whiplash injury is a neck injury caused by sudden forward and backward movements of the head during rear - end automobile collisions like the motion of a whip . the term of ' whiplash ' was first used in 1928 to describe the mechanism of delayed neck injury after motor vehicle accidents10 ) . in more past more severe and chronic status is referred as " whiplash associated disorders"24 ) . the incidence of whiplash injury is reported to be 28 - 834/100000 ( person ) per year8 ) . whiplash injury is mainly caused by rear - end collision but also resulted from head on / side collision . the injury is observed in 40% of traffic accidents but also found after trauma such as diving accidents . whiplash injury was found in 38% of passengers but other injuries were reported only in 0.7% . also , cervical spine soft tissue injuries occurred in 16% of traffic accidents and in 38% of rear - end collisions but they increased to 20% when the seat belt was fasten and decreased to 8% otherwise19 ) . cervical spine soft tissue injuries were mainly occurred after low speed rear - end collisions . however , painful experience secondary to these injuries is subjective and it is difficult to visualize the symptom . this study aims to objectively visualize the neck and shoulder pain and any improvements before and after the treatment of whiplash injury using visual analogue scale ( vas ) and infrared ( ir ) thermography . ir thermography was performed for 42 patients who were diagnosed with whiplash injury in our hospital between march 2008 and december 2013 ( table 1 ) . whiplash injury was diagnosed with symptoms , even though it was normal in imaging study . after 2 week conservative treatment , the results of ir thermography and vas were compared with immediately initial assessment after injury ( fig . the test was performed without light and heat and the room temperature was maintained at 23 - 25 ( recorded by the thermometer installed the room or the thermometer of the heating system ) . subjects kept for about 15 - 20 minutes without upper garments so that they could accommodate the room temperature and eliminate abnormal thermal differences . all patients were conservatively treated for 2 weeks after initial whiplash injury ( bed rest and nsaids ) . the thermal differences ( t ) of the anterior and posterior neck and the right and left shoulder were compared to evaluate the symmetry and to obtain basic data . then the changes in thermal difference ( dt ) before and after treatment were analyzed . neck and shoulder pain was assessed using vas immediately after the injury and after 2 week conservative management and the change in difference ( vas ) was analyzed . data was analyzed by paired t - test and bivariate correlation test using spss 20 ( spss inc . , there were 19 male and 23 female patients and the mean age was 43.12 years ( range ; 21 - 58 years ) . t of the anterior and posterior neck and the right and left shoulder , and dt in thermal differences before and after treatment were analyzed . in addition , vas of neck and shoulder immediately after the injury and after 2 week conservative management was measured and vas were analyzed . the initial skin surface temperature was 34.712.72 at the anterior neck , 34.642.81 at the posterior neck , 33.912.57 at the right shoulder and 33.762.62 at the left shoulder . on the completion of 2 week conservative management , the skin surface temperature was 33.992.82 at the anterior neck , 34.032.81 at the posterior neck , 33.042.61 at the right shoulder and 33.082.63 at the left shoulder . the skin temperature of the neck and shoulder immediately after injury showed 1 - 2 hyperthermia than normal . t of the anterior and posterior neck and the right and left shoulder immediately after the injury were 0.30.16 and 0.380.2 , and those after the conservative treatment were 0.280.19 and 0.160.10 , maintaining the symmetry . they did n't exceed the criteria ( t<0.5 ) for test errors or pathologic conditions and were found to be significant ( table 2 ) . dt was 0.720.56 at the anterior neck , 0.620.44 at the posterior neck , 0.870.57 at the right shoulder and , 0.710.57 at the left shoulder . these changes were statistically significant ( p<0.05 ) ( table 3 ) . the thermal difference after immediately injury is higher than normal value , but it gradually decreased after two weeks . vas for neck pain was 7.860.65 immediately after trauma and was reduced to 3.431.06 after conservative management . vas for shoulder pain was 7.690.6 initially but was also reduced to 3.521.23 after conservative management ( fig . vas of the neck and shoulder were significantly reduced after 2 week and were statistically significant ( p=0.001 ) ( table 4 ) . also , bivariate correlation analysis showed that there was significant correlation between dt of the neck and shoulder and vas in vas before and after the treatment ( the neck ; r=0.412 , p<0.007 ) ( the shoulder ; r=0.648 , p<0.000 ) ( fig . the initial skin surface temperature was 34.712.72 at the anterior neck , 34.642.81 at the posterior neck , 33.912.57 at the right shoulder and 33.762.62 at the left shoulder . on the completion of 2 week conservative management , the skin surface temperature was 33.992.82 at the anterior neck , 34.032.81 at the posterior neck , 33.042.61 at the right shoulder and 33.082.63 at the left shoulder . the skin temperature of the neck and shoulder immediately after injury showed 1 - 2 hyperthermia than normal . after two weeks , the skin temperature was almost normal . t of the anterior and posterior neck and the right and left shoulder immediately after the injury were 0.30.16 and 0.380.2 , and those after the conservative treatment were 0.280.19 and 0.160.10 , maintaining the symmetry . they did n't exceed the criteria ( t<0.5 ) for test errors or pathologic conditions and were found to be significant ( table 2 ) . dt was 0.720.56 at the anterior neck , 0.620.44 at the posterior neck , 0.870.57 at the right shoulder and , 0.710.57 at the left shoulder . these changes were statistically significant ( p<0.05 ) ( table 3 ) . the thermal difference after immediately injury is higher than normal value , but it gradually decreased after two weeks . vas for neck pain was 7.860.65 immediately after trauma and was reduced to 3.431.06 after conservative management . vas for shoulder pain was 7.690.6 initially but was also reduced to 3.521.23 after conservative management ( fig . vas of the neck and shoulder were significantly reduced after 2 week and were statistically significant ( p=0.001 ) ( table 4 ) . also , bivariate correlation analysis showed that there was significant correlation between dt of the neck and shoulder and vas in vas before and after the treatment ( the neck ; r=0.412 , p<0.007 ) ( the shoulder ; r=0.648 , p<0.000 ) ( fig . with advances in technology and emergency treatment , the diagnosis of whiplash injury has been increasing . symptoms of whiplash injury are variously reported from simple neck pain to radiating arm pain28 ) . however , patients are often undiagnosed or misdiagnosed with ruptured cervical disk even with more specific investigations . it was reported that abnormality was started to show on electromyogram 2 weeks after the injury and then investigations were usually commenced . thermography is a useful tool to visualize and quantify the symptoms of whiplash injury by measuring skin surface temperature19 ) . it is expected that patients will understand better about their condition and any improvement when the imaging is shown . on thermography of a healthy individual without injury , the thermal difference of the anterior and posterior neck and that of the right and left shoulder are trivial , showing symmetric distribution . in a person with injury , there are significant thermal differences . based on this idea thermography is a useful tool that provides objective guidelines for the diagnosis and treatment of pain and the effectiveness of thermography has been evaluated in several studies1,22 ) . wexler27 ) first utilized thermography to evaluate pain , there were cold areas on the affected side of the patients with traumatic cervical syndrome and abnormal skin surface temperature related to spinal problem was identified as hypothermia . the majority of traumatic cervical syndrome was sprain in his study . in studies with myofascial pain syndrome , it was reported that trigger points on thermography could be appeared as either 5 - 10 cm of hot spots or cold spots14 ) . despite of that , it is generally accepted that areas of pain are usually shown as hot spots and areas of nerve damage are detected as hot spots during the acute phase and cold spots during the chronic phase . the diagnostic sensitivity of thermography was high when trigger points were detected as hot spots9,11,14 ) . our study was conducted with patients with whiplash injury who complained neck pain and shoulder pain only . previous studies on the natural history of whiplash injury are mostly small retrospective studies . during a collision , the 6th cervical vertebral body extends upwards as the body moves upwards and the segments above the 6th cervical vertebrae flex at first , creating s - shape . the lowest collision speed which can cause whiplash injury is estimated to be 8 km / hr . in a head - on collision , the movement of head is decelerated by the neck , and the occipitoatlantal joint and the 6th cervical vertebrae are involved in the deceleration force . then the head and the neck extend due to the elastic force of the occipital and cervical structures . at this point it is important fact that neck is passively moved regardless the direction of the shock . due to this passive movement , cervical muscle loses an opportunity to prepare for the shock and acquires injury secondary to eccentric contraction4 ) . sixty percent of the whiplash injury symptoms are neck pain and headache originated from cervical spine and 50% of them are occurred at the 2 - 3th cervical vertebrae17,24 ) . there have been a number of studies about the mechanism of whiplash injury which help understand the symptoms . in fact , hot spots were detected on the affected area on thermography immediately after whiplash injury19 ) . it was estimated that the thermal increase was resulted from inflammation , local vasodilation and the secretion of chemical messengers [ substance p , calcitonin gene - related peptide , nitric oxide ( no ) ] from nerve endings in response to painful stimuli3 ) . acute inflammation facilitates the secretion of substance p from nerve endings and increases vasodilation and vascular permeability escalating the effects of nerupeptides such as bradykinin and histamine . , local perfusion is increased by no produced by nerve stimulus or humoral factors and regulatory chemical messengers , resulting in an increase of skin surface temperature2 ) . this means that the degree of high temperature indicating