Flexion and extension radiography of the lumbar spine: a comparison with lumbar discography

Four methods of quantifying relative intervertebral body movement from static flexion/extension radiographs are reviewed and the ability of each of these techniques to indicate the site(s) of disc degeneration is compared with that of lumbar discography. Of the methods examined, that of measuring the linear displacement of one vertebra in the antero-posterior plane was found to be the most accurate method of indicating disc degeneracy. None of the methods examined was free from artefacts. With regard to the clinical usefulness of flexion/extension radiography, we discuss two separate situations. Firstly, the taking of a single set of flexion/extension radiographs is concluded to be of little value in the management of patients with low back pain. Secondly, flexion/extension radiography, on a serial basis, is considered to be of possible value in specific situations (for example, follow-up of a spinal fusion).     

脊柱动态测量仪对正常人和腰痛患者脊柱运动能力的量化测量

目的：量化测量脊柱各个椎体椎间角度变化,评估腰痛患者运动能力下降程度。方法：使用脊柱动态测量仪测量112例正常人和60例腰痛患者不同姿势下的脊柱形态,得出量化脊柱各个椎体之间椎间角角度,并进行独立样本t检验和配对样本t检验。结果：腰痛患者脊柱前屈运动能力比正常人下降80%,后伸要比正常人要下降60%,P〈0.05。前屈时腰痛患者的胸段脊柱（T1～7）后凸增加不明显,没有显著差异,但是下胸段与腰段前凸转为后凸,椎间角度变化存在显著差异,P〈0.05。正常人的下腰段后伸能力变化最大的L4～5、L5～S1、L3～4椎间隙,在腰痛患者则表现为此3个节段的脊柱僵硬,后伸位与伸直位时椎间角比较没有显著差异。结论：脊柱动态测量仪可以直接、方便的测量出胸、腰椎各个椎间角变化,并且存在很好的可靠性、重复性和可信性,是脊柱各个节段运动能力评定的良好工具。     

Spinal injury analysis for typical snowboarding backward falls

Spinal injury (SPI) often causes death and disability in snow‐sport accidents. SPIs often result from spinal compression and flexion, but the injury risks due to over flexion have not been studied. Back protectors are used to prevent SPIs but the testing standards do not evaluate the flexion‐extension resistance. To investigate SPI risks and to better define back‐protector specifications, this study quantified the flexion‐extension range of motions (ROMs) of the thoracic‐lumbar spine during typical snowboarding backward falls. A human facet‐multibody model, which was calibrated against spinal flexion‐extension responses and validated against vehicle‐pedestrian impact and snowboarding backward fall, was used to reproduce typical snowboarding backward falls considering various initial conditions (initial velocity, slope steepness, body posture, angle of approach, anthropometry, and snow stiffness). The SPI risks were quantified by normalizing the numerical spinal flexion‐extension ROMs against the corresponding ROM thresholds from literature. A high risk of SPI was found in most of the 324 accident scenarios. The thoracic segment T6‐T7 had the highest injury risk and incidence. The thoracic spine was found more vulnerable than the lumbar spine. Larger anthropometries and higher initial velocities tended to increase SPI risks while bigger angles of approach helped to reduce the risks. SPIs can result from excessive spinal flexion‐extension during snowboarding backward falls. Additional evaluation of back protector's flexion‐extension resistance should be included in current testing standards. An ideal back protector should consider the vulnerable spinal segments, the snowboarder's skill level and anthropometry.     

