Facet Preserving Technique by En Bloc Flavectomy in Microscopic Posterior Decompression Surgery for Lumbar Spinal Stenosis: Semicircumferential Decompression (SCD).

Posterior decompression surgery which enlarges the spinal canal in cases with lumbar spinal stenosis is the most fundamental technique in spine surgery, but controversy still remains for the exact technique. Because nerve roots run under the ventral side on the superior articular process (SAP), achieving both facet joint preservation and nerve root decompression is problematic. In conventional laminotomies or laminectomies, medial facetectomies are performed to decompress the nerve root, but it is ideal to preserve the facet joints completely for preserving joint stability. We handle this problem with an original decompression technique, called "semicircumferential decompression." The main features of this procedure are an en bloc flavectomy and total preservation of facet joints. The procedure is performed under the microscope with a midline approach. The flavum is detached from the ventral surface of the SAP using a currete without disturbing the SAP. The facet joints are preserved completely. The advantage of an en bloc flavectomy is that we can remove the flavum attachment to the ventral surface of SAP totally without a medial facetectomy. Since 1991, we have performed this technique in more than 5000 cases. In this paper, we will explain the tips, pitfalls, and advantages of this technique.

Morphology and clinical importance of epidural membrane and periradicular fibrous tissue in lumbar spinal stenosis.

PURPOSE: Compared to the ligamentum flavum (LF), morphology of the epidural membrane (EM) and the periradicular fibrous tissue (PRFT) has been largely ignored in studies of lumbar spinal stenosis (LSS). The aim of this prospective study was to elucidate the morphologies and clinical importance of the EM and PRFT in LSS. METHODS: Before starting this study, neural compressive EM (c-EM) and PRFT (c-PRFT) were defined as follows based on our microsurgical experience and a literature review. The c-EM is a constriction band or membrane obstructing dural tube expansion, and the c-PRFT is a fibrous tissue that compresses the nerve root and/or restricts its mobility. This study enrolled 134 patients who underwent microscopic decompression at L4/5. The morphologies of each patient's EM and PRFT were observed and recorded. Specimens were obtained from randomly selected patients for histological evaluation. RESULTS: The EM and PRFT exhibited a wide morphological spectrum, from a fine strand to a substantial membrane. The c-EM alone was observed in four cases, the c-PRFT alone in 37 cases, and both in three cases. The c-PRFT was more frequently observed in patients with degenerative spondylolisthesis than in those without olisthesis (P < 0.05). Several cases exhibited interesting histological findings including many small arteries, chondrometaplasia, ganglion-like cyst formation, and hyalinized collagen fibers. CONCLUSIONS: Some EM and PRFT transform into degenerative and substantial fibrous tissues during the process of symptomatic LSS development. Such morphological and histological changes can cause dural tear, symptomatic epidural hematoma, and/or inadequate decompression.

Microscopic Posterior Transdural Resection of Cervical Retro-Odontoid Pseudotumors.

Retro-odontoid pseudotumors are noninflammatory masses formed posterior to the odontoid process. Because of their anatomy, the optimal surgical approach for resecting pseudotumors is controversial. Conventionally, 3 approaches are used: the anterior transoral approach, the lateral approach, and the posterior extradural approach; however, each approach has its limitations. The posterior extradural approach is the most common; however, it remains challenging due to severe epidural veins. Although regression of pseudotumors after fusion surgery has been reported, direct decompression and a pathologic diagnosis are ideal when the pseudotumor is large. We therefore developed a new microscopic surgical technique; transdural resection. After C1 laminectomy, the dorsal and ventral dura was incised while preserving the arachnoid. Removal of the pseudotumor was performed and both of the dura were repaired. The patient's clinical symptoms subsequently improved and the pathologic findings showed degenerative fibrocartilaginous tissue. In addition, no neurological deterioration, central spinal fluid leakage, or arachnoiditis was observed. Currently, the usefulness of the transdural approach has been reported for cervical and thoracic disk herniation. According to our results, the transdural approach is recommended for resection of retro-odontoid pseudotumors because it enables direct decompression of the spinal cord and a pathologic diagnosis.

Long-term clinical results of microsurgical transdural discectomy with laminoplasty: follow-up results over 10 years.

