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

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