Physical Therapy Korea

The shape of the thoracic spine is primarily influenced by age, but recent trends in smartphone and computer use have contributed to an increase in individuals with thoracic kyphosis [1]. This condition can lead to a variety of health issues, including musculoskeletal problems, sleep disorders, and limitations in respiratory function [2,3]. Regarding musculoskeletal disorders, thoracic kyphosis with a Cobb angle > 40° has been associated with shoulder position alteration, leading to protraction, anterior tilting, and shoulder malalignment, such as forward shoulder posture [3,4]. Moreover, anterior tilting of the scapula can narrow the subacromial space, increasing the risk of shoulder impingement [5-8]. Regarding sleep disorders, thoracic kyphosis has been shown to disrupt sleep patterns due to abnormal spine alignment. This predisposes one’s body to uneven pressure distributions during sleep, causing discomfort, frequent tossing and turning, and ultimately affecting sleep quality [9-11]. In conclusion, people with thoracic kyphosis often exhibit significantly lower forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁) than those without the condition [12,13]. This musculoskeletal abnormality limits the expansion and contraction of the thoracic cage, reduces chest wall movement during breathing, and restricts diaphragm mobility, which can weaken the respiratory muscles [13]. Additionally, the chest wall deformity associated with thoracic kyphosis can decrease lung volume and lead to a restrictive ventilatory pattern [14].

Previous studies have demonstrated that thoracic mobilization therapy is effective in improving thoracic kyphosis angles and forward shoulder posture. The use of a thoracic mobilization device for 25 minutes on patients with thoracic kyphosis has shown positive effects on both thoracic kyphosis and forward shoulder posture [12]. However, while effective, the thoracic mobilization device is large in size and requires motorized power due to its mat-like structure. In this study, we aim to determine whether a simpler tool can be effective in improving thoracic kyphosis angles and forward shoulder posture. For this purpose, we developed and applied a "scapula supporting pillow." This pillow is designed ergonomically to maintain the normal angles of the thoracic and cervical spine when lying down; thereby, promoting the improvement of thoracic kyphosis.

This study aims to evaluate the effects of the "scapula supporting pillow" on improving thoracic kyphosis and forward shoulder posture in patients with thoracic kyphosis. We plan to measure the changes in the angles of thoracic kyphosis and forward shoulder posture, and assess the impact on respiratory function by examining changes in chest expansion, FVC, and FEV₁.

1. Participants

The study participants were adults aged 20–60 years without any spinal pain. Individuals with a Cobb angle > 40°, as measured using the Spinal Mouse (Spinal Mouse m360; Idiag AG), were eligible for inclusion. Individuals with the following characteristics were excluded: scoliosis, spinal fractures, tumors, other spine-related cancers, congenital spinal deformities, and rheumatoid arthritis [11]. Based on a pilot study, an a priori power analysis was conducted using G*Power ver. 3.1 to determine the necessary sample size. With an alpha level of 0.05 and an effect size of 0.88 for thoracic kyphosis, the analysis revealed that a minimum of 34 participants would be needed to achieve a power of 0.95, as indicated by the pilot study involving five participants.

All participants provided written informed consent by after fully understanding the purpose and methods of the study. The study was approved by the Institutional Review Board of Yonsei University Mirae campus (IRB no. 1041849-202401-BM-012-01).

2. Procedure

Prior to the intervention, the thoracic spine angle, respiratory function, and posture were assessed. Respiratory function was measured using FVC and FEV₁, whereas postural changes were evaluated by measuring spinal angle, chest expansion and the acromion-to-the-wall index. Following pre-intervention evaluation, participants were instructed to lay supine on the scapular support pillow for 30 minutes, ensuring full contact between the scapula and the pillow. Post-intervention evaluation was subsequently conducted by reassessing the same parameters to determine any changes.

