Biomechanical study of the spinal cord in thoracic ossification of the posterior longitudinal ligament

Background

Ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine produces myelopathy. This is often progressive and is not affected by conservative treatment. Therefore, decompressive surgery is usually chosen.

Objective

To conduct a stress analysis of the thoracic OPLL.

Methods

The three-dimensional finite element spinal cord model was established. We used local ossification angle (LOA) for the degree of compression of spinal cord. LOA was the medial angle at the intersection between a line from the superior posterior margin at the cranial vertebral body of maximum OPLL to the top of OPLL with beak type, and a line from the lower posterior margin at the caudal vertebral body of the maximum OPLL to the top of OPLL with beak type. LOA 20°, LOA 25°, and LOA 30° compression was applied to the spinal cord in a preoperative model, the posterior decompressive model, and a model for the development of kyphosis.

Results

In a preoperative model, at more than LOA 20° compression, high stress distributions in the spinal cord were observed. In a posterior decompressive model, the stresses were lower than in the preoperative model. In the model for development of kyphosis, high-stress distributions were observed in the spinal cord at more than LOA 20° compression.

Conclusions

Posterior decompression was an effective operative method. However, when the preoperative LOA is more than 20°, it is very likely that symptoms will worsen. If operation is performed at greater than LOA 20°, then correction of kyphosis by fixation of instruments or by forward decompression should be considered.     

Surgical outcome of ossification of the posterior longitudinal ligament (OPLL) of the thoracic spine: implication of the type of ossification and surgical options

OBJECTIVE: Ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine produces myelopathy through anterior spinal cord compression that is usually progressive and unaffected by conservative treatment. Therefore, early decompressive surgery is imperative. However, decompression surgery of thoracic myelopathy is difficult, and the outcome is often poor. A retrospective study was conducted to investigate the surgical outcome of 21 patients with thoracic OPLL to evaluate which type of surgical approach is better and which type of thoracic OPLL results in a better surgical outcome. METHODS: A total of 21 patients with thoracic OPLL (10 men and 11 women; mean age 54 years), who underwent surgical treatment at our department from March 1985 to October 2000, were included in the study. Seven patients exhibited the flat-type OPLL and underwent either anterior decompression and fusion (one patient), anterior decompression via a posterior approach (three patients), or expansive laminoplasty (three patients). Fourteen patients exhibited the beak-type OPLL and also underwent either anterior decompression and fusion (two patients), anterior decompression via a posterior approach (six patients), or expansive laminoplasty (six patients). RESULTS: Regarding of operative time and blood loss, there were no marked differences between the two types of OPLL, regardless of the type of surgical procedure; anterior decompression and fusion and anterior decompression via a posterior approach yielded longer operative times and larger blood loss volumes than expansive laminoplasty. Concerning clinical outcome, there were five cases of neurologic deterioration. All of the five deteriorated cases were of the beak-type OPLL treated by a posterior approach. Two of these patients were treated with expansive laminoplasty. CONCLUSIONS: There were five instances of neurologic deterioration in our thoracic OPLL series, and all of them exhibited beak-type OPLL. In the beak-type OPLL, a subtle alteration in the spinal alignment during posterior decompression procedures may increase spinal cord compression, leading to the deterioration of symptoms. A potential increase in kyphosis following laminectomy should be avoided by fixation with a temporary rod. If intraoperative monitoring suggests spinal cord dysfunction, an anterior decompression procedure should be attempted as soon as possible.     

