The 7 th cervical vertebra wall distance (C7WD) identifies balance control,functional mobility and the risk of multiple falls in elderly community-dwelling women with thoracic hyperkyphosis

Abstract

BACKGROUND:

Thoracic hyperkyphosis is common in the elderly, especially in women, and results in impaired balance control, impaired functional mobility and an increased risk of multiple falls. The 7 ${}^{\text{th}}$ cervical vertebra wall distance (C7WD) is a practical method for evaluating thoracic hyperkyphosis.

OBJECTIVE:

This study calculated C7WD cut-off scores that may identify impaired balance control, impaired functional mobility and an increased risk of multiple falls in elderly community-dwelling women with thoracic hyperkyphosis. This study also explored the correlation between C7WD, balance control and functional mobility.

METHODS:

Sixty participants were assessed for thoracic hyperkyphosis using the C7WD, balance control using the functional reach test (FRT), functional mobility using the timed up-and-go test (TUG) and a history of falls using their personal information.

RESULTS:

The data indicated that a C7WD of at least 7.95 cm, 8.1 cm and 8.8 cm had a good to excellent capability of identifying impaired balance control, impaired functional mobility and an increased risk of multiple falls, respectively. The C7WD results were significant and correlated with balance control ( $r_{s}=-$ 0.68) and functional mobility ( $r_{s}=$ 0.41).

CONCLUSIONS:

The C7WD may be utilised as a screening tool for these three impairments in this population.

Keywords

Hyperkyphosis gerontology screening community

1. Introduction

Thoracic kyphosis is an angular curvature of the spine, with the convexity of the curve posterior in the thoracic region. Following radiographic assessment, an individual is diagnosed with thoracic hyperkyphosis if the backwards deviation of the thoracic spine exceeds 40 ${}^{\circ}$ [1, 2]. Thoracic hyperkyphosis is common, affecting up to 40% of older adults worldwide [3]. In addition, many studies have reported that the prevalence of hyperkyphosis is higher in women than men after the fourth decade of life due to osteoporosis associated with menopause [4, 5, 6, 7]. The hyperkyphosis angle increases from 43 ${}^{\circ}$ in women aged 55–60 years to 52 ${}^{\circ}$ in women aged 76–80 years [8]. Moreover, women have a higher tendency to develop thoracic hyperkyphosis than men because they may adopt a stooped posture to hide the development of their breasts [9].

The prevalence of falls is at least 30–40% in adults over 65 years of age [10, 11]. The increase in thoracic kyphosis amongst the elderly population is an important issue because this condition leads to impaired balance control. Namely, it increases the curvature of the upper body and thus shifts the body’s centre of mass forwards. It promotes the displacement of the centre of gravity (COG) at levels close to the limits of stability [8, 12, 13, 14]. Patients with hyperkyphosis have an increased sway, lower functional mobility and higher risk of falling compared to those with normal kyphosis [15]. A previous study correlated an increase in thoracic kyphosis and lower bone mineral density with a higher risk of falls in the anteroposterior direction in elderly women [14]. Also, another previous study reported that older adults with thoracic hyperkyphosis had experienced falls and were 1.32 times more likely to report a fall than those with normal kyphosis [1]. However, no studies have identified, for a thoracic hyperkyphosis severity measure, the cut-off scores that indicate impaired balance control, impaired functional mobility and an increased risk of falls in patients with thoracic hyperkyphosis. Crucially, when planning appropriate prevention for their patients, healthcare professionals should consider assessing patients early for thoracic hyperkyphosis to reduce the risk of severe complications.

Cobb’s method is the gold standard technique for evaluating kyphosis in the standing position; this method is used to determine the angle of kyphosis, also known as the Cobb angle [1, 16, 17, 18]. Many studies have investigated the Cobb angle and balance control in older adults [3, 19]. A previous study associated the Cobb angle with the risk of falls [20]. Another study associated a 10 ${}^{\circ}$ increase in the Cobb angle with a decrease in gait speed and functional status [21]. However, this method may not be suitable for screening in communities due to concerns relating to radiation exposure (particularly in communities with people who tend to avoid radiation exposure), the method’s cost, and the need of a specialist to interpret the results and report the Cobb angle [22].

