Experimental Study of Failures of the Rigid Spinal Posterior Fixation System Under Compressive Load Conditions: A Cadaver Study.

Background Many studies have been conducted on the biomechanics of the spine to elucidate the fixation properties of spinal fusion surgery and the causes of instrumentation failure. Among these studies, there are some studies on load sharing in the spine and measurement using strain gauges and pressure gauges, but there is a lack of research on axial compressive loads. Methods Axial compressive load tests were performed on human cadaveric injured lumbar vertebrae fixed with pedicle screws (PS). Both the strain generated in the PS rod and the intradiscal pressure were measured. Subsequently, the stress generated in the PS rod and the load sharing of the spine and instrumentation were calculated. Results Even when only compressive load is applied, bending stress of more than 10 times the compression stress was generated in the rod, and the stress tended to concentrate on one rod. Rod deformation becomes kyphotic, in contrast to the lordotic deformation behavior of the lumbar spine. The stress shielding rate was approximately 40%, less than half. Conclusions This study obtained basic data useful for constructing and verifying numerical simulations that are effective for predicting and elucidating the causes of dislodgement and failure of spinal implants.

Incidence and Skeletal Features of Developmental Cervical and Lumbar Spinal Stenosis.

STUDY DESIGN: Cross-sectional study. PURPOSE: To report the prevalence and relationship of developmental cervical and lumbar spinal stenosis (DCSS and DLSS) with the bone parameters of the skull and extremities. OVERVIEW OF LITERATURE: DCSS and DLSS are found occasionally in daily practice. DCSS and DLSS can cause compressive myelopathy, radiculopathy, and cauda equina syndrome; however, data on their prevalence and correlation with skull and skeletal extremity profiles is scarce. METHODS: A cross-sectional measurement study of 293 whole-body dried-bone samples was conducted. We measured the anteroposterior (AP) and transverse diameter of the fourth to sixth cervical vertebrae (C4-C6) and third to fifth lumbar vertebrae (L3-L5). Stenosis of the cervical spine and lumbar spine was defined as an AP diameter of <12 mm and <13 mm, respectively. We also measured the skull circumference, the AP and transverse diameters of the foramen magnum, the inner and outer inter distances between the left and right orbital bones, the humerus length, and the femoral length. Kruskal-Wallis and post hoc analyses were used in the statistical analyses. RESULTS: The age was 22-93 years. DCSS was found in 59 (20.1%) and DLSS in 28 (9.6%). Twelve samples had both DCSS and DLSS (development spinal stenosis, DSS). When compared to the "no spinal stenosis sample," DSS (-), DCSS and DSS had a significantly smaller skull circumference, the transverse diameter of the foramen magnum, and inner and outer distance between the orbital bone (p<0.05). There was no significant difference in humeral length, femoral length, or AP diameter of the foramen magnum. CONCLUSIONS: DCSS was correlated with a small skull, a small transverse diameter of the foramen magnum, and a small orbital bone. A small skull was strongly associated with a small cervical canal. DLSS, on the other hand, was unrelated to either a small cervical canal or a small skull.

The new imaging findings: "Passing spine" without kissing.

ABSTRACT: Case-control studies by examining the lumbar spine computed tomography (CT) findings focusing on the spinous processes."Passing spine" was defined as a lumbar degenerative change observed on CT images. In contrast, kissing spine, which is also an image finding, has been acknowledged as an established clinical condition. Therefore, we compared the passing spine group and the kissing spine group to investigate whether the 2 groups belong to a similar disease group; this would help explain the clinical and imaging characteristics of patients with passing spine.Previous studies have described the gradual increase in the height and thickness of the lumbar vertebral spinous processes that can occur in individuals aged >40 years, and reported that this progressive degeneration can lead to a condition termed "kissing spine."We examined the CT imaging of 373 patients with lumbar spinal disease and divided patients into 2 groups, the kissing spine (K) group and the passing spine (P) group, and compared the clinical (age, sex, presence/absence of lower extremity pain) and imaging data (localization of kissing or passing spine, intervertebral disc height at the level of kissing or passing spine, lumbar lordosis (LL) angle, presence/absence of vacuum phenomenon (VP) in the intervertebral discs and spondylolisthesis at the level of kissing or passing spine between the 2 groups.Compared with patients with kissing spine, patients with passing spine had an increased incidence of lower extremity pain, lower intervertebral disc height at the level of passing spine, relatively static LL, and VP commonly observed in the intervertebral discs at the level of passing spine.Because the clinical and imaging characteristics of patients with passing spine are different from those of patients with kissing spine, passing spine might be a pathological condition distinct from kissing spine.

Pedicle Screw System May Not Control Severe Spinal Rotational Instability.

