Paper Information

Journal:   TEHRAN UNIVERSITY MEDICAL JOURNAL (TUMJ)   2006 , Volume 63 , Number 12; Page(s) 965 To 973.
 
Paper: 

THE INFLUENCE OF CONTROLLED CYCLIC MOVEMENTS UPON HEALING OF EXPERIMENTAL TIBIAL FRACTURES

 
Author(s):  SHADMEHR AZADEH, ESTEKI ALI, ALIAEI GHOLAM REZA, MADADI F., TORKAMAAN GITI, JALAEI SHOHREH
 
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Abstract: 

Background: Rate and eventual success of healing of bone fractures depend on factors such as: age, hormonal milieu, degree of trauma and particularly mechanical environment. Several investigators have demonstrated positive effect of controlled cyclic mechanical strain on fracture healing, but optimal parameters have not yet been established. The purpose of this study was to examine the effect of a well defined mechanical stimulation, externally applied to bone fixator, on the process of bone healing.
Materials and Methods: A randomized, prospective in vivo animal study was designed. Sixteen skeletally mature white rabbits (2-2.5 kg) were randomly assigned to four groups of four animals. A four- pin, double bar external fixator was fixed to the right tibia. The mid shaft of the tibia was then osteotomized, leaving a 2 mm gap.
External stimulation was performed on eight rabbits with the use of a motor- driven actuator unit. The actuator could provide a well controlled axial cyclic compressive movement to the osterotomized gap with frequency of Hz, amplitude of 0.5 mm and duration of 15 minutes per day; started 1 week after the operation and continued for 2 or 3 weeks. A force transducer built into the actuator measured the resisting force during application of the strain to keep the force lower than 50 N. The animals were sacrificed on postoperative day 14 or 21. callus quality and area were assessed by X-ray radiographs, and mechanical properties of healed bone were determined using a standard three- point bending test.
Results: Statistical significance was evaluated using nonparametric Mann- Whitney U test. Callus quality and area, and applied forces and total energy absorbed at failure point were significantly superior on the stimulated groups compared to the controls (P< 0.05). These differences were higher in 3 weeks postoperative.
Conclusion: Current study demonstrates the sensitivity of fracture healing to direct low frequency low amplitude mechanical stimulation. Our findings are consistent with the other's observations that there is an interesting relationship between bone formation and mechanical strain histories. Continuing studies with more sample size with aim to the precise strain environment and its relationship with potential mechanisms of bone healing.

 
Keyword(s): CONTROLLED CYCLIC MECHANICAL STRAIN, BONE FIXATOR, BONE HEALING
 
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