Inter-individual variation in vertebral kinematics affects predictions of neck musculoskeletal models

Experimental studies have found significant variation in cervical intervertebral kinematics (IVK) among healthy subjects, but the effect of this variation on biomechanical properties, such as neck strength, has not been explored. The goal of this study was to quantify variation in model predictions of extension strength, flexion strength and gravitational demand (the ratio of gravitational load from the weight of the head to neck muscle extension strength), due to inter-subject variation in IVK. IVK were measured from sagittal radiographs of 24 subjects (14F, 10M) in five postures: maximal extension, mid-extension, neutral, mid-flexion, and maximal flexion. IVK were defined by the position (anterior-posterior and superior-inferior) of each cervical vertebra with respect to T1 and its angle with respect to horizontal, and fit with a cubic polynomial over the range of motion. The IVK of each subject were scaled and incorporated into musculoskeletal models to create models that were identical in muscle force- and moment-generating properties but had subject-specific kinematics. The effect of inter-subject variation in IVK was quantified using the coefficient of variation (COV), the ratio of the standard deviation to the mean. COV of extension strength ranged from 8% to 15% over the range of motion, but COV of flexion strength was 20–80%. Moreover, the COV of gravitational demand was 80–90%, because the gravitational demand is affected by head position as well as neck strength. These results indicate that including inter-individual variation in models is important for evaluating neck musculoskeletal biomechanical properties.     

Chronic low back pain patients walk with locally altered spinal kinematics

Various studies have reported alterations of spinal kinematics in patients with chronic low back pain (CLBP) during gait. However, while recent findings stressed the importance of multi-segment analysis, most of prior gait studies modelled the lumbar spine as one segment, when it was not the entire trunk that was considered as a single segment. Therefore, there is a need for comprehensive multi-segment research that could improve our understanding of CLBP pathomechanism and thus possibly contribute to better care for CLBP. This study aimed at characterizing the angle patterns at the lower lumbar (LLS), upper lumbar (ULS), lower thoracic (LTS) and upper thoracic (UTS) joints in the three anatomical planes and at comparing CLBP patients and asymptomatic subjects. Spinal kinematics of 11 CLBP patients and 11 controls was measured using a marker-based motion capture system and described according to a previously proposed multi-segment biomechanical model. Characteristic patterns were observed at the UTS, LTS and ULS joints in the transverse plane and at the UTS, ULS and LLS joints in the frontal plane. CLBP patients walked with smaller frontal-plane LLS range of motion than controls. The results also suggested that patients had more asymmetrical LTS motion in the transverse plane. In conclusion, this work extended prior literature by showing specific CLBP-related alterations in multi-segment spinal kinematics during gait. Further research is necessary to understand the factors influencing kinematics alterations and how treatment strategies might improve motor behaviour in CLBP patients.     

Predicting muscle forces in gait from EMG signals and musculotendon kinematics

An EMG-driven muscle model for determining muscle force-time histories during gait is presented. The model, based on Hill's equation (1938), incorporates morphological data and accounts for changes in musculotendon length, velocity, and the level of muscle excitation for both concentric and eccentric contractions. Musculotendon kinematics were calculated using three-dimensional cinematography with a model of the musculoskeletal system. Muscle force-length-EMG relations were established from slow isokinetic calibrations. Walking muscle force-time histories were determined for two subjects. Joint moments calculated from the predicted muscle forces were compared with moments calculated using a linked segment, inverse dynamics approach. Moment curve correlations ranged from r = 0.72 to R = 0.97 and the root mean square (RMS) differences were from 10 to 20 Nm. Expressed as a relative RMS, the moment differences ranged from a low of 23% at the ankle to a high of 72% at the hip. No single reason for the differences between the two moment curves could be identified. Possible explanations discussed include the linear EMG-to-force assumption and how well the EMG-to-force calibration represented excitation for the whole muscle during gait, assumptions incorporated in the muscle modeling procedure, and errors inherent in validating joint moments predicted from the model to moments calculated using linked segment, inverse dynamics. The closeness with which the joint moment curves matched in the present study supports using the modeling approach proposed to determine muscle forces in gait.     

