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Int J Clin Exp Pathol 2013;6(2):212-223

Original Article
Does dynamic immobilization reduce chondrocyte
apoptosis and disturbance to the femoral head

Lian-Yong Li, Li-Jun Zhang, Jing-Yu Jia, Qun Zhao, En-bo Wang, Qi-Wei Li

Department of Pediatric Orthopedics, Shengjing Hospital of China Medical University, Shenyang City, Liaoning
Province, P.R. China

Received August 2, 2012; Accepted November 6, 2012; Epub January 15, 2013; Published February 1, 2013

Abstract: The purpose of this study is to investigate whether the dynamic hip immobilization is more favourable for
lessening ischemic injury to the immature femoral head than a static immobilization. 152 Japanese white rabbits
were divided into four groups randomly, and the hips were immobilized into “human” position (group A), “frog leg”
position (group B) and “dynamic frog leg” position (group C). Group D was used as control. Ten rabbits in each group
were killed, and the hip specimens were harvested at 1, 2, and 3 weeks after immobilization. Bcl-2/Bax expression
balance and chondrocytes apoptosis were analyzed. The remaining eight rabbits in each group were used to
measure the blood supply of capital femoral epiphysis by selective vascular perfusion with Indian ink. The Bcl-2/
Bax expression ratio in group C was significantly increased than that in group A and B (p<0.001), while that was not
significantly different from control group (p=0.0592). At three weeks after immobilization, the average apoptotic
ratio was 36.7%, 45.8%, and 26.7% in group A, B and C, respectively (p<0.01). There was no significant difference
between group C and normal control (p=0.0597). The perfusion ratio was 0.03±0.03, 0.03±0.02, and 0.08±0.03
in group A, B and C respectively, and 0.12±0.04 in control group (p<0.05). Thus, the dynamic immobilization model
exhibited a relatively less chondrocytes apoptosis and disturbance to the femoral head perfusion than other immobilizations
in vivo, which therefore may be useful for reducing avascular necrosis following the treatment of
developmental dysplasia of the hip. (IJCE1208003).

Keywords: Dynamic immobilization, femoral head, blood supply, apoptosis

Address all correspondence to:
Dr. Qun Zhao,
Department of Pediatric Orthopedics
Shengjing Hospital of China Medical University
Shenyang City, 110004, China.
Phone: 086 024 23263408; Fax: 086 024 83955092
E-mail: zh_qs@sina.com