OBJECT: In this retrospective analysis the authors describe the long-term clinical results of microsurgical transdural discectomy with laminoplasty (MTDL) in patients with cervical disc herniation (CDH). METHODS: Thirty patients (21 males, 9 females; mean age at surgery 55 years) with CDH had surgical treatments consisting of MTDL between 1990 and 1998. All patients demonstrated signs or symptoms of cervical myelopathy and/or radiculomyelopathy. Clinical outcomes were evaluated by the Japanese Orthopaedic Association (JOA) scoring system and by recovery rate (RR). The degenerative grades of the intervertebral discs were also evaluated based on preoperative, postoperative, and final follow-up MR images. The average follow-up period was 14.1 years (range 10-22 years). RESULTS: Twenty (67%) of the 30 patients completed the follow-up in this study. The preoperative JOA scores in these patients averaged 11.8, and the postoperative scores at the final follow-up averaged 15.5 (average RR 69.6%). None of these patients required reoperation after MTDL. Although disc degeneration progressed during the follow-up period, there were no cases of clinical deterioration, recurrence of disc herniation, or postoperative kyphotic deformity. CONCLUSIONS: Sufficient clinical results were obtained after the MTDL for a long-term follow-up period exceeding 10 years. The MTDL may be an option for an alternative procedure if the patients are correctly selected and the procedure is safely performed.

Morphological features and clinical significance of epidural membrane in the cervical spine.

STUDY DESIGN: A prospective clinical study. OBJECTIVE: To elucidate the histomorphological features and clinical significance of the epidural membrane (EM) in the cervical spine based on operative and histological findings. SUMMARY OF BACKGROUND DATA: The anatomical features of the EM have been mostly discussed on the basis of cadaver studies in the whole spine. However, the histomorphological features and clinical significance of the EM in the cervical spine based on operative findings have never been reported. METHODS: Eighty-seven patients with cervical spondylotic myelopathy who had undergone an expansive open-door laminoplasty under microscopy were evaluated with a more than 2-year follow-up period. The most damaged spinal segment was determined in each patient from the preoperative neurological and image findings along with the remaining symptoms at follow-up. The morphological features of the EM were observed and recorded in each patient during decompression. For histology, specimens of common and remarkable types of the EM obtained from 16 patients were examined. RESULTS: The age at surgery averaged 64.5 years; there were 58 men and 29 women. With regard to the most damaged spinal segment, there were 14 cases at the C3-C4 level, 37 at the C4-C5 level, 32 at the C5-C6 level, and 4 at the C6-C7 level. The EM was an adipo-fibro-vascular tissue with various histomorphologies, blending with the periradicular sheath. Some EMs showed notable findings: obstructing dural tube expansion (13 cases, 14.9%), compressing a nerve root or disturbing its mobility (4 cases, 4.6%), and the combined type (1 case, 1.1%). All of them were located at approximately the most damaged spinal segment. In addition, some EMs had interesting histological features, such as harboring many small arteries, calcified debris, and metaplastic bone fragments. CONCLUSION: The EM can develop into remarkable structures with spondylosis and aging in patients with cervical spondylotic myelopathy, affecting surgical outcomes as well as successful decompression procedures. A sound understanding of the histomorphological features of the EM is required to obtain satisfactory surgical outcomes in the limited field afforded by minimally invasive surgery.

Relationship between the histological findings of spondylolytic tissue, instability of the loose lamina, and low back pain.

STUDY DESIGN: We investigated the histomorphological features of the tissue occupying the spondylolytic defect (spondylolytic tissue), which was similar to ligament, and then graded the complete enthesis structure and the density of the fibrous portion. The relationships between the features, instability of the loose lamina against the affected vertebra, and the severity of low back pain were studied. OBJECTIVE: To elucidate the histomorphological features of spondylolytic tissue and the associations between the features, instability of the loose lamina, and low back pain. SUMMARY OF BACKGROUND DATA: Spondylolysis is thought to be caused primarily by a fatigue fracture and spondylolytic tissue has been recognized as being a fibrocartilaginous mass. Recently, innervation of the spondylolytic tissue was reported to be one of the sources of low back pain. METHODS: The spondylolytic tissue from 17 patients who underwent microscopic decompression of the pars defect was observed for histology including hematoxylin and eosin, elastica van Gieson, and immunohistochemical staining for S100 protein. Instability of the loose lamina against the affected vertebra was evaluated by flexion/extension radiographs. RESULTS: The spondylolytic tissue had a ligamentous structure without innervation. The histomorphological findings, instability of the loose lamina, and low back pain had no relationship to one another. CONCLUSION: Spondylolysis is a pseudarthorosis of the pars interarticularis and the spondylolytic tissue tends to develop noninnervated ligament-like tissue with an enthesis structure. The histomorphological features, instability of the loose lamina, and low back pain have no relationship to one another.

Clinical characterizations and radiologic findings of pure foraminal-type cervical disc herniation: CT discography as a useful adjuvant in its precise diagnosis.

