joint contracture occurs after a long period of fixation and/or immobilization due to 
 fracture or impaired consciousness .
the influence of the skin on joint contracture has been determined in 
 several studies based on the change in range of motion ( rom ) between the first measurement 
 after cast removal and the second measurement after skin resection1,2,3,4 .
studies investigating 
 multiple measurements of rom in joint contracture have reported that a single joint movement 
 can improve the rom5 , 6 .
therefore , the authors of these previous studies suggested that 
 joint contracture is influenced by both joint movement and skin incision .
however , no 
 studies have measured rom twice without skin resection to determine the changes in rom . in the present study ,
our purpose was to determine the effect of the joint movement through 
 rom measurements performed twice after removal of the cast , and the effect of the skin when 
 rom was measured once after the cast removal and once again after skin resection of rats 
 with plantar flexion contractures .
twelve , 8-week - old female , wistar rats with an initial body weight of 189.1  5.3  g were 
 used .
the animals were housed in a temperature - controlled room at 23  c with a 12-hour 
 light - dark cycle .
the 
 experiment was conducted in accordance with our university s guidelines for animal 
 experimentation ( no .
the rats were randomly divided into 2 groups . 
 under pentobarbital sodium anesthesia ( 40  mg / kg b.wt ) ,
the right ankle joint of each rat was 
 immobilized in full plantar flexion in a cast from the toes to above the knee joint . in 
 addition , the cast was covered with a stainless steel net to prevent breakage and falling . 

when the toes became edematous due to fixation , the cast was replaced . in the resection 
 group
( n = 6 ) , the skin of the right ankle was removed surgically , but it was not removed in 
 the non - resection group ( n = 6 ) . before the experiment and after 2 weeks , dorsiflexion of the ankle joint was measured . at 
 the end of the immobilization period ,
the rats were sacrificed with pentobarbital sodium 
 anesthesia ( 40  mg / kg b.wt ) , and blood was removed by cutting the abdominal aorta . in the 
 resection group ,
the first measurement of the dorsiflexion angle was obtained after the cast 
 was removed , followed by the second measurement after skin resection .
skin resection was carefully done without affecting 
 dorsiflexion of the ankle joint . in the non - resection group ,
both measurements of the 
 dorsiflexion angle were obtained in the same manner after the cast was removed . when 
 measuring dorsiflexion , the rat was positioned on its side with the hip and knee fixed in 
 flexion .
a force of 0.3 n was applied perpendicularly to the sole of the foot using a 
 tension meter7 ( kyowa co. , lts-1ka ) .
recorded videos were 
 downloaded to a computer to extract still images of dorsiflexion at the moment of 
 application of the 0.3 n force .
the rom of dorsiflexion was measured from the still images 
 using computer software ( imagej version 1.44p ; usa ) .
the rom of dorsiflexion was defined as 
 the angle obtained from a line parallel to the longitudinal axis of the fibula and a line 
 parallel to the bottom of the heel to eliminate forefoot movement from the measurement . 

dorsiflexion was measured 3 
 times , and the mean value was used in the analysis .
the wilcoxon test was used to compare the change in rom between the first and second 
 measurements .
the mann - whitney u test was used to compare the differences in measurements 
 between the two groups .
the changes in rom of ankle dorsiflexion ( in degrees)groupafter two weeksfirst measurementsecond measurementfirst  secondresection ( n=6)113.19.9103.911.59.272.8non - resection ( n=6)105.74.7102.13.83.641.0values are means  sd . a : significant decrease compared with first measurement 
 ( p<0.05 ) .
b : significant difference between resection and non - resection group 
 ( p<0.01 ) .
the rom measurements decreased significantly in both groups between the first 
 and second measurements . compared with the non - resection group ,
the resection group showed a 
 significant increase in rom between the first and second measurements .
values are means  sd . a : significant decrease compared with first measurement 
 ( p<0.05 ) .
skin contracture occurs after damage from 
 burns or wounds , such as hypertrophic scarring due to damage beyond the basement membrane 
 separating the epidermis and dermis9 . 

contracture of the skin and soft tissue that occurs after joint immobilization has been 
 investigated in previous animal experiments . in these studies ,
the cause and contribution 
 rate of soft tissue contracture were clarified by measuring the rom of the joints in 
 general .
ichihashi et al.3 fixed rats knees in 
 full flexion for 30 days and measured the rom of knee extension after removal of the cast , 
 and resection of the skin and muscles .
okamoto et al.4 fixed 
 rats in full plantar flexion for 1 , 2 , 4 , 8 , and 12 weeks and reported that the rom of 
 plantar flexion improved after cast removal and resection of the skin and muscles for all 
 time periods of immobility .
these previous studies indicate that skin affects contracture 
 formation resulting from joint immobilization . in our study , joint contractures occurred in 
 all rats after joint fixation .
the method of immobilization used in this study was 
 carried out in accordance with that reported by ono et al10 .
our results show that the rom of dorsiflexion increased between 
 the first and second measurements in both groups .
this indicates that the rom increase 
 observed in the second measurement in the non - resection group may be due to the stretching 
 of the skin , because the measurements were carried out using the same torque .
furthermore , 
 the increased rom in the second measurement in the resection group was considered to be the 
 sum of the stretching effect from moving the joint during the measurements and the skin 
 resection .
the change in the rom between the first and second measurements was greater in 
 the resection group than in the non - resection group .
the second rom measurement in the 
 resection group improved 9.27  2.8 degrees from the first measurement , an improvement of 
 approximately 12% of the full rom limitation . in the non - resection group ,
the rom improved 
 3.64  1.0 degrees , an improvement of approximately 5% of the full rom limitation . 

therefore , we estimate the skin effect was approximately 7% , the result of subtracting the 
 joint movement effect ( 5% ) from the change in rom ( 12% ) in the resection group .
skin contracture after burns and wounds is reported to be caused by excess proliferation of 
 fibroblasts11 , abnormal generation of 
 collagen fibers12 , and contraction of the 
 wound13 , followed by scar contracture . 

the 
 results of our study and previous studies demonstrate that skin has a critical role in the 
 formation and treatment of joint contracture , because we found that skin resection improved 
 rom after joint immobilization .
stretching of the skin by an open - window procedure14 , 15 
 may be effective when immobilization treatment is used after fracture . in the future
, it 
 will be necessary to examine how the skin itself changes during joint immobilization .
   the effect of skin resection on joint contracture was determined by comparing the first 
 measurement of range of motion after cast removal and the second measurement after the 
 skin resection . 
 this study aimed to verify that both the joint movement during the 
 measurement and skin affect range of motion . 
 [ subjects ] twelve female wistar rats were 
 used . 
 [ methods ] the right hind limb ankle of each rat was immobilized in complete plantar 
 flexion in a cast . in the resection group 
 ( n = 6 ) , the skin of the right hind limb ankle 
 was removed surgically , but not in the non - resection group ( n = 6 ) . in the resection 
 group , 
 the first measurement of the dorsiflexion angle was obtained after the cast was 
 removed , and the second measurement was obtained after skin resection . in the 
 non - resection group , 
 both measurements of the dorsiflexion angle were obtained soon after 
 the cast was removed . 
 [ results ] compared with the non - resection group , the resection group 
 showed a significant increase between the first and second measurements of range of 
 motion . 
 [ conclusion ] these results show that range of motion is substantially affected by 
 skin , in addition to joint movement , during measurement . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION