RESUMEN
BACKGROUND: We conducted a finite element study to assess the effectiveness of a novel pedicle screw design with two alterations in the distal and proximal portions. METHODS: Finite element (FE) models of 24 vertebrae were constructed using computed tomographic data. Pull-out strength of 4 different pedicle screws were compared. The basic screw design was a dual threaded one (PS0), in which the proximal portion is double-threaded (cortical thread), and the distal portion is single-threaded (cancellous thread). In PS1, the inter-thread double-core shape was added to PS0 in the distal portion. Compared to PS0, in PS2, the proximal portion was elongated by 5 mm. PS3 had both PS1 and PS2 features. In addition, the 24 vertebrae were classified into 3 groups based on volumetric bone mineral density (vBMD) of the vertebral body: low <120 mg/cm3, moderate 120-170 mg/cm3, and high >170 mg/cm3. RESULTS: The mean pull-out strengths (±SD) were 1137 ± 500 N, 1188 ± 520 N, 1191 ± 512 N, and 1242 ± 538 N for PS0, PS1, PS2, and PS3, respectively. In PS1, there was significant difference in the incremental ratio of pull-out strength to PS0 between the low and high vBMD groups (3.7 ± 1.6% vs. 5.0 ± 1.0%, p = 0.006). In PS2, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (7.6 ± 4.0% vs. 3.3 ± 1.8%, p < 0.001). In PS3, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (12.1 ± 4.8% vs. 8.5 ± 2.1%, p = 0.003). CONCLUSIONS: The two design alterations showed the combined additive effect in the PS3 design. The moderate vBMD group has a balanced bone property to reflect the combined effects of the PS1 and PS2 design alterations.
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Densidad Ósea , Simulación por Computador , Diseño de Equipo , Ensayo de Materiales/instrumentación , Modelos Anatómicos , Tornillos Pediculares , Adulto , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Femenino , Análisis de Elementos Finitos , Humanos , Vértebras Lumbares/cirugía , Masculino , Persona de Mediana Edad , Estrés MecánicoRESUMEN
STUDY DESIGN: This is a retrospective study. OBJECTIVES: The aim of this study was to determine the extent of damage to the paravertebral muscles after muscle-preserving interlaminar decompression (MILD) using magnetic resonance imaging to evaluate changes in the multifidus muscle (MF). SUMMARY OF BACKGROUND DATA: Short-term surgical outcomes of MILD for lumbar spinal canal stenosis (LSCS) are satisfactory; however, the extent of damage to the paravertebral muscles after MILD remains unclear. METHODS: Thirty-four patients (18 men/16 women; mean age: 72.6 y) who had LSCS treated with MILD were retrospectively investigated. A total of 61 decompressed disk levels [L2/3(5); L3/4(21); L4/5(30); L5/S(5)] and 34 nondecompressed levels (L1/2) were assessed. There was 1 decompressed disk level in 12 cases, 2 in 17 cases, and 3 in 5 cases. Magnetic resonance imaging scans were obtained before surgery and at 3 and 12-18 months after surgery, using the same scanner. The rate of paravertebral muscle atrophy was evaluated to compare the area of the MF in the T2-weighted axial plane (intervertebral disk level) preoperatively and postoperatively, using OsiriX Medical Imaging Software. Changes in muscle signal intensity were also recorded. Statistical analysis was performed using 3-way analysis of variance with the post hoc Fisher PSLD test. RESULTS: The rate of MF atrophy was 4.0% at the decompressed levels and 2.1% at the nondecompressed levels. There were no changes of signal intensity in the MF between the preoperative and postoperative periods. In decompressed levels, muscle atrophy and signal intensity were significantly improved from 3 months to 12-18 months after surgery. The number and level of the decompressed disks did not affect the extent of muscle injury. CONCLUSIONS: The extent of paravertebral muscle injury after MILD is satisfactory. The midline interlaminar approach used in this technique may prevent local denervation and irreversible damage to the paravertebral muscles. These results indicate that MILD is useful to treat LSCS less invasively.
