the car is a convenient means of transport and enables people to expand their range of 
 activity . in particular , for people with disability of the lower extremities who must use a 
 wheelchair have limited use of public transportation , it is very important to be able to 
 drive a car . the ability to drive is associated with employment , community participation , 
 and overall satisfaction in individuals with spinal cord injury1,2,3,4 . to be able to drive 
 independently , these individuals need to transfer to the driver s seat ( i.e. , car transfer 
 [ ct ] ) , operate the steering wheel , and load their wheelchairs in their car by themselves . 
 among these activities , the ct movement to the driver s seat is particularly important 
 because it is related to other transfer movements in daily living . kinematic analysis of the 
 ct movement in individuals with c6 tetraplegia showed that these individuals prefer the 
 rotatory movement pattern in which their head moves in the opposite direction to their 
 buttocks5 . in an analysis of the ct 
 movement in individuals with tetraplegia , the subjects confirmed that they could move their 
 buttocks by inclining their trunk forward inclination by via neck control , because of trunk 
 muscle paralysis5 . however , this previous 
 study only analyzed the head , trunk , and buttocks during ct movement in individuals with 
 tetraplegia , and it did not examine the position of the lower limbs whereby individuals with 
 c6 tetraplegia could control their paralyzed trunks . several studies have been conducted on transfer movement in individuals with spinal cord 
 injury . these earlier studies indicated the importance of the eccentric control of trunk 
 forward flexion and the coordinated flexion movement between the head and trunk to assist 
 the buttocks to lift off the seat during transfer movement6,7,8,9 . individuals with tetraplegia used a variety of methods to facilitate the ct movement . for 
 example , they perform ct after placing one or both legs in the car or they fix their head 
 against the door during the movement . for individuals with tetraplegia to participate 
 socially , it is very important them to achieve more efficient ct movement . however , few 
 studies have kinematically examined ct movement in individuals with tetraplegia . the purpose of the present study was to examine the kinematic characteristics and explore 
 the most efficient methods of ct movement in individuals with tetraplegia , focusing on trunk 
 and hip joint movement . eleven adult males with c6 tetraplegia , with grade a impairment according to the american 
 spinal injury association ( asia ) guidelines , participated in this study . their asia motor 
 scores ranged from 18 to 24 , while the time since injury was 1131  years ( age : 39.6  
 8.1yerars , height : 174.7  5.6  cm , weight : 55.3  6.8  kg ) . the inclusion criteria were as 
 follows : no limitation in range of motion or pain in the upper extremities and inability to 
 lift themselves off the buttocks . subject characteristics are presented in table 1table 1.subject characteristicssubjectsage ( years)height ( cm)weight ( kg)bmi ( kg / m)time since injury ( years)asia motor score of upper extremities ( /50)height of wheelchair seat ( cm)height of driver s seat ( cm)a41168.560.021.121195053b26175.055.018.012205053c39182.066.520.122225354d51168.056.019.831205358e51174.055.018.227185354f28167.045.016.110205252g39180.065.020.119245360h33172.047.015.911215452i42183.050.014.922215060j43178.051.616.327205554k42174.057.018.818205253mean  sd39.6  8.1174.7  5.655.3  6.818.1  2.120.0  6.920.5  1.652.3  1.754.8  3.0 . this study was approved by the ethics committee of the school of comprehensive 
 rehabilitation , osaka prefecture university ( 2013 - 108 ) . the purpose of the study was 
 explained to the subjects orally and in writing , and written informed consent was obtained 
 from all participants . subjects were instructed to perform ct movement as they would usually from their own 
 wheelchairs to their own cars . the difference between the height of the driver s seat and 
 the seat surface of the wheelchairs was less than 10  cm ( table 1 ) . the wheelchair was positioned on the correct side of the 
 car , and the subjects attempted to transfer themselves from the wheelchair into the driver s 
 seat . the passenger - side door was held open maximally , and a digital video camera ( 30  hz ) 
 was placed on the passenger side ( fig . the passenger - side door was held open maximally , and a digital video camera was 
 placed on the passenger side . ) . the passenger - side door was held open maximally , and a digital video camera was 