The 7 ${}^{\text{th}}$ cervical vertebra wall distance (C7WD) is a simple screening and monitoring tool used to determine the presence of thoracic hyperkyphosis [23, 24]. Because it is easy, convenient and quick, the C7WD is suitable for use in community areas [23, 25]. Moreover, this method has excellent concurrent validity with the standard method [24]. Nevertheless, no previous study has investigated the correlation between the C7WD, impaired balance control and impaired functional mobility in elderly women with thoracic hyperkyphosis. In addition, no previous study has reported the hyperkyphosis severity test cut-off scores that can be associated with balance control, functional mobility and the risk of falls. Therefore, the current study investigated the cut-off scores of the C7WD that can be used to determine impaired balance control, impaired functional mobility and the risk of falls in elderly community-dwelling women with thoracic hyperkyphosis. This study also explored the correlation between C7WD score, balance control and functional mobility.

2. Materials and methods

2.1 Participants

This cross-sectional study focused on elderly community-dwelling women with thoracic hyperkyphosis. The participants were recruited from rural communities in Khon Kaen, Thailand. All participants were women aged at least 60 years and over, had a body mass index of 18.5–29.9 kg/m ${}^{2}$ and had different degrees of thoracic hyperkyphosis, which were determined using the C7WD of at least 7.5 cm [24]. The exclusion criteria were any signs or symptoms that might limit the location of C7 bony prominence and protocol measurements, including buffalo hump, wing scapula, scoliosis, amputation, leg length discrepancy, musculoskeletal pain, limited range of motion (ROM) in the shoulder joint, inability to stand and walk independently and inability to understand and follow simple commands [24]. Based on the sample size calculation from a pilot study, the present study required at least 60 participants [26]. All study procedures were in accordance with the standards of the Ethics Committee in Human Research, Khon Kaen University (HE632188). Eligible participants completed a written informed consent form before participating in this study.

2.2 Protocol

The first examiner, a physiotherapist with seven years of experience, interviewed the participants to collect their demographic information and history of falls within the previous six months. Next, the second examiner, a physiotherapist with more than nine years of experience, assessed the participants for thoracic hyperkyphosis using the C7WD, functional reach test (FRT) and timed up and go test (TUG) in that order.

2.2.1 Fall history

The first examiner asked the participants about their falls in the previous six months. For each fall, details related to the fall – including the circumstances, place and consequences of the fall – were confirmed. A fall was defined as an unplanned, unexpected or unintentional event that occurs while changing posture, standing or walking and that results in a person coming to rest on the ground or other lower supporting surface [27, 28, 29]. Those participants who had fallen at least twice were considered to have experienced multiple falls.

2.2.2 C7WD

On their bare feet, the participants stood upright as tall as possible against the wall with their heels, sacrum and back touching the wall and their head in a neutral position. The assessor used two rulers to quantify the outcomes. The assessor placed the first ruler on the C7 bony prominence and used the second ruler to quantify the perpendicular distance from the wall to the landmark. The assessor repeated the measurement in three trials, and we used the average outcomes in our data analysis [23, 24]. The participants could rest for one minute or longer between the trials. In this study, we estimated that the intraclass correlation coefficient (ICC) for the C7WD was 0.93 (95% confidence interval: 0.86–0.95) for 10 elderly women.

2.2.3 FRT

The FRT is an excellent reliability test (ICC $=$ 0.90–0.98) that is usually applied to reflect the stability limit and dynamic balance in a simple task. This method measures the distance between a patient’s outstretched arm in a maximal forwards reach and their standing position while they maintain a fixed base of support [30, 31, 32]. In this study, the assessor instructed the participants to reach forwards as far as possible without stepping or falling. The assessor then marked and recorded the location at the end of the middle finger [31, 33]. The assessor repeated the measurement in three trials, and the rest period between the trials was either one minute to prevent fatigue or the time needed for each participant’s fatigue to disappear. We used the average outcome in our data analysis.