Pathophysiology of low back pain during exposure to microgravity

Astronauts exposed to microgravity frequently report low back pain. This pain is described as moderate to severe in intensity. This condition warrants investigation as low back pain may hinder an astronaut's ability to perform challenging tasks by virtue of disruption of sleep and, subsequently, mental concentration. It is reported by astronauts that a "fetal tuck position" described as knees to chest position relieves back pain. It is possible that the pathogenesis of back pain in microgravity is discogenic (or mechanical) and somatic, referred from the sinuvertebral nerves due to excessive expansion of the lumbar intervertebral discs associated with reduction of gravitational compressive loads in space. The fetal tuck position may increase lumbar intervertebral disc hydrostatic pressure by flexion and transfer of spinal compressive forces toward the anterior region of the lumbar discs, subsequently reducing disc volume. Moreover, this position may reduce Type IV mechanoreceptor facilitation and nerve impulse propagation from the sinuvertebral nerves of the annulus fibrosus, and thus diminish low back pain perception. Elongated posterior soft tissues (apophyseal joint capsules and ligaments) with spinal flexion may potentially stimulate Type I and II mechanoreceptors. This neutralizes substance P in the spinal cord dorsal horn by increasing naturally occurring opioids such as enkephalins. Separately, other investigators have reported a higher incidence of herniated discs (HNP) in astronauts postflight. Further studies of countermeasures are recommended to prevent excessive spinal elongation and disc expansion, reduce low back pain in microgravity, and simulate 1-G disc homeostasis, which may also help prevent HNPs postflight.     

Effects of flexibility training on enhancing spinal mobility in older women.

The purpose of this study was to examine the extent to which spinal flexion and extension, or spinal mobility, could be improved in a population of older adults participating in a 10 week flexibility training program. Twenty female volunteers, mean age 71.8, were randomly assigned to either the experimental group (flexibility training) or the control group (no training). Prior to the initiation of training, all subjects were tested for total spinal mobility, the combined sum of spinal flexion and extension. Subjects in the experimental group were exposed to a series of flexibility exercises, three times per week, for 20-30 minutes in duration, for a total of 10 weeks. The control group participated in an alternative exercise program with the experimental group, including walking, swimming, dance, and other locomotor activities, however, they did not receive the additional flexibility training. At the conclusion of the 10 week period, all subjects were retested for spinal mobility, using back flexion and extension measures. Results indicated a significant improvement in spinal mobility in the experimental group, and virtually no measurable change in the control group. This study suggests that specialized training in back flexibility for older adults is warranted, and that significant gains in spinal mobility can be obtained, regardless of age.     

歼击机飞行员非特异性慢性腰背痛患者腰部竖脊肌表面肌电特征

目的测量分析非特异性慢性腰背痛歼击机飞行员与对照组歼击机飞行员腰部竖脊肌表面肌电（surface electromyography,sEMG）,为歼击机飞行员非特异性慢性腰背痛患者的客观诊断评价提供参考依据。方法芬兰ME6000-T8表面肌电仪测量39名非特异性慢性腰背痛歼击机飞行员（病例组）与12名无症状歼击机飞行员（对照组）腰部竖脊肌俯卧位等长收缩、站立位屈伸运动时的表面肌电。MEGAWIN700046,2．4版软件处理等长收缩时疲劳性肌电信号,获取中位频率下降率（median frequency slope,MFs）、平均功率频率下降率（mean power frequency slope,MPFs）、过零率下降频率（zero crossing rate slope,ZCRs）、平均电压下降率（average electromyography slope,AEMGs）,分析屈伸动作时的肌电信号,得出屈曲伸直动作时的平均肌电电压（averageelectromyography,AEMG）,并由此计算屈曲伸直比（flexion extension ratio,FER）。分析病例组与对照组各指标的差别。结果竖脊肌等长收缩时病例组与对照组疲劳性肌电指标之间无统计学差异。屈伸运动时病例组与对照组AEMG及FER指标有统计学差异（t=1．979～5．387,P％0．05或P％0．01）。结论非特异性慢性腰背痛歼击机飞行员与无症状歼击机飞行员之间的表面肌电指标FER差异显著,屈曲时竖脊肌AEMG增高,伸直时竖脊肌AEMG降低,FER可以作为歼击机飞行员非特异性慢性腰背痛诊断及疗效评价的客观量化参考指标。     

Comparison of 3D spinal motions during stair-climbing between individuals with and without low back pain

