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Kazuhiro Hasegawa and Takao Homma

✓ Surgery for degenerative lumbar kyphoscoliosis (DLKS) is very challenging because the curve has become rigid due to circumferential osteoarthritic changes. Therefore, a standard procedure involving correction and fusion after decompression of the nerves has not yet been established. The authors have been searching for an effective procedure that provides adequate decompression and three-dimensional (3D) correction for symptomatic DLKS. In this report they describe a new 3D correction and fusion technique involving multilevel posterior lumbar interbody fusion. They analyze the results obtained in the first 23 cases and discuss the advantages and disadvantages of the procedure. The correction effect was excellent, and compared with other instrumentation-assisted procedures, this surgery is not remarkably invasive. Although the procedure is limited in achieving normal sagittal alignment and the acceleration rate of adjacent-disc degeneration remains relatively high, it is an option for the rigid deformity characterized by DLKS.

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Kei Watanabe, Kazuhiro Hasegawa, and Kou Takano

✓ The authors describe a very rare case of cervical cord compression caused by anomalous bilateral vertebral arteries (VAs). A 65-year-old woman had been suffering from intractable nape pain and torticollis. Magnetic resonance imaging revealed a signal void region in which spinal cord compression was present. Angiography demonstrated anomalous bilateral VAs compressing the spinal cord. Microvascular decompressive surgery was successfully performed. Neuroradiological and intraoperative findings are presented.

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Kazuhiro Hasegawa, Akira Ogose, Hiroto Kobayashi, Tetsuro Morita, and Yasuharu Hirata

✓ In cases of primary malignant extradural tumors of the spine, the main goal of the surgery is en bloc resection and reconstruction of the spine. After placing the patient in the lateral position, an en bloc resection of a chondrosarcoma that arose from the right seventh rib head and invaded the adjacent vertebra was performed using a simultaneous anterior—posterior approach followed by spinal reconstruction. The technical details are reported. Paraspinal malignant tumors of the thoracic spine can be safely removed en bloc and the spine reconstructed using this approach.

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Kazuhiro Hasegawa, Ko Kitahara, Haruka Shimoda, and Toshiaki Hara

Object

This study aimed to clarify changes in segmental instability following a unilateral approach for microendoscopic posterior decompression and muscle-preserving interlaminar decompression compared with traditional procedures and destabilized models.

Methods

An ex vivo experiment was performed using 30 fresh frozen porcine functional spinal units (FSUs). Each intact specimen was initially tested for flexion-extension, lateral bending, and torsion up to 1.5° using a material testing system at an angular velocity of 0.1°/second under a preload of 70 N. Microendoscopic posterior decompression, muscle-preserving interlaminar decompression, bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy were then performed, followed by mechanical testing with the same loading conditions, in 6 randomized FSUs from each group. Stiffness and neutral zone were standardized by dividing the experimental values by the baseline values and were then compared among groups.

Results

Mean standardized stiffness values for all loading modes tended to decrease in the order of muscle-preserving interlaminar decompression, microendoscopic posterior decompression, bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy. In contrast, mean standardized neutral zone values tended to increase in the order of muscle-preserving interlaminar decompression, microendoscopic posterior decompression, bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy. In flexion, values for standardized stiffness following microendoscopic posterior decompression and muscle-preserving interlaminar decompression were higher and standardized neutral zone following microendoscopic posterior decompression and muscle-preserving interlaminar decompression were lower than the values following left unilateral total facetectomy and bilateral total facetectomy while there was no significant difference among bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy. Values of standardized stiffness and standardized neutral zone in left torsion following microendoscopic posterior decompression, muscle-preserving interlaminar decompression, and bilateral medial facetectomy were equally superior to values of the destabilization models (left unilateral total facetectomy and bilateral total facetectomy). Except for standardized stiffness in left bending, the values of the parameters for each bending tended to be the same as in the other loading modes.

Conclusions

The present biomechanical study showed that overall stability of the FSUs was maintained following microendoscopic posterior decompression, muscle-preserving interlaminar decompression, and bilateral medial facetectomy compared with the destabilization models of left unilateral total facetectomy or bilateral total facetectomy. Comparison of the postoperative stability following microendoscopic posterior decompression, muscle-preserving interlaminar decompression, and bilateral medial facetectomy revealed that muscle-preserving interlaminar decompression tended to be superior, followed by microendoscopic posterior decompression and bilateral medial facetectomy.

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Kazuhiro Hasegawa, Ko Kitahara, Haruka Shimoda, and Toshiaki Hara

Object

The objective of this study was, using a novel intraoperative measurement (IOM) system, to test the hypothesis that an increased facet joint volume is evidence of spinal instability.