2.2.4 TUG

The TUG is an excellent reliability test (ICC $=$ 0.89–0.97) that was designed to measure mobility, balance, walking ability and fall risk [34]. The assessor instructed the participants to stand up from a chair, walk around a traffic cone located 3 m away from the chair and then return to sit down in the chair [35]. The assessor recorded the time on a stopwatch in seconds from the command “Go” until each participant’s back rested against the backrest of the chair [36, 37]. The assessor repeated the measurement in three trials, and the participants could rest for one minute or longer between the trials, depending on their fatigue. We used the average outcome in our data analysis.

2.3 Data analysis

The descriptive analysis used the mean $\pm$ standard deviation based on the results of the Kolmogorov-Smirnov test, which we conducted to test the assumption of normality. For non-normal distributions, we utilised Spearman’s correlation coefficient ( $r_{s}$ ) to explain the levels of correlation between the results of the C7WD, FRT and TUG. We defined the strength of each correlation as either low ( $r_{s}=$ 0.3–0.5), moderate ( $r_{s}=$ 0.5–0.7), high ( $r_{s}=$ 0.7–0.9) or very high ( $r_{s}=$ 0.90–1.00) [38]. We applied receiver-operating characteristic (ROC) curves to explore the optimal cut-off score, sensitivity, specificity and area under the receiver characteristic curve (AUC) for the C7WD to indicate impaired balance control, impaired stability and increased risk of falls. Sensitivity is the ability of a test to correctly identify patients with a disease. Specificity is the ability of a test to correctly identify people without the disease [39]. The AUC can be used to evaluate the diagnostic ability of a test to determine the true disease status of a patient. We interpreted the AUC values: 0.91–1.0 as excellent, 0.75–0.90 as good, 0.50–0.74 as poor and $<$ 0.50 as failure [40]. We set the level of statistical significance at $p<$ 0.05. Finally, we used SPSS Statistics version 17 for our analysis.

Figure 1.

The receiver-operating characteristic curves of sensitivity and specificity of the C7WD measurement to predict impaired balance control (A), impaired functional mobility (B) and risk of multiple fall (C).

Table 1

Demographic characteristic of participants ( $n=$ 60)

Variables	Findings
Age (years) ${}^{\text{a}}$	70.93 $\pm$ 6.30 (69.31–72.56)
Weight (kg) ${}^{\text{a}}$	56.35 $\pm$ 8.81 (54.07–58.63)
Height (cm) ${}^{\text{a}}$	153.97 $\pm$ 6.26 (152.35–155.58)
Body mass index (kg/m ${}^{2}$ ) ${}^{\text{a}}$	23.80 $\pm$ 3.70 (22.84–24.76)
C7WD (cm) ${}^{\text{a}}$	8.15 $\pm$ 0.81 (7.94–8.36)
History of falls ${}^{\text{b}}$
No fall	42 (70)
Single fall	12 (20)
Multiple falls	6 (10)

Note: ${}^{\text{a}}$ Data are presented using mean $\pm$ standard deviation and 95% confidence interval. ${}^{\text{b}}$ Data are presented using number (%). Abbreviation: kg, kilogram; cm, centimeter; kg/m ${}^{2}$ , kilogram per square meter.

Table 2

Cut-off scores of the C7WD for determining impaired balance control, impaired functional mobility and the risk of falls

C7WD	Cut-off scores (cm)	Sensitivity (%)	Specificity (%)	AUC
Impaired balance control	7.95	72.7	81.5	0.86
Impaired functional mobility	8.1	78.6	82.6	0.87
Risk of multiple falls	8.8	83.3	90.7	0.83

Table 3

Correlation between C7WD and other variables ( $n=$ 60)

Variables	Mean $\pm$ SD	$r_{s}$
Functional reach test (inch) ${}^{\text{a}}$	7.95 $\pm$ 2.07	$-$ 0.68 ${}^{\ast\ast}$
Timed up and go test (s) ${}^{\text{a}}$	12.50 $\pm$ 4.06	0.41 ${}^{\ast\ast}$

Note: ${}^{\text{a}}$ the data were analyzed using the Spearman’s correlation coefficient. ${}^{\ast\ast}p<$ 0.01.