In spite of the importance of stair-climbing (SC) as an activity of daily living, 3D spinal motion during SC has not been investigated in association with low back pain (LBP). The purpose of this research is to investigate the differences of the spinal motions during SC between an LBP group and a healthy control group, in order to provide insight into the LBP effect on the spinal motions. During two types of SC tests (single and double step SCs), we measured 3D angular motions (flexion/extension, lateral bending, and twist) of the pelvis, lumbar spine and thoracic spine using an inertial sensing-based, portable spinal motion measurement system. For the nine motion variables (i.e. three anatomical planes × three segments), range of motions (ROM) and movement patterns were compared to determine the differences between the two groups. It was found that the only variable having the p-value of a t-test lower than 0.05 was the flexion/extension of the lumbar spine in both SCs (i.e. the LBP group's ROM < the control group's ROM). Although the strength of this finding is limited due to the small number of subjects (i.e. 10 subjects for each group) and the small ROM differences between the groups, the comparison result of the t-test along with the motion pattern shows that the effect of LBP during SC may be localized to the lumbar spinal flexion/extension, making it an important measure to be considered in the rehabilitation and treatment of LBP patients.     

坦克乘员腰痛的评定与分析

目的　分析腰前屈活动范围 ,腰肌肌力与腰痛问卷得分的相关性 ,探讨影响坦克乘员腰痛患者生活质量的主要原因。方法　对 2 6 7例腰痛坦克乘员进行髋关节和腰部活动范围测量 ,表面肌电图 (SEMG)检查和改良Oswestry腰痛问卷评分 ,将结果进行相关性和回归分析。结果　腰痛问卷得分与腰肌SEMG、腰屈曲范围和双直腿抬高角度之差显著性相关 ,腰痛问卷得分的 6 7.0 %可以用腰屈曲范围和腰肌SEMG来预测。结论　腰肌SEMG测定方法简单 ,可以作为评定腰痛坦克乘员腰肌肌力的方法 ,增加腰活动性和腰伸肌肌力可以改善患者的生活质量。     

Occult lumbar lateral spinal stenosis in neural foramina subjected to physiologic loading.

PURPOSETo measure the effect of extension, flexion, lateral bending, and axial rotation loads applied to the spine on the anatomic relationship of the spinal nerves in the neural foramen to the ligamentum flavum and the intervertebral disk, anc to determine the effect of disk degeneration on the response to loading.METHODSCadaveric lumbar motion segments were examined with CT and MR imaging, loaded with pure moment forces, frozen in situ, reexamined with CT, and sectioned with a cryomicrotome. The morphology of the intervertebral disks was classified on the basis of the appearance of the cryomicrotome sections. The neural foramina were classified as having no evident stenosis, as being stenotic, as having occult stenosis, or as showing resolved stenosis on the basis of the images and sections before and after loading. The stenotic and nonstenotic foramina were stratified by disk level, intervertebral disk classification, and type of loading applied. The effect of spinal level, disk type, and load type on the prevalence of stenosis was studied.RESULTSOn average, extension, flexion, lateral bending, and axial rotation resulted in the ligamentum flavum or intervertebral disk contacting or compressing the spinal nerve in 18% of the neural foramina. Extension loading produced the most cases of nerve root contact, and lateral bending produced the fewest cases. Each of the loading types resulted also in diminished contact between the spinal nerve and the intervertebral disk or ligamentum flavum in some cases. Disk degeneration significantly increased the prevalence of spinal stenosis. All foramina associated with advanced disk degeneration and half of the foramina associated with disks having radial tears of the annulus fibrosus either developed occult stenosis or were stenotic before loading.CONCLUSIONSThe study supports the concept of dynamic spinal stenosis; that is, intermittent stenosis of the neural foramina. Flexion, extension, lateral bending, and axial rotation significantly changed the anatomic relationships of the ligamentum flavum and intervertebral disk to the spinal nerve roots.     

Positional MR imaging of the lumbar spine: does it demonstrate nerve root compromise not visible at conventional MR imaging?