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Descompresión Quirúrgica/métodos , Músculos Paraespinales/fisiopatología , Estenosis Espinal/patología , Estenosis Espinal/cirugía , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Enfermedades Musculares/diagnóstico por imagen , Enfermedades Musculares/etiología , Músculos Paraespinales/diagnóstico por imagen , Estudios Retrospectivos , Estenosis Espinal/complicaciones , Estenosis Espinal/diagnóstico por imagenRESUMEN
INTRODUCTION: Polymethylmethacrylate (PMMA) cement is useful for spinal reconstruction, but can cause complications including new vertebral fractures, neurological disorders and pulmonary embolism. We report a case in PMMA cement used for spinal reconstruction after tumor curettage dislodged and penetrated the gastrointestinal tract. DIAGNOSES: The patient was diagnosed with a retroperitoneal extragonadal germ cell tumor at age 27 years. After chemotherapy and tumor resection, the tumor remained. It gradually increased in size and infiltrated lumbosacral vertebrae, causing him to present at age 35 years with increased low back pain. Image findings showed bone destruction in the vertebral bodies accompanied by neoplastic lesions. The left and right common iliac arteries and inferior vena cava were enclosed in the tumor on the anterior side of the vertebral bodies. Lumbosacral bone tumor due to direct extragonadal germ cell tumor infiltration was diagnosed. A 2-step operation was planned; first, fixation of the posterior side of the vertebral bodies, followed by tumor resection using an anterior transperitoneal approach, and spinal reconstruction using PMMA cement. After surgery, the PMMA cement gradually dislodged towards the anterior side and, 2 years 9 months after surgery, it had penetrated the retroperitoneum. The patient subsequently developed nausea and abdominal pain and was readmitted to hospital. The diagnosis was intestinal blockage with dislodged PMMA cement, and an operation was performed to remove the cement present in the small intestine. There was strong intra-abdominal adhesion, the peritoneum between the vertebral bodies and intestine could not be identified, and no additional treatment for vertebral body defects could be performed. After surgery, gastrointestinal symptoms resolved. CONCLUSION: Although this was a rare case, when using bone cement for vertebral body reconstruction, the way of anchoring for the cement must be thoroughly planned to assure no cement dislodgement can occur.
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Cementos para Huesos/efectos adversos , Migración de Cuerpo Extraño/diagnóstico , Intestino Delgado , Vértebras Lumbares , Neoplasias de la Columna Vertebral/cirugía , Vertebroplastia/efectos adversos , Adulto , Procedimientos Quirúrgicos del Sistema Digestivo/métodos , Estudios de Seguimiento , Migración de Cuerpo Extraño/etiología , Migración de Cuerpo Extraño/cirugía , Humanos , Imagen por Resonancia Magnética , Masculino , Radiografía Abdominal , Neoplasias de la Columna Vertebral/diagnósticoRESUMEN
STUDY DESIGN: A case-series study. OBJECTIVES: To measure the 3-dimensional (3D) morphology and kinematics of the craniovertebral junction (CVJ) using a 3D computed tomography (CT) model; to reveal abnormal patterns and the relationships between pathology and kinematics. SUMMARY OF BACKGROUND DATA: Evaluations using radiography, 2-dimensional (2D) CT and magnetic resonance imaging have limitations because of the complex 3D structure of the CVJ. METHODS: Twenty-four rheumatoid arthritis patients (21 females, 3 males) with cervical involvement underwent CT scanning of the cervical spine from the basilar process of the occipital bone to the first thoracic vertebra in neutral and flexed positions. The 3D morphology of the occipital condyle, atlas, and axis were classified based on the type of deformity observed. Periodontoid lesions (continuous bony lesions between the atlas and the odontoid process) were also noted. The 3D kinematics in the atlanto-occipital and atlantoaxial joints were evaluated using the volume merge method. RESULTS: Deformities in the atlanto-occipital joints appeared more frequently than those in the atlantoaxial joints. The most common instability pattern was flexural rotation during flexion at the CVJ. The direction of translational motions during flexion was posterior in the atlanto-occipital joint and anterior and caudal in the atlantoaxial joint. CONCLUSION: The results suggest that bilateral occipital condyle deformation, unilateral and bilateral mass collapse, and periodontoid lesions may affect flexion/extension rotational instability in the atlantoaxial joint. In addition, unilateral occipital condyle deformation and atlantoaxial joint stability may affect sagittal translational instability to the posterior side in the atlanto-occipital joint. The noninvasive 3D CT imaging technique employed here would be useful for predicting the prognosis of patients with rheumatoid deformities at the CVJ.
