Relationship between neck kinematics and neck dissability index. An approach based on functional regression.

Numerous studies use numerical variables of neck movement to predict the level of severity of a pathology. However, the correlation between these numerical variables and disability levels is low, less than 0.4 in the best cases, even less in subjects with nonspecific neck pain. This work aims to use Functional Data Analysis (FDA), in particular scalar-on-function regression, to predict the Neck Disability Index (NDI) of subjects with nonspecific neck pain using the complete movement as predictors. Several functional regression models have been implemented, doubling the multiple correlation coefficient obtained when only scalar predictors are used. The best predictive model considers the angular velocity curves as a predictor, obtaining a multiple correlation coefficient of 0.64. In addition, functional models facilitate the interpretation of the relationship between the kinematic curves and the NDI since they allow identifying which parts of the curves most influence the differences in the predicted variable. In this case, the movement's braking phases contribute to a greater or lesser NDI. So, it is concluded that functional regression models have greater predictive capacity than usual ones by considering practically all the information in the curve while allowing a physical interpretation of the results.

Immediate Effects of a Single Session of Cervical Spine Manipulation on Cervical Movement Patterns in People With Nonspecific Neck Pain: A Randomized Controlled Trial.

OBJECTIVE: The aim of the present study was to assess the immediate effects of a single session of cervical spine manipulation on cervical movement patterns, disability, and the patient's perceived improvement in people with nonspecific neck pain. METHODS: A single-blinded, randomized, sham-controlled trial was carried out at a biomechanics institute. Fifty participants diagnosed with acute and chronic nonspecific neck pain (minimum duration of the symptoms being 1 month) were randomized to an experimental group (EG, n = 25) or a sham-control group (CG, n = 25, 23 of whom completed the study). EG received a single cervical spine manipulation session; CG received a single placebo intervention. Both groups received manipulation or sham from the same physiotherapist. Main outcome measures were neck kinematics (ie, range of motion and movement harmony) during cyclic movements, self-reported neck disability, and impression of change assessed before and 5 minutes after treatment. RESULTS: The EG showed no significant improvements (P > .05) in any of the studied biomechanical variables, except for right-side bending and left rotation, in which we found a range of motion significant mean difference of 1.97° and 1.95°, respectively (P < .05). The CG showed enhanced harmonic motion during flexion (P < .05). Both groups showed a significant decrease in self-reported neck disability after treatment (P < .05), and EG participants perceived a significantly larger improvement after manipulation compared with the CG (P < .05). CONCLUSIONS: A single session of cervical manipulation provided by a physiotherapist had no impact on cervical motion during cyclic movements, but rather induced self-reported perceived improvement in neck disability and impression of change after treatment in people with nonspecific neck pain.

Effect of non-specific neck pain on the path of the instantaneous axis of rotation of the neck during its flexion-extension movement.

Non-specific neck pain is a common musculoskeletal disorder with a high prevalence and involves impaired joint movement pattern. Therefore, this study aimed to compare the trajectory of the instantaneous axis of rotation(IAR) in flexion-extension movements of the neck between people with and without nonspecific neck pain, using functional data analysis techniques. Furthermore, possible relationships between neck kinematics and perceived pain and disability were explored. Seventy-three volunteers participated in this cross-sectional study. They were allocated in a non-specific pain group (PG, n = 28) and a control group (CG, n = 45). A cyclic flexion-extension movement was assessed by a video photogrammetry system and numerical and functional variables were computed to analyze IAR trajectory during movement. Moreover, to explore possible relationships of these variables with pain and neck disability, a visual analogue scale (VAS) and the neck disability index (NDI) were used. The instantaneous axis of rotation trajectory during the flexion-extension cyclic movement described a path like Greek letter rho both in the CG and the PG, but this trajectory was shorter and displaced upward in the PG, compared to the CG. A reduction of the displacement range and a rise in the vertical position of the IAR were related to VAS and NDI scores. Non-specific neck pain is associated with a higher location of the instantaneous axis of rotation and a decrease in length of the path traveled during the flexion-extension movement. This study contributes to a better description of neck movement in people with non-specific neck pain, which would help to plan an individualized treatment.

Paths of the cervical instantaneous axis of rotation during active movements-patterns and reliability.

The instantaneous helical axis (IHA) is a characteristic of neck movement that is very sensitive to changes in coordination and that has potential in the assessment of functional alterations. For its application in the clinical setting, normative patterns must be available, and its reliability must be established. The purpose of this work is to describe the continuous paths of the IHA during cyclic movements of flexion-extension (FE), lateral bending (LB), and axial rotation (AR) and to quantify their reliability. Fifteen healthy volunteers participated in the study; two repetitions were made on the same day (by different operators) and over an 8-day interval (by the same operator) to evaluate the inter-operator and inter-session reliability, respectively. The paths described by the IHA suggest a sequential movement of the vertebrae in the FE movement, with a large vertical displacement (mean, 10 cm). The IHA displacement in LB and AR movements are smaller. The paths described by the IHAs have a very high reliability for FE movement, although it is somewhat lower for LB and RA movements. The standard error of measurement (SEM) is less than 0.5 cm. These results show that the paths of the IHA are reliable enough to evaluate changes in the coordination of intervertebral movement. Graphical abstract A video photogrammetry system is used to record the cyclic movements of the neck, from which the continuous trajectories of the associated instantaneous helical axis (IHA) are calculated. We have analyzed the movements of flexion-extension (FE), lateral flexion (LB), and axial rotation (AR) for a sample of 15 healthy subjects. The measurements have been repeated with two different operators (in the same session) and in two separate sessions (same operator). IHA displacement patterns have been obtained in each movement, and the reliability of the measurement of such IHA trajectories has been estimated.