PURPOSE: To evaluate whether positional magnetic resonance (MR) images of the lumbar spine demonstrate nerve root compromise not visible on MR images obtained with the patient in a supine position (conventional MR images). MATERIALS AND METHODS: Thirty patients with chronic low back pain unresponsive to nonsurgical treatment and with disk abnormalities but without compression of neural structures were included. Positional MR images were obtained by using an open-configuration, 0.5-T MR imager with the patients seated and with flexion and extension of their backs. The disk and nerve root were related to the body position. Nerve root compression and foraminal size were correlated with the patient's symptoms, as assessed with a visual analogue scale. RESULTS: Nerve root contact without deviation was present in 34 of 152 instances in the supine position, in 62 instances in the seated flexion position, and in 45 instances in the seated extension position. As compared with the supine position, in the seated flexion position nerve root deviation decreased from 10 to eight instances; in the seated extension position, it increased from 10 to 13 instances. Nerve root compression was seen in one patient in the seated extension position. Positional pain score differences were significantly related to changes in foraminal size (P =.046) but not to differences in nerve root compromise. CONCLUSION: Positional MR imaging more frequently demonstrates minor neural compromise than does conventional MR imaging. Positional pain differences are related to position-dependent changes in foraminal size.     

Inter-joint coordination and the flexion-relaxation phenomenon among adults with low back pain during bending

BackgroundAltered inter-joint coordination and reduced flexion-relaxation at end-range trunk flexion are common in people with low back pain. Inconsistencies in these behaviors, however, make assessment and treatment challenging for this population.Research questionThe study objective was to investigate patterns of regional lumbo-pelvic coordination and flexion-relaxation in adults with and without low back pain, during a bending task.MethodsAdults with low back pain (n = 16) and a healthy group (n = 21) performed three trials of a bending task. Motion capture and surface electromyography systems measured joint kinematics (hip, lower and upper lumbar spine) and muscle activity (erector spinae longissimus, iliocostalis, and multifidus). Continuous relative phase analysis determined inter-joint coordination of the hip/lower lumbar and lower lumbar/upper lumbar joint pairs, during flexion and extension periods. Flexion-relaxation ratios using normalized surface electromyography data determined the extent of flexion-relaxation for each muscle, during each period. For inter-joint coordination, two-way repeated measure mixed ANOVAs calculated the effects of group (healthy/low back pain), period, and their interactions. Separate hierarchical linear models were constructed and tested relationships between flexion-relaxation ratios and our independent variables, group and muscle, while controlling for patient characteristics.ResultsThe low back pain group had more out-of-phase coordination of the hip/lower lumbar joint pair compared to the healthy group (mean difference = 24.7°; 95 % confidence interval = 3.93–45.4), independent of movement period. No significant between group differences in lower lumbar/upper lumbar coordination were observed. The low back pain group demonstrated reduced flexion-relaxation of all muscles during full flexion (21.7 % reduction on average), with multifidus showing the least relaxation.SignificanceRegional differences in the lumbar spine and the possibility of subgroups with distinct movement pattern should be considered when analyzing coordination in people with low back pain. Multifidus showed the largest changes in flexion-relaxation and should be included when measuring this construct.     

Low back pain in young athletes. A practical approach.