Circumspinal decompression for thoracic myelopathy due to combined ossification of the posterior longitudinal ligament and ligamentum flavum

Ossification of the posterior longitudinal ligament (OPLL) combined with ossification of the ligamentum flavum (OLF) in the thoracic spine can result in serious myelopathy, leading to circumferential compression of the spinal cord in advanced stages of the disease. The authors performed circumspinal decompression (circumferential decompression of the spinal cord) on these patients. This operation consists of two steps: posterior and lateral decompression of the spinal cord by removal of the OLF (first step) and anterior removal of the OPLL for anterior decompression (second step), followed by interbody fusion. In the first step, two deep parallel gutters, covering the extent of the OPLL to be removed anteriorly, are drilled down from the rear into the vertebral body along both sides of the dura to easily and safely remove the OPLL anteriorly at the second step. In the second step, the surgical approach varies according to the affected level; costotransversectomy in the upper thoracic spine and standard thoracotomy in the middle or lower thoracic spine. According to the authors, circumspinal decompression is not an easy procedure, but from their results in 10 patients, they identify it as a radical and promising surgical procedure.     

Total decompression of the spinal cord for combined ossification of posterior longitudinal ligament and yellow ligament in the thoracic spine

Summary One of the causes of hyperostosis in the spinal canal, ossification of the posterior longitudinal ligament (OPLL) combined with ossification of the yellow ligament (OYL) in the thoracic spine, can result in serious myelopathy, leading to sandwich-type compression of the spinal cord from anterior and posterior. For such cases we devised a treatment of total decompression of the spinal cord and intervertebral body fusion. This operation consists of two steps. The first step is designed for posterior and lateral decompression of the spinal cord by removal of the OYL following wide laminectomy. The second step is removal of the OPLL anteriorly for anterior decompression, followed by interbody fusion. As the final procedure of the first step, two deep parallel gutters, covering the extent of the OPLL to be removed anteriorly, are drilled down from the rear into the vertebral body along both sides of the dura. This pretreatment makes removal of the OPLL anteriorly during the second stage much easier, faster, and safer. This operation is lengthy and demanding. However, based on our experience so far, it appears to be a promising surgical procedure.

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Zusammenfassung Die Verknöcherung des Ligamentum longitudinale posterius (OPLL) in Kombination mit der Verknöcherung des Ligamentum flavum (OYL) am Brustwirbel, die als eine Erkrankung der Wirbelkanal-hyperostose genannt wird, kann schwere Myelopathie verursachen, die zur Sandwich-Abdrückung des Rückenmarks von der Vorder- und Rückseite aus kommt. Für diesen Fall haben wir uns eine totale Druckentlastungstechnik des Rückenmarks und eine Spondylosynthese (spinal fusion) des Wirbelkörpers ausgedacht. Diese Operationstechnik besteht aus zwei Stufen. Die erste Stufe zielt auf die vordere und laterale Druckentlastung des Rückenmarks, die mit Entfernung des OYL nach der umfangreichen Laminektomie erreicht werden kann. Die zweite Stufe ist die vordere Entfernung des OPLL für vordere Druckentlastung, die durch die Spondylosynthese des Wirbelkörpers erreicht werden kann. Als letztes Verfahren der ersten Stufe werden zwei parallele tiefe Furchen, die bis an den Bereich des OPLL reichen, mit dem Drillbohrer von der Rückseite in den Wirbelkörper entlang den beiden Seiten des dura mater spinalis gebohrt. Diese Vorbehandlung macht die Entfernung des OPLL von stirnseitiger Richtung aus bei der zweiten Stufe noch leichter, schneller und sicherer. Diese Operation nimmt viel Zeit in Anspruch. Jedoch scheint es uns nach unseren vorliegenden Erfahrungen, daß these Operation ein vielversprechendes Verfahren sei.

     

Cervical ossification of the posterior longitudinal ligament: Biomechanical analysis of the influence of static and dynamic factors

Objective

Cervical myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is induced by static factors, dynamic factors, or a combination of both. We used a three-dimensional finite element method (3D-FEM) to analyze the stress distributions in the cervical spinal cord under static compression, dynamic compression, or a combination of both in the context of OPLL.

Methods

Experimental conditions were established for the 3D-FEM spinal cord, lamina, and hill-shaped OPLL. To simulate static compression of the spinal cord, anterior compression at 10, 20, and 30% of the anterior–posterior diameter of the spinal cord was applied by the OPLL. To simulate dynamic compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction. To simulate combined static and dynamic compression under 10 and 20% anterior static compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction.

