The global end-ranges of neck flexion and extension do not represent the maximum rotational ranges of the cervical intervertebral joints in healthy adults - an observational study.

BACKGROUND: In clinical diagnosis, the maximum motion of a cervical joint is thought to be found at the joint's end-range and it is this perception that forms the basis for the interpretation of flexion/extension imaging studies. There have however, been representative cases of joints producing their maximum motion before end-range, but this phenomenon is yet to be quantified. PURPOSE: To provide a quantitative assessment of the difference between maximum joint motion and joint end-range in healthy subjects. Secondarily to classify joints into type based on their motion and to assess the proportions of these joint types. STUDY DESIGN: This is an observational study. SUBJECT SAMPLE: Thirty-three healthy subjects participated in the study. OUTCOME MEASURES: Maximum motion, end-range motion and surplus motion (the difference between maximum motion and end-range) in degrees were extracted from each cervical joint. METHODS: Thirty-three subjects performed one flexion and one extension motion excursion under video fluoroscopy. The motion excursions were divided into 10% epochs, from which maximum motion, end-range and surplus motion were extracted. Surplus motion was then assessed in quartiles and joints were classified into type according to end-range. RESULTS: For flexion 48.9% and for extension 47.2% of joints produced maximum motion before joint end-range (type S). For flexion 45.9% and for extension 46.8% of joints produced maximum motion at joint end-range (type C). For flexion 5.2% of joints and for extension 6.1% of joints concluded their motion anti-directionally (type A). Significant differences were found for C2/C3 (P = 0.000), C3/C4 (P = 0.001) and C4/C5 (P = 0.005) in flexion and C1/C2 (P = 0.004), C3/C4 (P = 0.013) and C6/C7 (P = 0.013) in extension when comparing the joint end- range of type C and type S. The average pro-directional (motion in the direction of neck motion) surplus motion was 2.41° ± 2.12° with a range of (0.07° -14.23°) for flexion and 2.02° ± 1.70° with a range of (0.04°-6.97°) for extension. CONCLUSION: This is the first study to categorise joints by type of motion. It cannot be assumed that end-range is a demonstration of a joint's maximum motion, as type S constituted approximately half of the joints analysed in this study.

Motion analysis of the cervical spine during extension and flexion: Reliability of the vertebral marking procedure.

Cervical spine motion analysis using videofluoroscopy is currently a technique without a gold standard. We demonstrate the reliability of a rigid and reliable analysis methodology for cervical motion using videofluoroscopic images, representing the entire range of motion during flexion and extension, from the neutral position to the end-range in the sagittal plane. Two researchers with radiography and vertebral marking expertise, and two inexperienced researchers with 10 hours of training manually marked anatomical structures on fluoroscopic images in a procedure designed to control for vertebral rotation around the mid-plane axis. The average marking error across examiners and images was -0.12∘ (standard deviation: 0.88°), and the intraexaminer error ranged from -1.00∘ to 1.61° (standard deviation range: 0.27°-1.19°). Our method demonstrated lower errors compared to the higher resolution X-ray studies, and proved that vertebral marking can be performed by persons with no experience in radiographic image analysis.

Repeatability of Cervical Joint Flexion and Extension Within and Between Days.

OBJECTIVE: The purpose of this study was to investigate within- and between-day repeatability of free and unrestricted healthy cervical flexion and extension motion when assessing dynamic cervical spine motion. METHODS: Fluoroscopy videos of 2 repeated cervical flexion and 2 repeated extension motions were examined for within-day repeatability (20-second interval) for 18 participants (6 females) and between-day repeatability (1-week interval) for 15 participants (6 females). The dynamic cervical motions were free and unrestricted from neutral to end range. The flexion videos and extension videos were evenly divided into 10% epochs of the C0-to-C7 range of motion. Within-day and between-day repeatability of joint motion angles (all 7 joints and epochs, respectively) was tested in a repeated-measures analysis of variance. Joint motion angle differences between repetitions were calculated for each epoch and joint (7 joints), and these joint motion angle differences between within-day and between-day repetitions were tested in mixed-model analysis of variance. RESULTS: For all joints and epochs, respectively, no significant differences were found in joint motion angle between within-day or between-day repetitions. There were no significant effects of joint motion angle differences between within-day and between-day repetitions. The average within-day joint motion angle differences across all joints and epochs were 0.00° ± 2.98° and 0.00° ± 3.05° for flexion and extension, respectively. The average between-day joint motion angle differences were 0.02° ± 2.56° and 0.05° ± 2.40° for flexion and extension, respectively. CONCLUSIONS: This is the first study to report the within-day and between-day joint motion angle differences of repeated cervical flexion and extension. This study supports the idea that cervical joints repeat their motion accurately.

