Intramembranous bone formation after callus distraction is augmented by increasing axial compressive strain

Abstract

The mechanical environment is a primary factor in the success of distraction osteogenesis. It is known that the interfragmentary movement during the distraction and maturation phase effects the callus formation. In addition to cyclic compression, other movements like shear and bending influence the bone formation process as shown in previous callus distraction studies. Reports of cartilage presence and endochondral ossification in the regenerative zone have been associated with a lack of fixation stability and delayed healing. So far the effects of the direction of interfragmentary movements could not be studied separately. By means of a unique lateral callus distraction model, we investigated the effects of small (0.1 mm) and moderate (0.6 mm), purely axial compression on ossification during callus maturation in sheep. A distraction device incorporating a mobile titanium plate was mounted on the tibia. Following lateral callus distraction, electromechanically controlled movements allowed purely axial cyclic compression of the tissue regenerate. Seven weeks post-operatively, the tissue regenerates were investigated using μCT, histology and immunohistochemistry. The larger amplitude significantly increased bone formation (Fractional bone volume: 19.4% vs. 5.2%, p = 0.03; trabecular thickness: 0.1 mm vs. 0.06 mm, p = 0.006; mean spicule height: 2.6 mm vs. 1.1 mm, p = 0.02) however, no endochondral ossification occurred. The elimination of shear movement, unimpaired neovascularization as well as the tensile strain stimuli during the distraction phase suppressing chondrogenic differentiation may all contribute to the absence of cartilage. In clinical application of distraction osteogenesis, moderate axial interfragmentary movement augments intramembranous ossification provided shear strain is minimized.

The mode of interfragmentary movement affects bone formation and revascularization after callus distraction

“…The compressive strain resulting from the chosen cyclic movement in this lateral callus distraction study falls within this strain range (> 16% at the beginning and < 50% at the end of stimulation). Therefore, it is not surprising that under this 0.6 mm cyclic compression significantly more bone was formed than under 0.1 mm movement as shown in our previous study [ 19 ]. Under the very small cyclic compressive movement (0.1 mm), comparable with a very stable fixation during callus distraction and maturation (< 5% interfragmentary strain), only a small amount of intramembranous bone was formed in the same experimental model [ 19 ].…”

“…The sheep showed no marked signs of pain or discomfort during manipulations. The data of Group C were already published previously and served as a basis for comparison in this publication [ 19 ].…”

“…B) Blood vessel density in the newly formed bone after cyclic compression, tensile and shear stimulation (* p<0.01). The compression data are already published in [ 19 ] and shown for comparison.…”

Woven bone overview: structural classification based on its integral role in developmental, repair and pathological bone formation throughout vertebrate groups

“…Woven bone initiated repair, was elongated along the longitudinal axis with distraction and served as a scaffold for SOBLs forming trabecular and cortical bone ( Fig. 9a-e) (Schuelke et al, 2018).…”

Comment to the Article „«Ischemic» Distraction Regenerate: Interpretation, Definition, Problems and Solutions

“…одномоментная, или дискретная, компрессия на уровне гипотрофического или «ишемического регенерата» описана как вариант решения проблемы, но применяется в отдельных случаях [6,7]. Благоприятное влияние осевой компрессии на костеобразование подтверждается и в экспериментальных работах [8,9]. но группы во всех исследованиях малочисленны, как и у авторов статьи, что не позволяет четко сравнить этот метод с другими хирургическими подходами.…”