1.Influence of Immobilization on the Pathogenesis of Chronic Pain:Besed on the Mechanism of Immobilization-induced Muscle Atrophy, Muscle Contracture, and Muscle Pain
Minoru OKITA ; Yuichiro HONDA ; Natsumi TANAKA ; Junya SAKAMOTO
The Japanese Journal of Rehabilitation Medicine 2021;58(11):1221-1228
2.Microstructure Analysis of Immobilized Osteopenia Using Microcomputed Tomography:An In Vivo Study
Hironobu Koseki ; Makoto Osaki ; Hidehiko Horiuchi ; Yuichiro Honda ; Ryo Sasabe ; Junya Sakamoto ; Takashi Higuchi ; Sinya Sunagawa ; Minoru Okita
The Japanese Journal of Rehabilitation Medicine 2017;54(9):718-723
Objective:To assess the effects of immobilization on the three-dimensional microstructure of cortical and cancellous bone.
Methods:Eight-week-old specific-pathogen-free Wistar rats were divided into two groups:the control (n=12) and immobilized group (n=12). The hind limbs of the rats in the immobilized group were fixed using orthopedic casts for 4 weeks. The cortical bone at the mid-shaft and the cancellous bone at the distal metaphysis of the femur were analyzed using micro-computed tomography.
Results:The values of total cross-sectional area, cortical bone area, and cortical thickness in the immobilized group were significantly lower than those in the control group. Meanwhile, the relative bone volume (bone volume/total volume) and mean trabecular thickness in the immobilized group decreased and the structure model index significantly increased compared with the values in the control group (P<0.05).
Conclusion:Our rat model can evaluate the effects of load-permitting immobilization. The results of this study indicate that structural changes in immobilized osteopenia-affected bone arise mainly from thinning of the cortex and reduction of cancellous bone volume caused by a reduction of trabecular width.
3.Mechanical Bone Strength in Immobilized Osteopenia:An In Vivo Study
Hironobu KOSEKI ; Yuichiro HONDA ; Shinya SUNAGAWA ; Umi MATSUMURA ; Junya SAKAMOTO ; Minoru OKITA
The Japanese Journal of Rehabilitation Medicine 2021;58(5):565-571
Objective:This study aimed to evaluate the mechanical strength of immobilized osteopenia using a fixed limb rat model.Methods:Eight-week-old specific-pathogen-free male Wistar rats were divided into two groups, a control group (n=32) and an immobilized group (n=32). The hind limbs of the immobilized group were fixed using an orthopedic cast, and the fixation periods were set for 1, 4, 8, and 12 weeks. Feeding and weight-bearing were permitted. After each fixation period, the length of the right femoral bone was measured, and three-point bending at the midshaft and uniaxial compression test at the distal metaphysis were performed with a universal material testing apparatus. The maximum force and breaking force in the bending test and ultimate load in the compression test were statistically analyzed.Results:The values of the maximum force and breaking force in the immobilized group were significantly lower than those in the control group at 4, 8, and 12 weeks (p<0.05). The ultimate load of the distal metaphysis in the immobilized group decreased from 1 week after fixation, and the gap with the control group widened as the fixation period extended.Conclusion:The results of this study indicate that bone weakness caused by immobilized osteopenia arises after 1 week in the metaphysis and after 4 weeks in the midshaft.