3. Results

Table 1 shows the demographic characteristics of the participants. In total, 87% of the participants scored at least 7.5 cm on the C7WD and 13% at least 9.5 cm [24]. Moreover, 10% had experienced multiple falls. Also, 55% had impaired balance control, whereas 23% had impaired functional mobility.

The ROC curves for all parameters are shown in Fig. 1. All parameters demonstrated good AUC values ( $>$ 0.80) with statistical significance. The data indicated that a C7WD of at least 7.95 cm (sensitivity 72.7%, specificity 81.5%), at least 8.1 cm (sensitivity 78.6 %, specificity 82.6%) and at least 8.8 cm (sensitivity 83.3%, specificity 90.7%) had the capability of effectively predicting impaired balance control, impaired functional mobility and an increased risk of multiple falls, respectively (Table 2). Moreover, as demonstrated in Table 3, the C7WD was significant and had low-to-moderate correlation with the FRT ( $r_{s}=-$ 0.68) and TUG scores ( $r_{s}=$ 0.41) ( $p<$ 0.05).

4. Discussion

The C7WD is a screening tool for thoracic hyperkyphosis that is frequently used in epidemiological studies because of its ease of use and minimal equipment requirements [23, 24, 25, 41]. This assessment is a promising tool for effectively identifying impaired balance control, impaired functional mobility and risk of multiple falls in participants with risk of thoracic hyperkyphosis. This study determined C7WD cut-off scores that may be used to identify impaired balance control, impaired functional mobility and an increased risk of falls, which were measured with the FRT, the TUG and each participant’s history of falls, respectively. The results correlated C7WD measured thoracic hyperkyphosis with balance control and functional mobility in elderly community-dwelling women.

Individuals with hyperkyphosis have increased convexity of the thoracic curve in the backwards direction. Because hyperkyphosis changes the spinal alignment of the upper body, it may promote increased flexion moment and consequently move the COG in the anterior direction [13, 41]. Thoracic hyperkyphosis increases body sway and the risk of falls [8, 15, 42]. A previous study found that elderly women with angles of thoracic hyperkyphosis greater than 50 ${}^{\circ}$ had greater anteroposterior body sway in the standing position than healthy individuals [14]. Another study reported that elderly patients with an average thoracic hyperkyphosis angle of 37 ${}^{\circ}$ had greater anteroposterior sway than lateral sway, indicating a postural imbalance in the standing position [13]. In our study, we found that a C7WD of at least 7.95 cm was a good indicator of impaired balance control, which we measured using the FRT (sensitivity 72.7%, specificity 81.5%, and AUC $=$ 0.86). In addition, our study found a moderate negative correlation between the C7WD and the FRT. The FRT is a clinical assessment of anteroposterior stability associated with an anteroposterior-direction change in the thoracic kyphosis angle, which causes the COG to shift forward affecting one’s balance control while standing [43, 44]. This is consistent with previous studies on elderly women that used a flexicurve or a spinal mouse to measure thoracic hyperkyphosis and reported a low-to-moderate negative correlation between thoracic hyperkyphosis and the FRT [45, 46].

