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many patients present with symptoms related to the cervicothoracic spine , such as neck pain , scapular pain , and headaches7 ) .
changing pillows can significantly relieve cervical pain , scapular pain , and headaches25679 ) , although many people appear to have made poor pillow choices , as low pillow comfort and cervicothoracic symptoms upon waking are commonly reported4 ) . while patients continue to seek advice on pillow choice
, there has been limited research to assess the effects of varying pillow heights on cervical spine posture . as such
this study reports the effects of three different pillow heights on the slope of the cervicothoracic spine segments when resting in the supine position .
a cohort of 16 asymptomatic adult volunteers , aged between 20 and 30 years , were enrolled in this study .
we included individuals who had no history of any spinal diagnosis , symptoms , or treatment , and excluded cases where there was an accident or injury to the cervicothoracic spine in the preceding year .
participants were permitted to sit up briefly to stretch and move their necks between each pillow trial .
participants assumed a standard supine position with their head resting on the pillow with the external occipital protuberance at the center of the pillow .
these parameters consisted of the thoracic inlet angle ( tia ) , t1 slope ( t1s ) , neck tilt ( nt ) , and c2 - 7 cobb 's angle . as depicted in fig .
1 , the tia was considered the angle formed by a line from the center of the t1 upper endplate ( t1uep ) vertical to the t1uep , and a line connecting the center of the t1uep and the upper end of the sternum .
the t1s was defined as the angle formed between the horizontal plane and the t1uep .
the nt was defined as the angle formed by a line drawn in the upper end of the sternum and a line connecting the center of the t1uep and the upper end of the sternum .
the c2-c7 angle was measured by the formal cobb methods as the angle between the horizontal line of the c2 lower endplate and the horizontal line of the c7 lower endplate ( fig . 1 and 2 ) .
the pacs system(p view , infinitt , seoul , korea ) was determined by one observer for the measurement .
correlations between parameters of interest in this study were analyzed with the mann - whitney test and spearman coefficients .
all statistical analyses were performed using spss ( version 18.0 , spss , chicago , il , usa ) .
a cohort of 16 asymptomatic adult volunteers , aged between 20 and 30 years , were enrolled in this study .
we included individuals who had no history of any spinal diagnosis , symptoms , or treatment , and excluded cases where there was an accident or injury to the cervicothoracic spine in the preceding year .
participants were permitted to sit up briefly to stretch and move their necks between each pillow trial .
participants assumed a standard supine position with their head resting on the pillow with the external occipital protuberance at the center of the pillow .
we measured four morphological parameters . these parameters consisted of the thoracic inlet angle ( tia ) , t1 slope ( t1s ) , neck tilt ( nt ) , and c2 - 7 cobb 's angle .
1 , the tia was considered the angle formed by a line from the center of the t1 upper endplate ( t1uep ) vertical to the t1uep , and a line connecting the center of the t1uep and the upper end of the sternum .
the t1s was defined as the angle formed between the horizontal plane and the t1uep .
the nt was defined as the angle formed by a line drawn in the upper end of the sternum and a line connecting the center of the t1uep and the upper end of the sternum .
the c2-c7 angle was measured by the formal cobb methods as the angle between the horizontal line of the c2 lower endplate and the horizontal line of the c7 lower endplate ( fig . 1 and 2 ) .
the pacs system(p view , infinitt , seoul , korea ) was determined by one observer for the measurement .
correlations between parameters of interest in this study were analyzed with the mann - whitney test and spearman coefficients .
all statistical analyses were performed using spss ( version 18.0 , spss , chicago , il , usa ) .
the mean ages of the study participants were 29.382.23 and 29.253.11 years for men and women , respectively .
table 1 shows the mean values for each of the measured parameters stratified by sex . with a greater pillow height ,
for pillow heights of 0 , 10 , and 20 cm , the t1s were 12.925.71 , 17.337.42 and 28.795.71 , respectively ; and the c2 - 7 cobb 's angles were 10.347.37 , 14.936.77 , and 17.407.33 , respectively .
additionally , with increasing pillow height , the nt value tended to decrease , and the tia values remained constant with the 0 cm and 10 cm pillow .
however , the tia values with 20-cm pillow were different from the other pillow heights .
the tia with the 10 cm pillow had a significant correlation ( p<0.05 ) with the t1s with the 10 cm pillow(r=0.829 ) and the nt with the 10 cm pillow(r=0.812 ) .
in addition , the tia with the 20 cm pillow had a significant correlation ( p<0.05 ) with the nt with the 20 cm pillow(r=0.821 ) .
there were , however , no statistically significant differences in the measured parameters between male and female study participants , with the exception of differences in t1s with the 0 cm pillow(p=0.01 ) and the nt with the 20 cm pillow(p=0.01 ) .
as is already known , optimal sagittal alignment of the spine occurs when all components are in proper balance14 ) . the global balance and regional balance alignment
the t1s and other cervical parameters have been identified as radiographic parameters that are greatly correlated with cervical sagittal balance10 ) .
indeed , the t1 sagittal angle is a measurement that may be very useful in evaluating sagittal balance . in particular
lee et al.12 ) reported that the tia and t1s could be used to predict the physiological alignment of the cervical spine on radiographs .
patrick et al.11 ) demonstrated that patients whose t1s value falls outside the range of 13 to 25 should be sent for full - column radiographs for complete evaluation of their sagittal balance . on the other hand , although patients with a t1s value between 13 and 25 mostly had better sagittal balance than patients with values outside this range , its occurrence does not guarantee normal sagittal balance .