STUDY DESIGN: An in vitro biomechanical study. OBJECTIVE: The purpose of this study is to discuss whether pedicle screw systems can control spinal rotational instability in a functional spinal unit of lumbar spine on human cadaver. SUMMARY OF BACKGROUND DATA: Rotational experiments using deer lumbar cadaveric models showed that rotational range of motion (ROM) of the model fixed by a pedicle screw system with crosslinking after total facetectomy for both the sides was larger than that in the intact model, and stated that spinal rotational instability could not be controlled using a pedicle screw system. METHODS: A rotation experiment using 10 functional spinal units (L3-4) of lumbar spine on human cadavers was performed by preparing the four models (intact model, damaged model, pedicle screw model, and crosslink (CL) model) in stages, then calculating and comparing rotational ROM among the four models. RESULTS: Rotational ROM in the CL model was still larger than that of the intact model in all the samples. And, rotational ROM decreased in the order of damaged model >> pedicle screw model > CL model > intact model. Statistical analysis revealed significant differences between all models (P < 0.001). CONCLUSIONS: Pedicle screw systems may not control severe spinal rotational instability in human lumbar cadaveric models with total facetectomy on both the sides. This may represent a major biomechanical drawback to the pedicle screw system. LEVEL OF EVIDENCE: N/A.

Biomechanical Problems Related to the Pedicle Screw System.

AIM: To assess biomechanical problems related to pedicle screw (PS) systems. MATERIAL AND METHODS: Functional spinal units (L3-4) of deer were evaluated using a 6-axis material testing machine. For the specimen models, we prepared an intact model, a damaged model, a PS model, and a crosslink model. We checked the range of motion (ROM) during bending and rotation tests. Eight directions were measured in the bending test: anterior, right-anterior, right, right-posterior, posterior, left-posterior, left, and left-anterior, and 2 directions were measured in the rotation test (right and left). RESULTS: ROMs of the PS model were smaller than those of the intact model in all directions. However, ROMs of the PS model in the rotation test were smaller than those of the damaged model and larger than those of the intact model. The stability of the crosslink model was better than that of the PS model during the bending test, but ROMs of the crosslink model were larger than those of the intact model during the rotation test. CONCLUSION: Excessive bending rigidity and rotational instability are the biomechanical problems related to PS systems. Based on these results, we speculate that one of the most significant causes of adjacent segment disease is excessive bending rigidity and one of the most important causes of instrumentation failure is rotational instability.

A survey of workplace violence against physicians in the hospitals, Myanmar.

OBJECTIVE: Workplace violence in hospitals is recently becoming a major global concern in many countries. However, in Myanmar, we have felt that patients and their families have rarely made unreasonable complaints in hospitals, and then, the purpose of this study is to report the current state of workplace violence in hospitals in Myanmar. Participants are 196 physicians (108 males and 88 females) in hospitals in Myanmar. RESULTS: A descriptive survey was conducted in regard to verbal abuse and physical violence from patients or the people concerned. At the results of this study, the percentages of physicians who have encountered verbal abuse and those who have encountered physical violence are markedly low (8.7 and 1.0%, respectively). The present study is the first to report the frequencies of verbal abuse and physical violence against physicians in a least developed country, and the results of the present study are important in terms of discussing workplace violence in hospitals.

RETRACTED: Three-Minutes Sitting Test for evaluating lumbar foraminal stenosis: A preliminary report.

This article has been retracted.

Biomechanical Stability of a Cross-Rod Connection with a Pedicle Screw System.

BACKGROUND Surgery with pedicle screw instrumentation does not provide sufficient torsional stability. This leads to pseudoarthrosis, loosening of the pedicle screws, and, ultimately, implant failure. MATERIAL AND METHODS Functional spinal units from 18 deer were evaluated using a 6-axis material testing machine. As specimen models, we prepared an intact model, a damaged model, a cross-rod model, and a cross-link model. We measured the range of motion (ROM) during bending and rotation tests. RESULTS The range of motions of cross-rod model were almost equal to those of cross-link model during the bending test. In the rotation test, the average ranges of motion of the intact, cross-rod, and cross-link models were 2.9°, 3.1°, and 3.9° during right rotation and 2.9°, 3.1°, and 4.1° during left rotation, respectively. The range of motions of the cross-rod model were significantly smaller than those of the cross-link model during the rotation test. The range of motions of the intact model were significantly smaller than those of the cross-link model during the rotation test, but there were no statistically significant differences between the range of motions of intact model and cross-rod model during the rotation test. CONCLUSIONS The stability of spinal fixation such as cross-rod model is equal to the fixation using the pedicle screw system during bending tests and equal to that of the intact spine during rotation tests.

Trajectory of instantaneous axis of rotation in fixed lumbar spine with instrumentation.

BACKGROUND: Several studies showed instantaneous axis of rotation (IAR) in the intact spine. However, there has been no report on the trajectory of the IAR of a damaged spine or that of a fixed spine with instrumentation. It is the aim of this study to investigate the trajectory of the IAR of the lumbar spine using the vertebra of deer. METHODS: Functional spinal units (L5-6) from five deer were evaluated with six-axis material testing machine. As specimen models, we prepared a normal model, a damaged model, and a pedicle screw (PS) model. We measured the IAR during bending in the coronal and sagittal planes and axial rotation. In the bending test, four directions were measured: anterior, posterior, right, and left. In the rotation test, two directions were measured: right and left. RESULTS: The IAR of the normal model during bending moved in the bending direction. The IAR of the damaged model during bending moved in the bending direction, but the magnitude of displacement was bigger compared to that of the normal model. In the PS model, the IAR during bending test hardly moved. During rotation test, the IAR of the normal model and PS model located in the spinal canal, but the IAR of the damaged model located in the posterior part of the vertebral body. CONCLUSIONS: In this study, the IAR of damaged model was scattering and that of PS model was concentrating. This suggests that higher mechanical load applied to the dura tube and nerve roots in the damaged model and less mechanical load applied to that in the PS model.