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Artritis Reumatoide/diagnóstico por imagen , Articulación Atlantoaxoidea/diagnóstico por imagen , Articulación Atlantooccipital/diagnóstico por imagen , Vértebras Cervicales/diagnóstico por imagen , Inestabilidad de la Articulación/diagnóstico por imagen , Rango del Movimiento Articular/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Artritis Reumatoide/patología , Artritis Reumatoide/fisiopatología , Articulación Atlantoaxoidea/patología , Articulación Atlantoaxoidea/fisiopatología , Articulación Atlantooccipital/patología , Articulación Atlantooccipital/fisiopatología , Fenómenos Biomecánicos/fisiología , Vértebras Cervicales/patología , Vértebras Cervicales/fisiopatología , Femenino , Humanos , Inestabilidad de la Articulación/patología , Inestabilidad de la Articulación/fisiopatología , Masculino , Persona de Mediana Edad , RadiografíaRESUMEN
The study subjects included 54 patients with cervical spondylotic myelopathy who underwent a selective laminoplasty. The patients were divided into three groups according to the number of decompressed levels: two levels, three levels and four or five levels. The number of cord compressions at every intervertebral level was determined in the flexion, neutral, and extension position using a dynamic magnetic resonance imaging (MRI) scan in consideration of both static and dynamic compressions. For each group, the clinical outcomes were evaluated. Moreover, the patients were divided into two groups according to their age. Then, the appearance ratios of cord compression between the neutral and extension position were compared at each intervertebral level. The clinical outcomes were satisfactory. There were no statistical differences among the three groups, except for the age and operation time. The position of the neck influenced the number of cord compressions. The appearance ratios of cord compression, which were especially prominent at C2/3, C3/4 and C4/5, showed high scores in the aged. The preoperative dynamic MRI scan was clinically useful. In the aged, attention should be given to C2/3, C3/4 and C4/5.
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Descompresión Quirúrgica/métodos , Imagen por Resonancia Magnética/métodos , Cuidados Preoperatorios/métodos , Compresión de la Médula Espinal/cirugía , Espondilosis/cirugía , Anciano , Anciano de 80 o más Años , Vértebras Cervicales/patología , Vértebras Cervicales/cirugía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Compresión de la Médula Espinal/complicaciones , Espondilosis/complicacionesRESUMEN
STUDY DESIGN: Outcomes of muscle-preserving interlaminar decompression (MILD) for the lumbar spine are reported. OBJECTIVE: To verify the clinical findings of lumbar MILD. SUMMARY OF BACKGROUND DATA: A preliminary short-term follow-up study of lumbar MILD demonstrated satisfactory neural recovery and reduced invasiveness. METHODS.: The initial 105 consecutive patients with lumbar spinal canal stenosis were included in this study. A total of 210 intervertebral levels were decompressed. There were 48 women and 57 men, and the mean patient age was 68.8 years. The postoperative follow-up period ranged from 8 to 44 months (mean 21.3 months). Eighty-one patients showed cauda equina claudication, and 75 patients complained of radicular pain. Preoperative imaging studies demonstrated that all patients had moderate-to-severe spinal canal stenosis, 75 patients had degenerative spinal canal stenosis, and the remaining 30 had degenerative spondylolisthesis. Pre- and postoperative Japanese Orthopedic Association scores, intraoperative blood loss, surgical complications, and postoperative ambulation were recorded. RESULTS.: One hundred five patients underwent lumbar MILD procedure for 210 interspinous levels, 42 patients for 2 levels, 37 patients for 1 level, 17 for 3 levels, 7 for 4 levels, and 2 for 5 levels. Cerebrospinal fluid leakage due to dural tear occurred in 2 patients. Expansion of the operative field was not necessary to repair the dura mater. The mean operation time was 104.9 minutes per level, and mean intraoperative blood loss was 29.4 g per level. Neurologic improvement was demonstrated in all patients. The mean recovery rate calculated with pre- and postoperative Japanese Orthopedic Association scores was 64.9%. Patients started to stand or walk an average of 2.5 days after surgery. None of the patients presented with wound infection. There was no neurologic complication in this series. CONCLUSION: In MILD for the lumbar spine, damage to the posterior stabilizing structures such as the intervertebral facet joints, paravertebral muscles, thoracolumbar fascia, supra- and interspinous ligaments, can be minimized, while preserving the function of the spinous processes as lever arms for lumbar extension.