 placed on the passenger side . the duration of the movement , defined as the total time of buttocks movement from the 
 wheelchair to the driver s seat was determined from videos recorded on the camera . the 
 starting point was the moment that the buttocks movement was visible , when the left great 
 trochanter was confirmed to have moved forward . the end point was the moment that the 
 buttocks movement was completed when the participant was in the driver s seat . on the basis of the videos , the duration and the trunk inclination and hip angles the trunk inclination and hip angles 
 were calculated using image - j ( nih ) from static images . the trunk inclination angle was 
 defined as the angle from the left acromion process to the great trochanter and the vertical 
 line . the hip angle was defined as the angle between the left acromion process to the great 
 trochanter and the left great trochanter to the knee ( fig . the trunk inclination angle was defined as the angle from the left acromion process 
 to the great trochanter and the vertical line . the hip angle was defined as the angle 
 between the left acromion process to the great trochanter and the left great 
 trochanter to the knee . ) . in other words , a small hip angle indicates a high hip flexion angle . in the case 
 of multiple buttocks movements , these angles were calculated for each movement , and the 
 maximum angle was used in the data analysis . after the buttocks movement , the angles of the 
 moment their acromion and knee position closing were measured as the maximum angle . the trunk inclination angle was defined as the angle from the left acromion process 
 to the great trochanter and the vertical line . the hip angle was defined as the angle 
 between the left acromion process to the great trochanter and the left great 
 trochanter to the knee . the relationship of the trunk inclination and hip angles with duration were analyzed using 
 spearman s rank - correlation coefficient . the duration of the ct movement ranged from 9 to 39  s ( table 2table 2.duration of the ct movement , trunk inclination angle , and hip angle recorded for 
 all subjectssubjectasia motor score ( /50)duration of the ct movement ( s)maximum trunk inclination angle ( degrees)maximum hip angle ( degrees)a193245.461.9b203635.064.9c22937.746.4d202234.058.3e181842.564.1f201336.257.7g243932.066.9h212631.561.5i211940.581.8j202041.058.0k201737.654.8mean  sd20.5  1.622.8  9.537.6  4.461.5  8.8 ) . no correlation was found between the asia motor score and duration ( =0.07 , 
 p>0.05 ) . the maximum trunk inclination angle ranged from 31.5 to 45.4 degrees , while the 
 maximum hip angle ranged from 46.4 to 81.8 degrees ( table 2 ) . no correlation was observed between the trunk inclination angle and the duration of ct 
 movement . however , a significant correlation was observed between the hip angle and duration 
 ( =0.67 , p<0.05 ) . in other words , transfer movements are very common in daily life , and the ability to perform these 
 movements is one of the most important and meaningful skills for individuals with 
 tetraplegia . independence in transfer movement would encourage individuals with tetraplegia 
 to participate more fully in the community by allowing them to use a car . thus , 
 understanding the kinematic characteristics of patients with c6 tetraplegia is important in 
 order to promote their participation in the community . the purpose of this study was to examine the kinematic characteristics of individuals with 
 tetraplegia and identify the most efficient method of ct movement for them , with a focus on 
 trunk and hip joint movement . previous studies showed that coordinated flexion movement 
 between the head and trunk assist the buttocks to lift off the seat6,7,8 . additionally , the strategy of neck flexion and forward inclination 
 of the trunk was found to differ among subjects with c6 tetraplegia during ct movement5 . in the present study , no correlation was found between the asia motor score and the 
 duration of the ct movement . a reason for this could be that all subjects with c6 
 tetraplegia have paralyzed triceps brachii muscles , and the asia motor score of the upper 
 limbs does not significantly affect the ct movement . in addition , it has been reported that 
 the pectoralis major , latissimus dorsi , and serratus anterior muscles are important for the 
 ct movement in individuals with spinal cord injury8 and that in order to analyze the ct movement in individuals with c6 
 tetraplegia , these muscles should be tested in addition to those tested to determine the 
 asia motor score . further , the present study showed no correlation between the trunk 
