Background
Many people living in modern society experience neck pain. Moreover, the increasing use of smartphones has resulted in increasing incidence of neck pain [
1‐
3]. During smartphone use, the user’s neck is more bent than when looking at video display terminals in general [
4], and neck pain can occur because the cervical extensor becomes activated and the load on the erector spinae increases in order to adjust the neck balance [
4]. Additionally, touching the screen and using the smartphone for a long time without supporting the arm causes fatigue of the neck and shoulder, and increases the load on the cervical spine [
5]. Continuous load on the cervical spine leads to variations in the spinal curve, resulting in degenerative change of joints, a straight cervical spine, and forward head posture (FHP) [
6‐
8], which can worsen and progress to cervical herniation of the intervertebral disc [
9]. FHP is defined as increased extension of the upper cervical spine and increased flexion of the lower cervical spine and upper thoracic spine, with the head position around the sagittal plane showing forward deviation from the gravity line [
10,
11]. In the FHP position, the loads applied to the muscles around the neck and shoulder are 3.6 times the loads in the normal position [
12]. Particularly, FHP causes shortening of the sternocleidomastoid, scalenus anterior, and upper trapezius muscles, and lengthening of the levator scapulae and semispinalis capitis muscles, leading to abnormal activation of the cervical spine flexor and extensor muscles [
13].
Previous studies reported that 60% of patients with neck and shoulder pain presented with FHP [
14], and FHP caused asymmetric muscle activation in the spine (which is an important indicator of neck pain), restricted functional activity, and caused spine deviation and lateral inclination of the pelvis [
15‐
17]. Cervical instability results from hypomobility of the upper cervical spine and upper thoracic spine and hypermobility of the lower cervical spine. Particularly, the protective action of movement and the reaction force is decreased by the induced change in vertebral structures [
18]. Therefore, most clinicians examine the thoracic spine in individuals with neck pain [
19,
20]. Dysfunction of the lower cervical spine and articular disc lesions can be causes of pain in the upper thoracic spine, and dysfunction of the upper thoracic spine restricts the movement of the cervical spine and causes pain [
21,
22]. These biomechanical relations of the cervical spine and the thoracic spine are related to movement and become important factors causing neck pain [
23]. Some studies report that neck pain and range of motion were improved by applying manual therapy on the upper thoracic spine and on the cervical spine of patients with neck pain, thus improving their movement [
24,
25].
In clinical practice, physical therapists generally use different modalities, therapeutic exercises, non-thrust mobilization, and thrust manipulation as representative interventions to improve neck pain and FHP [
26‐
29]. A review of the literature highlights recent studies that investigated interventions with manual therapy and active exercise in acute and chronic cervical diseases [
30,
31]. Particularly, it was proposed that a combination of manual therapy and therapeutic exercise is effective for the management of mechanical neck pain [
28]. There are two types of manual therapy: joint mobilization and joint manipulation [
20,
32]. However, previous studies suggested that adverse effects, such as local discomfort, headache, dizziness, and malaise were fewer in mobilization than in manipulation [
33,
34]. A study on joint mobilization and manipulation therapy reported that the two types of therapies showed equivalent efficacy [
35].
Although many studies have been conducted on patients with neck pain, there is insufficient evidence on the effectiveness of the combination of joint mobilization and therapeutic exercise in individuals with FHP. Therefore, the purpose of this study was to identify the effect of the combination of joint mobilization and therapeutic exercises in improving pain and movement in individuals with FHP. In addition, although most previous studies focused on the cervical spine, this study aimed to identify the effect of intervention on the upper thoracic spine.
Results
The baseline characteristics were similar between the groups for all variables (
p > .42) (Table
1). The within-group change scores and between-group differences along with 95% confidence intervals (CI) for all outcome measures can be found in Tables
2 and
3. The participants reported no adverse events during the treatment period, nor were any identified during the 6-week follow-up.
