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

Quantitatively assessing the effect of cervical sagittal alignment on dynamic intervertebral kinematics by video-fluoroscopy technique

BACKGROUND

Cervical sagittal alignment is crucial for distributing the head load to lower cervical segments and maintaining normal cervical spine function, but its biomechanical effect on the cervical spine was not fully elucidated.

OBJECTIVE

To investigate the effect of cervical sagittal alignment on dynamic intervertebral kinematics.

DESIGN

Cross-sectional study.

METHODS

Healthy participants without neck pain were recruited and divided into lordosis, straight and kyphosis groups according to the C2-C7 Cobb angle at the neutral position. The anti-directional and total joint motions were extracted across 10 epochs of dynamic cervical flexion and extension movements.

RESULTS

/findings: The overall anti-directional joint motion during flexion is larger in the kyphosis group when compared with the lordosis group (p = 0.021), while the range of flexion is smaller in the kyphosis group than that in the lordosis group (p = 0.017). The C2/C3 anti-directional joint motion during extension in the straight group is larger than that in the lordosis group (p = 0016). The range of extension in the kyphosis group (p < 0.001) and the straight group (p = 0.002) are larger than that in the lordosis group. The increased range of extension in the kyphosis and straight groups were mainly from the C3/C4, C4/C5, and C5/C6 joints(p < 0.05).

CONCLUSION

Changes in cervical sagittal alignment alter both the quality and quantity of the individual joint motions. More adjustments are required by the cervical joints to complete neck movements with the loss of lordosis. The lordotic curvature is a relatively effort-saving mode for the cervical spine from a biomechanical perspective.

Sagittal intervertebral rotational motion: a deep learning-based measurement on flexion–neutral–extension cervical lateral radiographs

Background

The analysis of sagittal intervertebral rotational motion (SIRM) can provide important information for the evaluation of cervical diseases. Deep learning has been widely used in spinal parameter measurements, however, there are few investigations on spinal motion analysis. The purpose of this study is to develop a deep learning-based model for fully automated measurement of SIRM based on flexion–neutral–extension cervical lateral radiographs and to evaluate its applicability for the flexion–extension (F/E), flexion–neutral (F/N), and neutral–extension (N/E) motion analysis.

Methods

A total of 2796 flexion, neutral, and extension cervical lateral radiographs from 932 patients were analyzed. Radiographs from 100 patients were randomly selected as the test set, and those from the remaining 832 patients were used for training and validation. Landmarks were annotated for measuring SIRM at five segments from C2/3 to C6/7 on F/E, F/N, and N/E motion. High-Resolution Net (HRNet) was used as the main structure to train the landmark detection network. Landmark performance was assessed according to the percentage of correct key points (PCK) and mean of the percentage of correct key points (MPCK). Measurement performance was evaluated by intra-class correlation coefficient (ICC), Pearson correlation coefficient, mean absolute error (MAE), root mean square error (RMSE), and Bland-Altman plots.

Results

At a 2-mm distance threshold, the PCK for the model ranged from 94 to 100%. Compared with the reference standards, the model showed high accuracy for SIRM measurements for all segments on F/E and F/N motion. On N/E motion, the model provided reliable measurements from C3/4 to C6/7, but not C2/3. Compared with the radiologists’ measurements, the model showed similar performance to the radiologists.

Conclusions

The developed model can automatically measure SIRM on flexion–neutral–extension cervical lateral radiographs and showed comparable performance with radiologists. It may provide rapid, accurate, and comprehensive information for cervical motion analysis.

[Radiological features of degenerative cervical kyphosis and relationship between sagittal parameters]

OBJECTIVE

To investigate the radiological features of degenerative cervical kyphosis (DCK) and the relationship between cervical sagittal parameters.

METHODS

The quality of life scores and imaging data of 89 patients with DCK treated between February 2019 and February 2022 were retrospectively analysed. There were 47 males and 42 females, with an average age of 48.4 years (range, 25-81 years). Quality of life scores included visual analogue scale (VAS) score and neck disability index (NDI). The imaging data included C ₀-C ₂ angle, C ₂-C ₇ angle, C ₃-C ₇ inclination of zygapophyseal joints, C ₇ slope (C ₇S), cervical sagittal vertical axis (cSVA), kyphosis range, and kyphosis focal. The patients were grouped by gender, and the differences of the above parameters between the two groups were compared. Pearson correlation was used to analyze the relationship between age, quality of life scores, and cervical sagittal parameters, and the relationship between cervical sagittal parameters.

