining block were slight. The distal block’s changes were almost normal. The control group animals T10segment blocks histopathological changes were slight. The adjacent cord block’s changes were almost normal. TUNEL technique observation results:Large number of apoptosis glial cells were seen in the white matter in compressed blocks while apoptosis neuron were not seen in the gray matter. Apoptosis cells were less in the adjoining blocks than the compressed blocks (P<0.05). lactic dehydrogensase (LDH), acetylcholine esterase (AchE), adenosine triphosphatase (ATPase) were decreased in the compressed blocks(P<0.01), however, the phospholipase A2(PLA2) were increased to a higher level after spinal cord injury(P<0.01).Conclusion:1, mechanical compression can cause spinal cord neurons damage.2, the CSCI secondary lesion of mechanism may be related to apoptosis of nerve cells.3, the CSCI secondary lesion mechanism may be related to neural cells of LDH, AchE, ATP, PLA2activity are closely related.Part2Surgical Treatment of Thoracic Spinal Stenosis Using a Modified Transfacet ApproachBackground:The direct pathogenesy of Thoracic Spinal Canal Stenosis (TSS) is the blood circulation,sensory and motor conduction obstacles of thoracic spinal cord caused by things to press on it.It could be seen the most in clinical is the major degenerative changes as the main pathological.The main pathological factors caused TSS include Ossification of ligamentum flavum(OLF),ossification of posterior vertebral longitudinal ligament(OPLL), thoracic intervertebral disc herniation (thoracic disc herniation, TDH),etc.More than80%of thoracic myeloradiculopathy is now appreciated as OLF cause.Ossification of ligamentum flavum(OLF) is characterized by a heterotopic bone formation in the spinal ligamentum flavum that is normally composed of fibrous tissues.It has been reported more often in Asian populations,particularly in Japanese subjects.The incidence rate is as high as20%in Asian populations older than65years and the ratio of male to female subjects reported in the literature varies about2-4:1. In1912,LeDouble first found this kind of lesion when during the autopsy,but the disease was wrongly described as the vertebral plate hypertrophy or doubel vertebral plate structure for a long time.OLF can be seen in the cervical, thoracic and lumbar region,but it occur significantly more frequently in the lower thoracic region or the thoracic-lumbar junction.There have been confirmed that most people have thracic OLF,But Only a small of about5%OLF can compresses the spinal cord,resulting in serious neurological damages. Therefore,.Although en bloc laminectomy has been commonly used for treating the condition,the outcome of surgical treatment of thoracic OLF is not always satisfactory.Moreover,the delays of diagnosis,multilevel ossification and postoperative recurrence of ossification in the adjacent segment have a negative effect on functional recovery of the compressed spinal cord.There has been growing concern regarding OLF over the past two decades.Although numerous studies showed that systemic and local factors,including the genetic factors,mechanical stress,growth factors,cytokines,and the endocrine/metabolic abnormalities,were responsible for the pathogenesis of OLF,its precise pathogenesis has not been conclusively established. Histological studies in the OLF samples demonstrated that the ossific ligamentum flavum showed loss of elastic fibers and increase of collagen fibers,and the numerous fibrocartilaginous cells were observed within and around the ossification fronts,which supported this theory that the developmental mode of OLF was endochondral ossification.Immunohistochemical studies have also documented that osteogenesis cytokines,such as bone morphogenetic proteins(BMPs),transforming growth factor(TGF)-p,and the receptors of BMP(BMPRs) were localized around the ossification front.These causative factors could play a role in initiation of cellular events that ligamentum flavum(HLF)cells differentiate into chondrocytes and osteoblasts.There has been nearly50years since it was first reported in the year1960when Tsukimoto found this kind of lesion during the autopsy and demominated as OPLL in1964by Terayama. With the research going on, OPLL have been found in cervical thoracic and also lumbar segments in succession. Thoracic myelopathy caused by OPLL is rare compared to cervical OPLL. However, once myelopathy appears in patients with thoracic OPLL, it is progressive and often leads to serious paraplegia. Thoracic disc herniations (TDHs) are rarewhenly compared with those from either of cervical or lumbar discs. Their incidence has been reported to be between0.25%and0.75%of all disc herniations.1Although symptomatic TDH is much less likely to occur, its annual incidence has been estimated