Takeshi Hoshikawa

Spinal dumbbell tumors: an analysis of a series of 118 cases

OBJECT The authors analyzed a series of 118 cases of spinal dumbbell tumors to elucidate the feature of the tumors. METHODS Of 674 cases of spinal cord tumors, the incidence of dumbbell tumors was studied. The tumors were analyzed, and the authors focus on the distribution of age and sex, the pathological diagnoses, their locations, Eden classification, and the surgical methods used. RESULTS The incidence of dumbbell tumors was 18%. The mean patient age was 43 years, which was younger than that for all spinal cord tumors (mean 50 years). There were 11 patients younger than 10 years of age. The rate of dumbbell tumors in the cervical spine was significantly higher than that of all spinal cord tumors. Fifteen (18%) of the 81 schwannomas were observed in the C-2 nerve root, thus having a higher incidence than those in the other nerve roots. In 99 cases (84%), the tumors were removed through a hemilaminectomy with or without a facetectomy and posterior fusion. Of 118 cases, 69% of the tumors were schwannomas, and malignant tumors were found in 10 cases (8.5%). Seven (64%) of 11 patients younger than 10 years of age had malignant tumors. Three patients older than 10 years of age had malignant tumors, thus accounting for 2.8% of the 107 older patients. CONCLUSIONS The incidence of dumbbell tumors was 18%, and they are not uncommon. Malignant dumbbell tumors were more common in children younger than 10 years of age than in older patients.

Flexion-distraction injuries in the thoracolumbar spine: an in vitro study of the relation between flexion angle and the motion axis of fracture.

A new concept, the motion axis of fracture (MAF), which is defined as the transitional point from anterior compressive to posterior splitting failure on a lateral radiograph, has provided a true understanding of the mechanisms of flexion–distraction injuries in clinical cases. This study was designed to produce in vitro injuries that have MAFs and to clarify the relation between the flexion angle and the MAF location. Adolescent porcine thoracolumbar spines were exposed to a vertical compressive load to failure at three different flexion angles and then examined radiographically. The MAF location was recorded as the distance from the anterior border to the MAF expressed as a percentage of the anteroposterior diameter of the vertebral body. All specimens showed similar injuries, with MAFs consisting of anterior compression fractures in the vertebral bodies and posterior disruptions. A significant negative correlation emerged between the flexion angle and the MAF location (r = -0.890; p < 0.0001). These results suggest that even a vertical compressive load contributes to the production of a flexion–distraction injury with an MAF in the thoracolumbar spine. They also indicate that the flexion angle of the spine at which the vertical compressive load is applied is an important factor in determining the MAF location; that is, the larger the flexion angle, the more anterior the MAF.

Spine-shortening vertebral osteotomy in a patient with tethered cord syndrome and a vertebral fracture. Case report.

The authors report a rare case of tethered cord syndrome with low-placed conus medullaris complicated by a vertebral fracture that was successfully treated by a spine-shortening vertebral osteotomy. The patient was a 57-year-old woman whose neurological condition worsened after a T-12 vertebral fracture because a fracture fragment and the associated local kyphotic deformity directly compressed the tethered spinal cord. An osteotomy of the T-12 vertebra was performed in order to correct the kyphosis, remove the fracture fragment, and reduce the tension on the spinal cord. Postoperative radiographs showed the spine to be shortened by 22 mm, and the kyphosis between T-11 and L-1 improved from 23 degrees to 0 degrees . Two years after the surgery, the patients neurological symptoms were resolved. The bone union was complete with no loss of correction.

Sagittal alignment changes after thoracic laminectomy in adults.