Results

The stress distribution in the spinal cord increased following static and dynamic compression by cervical OPLL. However, the stress distribution did not increase throughout the entire spinal cord. For combined static and dynamic compression, the stress distribution increased as the static compression increased, even for a mild range of motion (ROM).

Conclusion

Symptoms may appear under static or dynamic compression only. However, under static compression, the stress distribution increases with the ROM of the responsible level and this makes it very likely that symptoms will worsen. We conclude that cervical OPLL myelopathy is induced by static factors, dynamic factors, and a combination of both.     

经后路脊柱前中柱次全切三柱重建治疗严重胸腰椎爆裂骨折

目的 探讨后路脊柱前中柱次全切三柱重建术治疗严重胸腰椎爆裂骨折的临床价值.方法 对36例严重胸腰椎爆裂骨折行此手术.采用ASIA分级对神经功能评估.比较术前、术后及末次随访时伤椎前缘压缩率、脊柱局部Cobb角、椎管矢状径侵占率,评估复位、减压及融合情况.结果 术后血气胸、脑脊液漏各1例,均治愈.平均随访17.8个月,无其他并发症.神经功能除A级外均有1～2级的恢复.伤椎前缘压缩率、脊柱局部Cobb角、椎管矢状径侵占率术后及末次随访时较术前有统计学差异(P＜0.05),末次随访时较术后无明显变化(P＞0.05).结论 该手术创伤小、并发症少、减压彻底,能有效重建脊柱三柱结构,防止复位丢失及内固定失败,是治疗严重胸腰椎爆裂骨折的理想手术方式.     

Anterior decompression via a wide transvertebral approach and a ceramic insert in a patient with cervical degenerative disease

BACKGROUND: The transvertebral approach is useful for decompression in patients with cervical radiculopathy; because the intervertebral disk is preserved, moveability is retained. We performed wide deletion of the vertebral body to increase the patient population eligible for treatment with this approach and include patients with compression of the cervical spinal cord. METHODS: In patients undergoing anterior decompression, we performed vertebrotomy (13 x 8 mm) at the midline of the cervical vertebral body at the upper level using a surgical saw. The resulting hole facilitates decompression of the cervical cord and nerve root; a ceramic insert is introduced in the area of deletion. To prevent graft extrusion, the bilateral wings of the bone graft are fastened with bioabsorbable screws. RESULTS: We used this approach in 163 patients with several cervical diseases. Collapse of the vertebral body and fusion of the operated intervertebral disk were encountered in only 1 patient (0.61%). There was no significant difference between pre- and postoperative alignment. Reoperation was required in 7 patients whose symptoms did not improve, in 1 with disk hernia, in 5 with severe spondylosis, and in 1 with combined-type OPLL. CONCLUSIONS: Although this approach is appropriate in patients undergoing cervical anterior decompression, the narrowness of the visual field may result in insufficient decompression, and its indication is restricted to patients with cervical disk hernia, mild cervical spondylosis, and segmental OPLL. In patients with segmental instability, continuous or combined OPLL, severe cervical spondylosis, and kyphosis, this approach should not be used.     

Spinal canal size in ossification of the posterior longitudinal ligament of the cervical spine

BACKGROUND: The size of the spinal canal is a factor that contributes to the neurologic deficits associated with cervical ossification of the posterior longitudinal ligament (OPLL). METHODS: Bone-window computed tomography (CT) examinations of the cervical spine in 64 patients with cervical OPLL were reviewed. Forty-two patients underwent surgical treatment (anterior decompression: 16 patients, posterior decompression: 26 patients). The remaining 22 patients were managed conservatively. Selection of the surgical approach, anterior or posterior, was based on the longitudinal extent of cord compression. RESULTS: The mean developmental size of the spinal canal in the posterior decompression group (10.7 mm at C4) was significantly smaller than the other 2 groups. The spinal canal was narrowed by OPLL to 2.9 to 10.0 mm. The proportion of the patients showing motor deficits of the lower extremities significantly increased when the sagittal canal diameter was narrowed to less than 8 mm. CONCLUSIONS: This study demonstrates critical values of CT-determined spinal canal stenosis. Developmental size of the spinal canal and the residual anterior-posterior canal diameters resulting from OPLL spinal cord compression are important factors influencing clinical management and the neurologic state.     