Lumbar spine pain accounts for 5 to 8% of athletic injuries. Although back pain is not the most common injury, it is one of the most challenging for the sports physician to diagnose and treat. Factors predisposing the young athlete to back injury include the growth spurt, abrupt increases in training intensity or frequency, improper technique, unsuitable sports equipment, and leg-length inequality. Poor strength of the back extensor and abdominal musculature, and inflexibility of the lumbar spine, hamstrings and hip flexor muscles may contribute to chronic low back pain. Excessive lifting and twisting may produce sprains and strains, the most common cause of low back pain in adolescents. Blows to the spine may create contusions or fractures. Fractures in adolescents from severe trauma include compression fracture, comminuted fracture, fracture of the growth plate at the vertebral end plate, lumbar transverse process fracture, and a fracture of the spinous process. Athletes who participate in sports involving repeated and forceful hyperextension of the spine may suffer from lumbar facet syndrome, spondylolysis, or spondylolisthesis. The large sacroiliac joint is also prone to irritation. The signs and symptoms of disc herniation in adolescents may be more subtle than in adults. Disorders simulating athletic injury include tumours and inflammatory connective tissue disease. Often, however, a specific diagnosis cannot be made in the young athlete with a low back injury due to the lack of pain localisation and the anatomic complexity of the lumbar spine. A thorough history and physical examination are usually more productive in determining a diagnosis and guiding treatment than imaging techniques. Diagnostic tests may be considered, though, for the adolescent athlete whose back pain is severe, was caused by acute trauma, or fails to improve with conservative therapy after several weeks. Radiographs, bone scanning, computed tomography, and magnetic resonance imaging may help identify, or exclude serious pathology. Fortunately, the majority of cases of low back pain in adolescents respond to conservative therapy. Immediate treatment of an acute injury, such as a sprain or strain, includes cryotherapy, electrogalvanic stimulation, anti-inflammatory medications and gentle exercises. Prolonged bed rest should be avoided since atrophy may occur rapidly. Strong analgesics are also usually contraindicated, except for sleep, since they mask pain and may allow overvigorous activity. Early strengthening exercises include the Williams flexion exercises and/or McKenzie extension exercises. Both exercise motions may often be prescribed. Athletes with an acute disc herniation, however, should only perform extension exercises initially. Athletes with spondylolysis, spondylolisthesis and facet joint irritation should initially be limited to flexion exercises.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dynamics of the spinal cord: an analysis of functional myelography by CT scan

Summary The antero-posterior movement of the spinal cord with flexion and extension of the neck was analyzed in order to clarify the mechanism of spinal cord compression in cases with postoperative spinal deformity, and to contribute to the improvement of the surgical methods of conventional laminectomy. The control subjects were 47 cases without cervico-thoracic neurological symptoms, who underwent CT myelography in flexion and extension of the neck; the cervical spinal cord was examined in 27 of these cases and the thoracic cord in the other 20. CT myelography was also carried out in 16 patients with cervical myelopathy and in 5 patients after posterior decompression surgery (suspension laminotomy). CT sections in flexion and extension of the neck were analyzed for 1) change of configuration of the dura mater and the spinal cord, and 2) antero-posterior shift of the spinal cord in the subarachnoid space. In the control subjects, the configuration of the dura mater was slightly flattened at C5/6, C6 and C6/7 in extension of the neck. The cervical spinal cord shifted anteriorly in flexion and posteriorly in extension of the neck, and was flattened at the midcervical level in flexion in the control subjects. There was a statistically significant correlation between the location of the spinal cord and the adjacent intervertebral angles at the levels of C4, C5 and C6. These results were compared with the results from the 16 patients with cervical myelopathy and 5 patients after suspension laminotomy. The thoracic spinal cord shifted anteriorly in neck flexion and posteriorly in extension, especially at upper thoracic level. In order to avoid spinal cord compression due to anterior shift of the spinal cord caused by postoperative kyphosis, it is necessary to employ the surgical method which can prevent postoperative kyphotic deformity.Presented at the 17th World Congress of the Société Internationale de Chirurgie Orthopédique et de Traumatologie (SICOT 87), Munich, FRG, 16–21 August 1987     

Positional lumbar imaging using a positional device in a horizontally open-configuration MR unit - initial experience

PURPOSE: To evaluate whether positional MR images of the lumbar spine, obtained with a horizontally open-configuration MR unit, demonstrate positional changes of the dural sac, and to assess whether there are significant differences in positional changes between healthy volunteers and patients with chronic low back pain. MATERIALS AND METHODS: The study population consisted of 15 patients with chronic low back pain and 14 healthy volunteers. MR images were obtained using a horizontally open-configuration 0.4-T MR unit. After conventional lumbar MR examinations, images were obtained in the flexion, neutral, and extension positions, using a positioning device. The anteroposterior diameter of the dural sac at the level of each lumbar disk was measured in the three positions and quantitative data were compared. RESULTS: Our MR protocol was tolerated by all patients. In both patients and volunteers, the mean anteroposterior diameter of the dural sac was smaller in the extension positions than in the flexion positions. In the mean rate of change (RC) in the dural sac diameter at the site of the degenerated disks, the difference between the volunteers and patients was significant (P < 0.05). There was no significant difference in the mean RC between patients and volunteers without degenerative disks. CONCLUSION: Using a horizontally open-configuration MR unit, positional MR imaging provided position-dependent change of the dural sac. Positional changes at the site of the degenerated disks may be different in patients with and without chronic low back pain.     