Tumoral calcinosis in the cervical spine: a case report and review of the literature.

BACKGROUND: Tumoral calcinosis is rarely located in spine. A 55-year-old Japanese woman with cervical tumoral calcinosis is presented, along with a review of the literature relating to tumoral calcinosis in the spine. We discussed the etiology, diagnosis, and management of this condition. CASE PRESENTATION: We report a case of a patient with cervical tumoral calcinosis with end-stage renal disease. A computed tomography scan showed a lobulated, calcified mass around the right facet joint at the fourth-fifth cervical spine and calcifications were also observed in the right intervertebral foramens at fourth-fifth cervical spine and fifth-sixth cervical spine levels and the anterior wall of the spinal canal. By performing a cervical decompression and stabilization, the patient recovered from her neurological symptoms. CONCLUSIONS: Although tumoral calcinosis is rarely located in the spine, it should be considered in the differential diagnosis of spinal lesions. If a calcified mass causes acute neurological symptoms, resection of the mass is still the most important treatment.

Characteristics of Patients with High Lie Scores in a Personality Test.

BACKGROUND: It is reported that persons with high Lie score (L score) of a personality test are aggressively self-confident and are also related to depression or schizophrenia In this study, we examined the characteristics of patients with high L scores on the Maudsley Personality Inventory (MPI) and examined the significance of the L score. MATERIALS AND METHODS: We collected the data of 10789 subjects and examined the relationship between L score or the number of characteristic biased persons and the parameters of age, sex, education level, occupation, and degree of pain. Furthermore, we examined the changes in extraversion-introversion (E score), neuroticism (N score), and L scores at approximately 1 year after surgery in 1711 patients who underwent surgery at our university hospital or affiliated hospitals. RESULTS: L score was significantly higher among persons with a high degree of pain, and ratio of the characteristic biased persons in L score was significantly high among persons in their 40s to 60s, healthcare professionals and those with a high degree of pain. Moreover, L score scarcely changed between before and after surgery when compared with E score and N score. CONCLUSION: L score is not greatly influenced by an individual's state of mind or situation at different times, and may indicate the personality traits proper to the person. It is shown that L score may indicate the personality trait characteristics of persons who want to make themselves look good in the eyes of other.

Relief of Lower Back and Leg Pain after Myelography.

INTRODUCTION: It is well-known that many patients will have adverse reactions such as headache and nausea after undergoing myelography, but we have often seen cases where symptoms such as lower back pain and leg pain were alleviated following myelography. To the best of our knowledge, such clinical cases of post-myelographic alleviation have not been reported. MATERIALS AND METHODS: A total of 325 patients with a degenerative lumbar spinal disorder who underwent myelography were prospectively investigated at four hospitals from April 2012 to March 2014 to survey the post-myelographic alleviation of lower back and leg pain prospectively. The severities of lower back pain, leg pain and numbness of the lower extremities were evaluated and intermittent claudication distance was measured before myelography. The magnetic resonance imaging (MRI) findings and myelographic findings were also evaluated for the patients that their symptoms were improved. RESULTS: Thirty-five of 325 cases (10.8%) of these patients had their symptoms alleviated after undergoing myelography; 26 cases of lower back pain, two cases of leg pain, two cases of numbness of the lower extremity, and five cases of intermittent claudication. CONCLUSION: In the patients of a degenerative lumbar spinal disorder, about 10% cases with lower back pain or intermittent claudication had post-myelographic alleviation. Intradural injection therapy might be a therapeutic method to alleviate these symptoms.

Biomechanical study of rotational micromovement of the pedicle screw.

BACKGROUND: In regard to the fixation using a pedicle screw (PS) and rod system, the mechanism from the onset of the clear zone up to the development of loosening of the pedicle screw is not completely clarified. The purpose of this study is to determine the cause of the pedicle screw loosening by performing a biomechanical study with three-dimensional movie analysis. METHODS: Ten PS fixation model of the lumbar spines (L3-4) of boar cadavers were used. The rotational angles of the L3 and L4 vertebral body and the screw at the time of applying a ±5 Nm load in the left anterior and right posterior flexion directions respectively were calculated based on those at the time of applying no load. The absolute value of the difference in the rotational angles between each vertebral body with left anterior flexion and right posterior flexion and the inserted screws was defined as rotational micromovement. RESULTS: In both the left anterior and right posterior flexion directions, there were significant differences (p < 0.05) in the rotational angles between the screw and the vertebral body for both the L3 and L4 vertebral bodies. CONCLUSION: Our biomechanical results showed that rotational micromovement occurred between the PS and the vertebral body, and repeated rotational micromovement might cause loosening of the screw or pullout of PS fixation.