Cervical spine lateral approach for myeloradiculopathy: technique and pitfalls

BackgroundThe authors describe the rationale of cervical spine lateral approach technique to manage spondylotic myeloradiculopathy with its advantages, disadvantages, complications, and pitfalls.MethodsThe cervical lateral approach could be indicated to treat spondylotic myeloradiculopathy where anterior compression is predominant and the spine is straight or kyphotic without instability.ResultsUsing the present approach the lateral aspect of the cervical spine is easily reached and the vertebral artery is well controlled. The lateral part of the pathological intervertebral discs, uncovertebral joints, vertebral bodies and posterior longitudinal ligament are removed as necessary and decompression tailored to each patient to completely free the nerve roots and/or spinal cord.ConclusionThe cervical lateral multilevel corpectomy/foraminotomy technique allows wide anterior decompression of the spinal cord and complete unilateral nerve root decompression preserving spinal stability and physiological spinal motion.     

Management of thoracic myelopathy caused by ossification of the posterior longitudinal ligament combined with ossification of the ligamentum flavum—a retrospective study

Background contextOssification of the posterior longitudinal ligament (OPLL) or ossification of the ligamentum flavum (OLF) is being increasingly recognized as a cause of thoracic myelopathy and is relatively common in the Japanese population and literature. However, no series of OPLL combined with OLF has been previously published. Many different surgical procedures have been used for the treatment of thoracic OPLL or OLF. However, the possibility of postoperative paraplegia remains a major risk, and consistent protocols and procedures for surgical treatment of thoracic OPLL combined with OLF have also not been established.PurposeTo compare the effect of thoracic myelopathy treatment and safety of posterior decompression with or without instrumented fusion and circumferential spinal cord decompression via a posterior approach in Chinese patients of OPLL combined with OLF at a single institution.Study designThis retrospective clinical study of 31 cases was conducted to investigate the clinical outcomes of three kinds of surgical procedures for thoracic myelopathy caused by OPLL combined with OLF in Chinese population.Patient sampleProcedure was performed in 31 patients.Outcome measuresNeurologic status was evaluated using the Japanese Orthopaedic Association (JOA) score and Hirabayashi recovery rate before and after surgery.MethodsA total of 31 patients who underwent surgery for thoracic OPLL combined with OLF were classified into three groups: posterior decompression group (13 patients); circumferential decompression group (seven patients), which included four who underwent extirpation and the other three underwent the floating procedure; and posterior decompression and fusion group (11 patients), all of whom underwent laminectomy with posterior instrumented fusion. In each group, JOA score was used to evaluate thoracic myelopathy, and Hirabayashi recovery rate was calculated 1 year after surgery and at final examination.ResultsMean recovery rate at the final follow-up was 46.5% in the posterior decompression group, 65.1% in the circumferential decompression group, and 62.7% in the posterior decompression and fusion group. Postoperative paralysis occurred in three patients in the posterior decompression group, one in the circumferential decompression group, and one in the posterior decompression and fusion group. In the circumferential decompression group, leakage of cerebrospinal fluid occurred in four patients. Urinary tract infection occurred in two patients, and superficial wound disruption occurred in one patient. Late neurologic deterioration occurred in four patients in the posterior decompression group. There were no cases of postoperative paralysis or late neurologic deterioration in the posterior decompression and fusion group.ConclusionsThoracic OPLL combined with OLF is an uncommon cause of myelopathy in the Chinese population. It can present acutely after minor trauma. A considerable degree of neurologic recovery was obtained by posterior decompression with instrumented fusion, despite the anterior impingement of the spinal cord by the remaining OPLL. In addition, the rate of postoperative complications was low with this procedure. We consider that one-stage posterior decompression and instrumented fusion be selected for patients in whom the spinal cord is severely damaged before surgery and/or when circumferential decompression is associated with an increased risk.     

