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EFFECTS OF FREE and RESTRICTED REMOBILIZATION ON THE BODYWEIGHT AND MID THIGH CIRCUMFERENCE OF RABBIT.

Byline: Samina Anjum, Liaqat Ali Minhas and Khadija Qamar

Abstract

Objective: To find out the effects of free and restricted remobilization on the generalized body weight and mid thigh circumference of rabbit. For this purpose, knee joints of rabbits were immobilized first. Study Design: Randomized Controlled Trials (RCT) Place and Duration of the study: Study was carried out in Army Medical College, Rawalpindi and National Institute of Health Sciences, Islamabad from April 2006 to April 2007. Materials and Methods: Twenty four adult New Zealand White rabbits were randomly divided into three groups using random numbers table. Group I served as a control group whereas the left knee joint along with ankle joint of the experimental groups II and III were immobilized in extension in a plaster of Paris cast for 4 weeks. At the end of 4 weeks plaster cast was removed and group II i.e. free mobility group and group III i.e. restricted mobility group (caged animals) were remobilized for another 4 weeks.

The generalized body weight and mid thigh circumference of all the animals were taken at the start of experiment, at the end of 4 weeks of immobilization and at the end of 4 weeks of remobilization in all groups. Results: Immobilization caused significant reduction in the body weight and mid thigh circumference of both the experimental groups. On remobilization the body weight increased but significant difference remained between the experimental and control groups. Although weight gain is more in the caged animals during remobilization phase but statistically insignificant difference was found when free and restricted mobility groups were compared. The difference in the mean mid thigh circumference between control and free mobility groups was statistically insignificant whereas the difference between control and restricted mobility groups was significant at the end of 4 weeks of remobilization.

Recovery in caged animals was slower as compared to free mobility group in terms of mid thigh circumference but when these two groups were compared statistically insignificant difference existed at the end of 8 weeks. Conclusion: Immobilization induced reduction in body weight and mid thigh circumference which is to a great extent reversible in both free and restricted mobility groups. Both the groups responded almost equally to immobilization stress and confinement did not prevent restoration of bodyweight and mid thigh circumference, however complete recovery of the body weight and mid thigh circumference to initial control values did not occur in 4 weeks.

Article

INTRODUCTION Immobilization of animals by a plaster cast is one of the popular methods used for the treatment of musculoskeletal injuries and is also one of the most widely used methods for immobilization in animal models1,2. The impact of immobilization on the body weight and skeletal muscles has been investigated in animal models. Zarzhevsky et al3. 2001 reported that several weeks of immobilization contributed to decrease both the body weight and weight of skeletal muscles in rats. Coutinho et al4., 2002 also described significant loss of body weight during 21 consecutive days of immobilization. Faraday et al5. 2005 also described that immobilization stress decreased both feeding and body weight in female rats5. However, the data on the effect of free verses restricted remobilization on the body weight was not documented. It was reported that mid thigh circumference served as an indicator for assessing the nutritional status of individual6,7.

Heerkens et al., 1987 reported a decrease in circumferential dimensions due to immobilization of human knee. They further reported that the difference between immobilized and unaffected leg remained even after 81 days of remobilization and this decrease in circumferential dimensions indicated atrophy of thigh and calf muscles8. Studies conducted in the past also reported the recovery from atrophic changes of skeletal muscle during remobilization9-11. However, the effect of free and restricted remobilization on mid thigh circumference of rabbit hind limb was not reported. In most of the studies animals were euthanized and skeletal muscles were then studied directly to see the atrophic changes. Therefore measurement of mid thigh circumference in animal models is an indirect way of assessing the nutritional status of the animal and atrophic changes in muscles.

In view of above the objective of the present study was to immobilize the stifle joint of rabbit first and then to see the subsequent effects of free and restricted remobilization on the body weight and mid thigh circumference of rabbit. MATERIALS AND METHODS These randomized controlled trials (RCT) were carried out at Army Medical College, Rawalpindi and National Institute of Health Sciences (NIH), Islamabad. In this study twenty four adult New Zealand white rabbits [approx. ages 4-6 months; weights 1.3-1.7 kg] were taken. Animals were randomly divided into three groups using random numbers table. Each group comprised of 08 animals. Group I served as control. The left knee joints along with ankle joints of groups II and III were immobilized in extension in a long leg padded plaster of Paris cast. The animals remained ambulant during the period of immobilization (Fig.1). All the animals were given water and standard animal house diet ad libitum prepared at National Institute of Health (NIH), Islamabad.

At the end of 4 weeks of immobilization plaster cast was removed and animals were remobilized for another 4 weeks by either allowing free mobility as in group II or restricted mobility in a cage (Fig. 2) as in group III. The body weight and mid thigh circumference (MTC) of all the animals were taken at different intervals. Mid thigh circumference was measured by a measuring tape. First a diagonal length was taken from the epicondylus medialis (the most prominent point on medial side of lower end of femur of rabbit) to the most prominent ventral point on the crista iliaca of os coxa (Hipbone). Then the mid point of this diagonal is taken which approximately lies 5.5 cm above the knee joint. At this point mid thigh circumference of thigh was measured. Data was entered in a database using SPSS for windows version 11. The statistical significance of difference between two means was evaluated by Student's't' test. The comparison was done between the groups by Independent Sample't' test.