STUDY DESIGN: A retrospective study of 15 cases of pure foraminal type cervical disc herniation (CDH) was performed. OBJECTIVES: The objectives were to describe the clinical characteristics and to assess the radiologic findings. SUMMARY OF BACKGROUND DATA: Although foraminal lumbar disc herniation has been reported, pure foraminal-type CDH has not been fully elucidated. It is not only a rare condition but also a difficult one to diagnose. METHODS: All patients underwent MRI, CT myelography (CTM), and CT discography (CTD). Herniated discs were removed by the posterior approach. Clinical symptoms were evaluated at preoperative and postoperative period. RESULTS: On MRI, 2 cases were positive, 6 cases were suspected, and 7 cases were negative. On CTM, 7 cases were positive and 8 cases were negative; and on CTD, all cases were positive. As to the association between the herniated disc and posterior longitudinal ligament, 12 cases were intraligamentous. The association between the herniated disc and nerve root revealed that 10 discs were at the axillary portion of the nerve root. CONCLUSIONS: Pure foraminal-type CDH may be overlooked with conventional MRI or CTM, so CTD should be performed. It provides valuable and additional information in difficult or ambiguous cases such as pure foraminal type.

The pathology of ligamentum flavum in degenerative lumbar disease.

STUDY DESIGN: A pathologic study of the ligamentum flavum in degenerative lumbar disease. OBJECTIVES: To elucidate the clinical significance of each pathologic finding of the ligamentum flavum. SUMMARY OF BACKGROUND DATA: In many reports, researchers observed the ligamentum flavum removed partially during surgery and did not evaluate the whole image of the ligamentum flavum. In addition, there are only a few reports that examined the possible association between various histologic findings and clinical findings. And, thus, there are many unclear points in the clinical significance indicated by each pathologic finding. METHODS: The study participants were 50 patients with degenerative lumbar diseases who underwent surgical decompression with removal of the ligamentum flavum of the affected spinal level. Tissue specimens of the removed ligamentum flavum in cross section were prepared, and changes in the elastic fibers and collagen fibers were evaluated in three grades to evaluate the whole image. In addition, we observed the presence or absence of any focal lesions and statistically analyzed the possible association between these histologic findings and clinical symptoms or image findings. RESULTS: In regard to the association between histologic findings and clinical symptoms or image findings, calcification was observed in significantly older patients, who tended to have low scores in preoperative JOA score, and was frequently observed in patients with cauda equina symptoms. Patients with ossification had a significantly greater % slip, and chondroid cells were frequently observed in patients with spondylolisthesis. CONCLUSION: Various pathologic findings provided important foundations for discussing the pathogenesis of lesions in ligamentum flavum. Calcification was frequently observed in elderly patients and those with cauda equina symptoms, and these patients tended to have severer preoperative symptoms. Chondroid cells were frequently observed in patients with spondylolisthesis, and patients with ossification had a greater % slip, suggesting involvement of mechanical load in ossification of ligaments. The pathologic findings were significantly related to the clinical features, and these findings will be profitable for understanding the pathogenesis of degenerative lumbar disease.

Microsurgical transdural discectomy with laminoplasty: New treatment for paracentral and paracentroforaminal cervical disc herniation associated with spinal canal stenosis.

STUDY DESIGN: A clinical study of the surgical procedure for cervical disc herniation was conducted. OBJECTIVES: To describe microsurgical transdural discectomy with laminoplasty, and to assess the clinical outcome of this surgical technique. SUMMARY OF BACKGROUND DATA: A posterior approach for cervical disc herniation has been considered risky, and few reports on a transdural approach to this disorder have appeared in the past decade. However, a transdural approach with recent innovations (a microsurgical technique, intraoperative spinal cord monitoring, and laminoplasty) has not been reported. METHODS: For this study, 30 patients with myelopathy or radiculomyelopathy accompanied by cervical disc herniation, aged 30 to 77 years (mean, 55 years), underwent microsurgical transdural discectomy with laminoplasty. Preoperative images showed multisegmental disc degeneration, developmental canal stenosis, or both for all the patients. The intraoperative evoked spinal cord potentials were recorded for neurophysiologic assessment. The follow-up period averaged 52 months (range, 24-118 months). RESULTS: The operative time averaged 239 minutes (range, 160-340 minutes), and the mean blood loss was 169 mL (range, 30-701 mL). The Japanese Orthopedic Association score improved from 3.5 to 15 (mean, 11.4) before surgery to 9 to 17 (mean, 15.2) after surgery. The intraoperative evoked spinal cord potentials indicated the affected spinal cord level and reflected the severity of myelopathy. Postoperative cerebrospinal fluid leakage, pseudomeningocele, and progression to cervical deformity were not observed. Transient palsy of the C5 nerve root was observed in two patients with C4-C5 central cervical disc herniation. CONCLUSIONS: Microsurgical transdural discectomy with laminoplasty can be performed safely as a selected surgical option for paracentral and paracentroforaminal cervical disc herniation with multisegmental canal stenosis.