Transient paraparesis after laminectomy for thoracic ossification of the posterior longitudinal ligament and ossification of the ligamentum flavum

STUDY DESIGN: Case report. OBJECTIVES: To report a case with thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF), in which postoperative paralysis occurred after laminectomy and was reversed after an additional posterior instrumented fusion. SETTING: A University Hospital in Japan. CASE REPORT: A 71-year-old woman, with a spastic palsy of both lower extremities, had OPLL and OLF at T10-T11, which pinched the spinal cord anteriorly and posteriorly. She underwent a laminectomy at T10-T11, and no further neurological deterioration was seen immediately after surgery. Over the next 18 h, however, myelopathy worsened, showing severe paraparesis. An additional posterior instrumented fusion at T7-L1 was performed without correction of the kyphosis. After fusion, neurological deficits gradually recovered, despite the presence of residual anterior impingement of spinal cord by the OPLL. CONCLUSIONS: The present case provides evidence for the possibility that laminectomy alone produces postoperative paralysis for combined thoracic OPLL and OLF, and we recommend that a posterior instrumented fusion should be added when posterior decompression is performed for this disorder.     

Simultaneous anterior decompression and posterior instrumentation of the tuberculous spine using an anterolateral extrapleural approach

Injury to the spinal cord and kyphosis are the two most feared complications of tuberculosis of the spine. Since tuberculosis affects principally the vertebral bodies, anterior decompression is usually recommended. Concomitant posterior instrumentation is indicated to neutralise gross instability from panvertebral disease, to protect the anterior bone graft, to prevent graft-related complications after anterior decompression in long-segment disease and to correct a kyphosis. Two-stage surgery is usually performed in these cases. We present 38 consecutive patients with tuberculosis of the spine for whom anterior decompression, posterior instrumentation, with or without correction of the kyphus, and anterior and posterior fusion was performed in a single stage through an anterolateral extrapleural approach. Their mean age was 20.4 years (2.0 to 57.0). The indications for surgery were panvertebral disease, neurological deficit and severe kyphosis. The patients were operated on in the left lateral position using a 'T'-shaped incision sited at the apex of kyphosis or lesion. Three ribs were removed in 34 patients and two in four and anterior decompression of the spinal cord was carried out. The posterior vertebral column was shortened to correct the kyphus, if necessary, and was stabilised by a Hartshill rectangle and sublaminar wires. Anterior and posterior bone grafting was performed. The mean number of vertebral bodies affected was 3.24 (2.0 to 9.0). The mean pre-operative kyphosis in patients operated on for correction of the kyphus was 49.08 degrees (30 degrees to 72 degrees) and there was a mean correction of 25 degrees (6 degrees to 42 degrees). All except one patient with a neural deficit recovered complete motor and sensory function. The mean intra-operative blood loss was 1175 ml (800 to 2600), and the mean duration of surgery 3.5 hours (2.7 to 5.0). Wound healing was uneventful in 33 of 38 patients. The mean follow-up was 33 months (11 to 74). None of the patients required intensive care. The extrapleural anterolateral approach provides simultaneous exposure of the anterior and posterior aspects of the spine, thereby allowing decompression of the spinal cord, posterior stabilisation and anterior and posterior bone grafting. This approach has much less morbidity than the two-stage approaches which have been previously described.     