Reliability of a new virtual reality test to measure cervicocephalic kinaesthesia

The aim of this study was to investigate the cervicocephalic kinaesthesia of healthy subjects for gender and age effects and its reliability in a new virtual reality test procedure. 57 healthy subjects (30 male, 27 females; 18-64 years) were immersed into a virtual 3D scene via a headmounted display, which generated specific head movements. The joint repositioning error was determined in a static and dynamic test at the times T0, T1 (T0 + 10 minutes) and T2 (T0 + 24 hours). The intrasession reliability (T0-T1) and the intersession reliability (T0-T2) were analysed. In both tests no gender- or age-specific effects were found. In the overall group the means of the static test were 6.2°-6.9° and of the dynamic test were 4.5°-4.9°. The intratest difference in the static test was -0.16° and the intertest difference was 0.47°. The intratest difference in the dynamic test was 0.42° and the intertest difference was 0.37°. The static and dynamic test was reproducible in healthy subjects, with minor deviations, irrespective of gender and age. The smaller interindividual differences in the dynamic test could be beneficial in the comparison of healthy individuals and individuals with cervical spine disorders.     

大菱鲆肌肉组织中的基因差异表达与体长性状的相关性研究

为了揭示出一些影响鱼类生长发育速度方面的遗传信息,本文应用mRNA差异显示技术,以同一批受精卵孵化的同池养殖的两组大菱鲆鱼为试验材料,检测了在相同生长发育条件下两组体长相差悬殊的3月龄大菱鲆肌肉组织的基因差异表达。结果：18对引物组合共显示出723条带,其中有527条带能够重现,差异显示条带的重现率为72.89%;在527条稳定的条带中有21条为差异带,其余506条为共有带（96.02%）。21条差异表达条带中有16条（3.04%）为阳性差异表达cDNA片段。这些差异表达cDNA片段的存在,说明体长差异悬殊的两组大菱鲆之间存在基因表达上的差异。试验结果对于进一步分析各种差异表达基因与大菱鲆的生长性状之间的相关关系奠定了基础;为深入研究大菱鲆的生长发育性状的分子遗传机制奠定了基础。     

Wavelet-based intensity analysis of mechanomyographic signals during single-legged stance following fatigue

The von Tscharner (2000) “intensity analysis” describes the power of a non-stationary signal as a function of both frequency and time. The present study applied a version of this intensity analysis that utilizes Morlet wavelets as a means of gaining insight into the application of this technique as alternative to power spectral analysis for the evaluation of postural control strategy during the single-legged stance and to examine the effects of fatigue. Ten subjects (gender balanced, age: 25 ± 3 years; height: 169.4 ± 11.7 cm; weight: 79.0 ± 16.9 kg) participated in two trials consisting of five 15-s dominant-leg stances. Three-uniaxial accelerometers were fixed to the surface of the dominant leg corresponding to VM, VL, SOL, and MMG was recorded at a sampling rate of 1000 Hz. Signals were later analyzed using a variation of the von Tscharner intensity analysis consisting of a filter bank of 11 Morlet wavelets (range: 2.1–131.1 Hz). Two Wingate anaerobic tests (WAnT) separated by a 2-min rest were performed to introduce fatigue. Repeated measures ANOVAs showed significant effects for time, gender, trial, and wavelet (p < 0.001) and significant interactions for muscle by wavelet, gender by trial, trial by wavelet, and gender by trial by wavelet (p < 0.001). Peak total MMG intensity (mean ± SD) was higher in males than females and higher following fatiguing exercise preWAnT (squared m s⁻²): 42.6 ± 4.5 vs. 19.2 ± 2.3; postWAnT (squared m s⁻²): 90.4 ± 9.1 vs. 28.4 ± 2.8. Peak total MMG intensity was compressed to the lower frequencies surrounding ∼12 Hz, corresponding to what might be considered physiologic tremor, and a lower peak at ∼42 Hz was most prominent in SOL. The intensity analysis is a useful tool in exploring postural control and in studying the effects of fatigue on the mechanical properties of skeletal muscle.     

