Purpose. Even though various factors have been associated with neck pain, skeletal muscle mechanical properties have been cited among the leading causes of neck pain. Changes in skeletal muscle stiffness may be related to chronic neck pain and these changes may be associated with the severity of pain and disability in patients with chronic neck pain. The purpose of the present study was to investigate differences in neck muscle stiffness between patients with chronic neck pain and asymptomatic control group. Another purpose of the study was to investigate the relationship of muscle stiffness with the severity of physical disability and pain in patients with chronic neck pain. Methods. A cross-sectional case-control study with 86 participants (43 patients with chronic neck pain and 43 age-matched asymptomatic controls) was designed. The present study included patients with a pain intensity level of 20 or more based on the Numerical Rating Scale (NRS) and a total disability level of 10 or more based on the Neck Disability Index (NDI). Ultrasonic evaluation of upper trapezius, splenius capitis, and sternocleidomastoid muscle performed with the ACUSON S3000 Ultrasonography Device using Siemens 9L4 (4–9 MHz) linear-array ultrasound probe. Shear Wave Velocity (SWV) of selected muscles was obtained using customized software, Virtual Touch Imaging and Quantification® (Siemens Medical Solution, Mountain View, CA, USA). Results. SWV of splenius capitis was similar in both groups (p=0.979); however, SWV of upper trapezius (p<0.001) and sternocleidomastoid (p=0.003) of the patients with chronic neck pain were higher compared to the asymptomatic controls groups. NRS score did not correlate with SWV of upper trapezius (r=−0.27, p=0.085), sternocleidomastoid (r=−0.02, p=0.879) and splenius capitis (r=0.01, p= 0.990). Similarly, NDI score did not correlate with SWV of upper trapezius (r=−0,09 p=0.567), sternocleidomastoid (r=0.15, p=0.345) and splenius capitis (r=0.18, p= 0.274). Conclusions. SWV of splenius capitis muscle stiffness was found similar in both groups, but SWV of upper trapezius and sternocleidomastoid muscle were found increased in patients with neck pain compared to asymptomatic controls groups. In addition, severity of pain and disability did not relate to stiffness of these muscles in patient with chronic neck pain

Background: Neck pain is a growing problem which is linked to occupational factors that include work above shoulder height or sustained neck flexion. These activities may induce fatigue in the neck muscles impairing the muscles’ ability to provide reflex contractions that protect against tissue injury. The aim of this study was to investigate the effect of neck muscle fatigue on reflex activation of the neck muscles. Methods: Healthy volunteers were subjected to one of two loading protocols. Isometric contractions of neck extensors at 60% MVC were sustained to the endurance limit (n=30) to induce high level fatigue in these muscles. A similar protocol for neck flexors (n=21) was used to initiate low level contraction of the extensors which are co-activated to stabilise the cervical spine under such circumstances. Before and after each loading protocol, reflex activation of the trapezius muscle was assessed using skin surface electromyography (EMG) to measure the latency and amplitude of muscle activation in response to a sudden perturbation of the head. Results: Reflex latencies increased from 73±17ms to 93±27ms (p=0.0041), and from 72±12ms to 97±28ms (p< 0.0001) following low and high level extensor fatigue, respectively. Time to peak EMG also increased from 122±32ms to 148±39ms (p=0.0093), and from 113±15ms to 138±25ms (p< 0.0001), respectively, although no change in peak EMG amplitude was observed. Conclusions: Reflex activation of trapezius was substantially delayed following both loading protocols. These findings suggest that even low level postural loading in the workplace may impair neck muscle reflexes rendering the underlying tissues more vulnerable to strain injury. Conflicts of Interest: None. Source of Funding: BBSRC (Biotechnology and Biological Sciences Research Council, UK)