颈椎病后路脊髓前外侧减压术及其解剖学基础

１９８９年作者设计的后路脊髓前外侧减压术是在直视下施行的一种治疗颈椎病的手术，特别是对后纵韧带骨化（ＯＰＬＬ）所致脊髓压迫，此手术可同时解除脊髓和神经根的压迫症状。４年来治疗３０例，效果很好。作者用５０具成人尸体按此手术的方法及程序就手术野进行了解剖，对肌层的血供、椎弓板、椎管以及神经根和脊髓进行了观测，并用这５０副成人颈椎标本测量了椎间孔、椎间管、钩突及横突孔。除总结手术方法及临床病例外，作者并通过解剖观察提出手术时应注意的事项。     

Choice of surgical approach for ossification of the posterior longitudinal ligament in combination with cervical disc hernia

Ossification of the posterior longitudinal ligament (OPLL) is a common spinal disorder that presents with or without cervical myelopathy. Furthermore, there is evidence suggesting that OPLL often coexists with cervical disc hernia (CDH), and that the latter is the more important compression factor. To raise the awareness of CDH in OPLL for spinal surgeons, we performed a retrospective study on 142 patients with radiologically proven OPLL who had received surgery between January 2004 and January 2008 in our hospital. Plain radiograph, three-dimensional computed tomography construction (3D CT), and magnetic resonance imaging (MRI) of the cervical spine were all performed. Twenty-six patients with obvious CDH (15 of segmental-type, nine of mixed-type, two of continuous-type) were selected via clinical and radiographic features, and intraoperative findings. By MRI, the most commonly involved level was C5/6, followed by C3/4, C4/5, and C6/7. The areas of greatest spinal cord compression were at the disc levels because of herniated cervical discs. Eight patients were decompressed via anterior cervical discectomy and fusion (ACDF), 13 patients via anterior cervical corpectomy and fusion (ACCF), and five patients via ACDF combined with posterior laminectomy and fusion. The outcomes were all favorable. In conclusion, surgeons should consider the potential for CDH when performing spinal cord decompression and deciding the surgical approach in patients presenting with OPLL.     

Staged spinal cord decompression through posterior approach for thoracic myelopathy caused by ossification of posterior longitudinal ligament.

STUDY DESIGN: Prospective clinical study of the effect of staged elimination of anatomic factors inhibiting posterior shift of the thoracic spinal cord on the degree of posterior shift of the thoracic spinal cord and its significance in augmenting the safety of ossification of posterior longitudinal ligament (OPLL) manipulation in thoracic OPLL myelopathy. OBJECTIVES: To develop a comprehensive method that enables safe and sufficient decompression of the spinal cord for thoracic OPLL myelopathy. SUMMARY OF BACKGROUND DATA: Decompression of the spinal cord by direct manipulations of thoracic OPLLs, via either anterior or posterior approach, caused some iatrogenic catastrophic spinal cord injuries, and methods to prevent such injuries during surgery have not yet been developed. METHODS: Procedures of elimination of anatomic factors inhibiting posterior shift of the thoracic spinal cord were performed in stages at intervals of between 1 month and 11 years depending on patients' neurologic status. The first stage operation consisted of extensive cervicothoracic laminoplastic decompression with or without posterior longitudinal durotomy, and if the decompression were insufficient, measures for OPLL-spinal cord separation with or without OPLL manipulation were added. RESULTS: All 17 patients with thoracic OPLL myelopathy showed improvements of neurology comparable with those with successful anterior approaches after decompression. The mean follow-up period was 42 months (range 6-101 months). Neurologic improvements persisted for the entire follow-up period in all patients except one patient who developed arachnoid cyst compressing the dorsum of the once-decompressed spinal cord 30 months after surgery. CONCLUSIONS: Staged posterior decompression to eliminate anatomic factors inhibiting posterior shift of the thoracic spinal cord is the safest and the most reliable method of spinal cord decompression to treat thoracic OPLL myelopathy, so far. However, long-term results are required before the methods can be established.     

Late paraparesis due to pseudarthrosis after posterior spinal fusion

The authors report three cases in which paraparesis related to a pseudarthrosis occurred several years after a posterior spinal fusion, but with a different mechanism (stretching of the spinal cord for progression of the deformity in kyphosis in two cases, and spinal cord compression for bone overgrowth within the canal in the site of pseudarthrosis in the third patient). Treatment was different. Partial correction of the deformity and stabilization of the spine by combined fusion (anterior and posterior) was sufficient in the first two cases for a complete neurological recovery. Posterior spinal cord decompression and stabilization of the spine by combined fusion was necessary for complete recovery in the third.     