Table 2
Within-group change score and pairwise comparisons of between-group change scores for cervical range of motion
Flexion (°) |
Cervical group | 49.3 (10.1) | 57.1 (9.3) | 53.2 (11.5) | 7.8 (2.8, 12.8) | 3.9 (−0.8, 8.7) | 2.2 (−3.4, 7.7); p = .428 | 4.7 (−1.0, 10.4); p = .104 |
Thoracic group | 50.6 (9.5) | 60.6 (9.0) | 59.3 (7.4) | 10.0 (7.1, 13.0) | 8.6 (5.0, 12.2) |
Extension (°) |
Cervical group | 63.3 (8.4) | 69.6 (8.1) | 64.6 (7.3) | 6.3 (2.4, 10.2) | 1.3 (−4.0, 6.6) | 3.9 (−0.9, 8.8); p = .108 | 6.2 (1.2, 11.2); p = .016 |
Thoracic group | 59.7 (9.5) | 70.0 (9.0) | 67.2 (8.0) | 10.3 (5.2, 15.3) | 7.5 (3.7, 11.3) |
Right lateral flexion (°) |
Cervical group | 39.8 (5.7) | 45.3 (5.3) | 42.9 (4.9) | 5.6 (3.0, 8.2) | 3.2 (0.0, 6.3) | 1.2 (−2.5, 4.9); p = .515 | −0.4 (−4.6, 3.8); p = .833 |
Thoracic group | 37.6 (6.1) | 44.4 (2.9) | 40.4 (4.4) | 6.8 (4.0, 9.6) | 2.8 (−0.3, 5.8) |
Left lateral flexion (°) |
Cervical group | 41.9 (6.0) | 45.8 (5.6) | 42.4 (4.9) | 3.9 (2.0, 5.9) | 0.5 (−2.2, 3.2) | 3.4 (0.3, 6.5); p = .033 | 3.5 (−0.1, 7.0); p = .051 |
Thoracic group | 37.2 (7.5) | 44.5 (4.9) | 41.2 (5.0) | 7.3 (4.7, 9.9) | 4.0 (1.6, 6.5) |
Right rotation (°) |
Cervical group | 67.4 (8.9) | 76.3 (5.7) | 74.3 (7.0) | 8.9 (5.3, 12.6) | 6.9 (3.7, 10.0) | 4.6 (−0.7, 1.0); p = .088 | 0.8 (−5.2, 6.7); p = .797 |
Thoracic group | 63.7 (12.0) | 77.3 (6.5) | 71.3 (8.6) | 13.6 (9.4, 17.8) | 7.6 (2.3, 12.9) |
Left rotation (°) |
Cervical group | 69.1 (8.1) | 78.3 (5.3) | 75.2 (6.3) | 9.1 (5.0, 13.3) | 6.1 (1.9, 10.2) | 5.9 (−0.1, 12.0); p = .054 | 3.3 (−3.9, 10.4); p = .054 |
Thoracic group | 63.6 (13.4) | 78.6 (8.3) | 72.9 (10.3) | 15.1 (10.3, 19.8) | 9.3 (3.1, 15.4) |
Table 3
Outcome data for craniovertebral angle, neck pain, pain sensitivity, and disability
CVA (sitting) |
Cervical group | 45.1 (3.9) | 50.6 (4.4) | 48.4 (5.7) | 5.4 (2.9, 7.9) | 3.3 (0.1, 6.4) | 0.9 (−2.1, 4.0); p = .536 | 2.1 (−1.6, 6.0); p = .252 |
Thoracic group | 43.6 (3.8) | 50.0 (3.8) | 49.1 (3.0) | 6.4 (4.4, 8.4) | 5.4 (3.0, 8.0) |
CVA (standing) |
Cervical group | 50.6 (4.8) | 52.0 (5.7) | 51.3 (5.2) | 1.4 (−1.2, 3.9) | 0.6 (−1.9, 3.1) | 4.3 (1.2, 7.4); p = .008 | 3.3 (0.1, 6.4); p = .042 |
Thoracic group | 48.4 (4.6) | 54.1 (4.3) | 52.3 (3.3) | 5.7 (3.7, 7.7) | 3.9 (1.8, 6.0) |
NPRS (0–10) |
Cervical group | 3.6 (1.4) | 2.3 (1.0) | 2.3 (1.0) | 1.3 (0.8, 1.8) | 1.3 (0.7, 1.9) | 1.3 (0.6, 2.1); p < .001 | 1.4 (0.6, 2.3); p = .002 |
Thoracic group | 4.2 (1.5) | 1.6 (0.8) | 1.4 (0.7) | 2.6 (2.0, 3.2) | 2.8 (2.0, 3.4) |
PPT (kPa) |
Cervical group | 35.9 (8.2) | 48.4 (10.5) | 46.8 (10.0) | 12.5 (9.7, 15.3) | 10.8 (8.2, 13.4) | 1.9 (−1.4, 5.2); p = .251 | −2.6 (−7.0, 1.9); p = .251 |
Thoracic group | 36.3 (12.7) | 50.6 (12.1) | 44.5 (11.2) | 14.4 (12.5, 16.3) | 8.3 (4.4, 12.1) |
NDI (0–50) |
Cervical group | 7.9 (4.3) | 5.4 (3.7) | 5.3 (3.9) | 2.4 (1.3, 3.6) | 2.6 (1.6, 3.7) | 3.3 (1.0, 5.6); p = .006 | 3.4 (1.0, 5.8); p = .008 |
Thoracic group | 10.4 (5.0) | 4.6 (2.2) | 4.3 (2.0) | 5.8 (3.7, 7.8) | 6.1 (3.8, 8.3) |
In this study, the active cervical extension showed a significant group-by-time interaction (F2,29 = 3.882, p = .026, η
p
2 = .115), with the thoracic group indicating significantly (t29 = 2.54, p = .016) better improvement in active cervical extension (7.5°; 95% CI: 3.7, 11.3) over time than those in the cervical group (1.3°; 95% CI: -4.0, 6.6). However, no significant group-by-time interaction was observed for CROM, as measured using flexion, lateral flexion, and rotation. The CVA (standing position) showed a significant group-by-time interaction (F2,29 = 4.549, p = .014, η
p