Abstract. Objectives. Catastrophic neck injuries in rugby tackling are rare (2 per 100,000 players per year) with 38% of these injuries occurring in the tackle. The aim of this study was to determine the primary mechanism of cervical spine injury during rugby tackling and to highlight the effect of tackling technique on intervertebral joint loads. Methods. In vivo and in vitro experimental data were integrated to generate realistic computer simulations representative of misdirected tackles. MRI images were used to inform the creation of a musculoskeletal model. In vivo kinematics and neck muscle excitations were collected during lab-based staged tackling of the player. Impact forces were collected in vitro using an instrumented anthropometric test device during experimental simulations of rugby collisions. Experimental kinematics and muscle excitations were prescribed to the model and impact forces applied to seven skull locations (three cranial and four lateral). To examine the effects of technique on intervertebral joint loads the model's neck angle was altered in steps of 5° about each rotational axis resulting in a total of 1,623 experimentally informed simulations of misdirected tackles. Results. Neck flexion angles and cranial impact locations had the largest effects on maximal compression, anterior shear and flexion moment loads. During posterior cranial impacts compression forces and flexion moments increased from 1500 to 3200 N and 30 to 60 Nm respectively between neck angles of 30° extension and 30° flexion. This was more evident at the C5-C6 and C6-C7 joints. Anterior shear loads remained stable throughout neck angle ranges however during anterior impacts they were directed posteriorly when the neck was flexed. Conclusions. The combination of estimated joint loads in the lower cervical spine support buckling as the primary injury mechanism of anterior bilateral facet dislocations observed in misdirected rugby tackles and highlights the importance of adopting a correct tackling technique. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Purpose of Study: The neck is the most mobile region of the spine, so neck muscles must provide stability, and control spinal movements. This action requires effective sensory and motor control mechanisms which, if impaired, may increase the risk of injury and pain. The aim of this study was to investigate sensorimotor function of neck muscles in healthy volunteers in order to provide normative data for comparative studies on neck pain patients. Methods: Thirty-one healthy volunteers participated. Position sense was evaluated using an electromagnetic tracking device (3-Space FASTRAK) to assess errors in repositioning the head in upright and flexed postures. Movement sense was assessed as time to detect head motion at 1°s-1 and 10°s-1, using a KinCom dynamometer. Latency of reflex muscle activation following rapid perturbation of the head was assessed bilaterally in trapezius and sternocleidomastoid muscles using surface electromyography. Results: Mean repositioning errors were 2.20±1.46° and 2.54±1.69° for upright and flexed postures respectively. Time to detect head motion was greater at 1°s-1 (739±349ms and 556±213ms, in extension and flexion respectively) compared to 10°s-1 (375±89ms and 377±66ms). Mean reflex latencies were shorter for trapezius (left: 77.9±43.4ms, right: 72.3±35.1ms) than for sternocledomastoid (left: 106.1±29.2ms, right: 102.7±35.9ms). Conclusion: Position sense in the cervical spine is superior to that reported in thoracolumbar regions, especially in flexed postures. Detection of head movement is velocity-dependent suggesting input occurs from both phasic and tonic mechanoreceptors. Reflex latencies were shorter for trapezius than for sternocledomastoid suggesting that stretch reflexes in trapezius play a predominant role in preventing excessive flexion of the cervical spine

Introduction: After whiplash injuries the majority of patients complain of pain, muscular dysfunctions and restricted movement of the cervical spine, however, the cause of these symptoms cannot be diagnosed. Against this background, the hypothesis is formulated that functional disturbances in the form of pathological activities of the neck muscles occur as a result of a whiplash injury of the cervical spine. These pathological muscle activities can be demonstrated electromyographically and differ from the patterns of activity of healthy subjects. Study Objective: Thus, the aim of this study was to establish an electromyographical method for the diagnosis of functional disturbances of the neck muscles after whiplash injuries of the cervical spine. Material/Method: Primarily, an intramuscular recording of the electromyographical activity of the semispinalis capitis muscle was performed during flexion/extension and axial rotation in 46 patients with chronic symptoms after a whiplash injury of the cervical spine (QTF grade II) and 29 healthy subjects. The movement was controlled with techniques of virtual reality. The subject is immersed into a virtual outer space environment with a head-mounted display (HMD). In this virtual scene, the patient follows paths of motion of a signal (globe) with his/her gaze. A subsequent study was conducted to validate the results that had been obtained. For this purpose, the electromyographical activity of the semispinalis capitis muscle was recorded in another subject group (n=20) and patients with acute symptoms as a result of a whiplash injury of the cervical spine (QTF grade II) (n=35). Results: Compared to the physiological muscle activities that were established in the first subject group, changes could be observed in the chronic patient group. Subjects in our study, for instance, show a decrease in electrical activity during flexion and the resulting stretching of the semispinalis capitis muscle, while the same movement causes an increase in activity in patients. On the basis of these differences, 93 % of subjects (specificity) and 83 % of patients (sensitivity) could be classified correctly with a discriminance analysis. In the second study, the specificity was 88 % while a sensitivity of 86 % was determined in the acute patient population. Conclusion: The results of these investigations enable a highly specific and sensitive diagnosis of muscular dysfunctions on the basis of the intramuscular recordings of the electromyographical patterns of activity of the semispinalis capitis muscle

