A randomized, comparative trial: does pillow type alter cervico-thoracic spinal posture when side lying?

This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.Background: Many patients ask for advice about choosing a pillow. This research was undertaken to determine if pillow type alters cervico-thoracic spine position when resting in the side-lying position. Aim: To investigate the effect of different pillow shape and content on the slope of cervico-thoracic spine segments when side lying. Materials and methods: The study was a randomized blinded comparative trial set in a laboratory that replicated a bedroom. The subjects were side sleepers aged over 18 years. Exclusion criteria were history of surgery to the cervico-thoracic spine, an injury or accident to the cervico-thoracic spine in the preceding year, or currently receiving treatment for neck symptoms. Each participant rested in a standardized side-lying position for 10 minutes on each of the trial pillows: regular shaped polyester, foam, feather, and latex pillows, and a contour shaped foam pillow. Reflective markers were placed on external occipital protuberance (EOP), C2, C4, C7, and T3, and digital images were recorded of subjects at 0 and 10 minutes on each pillow. Images were digitized using each reflective marker and the slope of each spinal segment calculated. Univariate analysis of variance models were used to investigate slope differences between pillows at 0 and 10 minutes. Significance was established at P < 0.01 to take account of chance effects from repeated measures and multiple comparisons. Results: At 0 and 10 minutes, the EOP-C2, C2-C4, and C4-C7 segmental slopes were significantly different across all pillows. Significant differences were identified when comparing the feather pillow with the latex, regular and contour foam pillows, and when comparing the polyester and foam contour pillows. The regular and contour foam pillows produced similar slopes at all spinal segments. Conclusion: Cervico-thoracic spinal segment slope alters significantly when people change from a foam, latex, or polyester pillow to a feather pillow and vice versa. The shape of a foam pillow (contour versus regular shape) does not significantly alter cervico-thoracic spinal segment slope

Pillow use: the behavior of cervical stiffness, headache and scapular/arm pain

Susan J Gordon1,2, Karen A Grimmer-Somers3, Patricia H Trott41Associate Professor, School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Townsville, Australia; 2Member, International Centre for Allied Health Evidence, University of South Australia, Australia; 3Professor of Allied Health, School of Health Sciences, University of South Australia, Director, International Centre for Allied Health Evidence, University of South Australia, Australia; 4Associate Professor, School of Health Sciences, University of South AustraliaBackground: Pillows are intended to support the head and neck in a neutral position to minimize biomechanical stresses on cervical structures whilst sleeping. Biomechanical stresses are associated with waking cervical symptoms. This paper adds to the scant body of research investigating whether different pillow types produce different types and frequencies of waking symptoms in asymptomatic subjects.Methods: A random-allocation block-design blinded field trial was conducted in a large South Australian regional town. Subjects were side-sleepers using one pillow only, and not receiving treatment for cervicothoracic problems. Waking cervical stiffness, headache and scapular/arm pain were recorded daily. Five experimental pillows (polyester, foam regular, foam contour, feather, and latex) were each trialed for a week. Subjects&amp;rsquo; &amp;lsquo;own&amp;rsquo; pillow was the control (a baseline week, and a washout week between each experimental pillow trial week). Subjects reported waking symptoms related to known factors (other than the pillow), and subjects could &amp;lsquo;drop out&amp;rsquo; of any trial pillow week.Results: Disturbed sleep unrelated to the pillow was common. Waking symptoms occurring at least once in the baseline week were reported by approximately 20% of the subjects on their &amp;lsquo;own&amp;rsquo; pillow. The feather trial pillow performed least well, producing the highest frequency of waking symptoms, while the latex pillow performed best. The greatest number of &amp;lsquo;drop outs&amp;rsquo; occurred on the feather pillow. The foam contour pillow performed no better than the foam regular pillow.Conclusion: &amp;lsquo;Own&amp;rsquo; pillows did not guarantee symptom-free waking, and thus were a questionable control. The trial pillows had different waking symptom profiles. Latex pillows can be recommended over any other type for control of waking headache and scapular/arm pain.Keywords: pillow type, cervical stiffness, arm pain, headach