OBJECT The increased kyphosis after thoracic laminectomy in adult patients was retrospectively evaluated and various factors affecting this spinal deformity were analyzed. METHODS The authors conducted a retrospective study of 58 cases in which laminectomy was performed and more than half of the facet joints were left intact. The study group included 44 men (mean age 59 years) and 14 women (mean age 61 years) with thoracic myelopathy due to ossifications of the ligamentum flavum and/or the posterior longitudinal ligament or due to posterior bone spurs. Patients were followed up for a minimum of 2 years. Their neurological condition was evaluated using the Japanese Orthopaedic Association (JOA) scale (a full score is 11), and the magnitude of local kyphosis in the laminectomized area was determined using the Cobb angle method. RESULTS The mean preoperative JOA score was 5.4; the mean postoperative score was 8.3. No relationship was found between postoperative JOA score and increased kyphotic angle. The mean preoperative kyphotic angle was 7.0 degrees . The mean postoperative kyphotic angle was 10.8 degrees . Thus local kyphosis in the treated area increased by only 3.8 degrees . The mean increase in kyphosis per spinal segment, calculated by dividing the kyphotic angle of the surgically decompressed area by the number of resected laminae, was 1.9 degrees . Female patients with >or= 3-level laminectomies showed a significant increase of kyphosis in both the laminectomized area and each spinal segment. CONCLUSIONS The increase in kyphosis after thoracic laminectomy is not large and thus spinal fusion is usually not necessary. In cases involving female patients who undergo long-segment laminectomies, however, careful radiographic follow-up is recommended.

Relationship between Gallium Concentration and Resistivity of Gallium-Doped Czochralski Silicon Crystals: Investigation of a Conversion Curve

The relationship between gallium (Ga) concentration and resistivity was studied in Ga-doped Czochralski (CZ) silicon (Si) single crystals in the dopant concentration range from 1×1014 to 2×1018 atoms/cm3 by the four-point probe method, inductively coupled plasma (ICP) analysis, and Hall-effect measurement. The resistivity of Ga-doped Si was found to be larger than that of B-doped Si, because Ga is not fully ionized at Ga concentrations higher than 1016 atoms/cm3 at 300 K. A conversion curve from resistivity to Ga concentration in the range from 1×1014 to 1×1017 atoms/cm3 is proposed.

Temperature Dependences of Acceptor Concentration, Conductivity Mobility, and Resistivity of Ga-Doped Czochralski-Si Crystals

The temperature dependences of acceptor concentration nA, conductivity mobility ?C, and resistivity ? of gallium (Ga)-doped Czochralski (CZ)-silicon (Si) crystals were studied in the temperature range from 220 to 360 K (-53 to 87 ?C). Crystals with Ga concentration NA from 6.1 ?1014 to 2.0 ?1018 atoms/cm3 were analyzed by Hall-effect measurements using the van der Pauw method in the temperature range from 80 to 360 K. The temperature dependences of nA and ? of crystals with less than 1016 atoms/cm3 showed the same trends as those of B-doped p-type Si crystals, while those of crystals with more than 1016 atoms/cm3 differed from those of B-doped crystals, mainly because the temperature dependence of nA is not in the saturation range and the degree of ionization nA/NA decreases with decreasing temperature from 360 to 220 K.

Tumor-induced osteomalacia caused by phosphaturic mesenchymal tumor of the cervical spine

IntroductionTumor-induced osteomalacia is a rare paraneoplastic syn-drome and patients with this syndrome frequently presentwith bone pain, fractures, and muscle weakness [1–4].Fibroblast growth factor 23 (FGF-23), which is a memberof the FGF protein family [5], is associated with osteo-malacia [6]. FGF-23 can decrease serum phosphorus levelsby inhibiting phosphorus reabsorption in the proximal renaltubules and intestinal tract [7]. This protein can be secretedfrom mesenchymal tumors, particularly phosphaturicmesenchymal tumors [8]. Spinal tumors of this type areextremely rare and to the best of our knowledge, only 10cases have been reported to date [1, 2, 4, 9–15].Osteomalacia is a generalized mineralization disorderof the osteoid matrix, characterized by decreasedincorporation of calcium and phosphate [16]. Osteomalaciareduces bone resistance with a decrease in cortical bonethickness and retards bone union. Therefore, spinalreconstruction after phosphaturic mesenchymal tumorresection carries a substantial risk of instrumental failure.In addition, there is a risk of non-union or delayed unioncaused by delayed callus calcification [17]. Here we reporta case of phosphaturic mesenchymal tumor-inducedosteomalacia at C5 vertebra, causing severe cervicalmyelopathy. The patient underwent tumor resection andnon-instrumented spinal fusion, which improved his neu-rological condition, relieved osteomalacic symptoms, andresulted in a complete bony union without loss of cervicallordosis.Case reportA72-year-oldmanfirstnoticed numbness in his left handin 2003. In 2005, he came to our hospital presenting withgait disturbance, numbness in the right hand, and muscleweakness in his left hand. He showed left-dominantclumsiness and spasticity in both legs. Muscle atrophywas detected in the supraspinatus, infraspinatus, triceps,and intrinsic muscles of the left side. Neurologicalexamination revealed muscle weakness of grades 3–4 forelbow extension, dorsal and palmer wrist flexion, andfinger extension of the left side as well as sensory dis-turbance in the left hand and upper arm. Bilateral bicepsand triceps tendon reflexes were decreased, whereasbilateral knee jerk was accelerated. He was diagnosed ashaving cervical myelopathy with a Japanese OrthopaedicAssociation (JOA) score of10points(fullscoreforcervical myelopathy= 17 points). Blood examinationrevealed hypophosphatemia (1.3 mg/dl; normal range