An increase in the thoracic hyperkyphosis angle could affect functional mobility, including standing up and walking [47, 48]. Some studies have observed that elderly patients with greater thoracic hyperkyphosis angles had more difficulty rising from a chair, a shorter stride and a slower gait speed [49, 50, 51]. The current study hypothesised that thoracic hyperkyphosis may cause alterations in balance control, which may decrease functional mobility. The TUG was used to assess the activities of the participants both standing up from a chair and walking. The TUG is usually used to assess functional mobility and walking ability [52, 53]. Using the TUG, one study on elderly community-dwelling women aged 55–80 years discovered that every 5 ${}^{\circ}$ increase in the thoracic hyperkyphosis angle increased mobility time by 0.02 seconds [47]. In addition, previous studies have conducted the TUG and found that elderly patients with thoracic hyperkyphosis had slow walking times. Our study is the first to reveal that participants with thoracic hyperkyphosis and C7WD scores of at least 8.1 cm had a clear indication of impaired functional mobility as determined by the TUG (sensitivity 78.6%, specificity 82.6%, and AUC $=$ 0.87). However, our study also found a low positive association between the C7WD and the TUG. This may be because the elements of the TUG are not caused by changes in balance control alone, unlike the FRT. Rather, the TUG requires many elements to execute its tasks, such as sitting to standing, standing, walking and muscle strength. Our results are consistent with those of previous studies on elderly women that reported a low positive correlation between the TUG and thoracic hyperkyphosis measured with an inclinometer [54] or a spinal mouse [46].

Changes in the postural alignment of the thoracic angle cause an anterior shift in the COG, resulting in impaired balance control and functional mobility, both of which may increase the risk of falls in patients with thoracic hyperkyphosis [12, 20, 55]. In our study, we found that approximately 10% of the participants had previously experienced multiple falls. The risk of fall measurement in this study was done by asking about the history of falls in the previous six months. Previous studies have used the Elderly Fall Screening Test (EFST) to measure the risk of falling, which is a good and multicomponent measurement. However, EFST may take longer and do not match the objectives of this study. Therefore, the study used a six-month fall history questionnaire consisting of: the event of the fall; date; time; place; circumstances; and consequences of the fall [56, 57]. Additionally, we determined that a C7WD score of at least 8.8 cm provided a good-to-excellent indication of an increased risk of multiple falls (sensitivity 83.4%, specificity 90.7%, and AUC $=$ 0.83). Similarly, a previous study reported that elderly women with a Cobb’s angle of 55–65 ${}^{\circ}$ were at a greater risk of falls than normal participants [15]. Furthermore, another study noted that elderly women with a Cobb’s angle greater than 50 ${}^{\circ}$ had a two-fold increase in their risk of falling over the course of a year [58].

To sum up, the present findings demonstrated that the participants who had risk of thoracic hyperkyphosis measured by C7WD of at least 7.5 cm as inclusion criteria began to experience impaired balance control, impaired functional mobility, and a risk of multiple falls. Therefore, the proposed C7WD cut-off score could be used as a screening tool for early detection of thoracic hyperkyphosis in community-dwelling elderly women, which may help for the prevention and reduction of consequences. However, there are some limitations of this study. The study only included elderly women, which may limit the generalizability of its findings to the elderly. Additionally, this study did not exclude women with vertebral fragility fractures, so the potential influence of vertebral fragility fractures on these findings should be considered carefully. Therefore, further studies should be conducted in men and consider vertebral fragility fractures as part of the participant selection criteria. Meanwhile, this study is the first to present cut-off scores for the C7WD and correlate it with impaired balance control, impaired functional mobility and an increased risk of multiple falls in elderly community-dwelling women with thoracic hyperkyphosis.

5. Conclusion

The findings suggested the optimal cut-off score of the C7WD to identify impaired balance control, impaired functional mobility, and an increased risk of multiple falls in community-dwelling elderly women with thoracic hyperkyphosis as distances of at least 7.95 cm, 8.1 cm, and 8.8 cm, respectively. Moreover, the study found a correlation between C7WD and balance control and functional mobility. The specific cut-off score values could help medical professionals early identify impaired balance control, impaired functional mobility, and an increased risk of multiple falls in order to plan an appropriate prevention and promote health status in community-dwelling elderly women with thoracic hyperkyphosis.

Footnotes

Acknowledgments

The authors have no acknowledgments.

Conflict of interest

There are no conflicts of interest to declare.

Funding

No funding was received for this study.

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