Methods

In 29 patients (male/female ratio 13:16; mean age 67.5 years, range 43–80 years)—17 with degenerative spondylolisthesis (DS) of the lumbar spine (Group DS) and 12 with canal stenosis (CS) of the lumbar spine (Group CS)—DICOM (Digital Imaging and Communications in Medicine) data derived from CT scans were transferred to a workstation. A 3D model of facet joint spaces was reconstructed and the average volume of the bilateral facets was calculated. Segmental properties—stiffness, absorption energy (AE), and neutral zone (NZ)—were measured using an IOM system, and values were compared between groups. Linear regression analyses were performed among biomechanical parameters and average volumes.

Results

Stiffness and AE did not differ significantly between groups. The NZ was significantly greater in Group DS than in Group CS (p < 0.05) and significantly positively correlated with the average volume (R2 = 0.141, p < 0.05). Stiffness tended to negatively correlate with average volume. Absorption energy did not correlate with average volume.

Conclusions

Biomechanical analyses using the IOM system verified that an increased facet joint volume is evidence of spinal instability, represented by NZ, in the degenerative lumbar spine.

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Minoru Tanaka, Soichiro Shibui, Kazuhiro Nomura, Yukihiro Nakanishi, Tadashi Hasegawa, and Takanori Hirose

✓ The authors present the clinical, radiological, and pathological features of a malignant intracerebral nerve sheath tumor that occurred in the right parietooccipital lobe of a 4-year-old girl. Computerized tomography scanning and magnetic resonance imaging demonstrated a 5 × 5 × 4—cm multiloculated mass with considerable enhancement of the irregularly shaped septa and clearly calcified areas within the mass. Among five cases reported in the literature, this patient is the youngest and represents the first case in which there is radiological evidence of intratumoral calcification.

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Kei Watanabe, Kazuhiro Hasegawa, Toru Hirano, Naoto Endo, Akiyoshi Yamazaki, and Takao Homma

Object

The mechanism underlying cervical flexion myelopathy (CFM) is unclear. The authors report the results of anterior decompression and fusion (ADF) in terms of neurological status and radiographically documented status in young patients and discuss the pathophysiological mechanism of the entity.

Methods

Twelve patients underwent ADF in which autogenous iliac bone graft was placed. The fusion area was one segment in four cases, two segments in seven, and three segments in one. Neurological status, as determined by the Japanese Orthopaedic Association (JOA) score, radiographic findings, and intraoperative findings were evaluated. The mean follow-up period was 63.3 months (range 20–180 months).

Grip strength was significantly improved and sensory disturbances resolved completely. Intrinsic muscle atrophy, however, persisted in all patients at the final follow-up examination. Local kyphosis in the flexed-neck position at the fusion levels was corrected by surgery. Preoperative computerized tomography myelography revealed that the cord compression index, which was calculated by anteroposterior and transverse diameters of the spinal cord, decreased to 33 ± 6.2% in the flexed-neck position from 39.7 ± 9.9% in the extended-neck position. The anterior dura mater—spinal cord distance decreased to 1.9 ± 0.7 mm in the flexed-neck position from 4 ± 1.2 mm in extended-neck position. The posterior dura mater—spinal cord distance increased to 2.5 ± 1.1 mm in the flexed-neck position from 1.3 ± 0.5 mm in the extended-neck position.

Conclusions

Postoperative neurological status was improved in terms of grip strength, sensory disturbance, and JOA score, and local kyphosis in the flexed-neck position at the fusion levels was reduced and stabilized by ADF.

In most cases local kyphosis in the flexed-neck position was demonstrated at the corresponding disc level, as were cervical cord compression and decrease of the anterior wall of the dura mater—spinal cord distance in the flexed-neck position. Therefore, the contact pressure between the spinal cord and anterior structures (intact vertebral bodies and intervertebral discs) in the mobile and kyphotic segments was considered to contribute to the onset of CFM. The ADF-related improvement of the clinical symptoms, preventing kyphotic alignment in flexion and decreasing movement of the cervical spine, supports the idea of a contact pressure mechanism. Furthermore, short ADF performed only at the corresponding segments can preserve more mobile segments compared with posterior fusion. Thus, ADF should be the first choice in the treatment of CFM.

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Shinji Kimura, John R. Hesselink, Steven R. Garfin, Yoichi Kawaji, Kazuhiro Hasegawa, and Alan R. Hargens

Object. The objectives of this study were to simulate the upright loading condition in the cervical spine by applying a new compression device during supine posture and to assess intervertebral angles and cross-sectional areas of the spinal cord and dural tube before and during axial compression.