1) Measurement of spinal angles

To determine the presence of thoracic kyphosis, the angle of the spine is measured using a Spinal Mouse, and a Cobb angle greater than 40° is confirmed [15,16]. The Spinal Mouse has high reliability (intraclass correlation coefficient [ICC] = 0.944–0.961, ICC = 0.873–0.959). The Spinal Mouse is a non-invasive device that shows a strong correlation (ICC = 0.872–0.933) with radiographic imaging, the gold standard method [17].

2) Acromion-to-the-wall-index

Participants were instructed to stand with their backs against the wall and slightly bent hip and knee joints. One end of the tape measure was then fixed to the wall, and the other end was placed on the acromion (the end of the shoulder bone) to measure the distance between the two [18]. This distance was measured twice on each side (left and right), and the average value was used as the acromion-to-the-wall index (Figure 1). The ICC was good to excellent (ICC = 0.840–0.920) [3,8].

Figure 1. Acromion wall index.

3) Chest expansion

Chest expansion was measured using a tape spanning from the third intercostal space to the spinous process of the fifth thoracic vertebra. Inhalation measurements were taken while participants were breathing in slowly through the nose, creating a sensation of resistance on the tape measure. Exhalation measurements were taken while participants exhaled completely through the mouth (Figure 2) [19]. The chest expansion test demonstrates high reliability. Reliability measures show ICC of 0.850–0.860 and ICC of 0.820–0.840 [20].

Figure 2. Chest expansion measurement. Revised from the article of Debouche et al. (J Manipulative Physiol Ther 2016;39:443-9) [19].

4) Respiratory function

Respiratory function was measured while patients were seated comfortably in a chair, with their hands on their cheeks and elbows on their knees. Upon the researcher’s prompt, participants were instructed to inhale and exhale as forcefully as possible into a portable spirometer (One flow FVC Spirometer; Clement Clarke International Ltd.), while maintaining a forward-leaning seated position. A total of three measurements were taken with a 30-second rest period between each measurement (Figure 3) [15].

Figure 3. Respiratory function test. Portable spirometer (One flow FVC spirometer; Clement Clarke International Ltd.). Revised from the article of Celli et al. (N Engl J Med 2004;350:1005-12) [15].

5) Scapular support pillow

Participants were instructed to lay supine on a scapular support pillow for approximately 30 minutes. After this period, their overall posture and respiratory function were assessed. In a normal spinal alignment, the head is positioned approximately 5° forward relative to the torso. To provide adequate support for the scapula in a supine position, a pillow is conventionally utilized to accommodate the angle of the thoracic spine, supporting the 1st to the 3rd thoracic vertebrae. Accordingly, an ideal pillow design should align the cervical spine (C7) to the thoracic spine (T3) along a vertical line. The angle between the pillow’s base and the back of the head should range from 4°–6°, whereas the angle supporting the back of the neck should be 12°–16°. To support the natural curvature of the neck, the pillow should also have a curvature of approximately 30° (5 cm in height). Additionally, the pillow should have a slight incline or curvature of approximately 10°–15° (2–3 cm) toward the shoulder area [16]. Using these measurements, this design would ideally provide the necessary support to both the cervical and thoracic regions, maintaining proper alignment and potentially improving comfort and posture (Figure 4).

Figure 4. (A) Scapular support pillow, (B) image of a participant lying supine on the scapular support pillow.

3. Statistical Analysis

To compare the characteristics of the subjects before and after using the scapular support pillow, Paired t-test was used. The respiratory function measurements (FVC, FEV₁, FEV₁/FVC ratio) and the posture change values (chest wall expansion, thoracic kyphosis angle, acromion-to-the-wall index) were compared before and after intervention. The level of statistical significance was set at p < 0.05. For statistical analysis, the commercial statistical software IBM SPSS Statistics for Windows, version 21.0 (IBM Co.) was used.

The variables measured in this experiment fall into two main categories before and after using the scapular support pillow. Respiratory function and postural changes. To assess respiratory function, FVC and FEV₁ were recorded. For postural changes, measurements included the spinal angle, chest expansion, and acromion-to-wall index.