2 = .132), with the thoracic group indicating significantly (t29 = 2.13, p = .042) better improvement in CVA (3.9°; 95% CI: 1.8, 6.0) over time than those in the cervical group (0.6°; 95% CI: -1.9, 3.1). However, the CVA (sitting position) demonstrated no significant group-by-time interaction. The NPRS showed a significant group-by-time interaction (F2,29 = 9.779, p = .001, η
p
2 = .246), with the thoracic group indicating better pain reduction over time than those in the cervical group. However, no significant group-by-time interaction was observed for PPT, as measured using a pressure algometer. The NDI showed a significant group-by-time interaction (F2,29 = 7.938, p = .004, η
p
2 = .209), with the thoracic group indicating better improvement in disability index over time than those in the cervical group. In case of GRC after 4 weeks, the thoracic group demonstrated significantly (t29 = 2.725, p = .011) better improvements on the GRC measure (mean ± standard deviation, +4.25 ± 1.06) than the cervical group (+3.37 ± 0.72), with a mean difference between groups of 0.87 points (95% CI: 0.2, 1.5).
Discussion
The results of this study corresponded with those of a previous research that shows the efficacy of manipulation and mobilization of the cervical and thoracic spine in patients with neck pain [
24,
56,
57]. The novelty of the current study is that the results suggest that the combination of upper thoracic mobilization and mobility exercise may provide short-term benefits to individuals with FHP.
FHP results in deformation of joints due to poor postures for a long time. Mobilization as treatment was conducted to improve the flexion of the upper cervical spine and to enhance the extension of the upper thoracic spine [
32]. According to the purpose of the mobilization, this study showed improvement of the CROM in both groups; however, there was a significant difference between the two groups in cervical spine extension. Previous studies also showed the increase of the range of motion by improving joint hypo-mobility and the adhesion between soft tissues when the joint mobilization technique was applied to patients with mechanical neck pain [
23,
58]. Particularly, it was reported that there were more improvements of movement limitation in patients with the most serious pain. In the case of therapeutic exercise, in this study, the stabilization exercise was conducted in the lower cervical spine and the mobility exercise was performed in the upper thoracic spine. The stabilization exercise for the cervical spine was a low-intensity isometric exercise, and the mobility exercise for the thoracic spine was a high-intensity exercise against gravity. Thus, better results were obtained in the thoracic spine owing to the difference in intensity despite performing both exercises at the same time. Although the CVA measured from profile photographs also indicated improved results in both groups, in the standing position, there was a significant difference between groups through flow of time and there was an interaction. A previous study reported that thoracic spine mobilization with continuous passive stimulus increased joint mobility and helped in improving the somatosensory system [
59]. Because of changes in these qualities and in the quantities of proprioception information, it was indicated that the improvement of spine alignment lead to the difference in CVA. However, the reason why there was no interaction in the sitting position was because the curve of the thoracic and lumbar spines consisted of slight flexion in a comfortable sitting position. Depending on the posture, the difference of spine alignment might be affected in the cervical spine.