at approximately one patient per million population.TDHs affect men more frequently than women, with a peak age of40-50years.Most (75%) symptomatic TDHs involve the lower levels (from T8-9to T11-12) with the highest propensity at for T11-12.The most common symptoms of TSS include axial back pain,unsteady steps, zonesthesia of the abdomen and lower limbs, difficulty with balance and climbing stairs, the presence or absence of unilateral/bilateral neurogenic claudication, and bladder and bowel involvement are oberseved in the late stage disease. Physical examination of the lower extremities reveals both long tract signs and posterior column signs.Onset and progression of symptoms can range from several hours to several years and as many as25%of patients may experience complete absence of pain.The vagueness of patient clinical history, their chronic presentation, masqueradingother pathological processes, and their lack of pathognomonic symptoms may contributes to delays in diagnosis and treatment. However, new techniques in computed tomography (CT) and magnetic resonance imaging (MRI) have resulted in simpler earlier and more accurate diagnoses.Immediate surgical intervention and appropriate rehabilitation play important roles in improving the functional outcomes of patients with myelopathy caused by TSS. Surgical decompression is the most common treatment of choice for patients with compressive myelopathy due to TSS. However, the surgical outcome is not always satisfactory.The choice of surgical approach is predicatedon several factors which include the training and experienceof the surgeon, neurological symptoms, localizationand consistency of the herniated disc, presence of spinaldeformity, and presence of osteophytes [25]. Patient-relatedfactors such as body habitus and other medicalcomorbidities may also influence the choice of approach.The posterior laminectomy and spinal decompression as one of the most prevalent methods has significant effect in the treatment of multi-level of ossification of the ligamentum flavum. In recent years,accompanied with the clinical application of high speed burr and thin blade osteotome,laminar shelling decompression and Lamina osteotomy and replantation with miniplate fixation as the new surgical technical had applied in clinical to treat OFL. Each surgical procedure has its own characteristics and accompanied by a variety of inadequacies. The en bloc resection of laminae usually has the complications of dural tear, cerebrospinal fluid leakage and neurological deterioration. The multi-level laminectomy tends to occurring segmental instability and local kyphosis. Lamina osteotomy and replantation with miniplate fixation is relative complex, Surgical treatment for thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) has been recognized as technically demanding and results tend to be unfavorable. Until now, various operative approaches and treatment strategies have been attempted to conquer this problem, and the procedure of posterior decompression with transfacet approach through improved exposure and for segmental reconstructionmay be the optimal tactic to treat the anterior-posterior compression in one step. It is comparatively less traumatic and with less serious complications. The aim of this work was to evaluate the clinical effectand complications in a consecutive series of patients with symptomatic thoracic spinal stenosis undergoing decompression using a modified transfacet approach.Materials and Methods:33patients with thoracic stenosis were included in this study. Course duration of the disease was from12days to36months, with less than1month in13patients. Of these,15patients were diagnosed with simple thoracic disc herniation,6were associated with ossified posterior longitudinal ligament, and12with ossified or hypertrophied yellow ligament. A total of45discs were involved. All the herniated discs and the ossified posterior longitudinal ligaments were excised using a modified transfacet approach. Laminectomy and replantation were performed for patients with ossified or hypertrophied yellow ligament. The screw-rod system was used on both sides in14patients and on one side in19patients.Results:27patients were followed up from12to63months, with an average of37months. Epstein and Schwall grading system based on15patients were graded as excellent and based on10as good, whereas2were graded as improved and2as poor. Of the three patients with postoperative complications, two had exacerbated preexisting defects and one had implant failure. Postoperative computed tomography or magnetic resonance imaging showed that all patients had well fused replanted lamina and completely decompressed canal.Conclusion:Thoracic canal decompression using a modified transfacet approach can significantly improve the clinical outcomes.