颈椎康复操对不同类型颈椎病患者康复训练效果的影响

目的:研究三种类型颈椎病患者在康复阶段采用颈椎康复操后的恢复效果。方法:将211例颈椎病患者纳入本次研究,在基础性治疗同时采用颈椎康复操进行康复训练,在训练前以及训练2个月、4个月后,分别检测患者颈部肌肉电生理状况,对其疼痛进行评分。结果:三种类型颈椎病患者的肌肉动作电位峰值、电位传导速度均具有显著统计学意义(P0.05);交感神经型与神经根型患者疼痛评分差异具有统计学意义(P0.05),但混合型患者差异无统计学意义(P0.05)。结论:颈椎康复操对不同类型颈椎病康复训练效果不同,有助于改善患者颈部肌肉运动,但在缓解疼痛方面存在差异,交感神经型、神经根型颈椎病采用颈椎康复操效果较好,但混合型颈椎病效果相对较小。     

The shape and mobility of the thoracic spine in asymptomatic adults – A systematic review of in vivo studies

A comprehensive knowledge of the thoracic shape and kinematics is essential for effective risk prevention, diagnose and proper management of thoracic disorders and assessment of treatment or rehabilitation strategies as well as for in silico and in vitro models for realistic applications of boundary conditions.After an extensive search of the existing literature, this study summarizes 45 studies on in vivo thoracic kyphosis and kinematics and creates a systematic and detailed database. The thoracic kyphosis over T1–12 determined using non-radiological devices (34°) was relatively less than measured using radiological devices (40°) during standing. The majority of kinematical measurements are based on non-radiological devices. The thoracic range of motion (RoM) was greatest during axial rotation (40°), followed by lateral bending (26°), and flexion (21°) when determined using non-radiological devices during standing. The smallest RoM was identified during extension (13°). The lower thoracic level (T8–12) contributed more to the RoM than the upper (T1–4) and middle (T4–8) levels during flexion and lateral bending. During axial rotation and extension, the middle level (T4–8) contributed the most. Coupled motion was evident, mostly during lateral bending and axial rotation. With aging, the thoracic kyphosis increased by about 3° per decade, whereas the RoM decreased by about 5° per decade for all load directions. These changes with aging mainly occurred in the lower region (T6–12). The influence of sex on thoracic kyphosis and the RoM has been described as partly contradictory. Obesity was found to decrease the thoracic RoM. Studies comparing standing, sitting and lying reported the effect of posture as significant.     

Further evaluation of an EMG technique for assessment of the deep cervical flexor muscles

A novel surface electromyographic (EMG) technique was recently described for the detection of deep cervical flexor muscle activity. Further investigation of this technique is warranted to ensure EMG activity from neighbouring muscles is not markedly influencing the signals recorded. This study compared deep cervical flexor (DCF) muscle activity with the activity of surrounding neck and jaw muscles during various anatomical movements of the neck and jaw in 10 volunteer subjects. DCF EMG activity was recorded with custom electrodes inserted via the nose and fixed by suction to the posterior mucosa of the oropharynx. Surface electrodes were placed over the sternocleidomastoid, anterior scalene, masseter and suprahyoid muscles. Positioned in supine, subjects performed isometric cranio-cervical flexion, cervical flexion, right and left cervical rotation, jaw clench and resisted jaw opening. Across all movements examined, EMG amplitude of the DCF muscles was greatest during neck movements that would require activity of the DCF muscles, particularly during cranio-cervical flexion, their primary anatomical action. The actions of jaw clench and resisted jaw opening demonstrated significantly less DCF EMG activity than the cranio-cervical flexion action (p < 0.05). Across all other movements, the neighbouring neck and jaw muscles demonstrated greatest EMG amplitude during their respective primary anatomical actions, which occurred in the absence of increased EMG amplitude recorded from the DCF muscles. The finding of substantial EMG activity of the DCF muscles only during neck actions that would require their activity, particularly cranio-cervical flexion, and not during actions involving the jaw, provide further assurance that the majority of myoelectric signals detected from the nasopharyngeal electrode are from the DCF muscles.     

胸腰椎爆裂性骨折的治疗新进展

胸腰椎爆裂骨折是常见的脊柱损伤性疾病之一,其发病率、致残率较高是由胸腰段脊柱的解剖学特点所决定。国内外有多种脊柱骨折的分类,临床中使用较多的有AO分类及Denis分类,脊柱载荷分享分类现多用于评价患者是否适合于后路手术,而不能应用于评估手术指征。目前国内外胸腰椎爆裂性骨折的治疗尚无统一定式,大多数学者倾向于积极的手术治疗,其中尤以后路手术治疗为主,后路手术多采取短节段椎弓根定内固定加植骨治疗。近些年又出现了经后路270°或360°椎管减压,重建脊柱的三柱稳定性。前路及前后路联合手术都有其各自的适应症。保守治疗多采取卧床休息、体位复位、外固定支具法及功能康复等。本文总结了近年来关于胸腰椎爆裂骨折的最新治疗进展。