颈椎病伴椎管狭窄患者再手术问题探讨

目的：探讨颈椎病伴椎管狭窄患者再手术的原因、手术方式及其相关问题。方法：我院2002年7月～2003年12月对40例颈椎病伴椎管狭窄术后疗效不佳或症状复发的患者进行了后路多节段（5个或以上）减压手术。根据其手术治疗方式及影像学资料分析再手术原因，并进行术后疗效评价。结果：经前路手术者再手术的主要原因为：（1）伴有多节段颈椎管狭窄因素时，只选择部分压迫重的节段行减压融合15例；（2）经前路多节段（≥3个节段）减压融合后，相邻节段继续退变，出现新的脊髓压迫表现及椎间不稳定9例；（3）伴有OPLL时，行部分节段前路减压融合后，病变呈进展表现，产生或加重对脊髓的压迫8例。经后路手术者再手术的原因为：（1）后路减压节段不够5例（包括1例前后路联合手术者）；（2）后路减压不充分3例。再手术后随访1．3～2．7年，平均2．1年，所有患者脊髓功能获得一定的提高，JOA评分改善率为51．3％。结论：颈椎病伴椎管狭窄病例再手术的主要原因为椎管狭窄因素仍然存在，经后路多节段（5个或以上）减压手术治疗可彻底去除颈椎管狭窄因素，有效解除脊髓前、后方所受的压迫，可获得较满意的临床疗效。     

Anterior cervical vertebrectomy and interbody fusion for multi-level spondylosis and ossification of the posterior longitudinal ligament

Multi-level cervical spondylosis and ossification of the posterior longitudinal ligament (OPLL) are well-documented causes of myelopathy. The choice of surgical procedures remain controversial. Between January 1983 and December 1987, we have performed anterior cervical vertebrectomy in 45 patients with cervical myelopathy caused by multi-level spondylosis and OPLL. They consisted of 19 patients with cervical spondylosis, 12 with OPLL, and 14 with combined lesions of both cervical spondylosis and OPLL. There were 32 men and 13 women. The mean age was 55 years, ranging from 35 to 70 years. In all of our 45 patients, anterior vertebrectomy, discectomy, removal of posterior osteophytes and OPLL, and interbody fusion were done for progressive myelopathy refractory to conservative treatment. In 2 of 45 patients, 5 vertebral bodies were resected; in 3 patients, 4 vertebral bodies were resected; in 12 patients, 3 vertebral bodies were resected, in 19 patients, 2 vertebral bodies were resected; and in 9 patients, 1 vertebral body was resected. Thirty-nine of 45 patients (87%) had good results. Neurological signs did not improve in 5 patients (11%). One patient died because of agranulocytosis secondary to treatment with antibiotics. In conclusion, cervical cord compression caused by lesions located principally in the anterior aspect of the spinal canal may be completely relieved via anterior vertebrectomy, discectomy, removal of the calcified ligament, and fusion.     

Indirect posterior decompression with corrective fusion for ossification of the posterior longitudinal ligament of the thoracic spine: is it possible to predict the surgical results?