1. General Characteristics of the Study Participants

A total of 41 participants were included in the study, consisting of 25 males and 16 females participants. The average age, height, weight, and body mass index of the participants were 47.3 ± 14.7 years, 168.1 ± 8.0 cm, 68.2 ± 10.2 kg, and 24.1 ± 2.8 kg/m², respectively. Table 1 presents the general characteristics of the study participants.

Table 1 . General characteristics of the study participants (N = 41).

Variable	Value
Sex (male/female)	25/16
Age (y)	47.3 ± 14.7
Height (cm)	168.1 ± 8.0
Weight (kg)	68.2 ± 10.2
Body mass index (kg/m2)	24.1 ± 2.8

Values are presented as number or mean ± standard deviation..

2. Respiratory Function

Comparing the values before and after using the scapula support pillow, both FVC and FEV₁ demonstrated a significant increase. This suggests that the scapula support pillow, as intended in this study, effectively enhances respiratory capacity. Table 2 presents measurements of respiratory function before and after using the scapular support pillow. The FVC value increased by 12.66% ± 0.27% (p < 0.001), and the FEV₁ value increased by 24.20% ± 0.32% (p < 0.001). The criteria for restrictive lung disease are an FVC < 80% of the normal value and an FEV₁/FVC ratio > 70%. The FEV₁/FVC ratios are 0.72 and 0.80, both of which meet the criterion of FEV₁/FVC ratio > 70%. The normal predicted FVC value is 4.93 for males and 3.28 for females. Before using the scapular supporting pillow, the FVC for males was 3.71 (75% of the normal value) and after using it, the FVC increased to 4.17 (84% of the normal value), indicating restrictive lung disease prior to the use of the scapular supporting pillow. Similarly, for females, the FVC was 2.62 (79% of the normal value) before using the pillow and increased to 2.81 (85% of the normal value) after using it, also indicating restrictive lung disease prior to the use of the scapular supporting pillow.

Table 2 . Measurements of respiratory function before and after using the scapular support pillow.

	Before	After	t	p-value
FVC (L)	3.19 ± 1.13	3.60 ± 1.17	–9.471	< 0.001
FEV1 (L)	2.31 ± 0.97	2.87 ± 0.99	–10.949	< 0.001
FEV1/FVC (%)	0.72 ± 0.11	0.80 ± 0.04	–5.665	< 0.001

Values are presented as mean ± standard deviation. FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second..

3. Postural Changes

A comparison of the measurements taken before and after using the scapula support pillow showed a significant increase in the spinal angle, chest expansion, and acromion-to-wall index. These results demonstrate that the use of the scapula support pillow, which is the primary focus of this study, effectively enhances posture. Table 3 presents measurements of posture before and after using the scapular support pillow. The spinal angle increased significantly by 4.49° ± 2.35° (p < 0.001), approximately a 10% increase. Chest expansion showed a significant increase of 2.00 ± 0.87 cm (p < 0.001), around 80%. The acromion-to-wall index also increased significantly by 1.54 ± 0.92 cm (p < 0.001), approximately 15%.

Table 3 . Measurements of posture before and after using the scapular support pillow.

	Before	After	t	p-value
Spinal angle (°)	43.22 ± 2.67	38.73 ± 3.74	–14.691	< 0.001
Chest expansion (cm)	2.49 ± 1.07	4.49 ± 1.56	12.246	< 0.001
AWI (cm)	9.97 ± 1.25	8.43 ± 1.64	10.714	< 0.001

Values are presented as mean ± standard deviation. AWI, acromion-wall index..

A previous study the effects of thoracic mobilization therapy on thoracic kyphosis angles and shoulder protraction posture were examined [12]. Another study researched the effectiveness of postural alignment exercises on chest function reduction caused by thoracic kyphosis [21]. This study aimed to investigate the correlation between postural changes and respiratory ability through the improvement of thoracic kyphosis angles. By using a "scapula support pillow" intervention for individuals with thoracic kyphosis, the study assessed the improvement in thoracic kyphosis, postural changes, and their impact on respiratory ability. The experiment measured changes in thoracic kyphosis angles and shoulder protraction posture to confirm significant postural improvements. Additionally, significant increases in chest expansion, FVC, and FEV₁ were observed, indicating an impact on respiratory function.