Void Growth in BCC Metals Simulated with Molecular Dynamics using the Finnis-Sinclair Potential

The process of fracture in ductile metals involves the nucleation, growth, and linking of voids. This process takes place both at the low rates involved in typical engineering applications and at the high rates associated with dynamic fracture processes such as spallation. Here we study the growth of a void in a single crystal at high rates using molecular dynamics (MD) based on Finnis-Sinclair interatomic potentials for the body-centred cubic (bcc) metals V, Nb, Mo, Ta, and W. The use of the Finnis-Sinclair potential enables the study of plasticity associated with void growth at the atomic level at room temperature and strain rates from 10^9/s down to 10^6/s and systems as large as 128 million atoms. The atomistic systems are observed to undergo a transition from twinning at the higher end of this range to dislocation flow at the lower end. We analyze the simulations for the specific mechanisms of plasticity associated with void growth as dislocation loops are punched out to accommodate the growing void. We also analyse the process of nucleation and growth of voids in simulations of nanocrystalline Ta expanding at different strain rates. We comment on differences in the plasticity associated with void growth in the bcc metals compared to earlier studies in face-centred cubic (fcc) metals.Comment: 24 pages, 12 figure

Multiple CSLs for the body centered cubic lattice

Ordinary Coincidence Site Lattices (CSLs) are defined as the intersection of a lattice $\Gamma$ with a rotated copy $R\Gamma$ of itself. They are useful for classifying grain boundaries and have been studied extensively since the mid sixties. Recently the interests turned to so-called multiple CSLs, i.e. intersections of $n$ rotated copies of a given lattice $\Gamma$, in particular in connection with lattice quantizers. Here we consider multiple CSLs for the 3-dimensional body centered cubic lattice. We discuss the spectrum of coincidence indices and their multiplicity, in particular we show that the latter is a multiplicative function and give an explicit expression of it for some special cases.Comment: 4 pages, SSPCM (31 August - 7 September 2005, Myczkowce, Poland

Reliability of upright posture measurements in primary school children

BACKGROUND: Correct upright posture is considered to be a measure of good musculoskeletal health. Little is known about the usual variability of children's upright standing posture. The aim of this study was to assess differences between repeated measures of upright posture in a group of primary school children. METHODS: Sagittal plane photographs of usual, relaxed upright standing posture of 38 boys and girls aged 5–12 years were taken twice within an hour. Reflective markers were placed over the canthus, tragus, C7 spinous process, greater trochanter and lateral malleolus. Digitising software was used to calculate the x,y plane coordinates, from which five postural angles were calculated (trunk, neck, gaze, head on neck, lower limb). Height, weight, motor control estimates (as measured by the Brace Tests) and presence of recent pain were recorded for each child, and the association between the first test measure of posture angles and these factors was assessed using linear regression and ANOVA models. Multiple ANOVA models were applied to analyse the effect of repeated testing, and significant predictors on the angles. RESULTS: Four of the five postural angles (trunk, neck, head on neck, lower limb) were significantly influenced by age. As age was strongly associated with height (r(2 )= 0.84) and moderately associated with weight and motor control (r(2 )= 0.67, 0.56 respectively), these developmental parameters may well explain the age effect on angles. There was no relationship between age and pain reported on either the testing day, or recently, and there was no gender influence on any angle. There was no significant effect of repeated testing on any angle (ICC>0.93). None of the hypothesized predictors were associated with differences in angles from repeated testing. CONCLUSION: This study outlined the variability of relaxed upright standing posture of children aged 5–12 years, when measured twice in an hour. Age influenced the size of the angles but not the variability. While the subject numbers in this study are small, the findings provide useful information on which further studies in posture and its development in pre-adolescent children can be based