The effect of latency on bone lengthening force and bone mineralization: an investigation using strain gauge mounted on internal distractor device

BACKGROUND: The purpose of this study was to investigate the effect of latency on the development of bone lengthening force and bone mineralization during mandible distraction osteogenesis. METHODS: Distraction tensions were investigated at different latency period in 36 rabbits using internal unilateral distractor. Strain gauges were prepared and attached to the distractor to directly assess the level of distraction tension during mandible lengthening. The tensile force environment of the mandible of rabbit during distraction was evaluated through in vivo experiments using two gauges. The animals were divided into 3 groups each containing 12 rabbits. Latency periods of 0, 4 and 7 days respectively were observed prior to beginning distraction. The distraction protocol consisted of a lengthening rate of 1 mm once daily for 8 days, followed by a consolidation phase of 2 weeks after which the animals were killed. Biopsies specimens were taken from the distracted area at the end of the distraction period. A non-distracted area of the mandible bone served as control. The specimens were analyzed by scanning electron microscopy to assess the ultrastructural pattern, and the bone mineralization. RESULTS: The resting tension acting on the distraction gap increases through distraction. The 7-day latency groups exhibit higher tension then those of 0-day and 4-days latency groups. Quantitative energy dispersive spectral analysis confirmed that immediate distractions were associated with lower calcium and phosphate atomic weight ratio. CONCLUSION: the latency periods could affect the bone lengthening tension and the bone mineralization process

The Mechanics of External Fixation

External fixation has evolved from being used primarily as a last resort fixation method to becoming a main stream technique used to treat a myriad of bone and soft tissue pathologies. Techniques in limb reconstruction continue to advance largely as a result of the use of these external devices. A thorough understanding of the biomechanical principles of external fixation is useful for all orthopedic surgeons as most will have to occasionally mount a fixator throughout their career. In this review, various types of external fixators and their common clinical applications are described with a focus on unilateral and circular frames. The biomechanical principles that govern bony and fixator stability are reviewed as well as the recommended techniques for applying external fixators to maximize stability. Additionally, we have illustrated methods for managing patients while they are in the external frames to facilitate function and shorten treatment duration

Mathematical Modeling in Wound Healing, Bone Regeneration and Tissue Engineering

The processes of wound healing and bone regeneration and problems in tissue engineering have been an active area for mathematical modeling in the last decade. Here we review a selection of recent models which aim at deriving strategies for improved healing. In wound healing, the models have particularly focused on the inflammatory response in order to improve the healing of chronic wound. For bone regeneration, the mathematical models have been applied to design optimal and new treatment strategies for normal and specific cases of impaired fracture healing. For the field of tissue engineering, we focus on mathematical models that analyze the interplay between cells and their biochemical cues within the scaffold to ensure optimal nutrient transport and maximal tissue production. Finally, we briefly comment on numerical issues arising from simulations of these mathematical models