Both prior researches applied a 30-minute intervention, and this study similarly employed a 30-minute intervention [12,21]. Previous study only two indicators, FVC and FEV₁, were used to calculate the FEV₁/FVC ratio and determine the presence of restrictive lung disease, based on the criteria of FVC < 80% of the normal value and an FEV₁/FVC ratio > 70% [21].

Patients with thoracic kyphosis experience changes in the shape and position of the thoracic vertebrae and ribs. As thoracic kyphosis worsens, proprioceptive feedback decreases, leading to impaired respiratory muscle function. Additionally, restricted rib movement can interfere with normal respiratory muscle function and cause muscle weakness [22]. Individuals with thoracic kyphosis often experience breathing difficulties, which can necessitate hospitalization and lead to severe health complications [23,24].

To evaluate postural changes in this study, three indicators were measured: thoracic angle, chest expansion, and acromion-wall index (AWI). The thoracic angle reflects the degree of kyphosis. As the thoracic angle increases, chest expansion is restricted, and inhalation capacity declines, which also affects the forward protrusion of the acromion. The AWI is the most suitable indicator for evaluating acromion protrusion [19]. This study identified limitations in chest expansion and AWI among individuals with thoracic kyphosis.

Respiratory function was assessed using a portable spirometer to measure FVC and FEV₁, which directly reflect respiratory capacity. The ratio of these values helps diagnose specific respiratory diseases. Normal predicted values for FVC and FEV₁ vary by age, weight, and height. For the study group, the predicted normal FVC value was 4.93 for males and 3.28 for females, while the predicted normal FEV₁ value was 4.03 for males and 2.65 for females [25]. The study found a decrease in actual respiratory capacity among thoracic kyphosis patients but observed improvement in respiratory function with the use of the scapula support pillow.

This study had several limitations:

1. Learning effect of the experimental tool. Participants might have affected the accuracy of initial measurements due to unfamiliarity with the portable spirometer, possibly making observed improvements attributable to increased familiarity with the equipment rather than actual improvements in respiratory function.

2. Difference between experimental and actual use time. The study evaluated respiratory function and postural changes 30 minutes after pillow use, while actual pillow use time is about 7–8 hours [26]. The difference between experimental use time and actual use time limits the applicability of the results. Future research should investigate the effects of using the pillow for 7–8 hours to provide more reliable results.

3. Sample age and generalizability. The average age of participants was 47.3 ± 14.7 years, including individuals in their 30s and 50s, so the results may not be generalizable to the elderly. FVC, FEV₁, and chest expansion are also influenced by age, body mass index, and sex. Future studies should consider these variables and include comparative groups to better explain causal relationships.

4. Absence of control group. The study used a practical pillow intervention without a control group, which limits the ability to clearly identify the causes of postural and respiratory function improvements. Future research should include control groups comparing the scapula support pillow with other treatments, such as manual therapy, to more clearly determine its therapeutic effectiveness [27].

This study aimed to investigate the effects of a scapular support pillow on respiratory function and posture in individuals with thoracic kyphosis. The results demonstrated improvements in both respiratory function and posture following a 30-minute use of the scapular support pillow. Our findings confirm that the scapular support pillow can serve as an alternative to scapular posterior tilting and thoracic mobilization. The significance of this research lies in providing diverse treatment approaches to provide more options that may be more suitable depending on the context of the patient.

None.

None to declare.

No potential conflicts of interest relevant to this article are reported.

Conceptualization: WL, IM, WS, CY. Data curation: WL, IM, WS, CY. Formal analysis: WL, IM, CY. Investigation: WL, WS, CY. Methodology: WL, CY. Project administration: WL, IM, WS, CY. Resources: WL, CY. Software: WL, CY. Supervision: WL, IM, CY. Validation: WL, CY. Visualization: WL, WS, CY. Writing - original draft: WL, CY. Writing - review & editing: WL, IM, CY.