the acute inflammation reflects the intensity of the vicious cycle of pain . therefore , during this period , anti - inflammatory agents and steroids will be effective to manage the symptoms and local anesthetics or radiofrequency nerve block can be administered to stop the vicious cycle of pain13,18,21 ) . generally , mild and moderate whiplash injury improves after 2 week conservative management with cervical brace , which alleviates the symptoms and helps the recovery , and the administration of anti - inflammatory agents and analgesics6 ) . some reported that patients were completely recovered whereas others reported that the symptoms continued for several years . compensation neurosis may be accompanied and some even files for a lawsuit23 ) . in this case , visualization of changes in skin surface temperature at painful areas using thermography will help provide the evidence of suffering and any improvement as well as establish treatment plans . once diagnosed with whiplash injury , the subjects were treated with absolute rest , anti - inflammatory agents and steroids . after 2 weeks , the symptoms were improved in most of the patients . to objectify subjective symptoms and any improvements , on thermography , skin surface temperature was becoming lower to the normal and symmetric imaging was created . the observation period was short because the subjects were selected from in - patients and the sample size was also not many because there were few patients with only whiplash injury , because this study was conducted in a university hospital where more complex patients are dealt with . in addition , patients with grade 1 - 2 whiplash injury ( quebec classification ) were only included in this study . this selection criterion was determined because it is difficult to perform thermography and to communicate with patients if there are severe cervical injuries causing other organ damages . the role of ir thermography is still limited as a diagnostic tool because it is doubtful that thermography is able to identify the entire characteristics of neurogenic dysfunction and disability . the significance of this study is that subjective pain ( expressed in vas score ) was objectively quantified with thermography ( the comparative analysis of thermal differences before and after the treatment ) under the same condition for a certain period of time . in this study , bias from asymmetric distribution was eliminated because the average thermal differences of the anterior and posterior neck and the right and left shoulder were about 0.16 - 0.3 which did not exceed 0.516,25,26 ) . furthermore , the thermal differences measured after 2 week treatment were very close to the normal skin surface temperature ( t<0.3)26 ) . therefore , it was judged that thermography was performed according to the standard guidelines . the changes ( dt ) of thermal differences greater than 0.5 in this study were also found to be significant . thus , comparing thermal differences using thermography will aid the understanding and evaluation of pain and undefined painful condition and it can be used in the case of a lawsuit . it is also expected that combined use with vas will also assist the evaluation and quantification of treatment . the skin temperature of sites with immediate whiplash injury is hyperthermia and gradually decreased after two weeks , it got close to normal temperature . symptoms of whiplash injury are highly varied and some of them are not yet pathophysiologically explained . although it seems that ir thermography is non - specific and has limited benefits , it can be used as a useful evaluation tool in undefined painful disorders such as whiplash injury because it is able to show objective data about pain experience and improvement .
objectivethis study aims to visualize the subjective symptoms before and after the treatment of whiplash injury using infrared ( ir ) thermography.methodsir thermography was performed for 42 patients who were diagnosed with whiplash injury . 
 there were 19 male and 23 female patients . 
 the mean age was 43.12 years . 
 thermal differences ( t ) in the neck and shoulder and changes in the thermal differences ( dt ) before and after treatment were analyzed . 
 pain after injury was evaluated using visual analogue scale ( vas ) before and after treatment ( vas ) . the correlations between dt and vas results before and after the treatment were examined . 
 we used digital infrared thermal imaging equipment of dorex company for ir thermography.resultsthe skin temperature of the neck and shoulder immediately after injury showed 1 - 2 hyperthermia than normal . 
 after two weeks , the skin temperature was normal range . 
 t after immediately injuy was higher than normal value , but it was gradually near the normal value after two weeks . 
 dt before and after treatment were statistically significant ( p<0.05 ) . 
 vas of the neck and shoulder significantly reduced after 2 week ( p=0.001 ) . 
 also , there was significant correlation between dt and reduced vas ( the neck ; r=0.412 , p<0.007 ) ( the shoulder ; r=0.648 , p<0.000).conclusionthe skin temperature of sites with whiplash injury is immediately hyperthermia and gradually decreased after two weeks , finally it got close to normal temperature . 
 these were highly correlated with reduced vas . 
 ir thermography can be a reliable tool to visualize the symptoms of whiplash injury and the effectiveness of treatment in clinical settings .