Lumbar disc arthroplasty: indications, biomechanics, types, and radiological criteria

Lumbar total disc replacement (TDR) was developed to treat a painful degenerative lumbar motion segment while avoiding the disadvantages of fusion surgery, such as adjacent segment instabilities. Early clinical results with TDR have shown a significant reduction in low back pain and a significant improvement in disability scores. When compared to fusion, the results with TDR tend to be superior in the short-term follow-up and initial rehabilitation is faster. The radiological assessment is an integral part of the preoperative work-up. Plain X-rays of the lumbar spine should be complemented by flexion - extension views in order to assess residual segmental mobility. Computed tomography is used to exclude osteoarthritis of the zygapophyseal joints, Baastrup's disease (kissing spines) and other sources of low back pain. Magnetic resonance imaging is useful to exclude substantial disc protrusions; it allows for the detection of disc dehydration and bone marrow edema in the case of activated spondylochondrosis. If osteoporosis is suspected, an osteodensitometry of the lumbar spine should be performed. Postoperative plain X-rays should include antero-posterior and lateral views as well as flexion - extension views in the later postoperative course. Measurements should determine the disc space height in the lateral view, the segmental and total lumbar lordosis as well as the segmental mobility in the flexion - extension views. The ideal position of a TDR is exactly central in the ap-view and close to the dorsal border of the vertebral endplates in the lateral view. Malpositioning may cause segmental hyperlordosis and unbalanced loading of the endplates with the risk of implant subsidence and migration.     

Lumbale Bandscheibenendoprothesen: Indikationen, Biomechanik, Typen und radiologische Kriterien

Lumbar total disc replacement (TDR) was developed to treat a painful degenerative lumbar motion segment while avoiding the disadvantages of fusion surgery, such as adjacent segment instabilities. Early clinical results with TDR have shown a significant reduction in low back pain and a significant improvement in disability scores. When compared to fusion, the results with TDR tend to be superior in the short-term follow-up and initial rehabilitation is faster. The radiological assessment is an integral part of the preoperative work-up. Plain X-rays of the lumbar spine should be complemented by flexion – extension views in order to assess residual segmental mobility. Computed tomography is used to exclude osteoarthritis of the zygapophyseal joints, Baastrup’s disease (kissing spines) and other sources of low back pain. Magnetic resonance imaging is useful to exclude substantial disc protrusions; it allows for the detection of disc dehydration and bone marrow edema in the case of activated spondylochondrosis. If osteoporosis is suspected, an osteodensitometry of the lumbar spine should be performed. Postoperative plain X-rays should include antero-posterior and lateral views as well as flexion – extension views in the later postoperative course. Measurements should determine the disc space height in the lateral view, the segmental and total lumbar lordosis as well as the segmental mobility in the flexion – extension views. The ideal position of a TDR is exactly central in the ap-view and close to the dorsal border of the vertebral endplates in the lateral view. Malpositioning may cause segmental hyperlordosis and unbalanced loading of the endplates with the risk of implant subsidence and migration.     