The difference of the MDC and MCID of NPRS in both groups is noteworthy. In the present study, the average change score exceeded both the MDC and MCID values in the thoracic group. Although the results indicated that there was a significant within-group difference in the thoracic group, no significant within-group difference can be concluded in the cervical group. The difference between the groups in NPRS was 1.4 points, which exceeded the MCID, indicating the clinically significant effect of the thoracic spine mobilization and mobility exercise. It was, however, considered that the 95% CI (0.6, 2.3) of the difference included lower values than the MCID. Therefore, although the difference in improvement between groups was statistically significant, the clinical importance was uncertain when the interpretation was performed on the basis of the 95% CI. For the NDI, although the average change score was 12.2% in the thoracic group only, which exceeded the MDC, the average difference in change scores between the two groups was 7%, which was lower than the MCID of NDI [
51]. Therefore, although the difference in improvement between groups for the NDI was again statistically significant, the gap could be of little importance clinically when the interpretation was performed on the basis of MCID. There was no interaction between the two groups in the pain sensitivity test of the upper trapezius muscle. The reason why the upper trapezius muscle was targeted was to identify the effect of position improvement after the treatment, because the tone of the upper trapezius muscle was increased and became tighter due to upper cross syndrome [
60]. This study indicated a significant effect in both groups at 4 weeks after the treatment. The muscle tone of the upper trapezius was decreased by the change of posture through joint mobilization, and cervical instability was improved through the therapeutic exercise. However, there was no interaction between the two groups, and the MCID of PPT was not exceeded because the intervention for the cervical and thoracic spine in this study had no direct effect on the sensitivity of the upper trapezius muscle [
49]. Although the mechanism of the effect of the manual therapy on neck pain was not clear, the sensitivity of the mechanical receptor might be changed through the application of continuous passive stimulus to soft tissue [
38,
61], and the mechanical stress of the pain generator might be reduced by improving the biomechanical relationship of the cervical spine and the thoracic spine [
62,
63]. In case of GRC, 68.8% of the participants in the thoracic group and 50% of the participants in the cervical group showed higher than +4 points, and the difference between the groups was significant. The patients’ satisfaction was affected by various factors such as individual pain and the belief and there may be inconsistencies in the results among participants owing to their different environments [
64]. However, the intervention for the thoracic group was shown to improve FHP better than the intervention for the cervical group based on the GRC in this study, which indicated that all participants were simultaneously improved in terms of the specific therapy technique.
The results of this study suggest that the correct posture of the cervical spine is important when using touchscreen smartphones; however, the correct alignment of the thoracic spine should be prioritized, and clinical interventions including the cervical spine and thoracic spine should be applied. The most important limitation of this study is the short-term follow-up of 6 weeks and the small sample size. Although the sample size was set by using the effect size of a previous study, it is difficult to generalize the study results to all patients with neck pain from FHP. Moreover, it is difficult to generalize the intervention results of this study to male patients with mechanical cervical pain because the sample comprised only 9 men (23 women). However, we considered that the study results can be generalized to the average population because recent studies have proved that women have a higher rate of neck pain than men [
65]. Future studies with a long-term follow-up and evaluating the placebo effect, by investigating three groups including a control group, should be conducted.
Conclusion
This study demonstrated that individuals with FHP who received the combination of upper thoracic spine mobilization and mobility exercise demonstrated better overall short-term outcomes in terms of the CVA (standing position), cervical extension, NPRS, NDI, and GRC than those who received upper cervical spine mobilization and stabilization exercise. Future studies should examine the effectiveness of different types and dosages of manual therapy, and perform long-term follow-up data collection.
Acknowledgments
The authors would like to thank DK Seo, WT Kim, SC Lee, and YS Ha for their participation in the data collection process of this study.