RESULTS

The preoperative VAS score was 0-9 (mean, 4.3); NDI was 16%-44% (mean, 30.0%). There was no significant difference in VAS score and NDI between male and female groups ( P>0.05). The kyphosis range of cervical spines was C _3-5 in 3 cases, C _3-6 in 41 cases, C _3-7 in 30 cases, C _4-6 in 4 cases, C _4-7 in 10 cases, C _5-7 in 1 case, and the kyphosis focal was mostly located between C ₄-C ₅ (78/89, 87.64%). The C ₃-C ₇ inclination of zygapophyseal joints were (60.25±5.56)°, (55.42±5.77)°, (53.03±6.33)°, (58.39±7.27)°, and (64.70±6.40)°, respectively. The C ₀-C ₂ angle, C ₂-C ₇ angle, C ₇S, and cSVA were (-23.81±6.74)°, (10.15±2.94)°, (15.31±4.59)°, and (2.37±1.19) mm, respectively. The C ₇S and cSVA of males were significantly larger than females ( P<0.05), with no significant difference in other parameters between male and female groups ( P>0.05). VAS score and NDI were negatively correlated with C ₀-C ₂ angle ( P<0.05), and positively correlated with C ₂-C ₇ angle and cSVA ( P<0.05); VAS score was negatively correlated with C ₇S ( P<0.05). Except VAS, NDI and all cervical sagittal parameters were affected by age. Age was positively correlated with NDI, C ₇S, and cSVA ( P<0.05), and negatively correlated with C ₀-C ₂ angle and C ₂-C ₇ angle ( P<0.05). The correlation analysis of cervical sagittal parameters showed that C ₀-C ₂ angle was negatively correlated with C ₂-C ₇ angle and cSVA ( P<0.05); C ₇S was negatively correlated with C ₂-C ₇ angle ( P<0.05) and positively correlated with cSVA ( P<0.05). There was no correlation among other parameters ( P>0.05).

CONCLUSION

The inclination of zygapophyseal joints of cervical spines of DCK patients is U-shaped in the kyphosis range, and the inclination at the kyphosis focal is the smallest. When cervical degenerative kyphosis occurs, in addition to the interaction of sagittal parameters, age, gender, neck pain, and dysfunction will also affect the cervical sagittal balance. Furthermore, cervical curvature and morphological changes are not purely local problems.

Effects of experimental pain on the cervical spine reposition errors

BACKGROUND

Healthy subjects showed normal variance of cervical spine reposition errors of approximately 2 degrees. Effects of experimental pain on cervical spine reposition errors were unknown; thus, the purpose of this study was to investigate the effects of experimental pain on cervical spine reposition errors.

METHODS

A repeated measured study design was applied. Thirty healthy subjects (12 males) were recruited. Reposition errors were extracted from upright cervical positions before and after cervical flexion movement in healthy subjects before and during experimental neck pain. Cervical spine reposition errors were calculated based on anatomical landmarks of each cervical joint. Reposition errors were extracted in degrees as constant errors and absolute errors for further statistical analysis. Repeated measures analysis of variance (RM-ANOVA) was applied to analyse experimental pain effects on either constant errors or absolute errors of different cervical joints.

RESULTS

The cervical spine showed non-significant difference in reposition errors regarding the constant errors (P>0.05) while larger reposition errors regarding the absolute errors during experimental pain compared to before experimental pain (P<0.001). In addition, the pain level joint (C4/C5) and its adjacent joints (C3/C4 and C5/C6) indicated larger reposition errors regarding absolute errors (P=0.035, P=0.329 and P=0.103, respectively).

CONCLUSIONS

This study firstly investigated the cervical spine reposition errors in experimental neck pain and further found the joints adjacent to the pain level showed larger errors compared to the distant joints regarding absolute errors. It may imply that the larger reposition errors in specific cervical joint indicate probable injury or pain existed adjacent to the joints.