 inclination angle and the duration of the ct movement . this could be because of the limited 
 space in which the movement was performed and because the subjects had paralyzed trunk 
 muscles . cars have several obstacles , such as the door , handle , and dashboard , and the 
 subjects had to incline their trunks forward in a limited space . however , these obstacles 
 might actually assist the subjects in inclining their paralyzed trunks forward and control 
 them . on the other hand , a significant correlation was observed between the hip angle and 
 duration of the ct movement . this could be because c6 tetraplegia enabled smooth ct by 
 allowing for control of trunk inclination , such as placing the lower extremities in the car 
 in order to tilt pelvis backward . although the hip flexion angle was high , the trunk inclination angle was low , despite which 
 the individuals with tetraplegia could perform the dynamic ct movement . as mentioned above , 
 it has been reported that for transfer movement among individuals with tetraplegia , head and 
 trunk flexion may facilitate efficient buttocks movement . however , with regard to transfer 
 movement in confined spaces such as ct movement , it has been suggested that the magnitude of 
 the hip flexion angle affects smooth movement of the buttocks . compare the 
 changes in the trunk and shoulder angles and reaction forces under the two hands elicited by 
 different hand base - of - support positions during sitting pivot transfer10 . they reported that the lower hand position should be 
 recommended as an effective and safe method for sitting pivot transfer for patients with 
 spinal cord injury , because this position was associated with a significantly high trunk 
 angle of forward and lateral flexion , even though the angle of rotation while transferring 
 to the 20-cm lower support position was reduced . in the present study , the difference 
 between the height of the driver s seat and the seat surface of the subjects wheelchair was 
 less than 10  cm . however , since even a small difference in these levels is considered to 
 influence the ct movement in individuals with c6 tetraplegia who have paralyzed upper limbs , 
 this factor needs further investigation . the trunk inclination angle probably showed no effect on the duration of the ct movement 
 because the movement was performed in a limited space and because the trunk muscles of the 
 subjects were paralyzed . in contrast , c6 tetraplegia enabled smooth ct by allowing for 
 control of trunk inclination , such as placing the lower extremities in the car , whereby the 
 pelvis backward tilt angle increased . a drawback of the present study was that the ct 
 movement was examined in a limited space , and the differences in the cars and wheelchairs 
 used by the subjects were not taken into consideration . third , the experimental conditions 
 were not fixed , and the subjects were allowed to select their own strategy for ct movement . further , the motions of the ct movement , including rotational motion , were examined by 
 two - dimensional analysis . the angles in the sagittal plane were determined , and the 
 numerical values of these angles are not precise . thus , although the trends of the trunk 
 inclination angles and hip angles required for the ct movement have been understood , further 
 studies are needed for a more accurate analysis with a greater number of subjects .
[ purpose ] the purpose of the present study was to investigate the relationship between 
 the duration of the car transfer ( ct ) movement and trunk inclination and hip angles during 
 this movement in individuals with tetraplegia . 
 [ subjects and methods ] eleven adult males 
 with c6 tetraplegia participated in this study . the ct movement was recorded from the 
 passenger side of the car using a digital video camera . from the video , the duration and 
 trunk inclination and hip joint angle 
 were recorded , and correlation coefficients were 
 calculated . 
 [ results ] no correlation was found between the trunk inclination angle and the 
 duration of the ct movement . 
 however , a significant correlation was found between the hip 
 angle and the duration of the ct movement : when the duration was short , the hip flexion 
 angle was substantial . 
 [ conclusion ] the trunk inclination angle probably showed no effect 
 on the duration of the ct movement because the movement was performed in a limited space 
 and because the trunk muscles of the subjects were paralyzed . 
 in contrast , c6 tetraplegia 
 enabled smooth ct by allowing for control of trunk inclination , such as placing the lower 
 extremities in the car , whereby the pelvis backward tilt angle increased .