Cervical myelopathy due to degenerative spondylolisthesis

Abstract Objective. To investigate clinical-radiological features of cervical myelopathy due to degenerative spondylolisthesis (DSL). Methods. A total of 448 patients were operated for cervical myelopathy at Nishitaga National Hospital between 2000 and 2003. Of these patients, DSL at the symptomatic disc level was observed in 22 (4.9%) patients. Clinical features were investigated by medical records, and radiological features were investigated by radiographs. Results. Disc levels of DSL were C3/4 in 6 cases and C4/5 in 16 cases. Distance of anterior slippage was 2 to 5 mm (average 2.9 mm) in flexion position. Space available for the spinal cord (SAC) was 11 to 15 mm (average 12.8 mm) in flexion position and 11 to 18 mm (average14.6 mm) in extension position; 11 cases were reducible and 11 cases were irreducible in extension position. Myelograms demonstrated compression of spinal cord by the ligamentum flavum in extension position. Compression of spinal cord was not demonstrated in flexion position. C5-7 lordosis angle was lower than control. C5-7 range of motion (ROM) was reduced compared to controls. These alterations were statistically significant. Conclusions. DSL occurs in the mid-cervical spine. Lower cervical spine demonstrated restricted ROM and lower lordosis angle. Pathogenesis of cervical myelopathy due to DSL is compression of spinal cord by the ligamentum flavum in extension position and not by reduced SAC in flexion position.

T1 radiculopathy caused by intervertebral disc herniation: symptomatic and neurological features.

Just as with cervical radiculopathy, T1 radiculopathy can be caused by degenerative processes of the spine, such as intervertebral disc herniation. Since it was fi rst described by Svien and Karavitis in 1954, to our knowledge, only 33 cases have been reported excluding 1 case of a tumorous lesion. Patients suffering from T1 radiculopathy are rare, so the comprehensive clinical features may not be familiar to orthopedists or even spinal surgeons. The symptomatic characteristics of T1 radiculopathy mimic those of C8 radiculopathy involving the upper limbs. It is occasionally diffi cult to distinguish between these two radiculopathies symptomatologically. Therefore, a summary of the neurological fi ndings of T1 radiculopathy in comparison to those of C8 radiculopathy should be helpful in making a correct clinical diagnosis. Morgan and Abood described the symptomatic and neurological features of T1 radiculopathy in 23 patients, but their description might be inadequate. This article reports one case of T1 radiculopathy caused by intervertebral disc herniation that was treated surgically. In addition, 33 patients with this radiculopathy were analyzed in more detail than the summarized description by Morgan and Abood, including the rate of characteristic neurological fi ndings. The patient described here was informed that his data would be submitted for publication and gave his consent.

Bilateral spondylolysis of inferior articular processes of the fourth lumbar vertebra: a case report

Abstract Lumbar spondylolysis, a well known cause of low back pain, usually affects the pars interarticularis of a lower lumbar vertebra and rarely involves the articular processes. We report a rare case of bilateral spondylolysis of inferior articular processes of L4 vertebra that caused spinal canal stenosis with a significant segmental instability at L4/5 and scoliosis. A 31-year-old male who had suffered from low back pain since he was a teenager presented with numbness of the right lower leg and scoliosis. Plain X-rays revealed bilateral spondylolysis of inferior articular processes of L4, anterolisthesis of the L4 vertebral body, and right lateral wedging of the L4/5 disc with compensatory scoliosis in the cephalad portion of the spine. MR images revealed spinal canal stenosis at the L4/5 disc level. Posterior lumbar interbody fusion of the L4/5 was performed, and his symptoms were relieved.