Association of Spinal Manipulative Therapy With Changes in Cervical Motion Segment Interactions in Patients With Neck Pain: An Observational Study With Matched Asymptomatic Controls

OBJECTIVE

The objectives of this study were to determine (1) if maximal intervertebral range of motion (IV-RoMmax) and laxity interactions exist in the cervical spine during flexion, (2) if there are differences in IV-RoMmax or laxity parameters between baseline and follow-up in both patients with neck pain and asymptomatic controls, and (3) if there is an effect on IV-RoMmax/laxity relationships in patients with neck pain after spinal manipulative therapy.

METHODS

Twenty-nine patients with subacute or chronic neck pain and 33 asymptomatic controls were imaged during flexion and extension, pre and post a course of cervical chiropractic manipulation (patient group only), using a standardized quantitative fluoroscopy acquisition protocol.

RESULTS

Significant correlations between IV-RoMs were found in both neck pain and neck pain-free populations at baseline and follow-up. Positive relationships were found between C2-C3 and C3-C4 and C4-C5 and C5-C6 IV-RoM in both populations. A negative correlation was found in the patient group at baseline between C1-C2 and C5-C6, but not at follow-up. Significant relationships were also found for segmental laxity, with a negative correlation found at C1-C2 and C5-C6 in the patient group only and at baseline only.

CONCLUSION

Distinct relationships were found between both intraregional IV-RoM and laxity, many of which were present in both groups at baseline and follow-up, suggestive of normal kinematic behaviors. Changes in correlations unique to the patient group may be indicative of a change in regional kinematics resulting from the manipulation intervention. Spinal manipulative therapy may have a therapeutic effect by influencing cervical kinematics at the regional level.

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.

Novel assessment of the variation in cervical inter-vertebral motor control in a healthy pain-free population

Spinal control at intervertebral levels is dependent on interactions between the active, passive and neural control elements. However, this has never been quantifiable, and has therefore been outside the reach of clinical assessments and research. This study used fluoroscopy during repeated unconstrained flexion and return neck movements to calculate intersegmental motor control (MC), defined as the difference and variation in repeated continuous angular motion from its average path. The study aimed to determine control values for MC at individual levels and its variability. Twenty male volunteers aged 19–29 received fluoroscopic screening of their cervical spines during 4 repetitions of neutral to full flexion and return motion. Moving vertebral images from C0–C1 to C6–C7 were tracked using cross-correlation codes written in Matlab. MC for each level was defined as the mean of the absolute differences between each repetition’s angular path and their mean and its variability as represented by the SD. 1-way ANOVA and Tukey multiple comparisons were used to identify significant contrasts between levels. The mean MC differences and SDs were highest at C1-2, suggesting that this level has the least control and the most variability. Results at this level alone were highly significant (F-ratio 10.88 and 9.79 P < 0.0001). Significant contrasts were only found between C1-C2 and all other levels. The mean MC difference for summed C1-6 levels was 3.4° (0.7–6.1). This study is the first to quantify intervertebral MC in the cervical spine in asymptomatic people. Studies of neck pain patients are now merited.

Recurrent neck pain patients exhibit altered joint motion pattern during cervical flexion and extension movements

BACKGROUND

Impaired sensorimotor ability has been demonstrated in recurrent neck pain patients. It is however not clear if cervical joint motion and pressure pain sensitivity in recurrent neck pain patients are different from asymptomatic controls.

METHODS

Cervical flexion and extension motions were examined by video-fluoroscopy and pressure pain thresholds were assessed bilaterally over C2/C3, C5/C6 facet joints and right tibialis anterior in eighteen recurrent neck pain patients and eighteen healthy subjects. Individual joint motion was analyzed by dividing fluoroscopic videos into 10 epochs. The motion opposite to the primary direction (anti-directional motion) and motion along with the primary direction (pro-directional motion) of each joint were extracted across epochs. Total joint motion was the sum of anti-directional and pro-directional motions. Joint motion variability was represented by the variance of joint motions across epochs.