Functional MRI of the lumbar spine in erect position in a superconducting open-configuration MR system: Preliminary results

The purpose of this study was to determine the feasibility of obtaining, and findings in, functional MRI of the lumbar spine in an erect position and with flexion and extension. Thirty subjects (including 5 volunteers) were imaged in a sitting position and while performing flexion and extension. The alternations in posterior disk margin, size of neural foramina, and central canal were evaluated. In addition, routine supine imaging was accomplished in 15 of these subjects. The foraminal size and posterior disk margins did not change appreciably from supine to upright position. With extension, there was an increased disk bulge in 27% of disks (40% of those with desiccation). Central canal size (50%) and foraminal size (27%) decreased with extension, especially at levels with disk desiccation. Images obtained with our open-configuration MR unit were diagnostically adequate, although of inferior quality compared with those obtained with a conventional unit. Our preliminary results show the feasibility of obtaining diagnostic images of the erect lumbar spine with flexion and extension. The results are in agreement with those obtained with cadaveric studies. The utility of this method in diagnostic imaging of patients with low back pain remains to be determined.     

经伤椎与跨伤椎万向钉置钉固定脊柱骨折的生物力学对比研究

目的 对比评估经伤椎6钉与跨伤椎4钉固定脊柱骨折的生物力学稳定性.方法 6具新鲜冰冻小牛腰椎标本L1～L5节段,制备成腰椎前中柱损伤模型.比较4钉固定组与6钉固定组的三维6个方向的运动范围.结果 生物力学试验证实,4钉固定组在屈曲、后伸运动方向上的稳定性都较对照组小,但差异无统计学意义.6钉固定组在屈曲、后伸运动方向上的稳定性均较完整对照组大,且差异有统计学意义(t=4.844,P＜0.01;t=3.722,P＜0.05).6钉固定组在各个方向的运动范围均小于4钉固定组,且两组在屈曲、后伸、侧屈、旋转运动方向差异均有统计学意义(P＜0.05,0.01).结论 6钉固定较4钉固定在屈曲、后伸、侧屈、旋转各运动上的生物力学强度强,为临床应用微创经皮万向钉6钉固定治疗胸腰椎骨折提供了理论依据.     

Management of medial epicondylitis inthe throwing athlete

Medial epicondylitis in the throwing athlete is typically a result of repetitive loading of the flexor pronator massor because of acute overload of the flexor pronator mass. It manifests itself as pain with or after a period of throwing and is typically associated with a more prolonged, frequent, or strenuous regimen. The mechanics in throwing include elbow extension, forearm pronation, and wrist palmar flexion in motion progressed from the acceleration phase to the release phase. The active contraction with forearm pronation and wrist palmar flexion, combined with extension at the elbow, results in an eccentric load being applied to the flexor pronator mass. The additional concern of valgus stress being applied with the throwing mechanism simply exacerbates this mechanical predisposition to overload of the flexor pronator mass.     

Effect of low back posture on the morphology of the spinal canal

Objective. To define the possible mechanism of posture-dependent symptoms of spinal stenosis by measuring the effect of low back posture on morphologic changes of the intervertebral discs and spinal canal in healthy young people. Design.Twenty healthy young volunteers underwent magnetic resonance imaging while supine with their spine in neutral, flexed, extended, and right and left rotational positions. The axial MR images at the middle of the intervertebral discs of L3–4 and L4–5 were analyzed to measure the difference in the size and shape of the intervertebral discs and spinal canal in each posture. Results.  Extension or rotation decreased the sagittal diameters and cross-sectional areas of the dural sac and spinal canal and increased the thickness of the ligamentum flavum, whereas flexion had the opposite effects. The gap between the convex posterior disc margin and the anterior margin of the facet joint on each side, represented as the subarticular sagittal diameter, increased with flexion and decreased with extension or rotation. The direction of rotation did not result in asymmetry of the subarticular sagittal diameter, but right rotation caused thickening of the right ligamentum flavum, and vice versa. The shape and dimensions of the disc did not change significantly according to the positions of the low back. Conclusions.With extension or rotation, the thickness of the ligamentum flavum increased and the posterior margin of the intervertebral disc was approximated to the facet joint without any change in shape and size of the disc. These phenomena result in a decrease in the size of the spinal canal and dural sac in extension or rotation postures in young healthy people without disc degeneration, and may explain the posture-dependent symptom of spinal stenosis. Received: 18 October 1999 Revision requested: 9 November 1999 Revision received: 13 December 1999 Accepted: 17 January 2000