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Descompresión Quirúrgica/métodos , Vértebras Lumbares/cirugía , Canal Medular/cirugía , Estenosis Espinal/cirugía , Anciano , Cauda Equina/patología , Descompresión Quirúrgica/efectos adversos , Femenino , Estudios de Seguimiento , Humanos , Vértebras Lumbares/patología , Masculino , Dolor Postoperatorio/etiología , Enfermedades del Sistema Nervioso Periférico/etiología , Canal Medular/patología , Estenosis Espinal/patología , Resultado del TratamientoRESUMEN
By using a Fourier-transform infrared spectrometer contained in an inert gas glovebox system (oxygen and water concentrations: <0.1 ppm), high-quality infrared absorption spectra have been observed for the radical anion and dianion of p-terphenyl in tetrahydrofuran solutions. Density functional theory with the B3LYP nonlocal exchange-correlation functional and the 6-311+G** basis set has been used for the calculations of the structures and infrared spectra of the neutral species, radical anion, and dianion of p-terphenyl. The observed infrared spectra of the radical anion and dianion are in good agreement with those calculated by density functional theory. The origin of the strong infrared absorption intensities characteristic of the radical anion and dianion are discussed in terms of changes in electronic structures induced by specific normal vibrations (electron-molecular vibration interaction).
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Algoritmos , Gases Nobles/química , Compuestos de Terfenilo/química , Electrones , Radicales Libres/química , Iones/química , Estructura Molecular , Soluciones/química , Espectroscopía Infrarroja por Transformada de Fourier/métodosRESUMEN
STUDY DESIGN: Posterior cervical spinal cord shifting after selective single laminectomy associated with partial laminotomies was compared with that after bilateral open-door laminoplasty between the C3 and C7 levels in relation to the clinical results of each procedure. OBJECTIVES: To investigate the clinical significance of posterior spinal cord shifting after extensive cervical laminoplasty. SUMMARY OF BACKGROUND DATA: Current techniques used for cervical laminoplasty for multisegmental cervical spondylotic myelopathy (CSM) are consecutively performed between the C3 and C6 or C7 levels with expectation that the spinal cord will shift backward to keep it clear of anterior compression. However, the clinical significance of the posterior spinal cord shifting remains controversial, and there has been no report verifying it by comparing limited posterior decompression procedures with conventional extensive ones. METHODS: Twenty-six patients with consecutive 2- to 3-level CSM who underwent selective laminoplasty (Group A) were enrolled in the study, and among 56 CSM patients who underwent bilateral open-door laminoplasty between the C3 and C7 levels, 25 who had consecutive 2- or 3- level stenosis identified by preoperative magnetic resonance imaging were used as controls (Group B). The recovery rate was calculated using preoperative and postoperative Japanese Orthopedic Association (JOA) scores for each patient, and for each patient's magnetic resonance imaging, the postoperative cervical curvature index was obtained according to Ishihara's method and the magnitude of postoperative backward shifting of the spinal cord was measured. RESULTS: There was no significant difference between the subjects in Groups A and B with respect to the spinal curvature index, preoperative JOA scores, and recovery rate, but the magnitude of the postoperative posterior shifting of the spinal cord was greater for those in Group B than for those in Group A. There was no correlation between the recovery rate and posterior shifting of the spinal cord for each group, and no correlation was also found between the curvature index and posterior shifting of the spinal cord. CONCLUSIONS: The outcome of posterior decompression surgery for multisegmental CSM is not correlated with the magnitude of postoperative backward shifting of the spinal cord. Extensive and consecutive decompression performed in conventional cervical laminoplasties is therefore not always necessary for multisegmental CSM.