unfortunately , there are no studies to date that have established normative sagittal t1s values . however , in the aforementioned study by patrick et al.14 ) , their analysis has shown that when the t1s was higher than 25 , all patients had at least 10 cm of positive sagittal imbalance .
their study also showed that patients with a negative sagittal balance had mostly low t1s values , usually below 13 of angulation11 ) . in our study
, we found that the t1s value with the 10 cm pillow height was between 13 and 25 for normal sagittal balance .
we could advise that the 10 cm pillow height is most suitable for optimal cervical alignment .
however , the pillow height of 10 cm is just a numerical value taking into consideration only the cervical parameter and not considering the comfort and satisfaction of patients .
although t1s is influenced by aging or posture , it is not a constant parameter . on the other hand , tia does not change with position or increase of thoracic kyphosis under any condition , similar to the pelvic inlet of the pelvis .
the tia is a constant parameter because , anatomically , the cervical spine is placed on top of the ti , a fixed circular bony structure without range of motion that is composed of the t1 vertebral body , the first ribs on both sides , and the upper part of the sternum17 ) .
the sagittal balance of the cervical spine adjusts and can be influenced by the shape and orientation of t1 .
park et al.14 ) assessed the sagittal parameters of the cervical spine using ct scans in the supine position and concluded that the c2-c7 angle increased as the t1s increased .
they also reconfirmed that the tia can be considered as a fixed reference value14 ) .
however , in our study , we measured different tia values with the 20 cm pillow than other pillow height .
although there are many reasons for this , we thought an error possibly occurred when measuring the angle and the higher pillow height changed the tia .
loss of cervical lordosis is a complicating factor in the treatment of the cervical spine , and understanding the effects and prognosis of a loss of cervical lordosis is crucial to treatment .
however , an embryological basis can be helpful for understanding the pathogenesis of cervical lordosis . in 1977 ,
bagnall et al.1 ) demonstrated that cervical lordosis is formed at 9.5 weeks of gestation . in 195 fetuses
, they found that at 9.5 weeks , 83% of fetuses have cervical lordosis , 11% have a military configuration , and only 6% of fetuses are in the kyphotic position of the cervical spine1 ) .
in other words , by 9.5 weeks 94% of fetuses begin to use their posterior cervical muscles to begin forming the cervical curve .
the lordosis begins to form before birth , and once the child begins to lift his / her head , the lordosis becomes clearer .
cervical lordosis has been theorized to exist for biomechanical reasons related to weight distribution , structural support , energy efficiency , and shock absorption . in daily activity
, cervical lordosis better distributes forces than a cervical spine which has lost its normal lordosis3 ) .
some studies also reported that an asymptomatic cervical spine did not always show normal lordotic alignment , as kyphotic alignment was revealed in 2% to 35% of individuals81316 ) .
although the cobb method works well for the rectangular vertebrae of the thoracic and lumbar spine , it may be less precise for measuring the cervical spine , which has trapezoidal vertebrae13 ) .
the gore method , which uses the posterior vertebral body line as opposed to the superior and inferior end plate lines used by the cobb method , is considered to be more reproducible when measuring the cervical sagittal alignment15 ) . in the present study , however , we did not use the gore method , because the cobb method was more familiar and generally known .
a limitation of the present study is the uneven distribution of data in the cohort . to estimate the result for a normative cohort we included only 16 individuals .
since our cohort might not contain all the representative patterns of sagittal alignment , we analyzed the non - parametric statistical test .
an additional study , with a larger number of cases , is still needed to be able to carry out an age , body weight , height , and sex - matched controlled investigation and confirm the result of the current study . in other words ,
our study is a preliminary study , so further studies with more participants are needed in the future . nevertheless , the study participants included were healthy , young , and without a history of spinal problems .
in addition , our study did not evaluate the comfort , pain relief , and level of satisfaction of each pillow , therefore , further study is required .
some studies propose an approximate average value for cervical sagittal alignment , but there is no " gold standard " established as yet , and additional investigations of cervical alignment are still necessary .
from the data obtained in this study , we recommend that the most suitable pillow height is 10 cm considering the normal cervical lordosis . additionally , the nt value decreased with increasing pillow height , whereas tia values tended to remain constant .
objectiveto investigate the effect of different pillow heights on the slope of the cervicothoracic spine segments.methodsa prospective analysis of data from 16 asymptomatic adults ( aged 20 to 30 years ) was carried out . 
 exclusion criteria were history of injury or accident to the cervicothoracic spine , cervicothoracic spine surgery , or treatment for neck symptoms . 
 we used three different pillow heights : flat ( 0 cm ) , 10-cm , and 20-cm pillows . 
 cervical sagittal parameters , measured with radiography , included ; c2 - 7 cobb 's angle , t1 slope ( t1s ) , thoracic inlet angle ( tia ) , and neck tilt ( nt ) . 
 statistical analyses were performed using spearman correlation coefficients.resultsas the height of the pillow increased , the t1s & c2 - 7 cobb 's angle increased while the nt values tended to decrease . 
 the tia values , however , remained constant . 
 additionally , there was a statistically significant sex difference in t1s with the 0-cm pillow ( p=0.01 ) , and in nt with the 20-cm pillow ( p=0.01).conclusionfrom the data obtained in this study , we recommend that the most suitable pillow height is 10 cm , considering the normal cervical lordosis .