To investigation of the outcomes of indirect posterior decompression with corrective fusion for myelopathy associated with thoracic ossification of the longitudinal ligament, and prognostic factors. Conservative treatment for myelopathy associated with thoracic ossification of the longitudinal ligament (OPLL) is mostly ineffective, and treatment is necessary. However, many authors have reported poor surgical outcomes, and no standard surgical procedure has been established. We have been performing indirect spinal cord decompression by posterior laminectomy and simultaneous corrective fusion of the thoracic kyphosis. Twenty patients underwent indirect posterior decompression with corrective fusion, and were included in this study. The follow-up period was minimum 2 years and averaged 2 years and 9 months (2–5 years 6 months). Operative results were examined using JOA scoring system (full marks: 11 points) and Hirabayashi’s recovery rate, as excellent (100–75%), good (74–50%), fair (49–25%), unchanged (24–0%) and deteriorated (i.e., decrease in score less than 0%). Cases in which the spinal cord is floating from OPLL on intraoperative ultrasonography were defined as the floating (+) group, and those without floating as the floating (−) group. In addition, we used compound muscle action potentials (CMAP) as intraoperative spinal cord monitoring and the cases were divided into three groups: Group A, no change in potential; Group B, potential decreased, and Group C, potential improved. The mean pre- and postoperative JOA scores were 6.2 and 8.9 points, respectively, and the recovery rate was 56%. The outcome was rated excellent in three, good in eight, fair in six, unchanged in two, and deteriorated in one. The mean preoperative thoracic kyphosis measured 58°, and was corrected to 51° after surgery. On intraoperative ultrasonography, 12 cases were included in the floating (+) and 8 in the floating (−) groups; the recovery rates were 58 and 52%, respectively, showing no significant difference between the recovery rates of the two groups. Regarding intraoperative CMAP, the outcome was excellent in one, good in seven, fair in four, and unchanged in one in Group A; fair in one, unchanged in one, and deteriorated in one in Group B, and excellent in two and good in one in Group C. The recovery rates were 50, 48 and 68.3% in Groups A, B and C, respectively, showing that the postoperative outcome was significantly poorer in Group B. Although indirect posterior decompression with corrective fusion using instruments obtained satisfactory outcomes, not all cases achieved good outcomes using this procedure. We consider that additional application of anterior decompressive fusion is preferable when improvement of symptoms occurs not satisfactory after indirect posterior decompression with corrective fusion using instruments. Intraoperative spinal cord monitoring of CMAP demonstrated that the spinal cord was already impaired during the laminectomy via the posterior approach. Concomitant intraoperative monitoring of CMAP to avoid impairment of the vulnerable spinal cord and corrective posterior spinal fusion with indirect spinal cord decompression is recommendable as a method capable of preventing postoperative neurological aggravation.     

Limitations of minimally invasive posterior cervical foraminotomy—a decompression method of posteriorly shifting the nerve root—in cases of large anterior osteophytes in cervical radiculopathy: A retrospective multicenter cohort study

BackgroundPosterior cervical foraminotomy against anterior osteophyte is an indirect decompression procedure but less invasive compared to anterior cervical discectomy and fusion. Residual compression to the nerve root may lead to poor surgical outcomes. Although clinical results of posterior cervical foraminotomy for osteophytes are not considered better than those of disk herniation, osteophyte size and the association of the decompression area with poor surgical outcomes remain unclear. This study aimed to identify the limitations of minimally invasive posterior cervical foraminotomy for cervical radiculopathy and discuss the methods to improve surgical outcomes.MethodsWe analyzed 55 consecutive patients with degenerative cervical radiculopathy who underwent minimally invasive posterior cervical foraminotomy. Minimum postoperative follow-up duration was 1 year. We divided the patients into nonimproved and improved groups. The cutoff value between preoperative and postoperative Neck Disability Index scores was 30% improvement. Preoperative imaging data comprised disk height, local kyphosis, spinal cord compression, anterior osteophytes in the foramen, and anterior osteophytes of >50% of the intervertebral foramen diameter. Postoperative imaging data comprised craniocaudal length and lateral width of decompressed lamina, preserved superior facet width, and area of decompressed lamina.ResultsFifty-five patients were divided into two groups: nonimproved (n = 19) and improved (n = 36). The presence of osteophytes itself was not significant; however, the presence of osteophytes of >50% of the foramen diameter increased in the nonimproved group (P = 0.004). Mean lateral width and mean area of decompressed lamina after surgery significantly increased in the improved group (P = 0.001, P = 0.03).ConclusionThe presence of anterior osteophytes >50% of the diameter of the foramen led to poor improvement of clinical outcomes in minimally invasive posterior cervical foraminotomy. However, the larger the lateral width and area of the decompressed lamina, the better the surgical outcome.