Cervical flexion and extension includes anti-directional cervical joint motion in healthy adults.

BACKGROUND CONTEXT: Anti-directional cervical joint motion has previously been demonstrated. However, quantitative studies of anti-directional and pro-directional cervical flexion and extension motions have not been published. PURPOSE: This study aimed for a quantitative assessment of directional and anti-directional cervical joint motion in healthy subjects. STUDY DESIGN: An observational study was carried out. PATIENTS SAMPLE: Eighteen healthy subjects comprised the study sample. OUTCOME MEASURES: Anti-directional and pro-directional cervical flexion and extension motion from each cervical joint in degrees were the outcome measures. METHODS: Fluoroscopy videos of cervical flexion and extension motions (from neutral to end-range) were acquired from 18 healthy subjects. The videos were divided into 10% epochs of C0/C7 range of motion (ROM). The pro-directional and anti-directional motions in each 10% epoch were extracted, and the ratios of anti-directional motions with respect to the pro-directional motions (0%=no anti-directional movement) were calculated for joints and 10% epochs. RESULTS: The flexion and extension ROM for C0/C7 were 51.9°±9.3° and 57.2°±12.2°. The anti-directional motions of flexion and extension ROM constituted 42.8%±9.7% and 41.2%±8.2% of the respective pro-directional movements. For flexion, the first three joints (C0/C1, C1/C2, C2/C3) demonstrated larger ratios compared with the last three joints (C4/C5, C5/C6, C6/C7) (p<.03). For extension, C1/C2 and C2/C3 ratios were larger compared with C0/C1, C4/C5, and C5/C6 (p<.03). Comparisons between flexion and extension motions showed larger C0/C1 ratio but smaller C5/C6 and C6/C7 ratios in extension (p<.05). CONCLUSIONS: This is the first report of quantified anti-directional cervical flexion and extension motion. The anti-directional motion is approximately 40% of the pro-directional motion. The results document that large proportions of anti-directional cervical flexion and extension motions were normal.

Muscle Pain Induces a Shift of the Spatial Distribution of Upper Trapezius Muscle Activity During a Repetitive Task: A Mechanism for Perpetuation of Pain With Repetitive Activity?

OBJECTIVE: An association exists between repetitive movements and the development or perpetuation of neck-shoulder muscle pain. The mechanisms underlying this association remain unclear. This observational study investigated the effect of upper trapezius muscle pain on the distribution of upper trapezius activity during repetitive lifting. It was hypothesized that nociception would change the distribution of activity resulting in activation of muscle regions which would not normally be active during the task. MATERIALS AND METHODS: Healthy men repeatedly lifted a box with a cycle time of 3 seconds for 50 cycles, at baseline, following injection of isotonic and hypertonic saline into the upper trapezius muscle and 15 minutes after the last injection. High-density surface electromyography (EMG) was recorded from the upper trapezius using a grid of 64 electrodes. The EMG amplitude was computed for each location to form a map of the EMG amplitude distribution. RESULTS: During the painful condition, the overall EMG amplitude was lower compared with all other conditions (P<0.05) and in addition, the center of upper trapezius activity was shifted toward the caudal region of the muscle (P<0.01), a region not normally active during the task. The described alterations of muscle activity likely play an important role in the perpetuation of pain during repetitive activity. DISCUSSION: Novel mapping of the spatial distribution of upper trapezius muscle activity showed that nociception induced a redistribution of activity during repetitive lifting. This knowledge provides new insights into the mechanisms underlying the perpetuation of pain with repetitive activity.

Cervical spine reposition errors after cervical flexion and extension.