Methods. A magnetic resonance (MR) imaging-compatible device was developed to create axial compression with the patient in the supine position. Lateral radiographs were obtained in upright and supine positions with an axial load of 0% (supine) and by applying a cervical compression device at 7, 10, and 13% of body weight (BW) in 18 control individuals and seven symptomatic patients with cervical degenerative disc disease (DDD). Additionally, cervical MR images acquired in 17 controls and 12 patients were compared before and during an axial load of 8.4% BW in terms of anteroposterior diameter and cross-sectional area of the dural sac.

The supine intervertebral angles with loads of 0, 7, 10, and 13% of the individuals' BW relative to upright posture were −8.1 ± 1.3, −2.3 ± 1.4, 1.3 ± 1.9, and 2.8 ± 2°, respectively. Subsequent axial force was interpolated as 8.9% of BW to simulate upright cervical spine alignment. Under an axial loading similar to that created by the upright posture, the dural sac narrowed at the C5–6 interspace in asymptomatic individuals and at the C6–7 interspace in patients with cervical DDD.

Conclusions. This cervical compression device may be a useful tool to simulate upright cervical spinal alignment. The results of this study help in understanding the pathophysiology of symptoms related to cervical degenerative disorders in upright posture.

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Kazuhiro Hasegawa, Ko Kitahara, Toshiaki Hara, Ko Takano, Haruka Shimoda, and Takao Homma

Object

In vivo quantitative measurement of lumbar segmental stability has not been established. The authors developed a new measurement system to determine intraoperative lumbar stability. The objective of this study was to clarify the biomechanical properties of degenerative lumbar segments by using the new method.

Methods

Twenty-two patients with a degenerative symptomatic segment were studied and their measurements compared with those obtained in normal or asymptomatic degenerative segments (Normal group). The measurement system produces cyclic flexion–extension through spinous process holders by using a computer-controlled motion generator with all ligamentous structures intact. The following biomechanical parameters were determined: stiffness, absorption energy (AE), and neutral zone (NZ). Discs with degeneration were divided into 2 groups based on magnetic resonance imaging grading: degeneration without collapse (Collapse[−]) and degeneration with collapse (Collapse[+]). Biomechanical parameters were compared among the groups. Relationships among the biomechanical parameters and age, diagnosis, or radiographic parameters were analyzed.

Results

The mean stiffness value in the Normal group was significantly greater than that in Collapse(−) or Collapse(+) group. There was no significant difference in the average AE value among the Normal, Collapse(−), and Collapse(+) groups. The NZ in the Collapse(−) was significantly higher than in the Normal or Collapse(+) groups. Stiffness was negatively and NZ was positively correlated with age. Stiffness demonstrated a significant negative and NZ a significant positive relationship with disc height, however.

Conclusions

There were no significant differences in stiffness between spines in the Collapse(−) and Collapse(+) groups. The values of a more sensitive parameter, NZ, were higher in Collapse(−) than in Collapse(+) groups, demonstrating that degenerative segments with preserved disc height have a latent instability compared to segments with collapsed discs.

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Tomoaki Suzuki, Hitoshi Hasegawa, Kouichirou Okamoto, Kazuhiro Ando, Kohei Shibuya, Haruhiko Takahashi, Shoji Saito, Makoto Oishi, and Yukihiko Fujii

BACKGROUND

Choroidal collaterals are a risk factor for hemorrhagic stroke, even in the nonhemorrhagic hemisphere, among patients with moyamoya disease (MMD). Peripheral choroidal aneurysms rupture in fragile collaterals; however, the development and natural course of these aneurysms remain elusive.

OBSERVATIONS

A 51-year-old woman, who had experienced a right cerebral hemorrhage 3 years earlier, presented with asymptomatic minor bleeding from a left lateral choroidal artery aneurysm in a predeveloped choroidal anastomosis. Although the aneurysm spontaneously thrombosed within 2 months, the choroidal collaterals persisted. After bypass surgery, the choroidal anastomosis regressed, and neither a de novo aneurysm nor a hemorrhagic stroke occurred. A 75-year-old woman with MMD, who had experienced a left frontal infarction 6 years earlier, experienced recurrent right intraventricular hemorrhage from a ruptured lateral choroidal artery aneurysm that developed in the choroidal anastomosis. The aneurysm spontaneously regressed 3 days after the rebleeding with no recurrence over the following 7 years.

LESSONS

Choroidal artery aneurysms may develop in the choroidal anastomosis and rupture in the nonsurgical or contralateral hemispheres. Patients with MMD who have a history of hemorrhagic or ischemic stroke and impaired cerebral blood flow require careful observation. Although aneurysms may rapidly regress spontaneously, bypass surgery can stabilize hemodynamic stress and prevent further hemorrhage.