The difference was regarded as statistically significant, if 'p' value was less than 0.05. RESULTS General Observations All the animals survived and remained active during the duration of experimental period. During immobilization intake of food among the experimental groups was reduced as evident by decreased intake of standard diet in 24 hrs assessed by left over food, however after remobilization food intake improved as the animals consumed almost whole of the diet in 24 hrs in both the groups II and III. The general condition of the animals remained healthy and they tolerated the plaster cast very well and remained ambulant with the plaster cast. Any subsequent cracks in the plaster cast were duly repaired. None of the animals developed any complications. After the removal of the cast in groups II and III left leg was examined and mid thigh circumference was taken. The body weights of all the animals were taken at different intervals. Initial body weight (W1) was taken at the start of experiment.

Then the weights were taken at 4 weeks of immobilization (W4) and at the end of 8 weeks (W8) i.e. 4 weeks of immobilization and 4 weeks of remobilization. The Mean body weights (g) of all animals in three groups were recorded as W1, W4 and W8 in (Table 1). Comparison of mean body weights between groups: W1: The mean body weight of group I was 1592.50 +- 47.72g, group II was 1622.50 ? 30.63g and group III was 1568.75 ? 27.93g (Table 1) and the difference in the mean body weights between groups I and II, I and III and II and III was statistically insignificant (p > 0.05, Table 2). W4: The mean body weight of group I was 1611.25 ? 46.03 g and group II was 1346.25 ? 43.79 g and group III was 1362.50 ? 40.03g (Table 1, Fig. 3) and the difference in the mean body weights between groups I and II, I and III was statistically significant (p 0.05, Table 2). W8: The mean body weight of group I was 1645.00 ? 45.00g and group II was 1378.75 ? 38.05g and group III was 1395.75? 37.42g (Table 1, Fig. 4) and the difference in the mean body weights between groups I and II and I and III was statistically significant (p 0.05, Table 2). Mid thigh circumference (MTC) of animals in centimetres (cm) was taken at different intervals. Initial MTC (C1) was taken at the start of experiment. Then the Mtc was taken at 4 weeks of immobilization (C4) and at the end of 8 weeks (C8) i.e. 4 weeks of immobilization and 4 weeks of remobilization. The mean MTC of all animals in three groups was recorded as C1, C4 and C8 in (Table-3). Comparison of mean MTC between groups: C1:

The mean MTC of group I was 12.36 ? 0.17cm, group II was12.46 s? 0.18cm and group III was 12.20 ? 0.15cm (Table 3) and the difference in the mean Mtc between groups I and II, I and III and II and III was statistically insignificant (p > 0.05, table 4). C4: The mean MTC of group I was 12.42? 0.15cm, group II was 11.93 ? 0.16cm and group III was 11.88 ? 0.08cm (Table-3, Fig.5) and the difference in the mean MTC between groups I and II and I and III was statistically significant (p 0.05, Table 4). C8: The mean MTC of group I was 12.55 ? 0.15cm, group II was 12.18 ? .13cm and group III was 12.12 ? 0.11cm (Table 3, Fig. 6) and the difference in the mean MTC between groups I and II and II and III was statistically insignificant (p > 0.05, Table 4). However, the difference between groups I and III was statistically significant (p 0.05).

This could be correlated with the initial body weights W1 of these groups, which were also statistically insignificant. When mean Mtc C4 of experimental groups II and III was compared between the groups I and II and I and III at the end of 4 weeks of immobilization, significant decrease was found. This decrease in mean Mtc could be related to under nutrition6,7 of animals during immobilization phase due to constant stress. This could also be attributed to disuse atrophy of skeletal muscles sduring immobilization11. Heerkens et al8. (1987) also concluded that immobilization resulted in decrease in circumferential dimensions of thigh and calf muscles of human knee. They added further that this difference in circumferential dimensions was present even after 81 days of remobilization. Comparison of mean Mtc C8 at the end of 4 weeks of remobilization between groups I and II was statistically insignificant and I and III was significant.

Perhaps this could be due to lack of free mobility and physical activity in caged animals. This was in accordance with Kannus et al., 1998 who reported that immobilization induced atrophy is a reversible phenomena if remobilization is intensified by physical training18. However, when mean Mtc C4 was compared between groups II and III, statistically insignificant difference was found showing that immobilization stress affected both the groups equally. Mean Mtc C8 improved in both the groups during remobilization indicating that there was some gain in muscle bulk with joint loading and motion. Also it was noted that the recovery in caged animals was slow as compared to freely mobile animals, yet statistically insignificant difference was found between groups II and III at the end of 8 weeks. Also this duration was not enough to completely restore the mid thigh circumference to control values.

CONCLUSION Immobilization stress induced significant reduction in the body weight and mid thigh circumference of animals which is to a great extent reversible in both free and restricted mobility groups. Although recovery of mid thigh circumference in caged animals was slower as compared to freely mobile group, yet both the groups responded almost equally to immobilization stress and confinement did not prevent restoration of bodyweight and mid thigh circumference. However, complete recovery of the body weight and mid thigh circumference to initial control values did not occur in 4 weeks.

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Publication:Pakistan Armed Forces Medical Journal
Article Type:Clinical report
Geographic Code:9PAKI
Date:Sep 30, 2010
Words:2622
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