Background: Neck muscles stabilise the head, but muscle tension imposes high compressive forces on the cervical spine. Little is known about which structures resist these high forces. Purpose: To quantify compressive load-sharing within the cervical spine. Methods: Seventeen cervical “motion segments” from cadavers aged 54–92 yr (mean 72 yr), were subjected to 200 N compression while positioned in simulated flexed and extended postures. Up to 5 Nm of bending was applied in various planes. Vertebral movements were recorded at 50 Hz using an optical MacReflex system. Tangent stiffness was calculated in compression and in bending. Load-sharing was evaluated from compressive stress measurements obtained by pulling a pressure transducer through the intervertebral disc. All measurements were repeated after 2 hr of creep loading at 150 N, and following sequential removal of the spinous process, apophyseal joints and uncovertebral joints. Results: Most compression was resisted by the disc. However, creep increased compressive load-bearing by the neural arch, from 21% to 28% in flexed posture, and from 27% to 45% in extended posture, with most of this loading being resisted by the apophyseal joints. Uncovertebral joints resisted 10% of compression in extended posture, and 20% in flexed posture. Flexion and extension movements were resisted primarily by ligaments of the neural arch, and by the apophyseal joints, respectively, whereas lateral bending was resisted mostly by the apophyseal and uncovertebral joints. Conclusion: Cervical apophyseal joints play a major role in compressive load-bearing, and also offer strong resistance to backwards and lateral bending. Uncovertebral joints primarily resist lateral bending. Conflicts of Interest: None. Source of Funding: Scholarship from the Greek Government

Introduction: Neck pain often arises without any evident trauma suggesting that everyday loading may cause fatigue damage to spinal tissues. However, little is known about the forces acting on the cervical spine in everyday life. The purpose of this study was to determine spinal compressive forces using an electromyo-graphic (EMG) technique. Methods: Eight subjects performed a number of tasks while cervical flexion/extension and surface EMG activity of upper trapezius and sternocleidomastoid were measured. Dynamic EMG signals were corrected for contraction speed, using a correction factor obtained from lumbar muscles, and were then compared with isometric calibrations in order to predict moment generation. Calibrations were performed in different amounts of cervical flexion/extension by each subject to account for changes in the EMG-moment relationship with muscle length. Compressive force on the C7-T1 intervertebral disc was determined by dividing the generated moments by the resultant lever arm of flexor or extensor muscles obtained from MRI scans on the same subjects. Results: Peak values (mean ± SD) of extensor and flexor moments increased from 1.9±1.6Nm and 1.4±1.0Nm respectively in standing to 52.7±32.2Nm and 4.2±1.8Nm when lifting above the head. Resultant muscle lever arms ranged between 3.0–5.2cm and 1.6–3.5cm for extensor and flexor muscles respectively. Therefore, peak compressive forces on the C7–T1 disc were 110±74N in standing and 1570±940N during overhead lifting. Conclusion: Neck muscles generate high forces in activities such as overhead lifting. If applied on a repetitive basis, such forces could lead to the accumulation of fatigue damage in life

Introduction: The cervical spine can be severely loaded in bending during sporting injuries and ‘whiplash’. Compressive loading could also be high if some advanced warning of impact stimulated vigorous (‘protective’) contraction of the neck muscles. Combined bending and compression can cause some lumbar discs to herniate in-vitro (. 1. ) but the outcome depends on spinal level, and may not be applicable to cervical discs. We test the hypotheses: a) that cervical discs can prolapse in-vitro, and b) that prolapse leads to irregular stress distributions inside the disc. Material and methods: Human cervical ‘motion segments’ (two vertebrae and intervening soft tissues) were obtained from cadavers aged 51–88yrs. Specimens were secured in cups of dental stone and subjected to static compressive loading (150N) for 20s. During this time, the distribution of vertically-acting compressive ‘stress’ was recorded along the postero-anterior diameter of the disc by pulling a 0.9mm-diameter pressure transducer through it (. 2. ). Injury was induced by compressing each specimen at 1mm/s while positioned in 20 deg of flexion, 15 deg of extension, or 8 deg of lateral bending. The distribution of compressive stress within the disc was then re-measured. Specimens were sectioned at 2mm intervals in order to ascertain soft tissue disruption. Results: In all six specimens tested to date, one or both of the apophyseal joint capsules were ruptured by the complex loading. Intervertebral disc prolapse also occurred in all six specimens, with the herniated nucleus appearing on the anterior, posterior and postero-lateral disc surface in extension, flexion and lateral bending respectively. All modes of failure affected intradiscal stresses: on average, nucleus pressure decreased by 75% (STD 7%), while stress concentrations in the annulus increased by 130% (STD 21%). Discussion: These preliminary results confirm that severe complex loading can cause cervical discs to prolapse. No particular state of disc degeneration is required, provided the loading is sufficiently severe. Indeed, the altered stress distributions suggest that cell-mediated changes would probably follow prolapse

Introduction: Magnetic Resonance Imaging (MRI) is the gold standard for imaging muscle and fatty infiltrate has featured in low back pain. However, there is little knowledge about in vivo features of neck muscles in chronic WAD. The purpose of this study was to quantitatively compare fatty infiltrate in the cervical extensors in patients with chronic WAD and controls across muscle and segmental level. Methods: Volunteer subjects were gained through referral from local practitioners and the local university fraternity. A previously established MRI measure was performed in 113 female subjects (79- WAD & 34 healthy controls). Subjects with chronic WAD (> three months – < three years) were included if, classifiable as WAD II per the Quebec Task Force. The cohort was restricted to females (18–45 years) as they best represent those with chronic WAD. Volunteers were excluded when. classified as WAD I, III or IV. lost consciousness as a result of a motor vehicle crash (MVC). previous history of MVC. previous non-traumatic neck pain. diagnosed with any neurological, metabolic or inflammatory conditions or. were pregnant. The measure was performed for the rectus capitis minor/major, multifidus, semispinalis cervicis/capitis, splenius capitis and upper trapezius. The values for all muscles were plotted for level and side and linear regression analysis was used to determine segmental trends (C3-7). A multi-factorial analysis of variance (MANOVA) was applied to investigate group means of whiplash and controls for fat indices across muscle, side and level. Bonferroni post-hoc comparisons were used to compare group by muscle interactions at each level. Multiple regression analyses were performed to determine if the score on the Neck Disability Index (NDI), age, Body Mass Index (BMI), compensation status and duration influenced fatty infiltrate. Significance was set at p < 0.05. Data presented as mean ± SD. Results: The demographic characteristics of the two groups are: WAD (n = 79): age: 29.7 ± 7.8 years, BMI (kg/m2): 25.1 ± 5.7; duration: 20.3 ± 9.6 months and NDI: 45.5 ± 15.9. Healthy Controls (n = 34): Age: 27.0 ± 5.6 years, BMI: 23.0 ± 4.4.. NDI was not collected in controls. MANOVA revealed significant main effects for group, muscle, segmental level and side (p < 0.0001), and significant interactions between Group:Muscle, Group:Level, Muscle:Level and Group:side (p < 0.0001). Sides were averaged for each muscle and level for post-hoc analysis. There was a linear decrease in the fat indices from C3 – C7 for each muscle in both groups. No significant differences in fat indices across muscle, levels and side were noted in controls (p = 0.09). For the WAD subjects, the multifidus muscle had significantly higher fat content at each level compared to the other segmental muscles (p < 0.0001) and was highest at C3 (p < 0.0001). There were higher fat indices in the whiplash group compared to the controls for the rcpmin and rcpmaj muscles (p < 0.0001). No relationship was found for fat indices in all WAD muscles and NDI scores (p = 0.81), age (p = 0.14), duration (p = 0.99), compensation (p = 0.37) or BMI (p = 0.74). Discussion: There is significantly greater fatty infiltration in neck extensors, especially in the deeper muscles, in females with chronic WAD when compared with controls. Future studies are required to investigate relationships between muscular degeneration and symptoms

Introduction

Studies have addressed the issue of increasing prevalence of work-related musculoskeletal (MSK) pain among different occupations. However, contributing factors to MSK pain have not been fully investigated among orthopaedic surgeons. Thus, this study aimed to approximate the prevalence and predictors of MSK pain among Saudi orthopaedic surgeons working in Riyadh, Saudi Arabia.