FINDINGS

Compared to controls, recurrent neck pain patients showed: 1) decreased anti-directional motion at C2/C3 and C3/C4 (P < 0.05) and increased anti-directional motion at C5/C6 and C6/C7 (P < 0.05) during extension motion. 2) Increased overall anti-direction motion during flexion motion (P < 0.05). 3) Lower joint motion variability at C3/C4 during extension motion (P < 0.05).

INTERPRETATION

Recurrent neck pain patients showed a redistribution of anti-directional motion between the middle cervical spine and the lower cervical spine during cervical extension and increased overall anti-directional motion during cervical flexion compared with healthy controls. The anti-directional motion was more sensitive to neck pain compared to other cervical joint motion parameters in the present study.

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.

Experimental cervical interspinous ligament pain altered cervical joint motion during dynamic extension movement

BACKGROUND

Although the cervical interspinous ligament is a potential source of neck pain, the effects on cervical joint motion and pressure pain sensitivity has never been investigated. The understanding of the relationship will broaden our understanding of cervical biomechanics and improve diagnosis and treatment of neck pain.

METHODS

Fluoroscopy videos of cervical flexion and extension movements and pressure pain thresholds over bilateral C2/C3 and C5/C6 facet joints were collected in fifteen healthy subjects before and after injections of hypertonic and isotonic saline in C4/C5 ISL. The videos were divided into 10 even epochs and the motion of individual joints during each epoch was extracted. Joint motion parameters including anti-directional motion, pro-directional motion, total joint motion and joint motion variability were extracted across epochs. Joint motion parameters and PPTs were compared before and after injection of hypertonic and isotonic saline separately.

FINDINGS

Compared with baselines: hypertonic saline injection 1) decreased anti-directional motion and joint motion variability at C4/C5 (P < 0.05) and increased at C2/C3 (P < 0.05) during extension; 2) increased total joint motion of C0/C1 during first half range (P < 0.05) and decreased during second half range of extension, and total joint motion of C2/C3 increased during second half range of extension (P < 0.05) and; 3) increased pressure pain thresholds over left C2/C3 facet joint (P < 0.01).

INTERPRETATION

The cervical interspinous ligament pain redistributed anti-directional motion between C4/C5 and C2/C3 during dynamic extension and decreased pressure pain sensitivity over the left C2/C3 facet joint.

Origin of neck pain and direction of movement influence dynamic cervical joint motion and pressure pain sensitivity

BACKGROUND

Patients with neck pain normally showed alterations in cervical motion and pressure pain sensitivity. Cervical joints show scattered motions opposite to (anti-directional) the primary motion direction (pro-directional) during dynamic cervical flexion and extension. This study aimed to assess dynamic cervical joint motion and pressure pain sensitivity when pain originated from different cervical muscles which may have clinical relevance in diagnosis of impairments related with neck pain.

METHODS

Fluoroscopic video recordings of cervical flexion and extension were collected from fifteen healthy subjects before and during hypertonic saline-induced pain in right multifidus and trapezius muscles. Cervical flexion and extension motions were divided into 10 epochs with respect to time. Pro-directional, anti-directional, and total joint motion were extracted across epochs as well as joint motion variability. Pressure pain thresholds (PPTs) were assessed bilaterally over C2/C3 and C5/C6 facet joints.

FINDINGS

Compared with baseline: 1) Multifidus muscle pain increased the C3/C4 anti-directional motion (P < 0.01), decreased the C6/C7 anti-directional motion (P < 0.05) during extension, and redistributed total joint motion between joints and between half ranges during flexion (P < 0.05). 2) Trapezius muscle pain decreased pro-directional motion (P < 0.05), anti-directional motion (P < 0.05), and joint motion variability (P < 0.05) during extension. 3) Trapezius and multifidus muscle pain increased the PPTs bilaterally over C2/C3 and on the left side of C5/C6 facet joints (P < 0.05).

INTERPRETATION

The direction of motion influenced the effects of experimental muscle pain on dynamic cervical joint kinematics, and deep muscle pain showed local effects on individual joints while superficial muscle pain showed global effects spread to all joints.

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.