BACKGROUND: Upright head and neck position has been frequently applied as baseline for diagnosis of neck problems. However, the variance of the position after cervical motions has never been demonstrated. Thus, it is unclear if the baseline position varies evenly across the cervical joints. The purpose was to assess reposition errors of upright cervical spine. METHODS: Cervical reposition errors were measured in twenty healthy subjects (6 females) using video-fluoroscopy. Two flexion movements were performed with a 20 s interval, the same was repeated for extension, with an interval of 5 min between flexion and extension movements. Cervical joint positions were assessed with anatomical landmarks and external markers in a Matlab program. Reposition errors were extracted in degrees (initial position minus reposition) as constant errors (CEs) and absolute errors (AEs). RESULTS: Twelve of twenty-eight CEs (7 joints times 4 repositions) exceeded the minimal detectable change (MDC), while all AEs exceeded the MDC. Averaged AEs across the cervical joints were larger after 5 min' intervals compared to 20 s intervals (p < 0.05). CONCLUSIONS: This is the first study to demonstrate single joint reposition errors of the cervical spine. The cervical spine returns to the upright positions with a 2° average absolute difference after cervical flexion and extension movements in healthy adults.

Current pain and fear of pain contribute to reduced maximum voluntary contraction of neck muscles in patients with chronic neck pain.

OBJECTIVE: To assess a range of physical and psychological factors and determine which factors contribute the most to reduced strength in patients with neck pain. DESIGN: Regression. SETTING: Laboratory. PARTICIPANTS: Women with chronic neck pain (n=34) and healthy controls (n=14). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Neck flexion, extension, and lateral flexion maximum voluntary contractions (MVC) were measured in patients and healthy controls. Additional parameters were collected for the patient group including: (1) questionnaires measuring general health (Medical Outcomes Study 36-Item Short-Form Health Survey), pain intensity, disability (Neck Disability Index [NDI]; Patient Specific Functional Scale), and fear of movement (Fear-Avoidance Beliefs Questionnaire [FABQ]), (2) pressure pain thresholds, (3) cross-sectional area of selected neck muscles, and (4) surface electromyography from selected neck muscles during a multidirectional isometric task. Univariate and multivariate regression analyses were applied with the average MVC (average of flexion, extension, and lateral flexion MVC) as the dependent variable. RESULTS: The average MVC was significantly lower in patients (mean ± SD, 130.0±6.0N) compared with controls (166.9±11.7N; P<.01). Univariate regression of the average MVC with the FABQ, NDI, or pain experienced during the MVC gave R(2) values of 13.4%, 13.8%, and 21.1%, respectively. Collectively, the FABQ and pain experienced during the MVCs resulted in an R(2) of 26.6% and the FABQ, contraction pain, and NDI, an R(2) of 28.2%. CONCLUSIONS: The average maximum voluntary force produced in neck flexion, extension, and lateral flexion is inversely and moderately correlated with the pain experienced during maximal contraction, fear of movement, and aspects of neck disability in patients with chronic neck pain.

Chronic trauma-induced neck pain impairs the neural control of the deep semispinalis cervicis muscle.

OBJECTIVE: The deep cervical extensors show structural changes in patients with neck pain however their activation has never been investigated in patients. This study is the first to present neurophysiological data from the deep semispinalis cervicis muscle in patients. METHODS: Ten women with chronic neck pain and 10 healthy controls participated. Activity of the semispinalis cervicis was measured as subjects performed isometric contractions at 15 and 30 N force with continuous change in force direction in the range 0-360°. Tuning curves of the EMG amplitude (average rectified value, ARV) were computed and the mean point of the ARV curves defined a directional vector, which determined the directional specificity of the muscle activity. RESULTS: Patients displayed reduced directional specificity of the semispinalis cervicis (P < 0.05). Furthermore, the EMG amplitude during the circular contraction was lower for the patients (86.3 ± 38.0 and 104.4 ± 47.0 µV for 15 and 30N, respectively) compared to controls (226.4 ± 128.5 and 315.8 ± 205.5 µV; P<0.05). CONCLUSIONS: The activity of the semispinalis cervicis muscle is reduced and less defined in patients with neck pain confirming a disturbance in the neural control of this muscle. SIGNIFICANCE: This finding suggests that exercises that target the deep semispinalis cervicis muscle may be relevant to include in the management of patients with neck pain.