R L Meeson
The influence of gap size on the development of fracture union with a micro external fixator
Meeson, R L; Moazen, M; Sanghani-Keri, A; Osagie-Clouard, L; Coathup, M; Blunn, G
Increasingly, the rat femoral fracture model is being used for preclinical investigations of fracture healing, however, the effect of gap size and its influence on mechanobiology is not well understood. We aimed to evaluate the influence of osteotomy gap on osteotomy healing between the previously published extremes of guaranteed union (0.5 mm) and non-union (3 mm) using this model.
A femoral osteotomy in 12–14 week old female Wistar rats was stabilised with a micro fixator (titanium blocks, carbon fiber bars) with an osteotomy gap of 1.0 mm (n = 5), 1.5 mm (n = 7), 2.0 mm (n = 6). After five weeks, the left femur was retrieved. The osteotomy gap was scanned using X-ray microtomography and then histologically evaluated. The radiographic union rate (complete mineralised bone bridging across the osteotomy) was three times higher for the 1.0 mm than the 2.0 mm gap. The 1.0 mm gap had the largest callus (0.069μm3) and bone volume (0.035μm3). Callus and bone volume were approximately 50% smaller within the 2.0 mm gap.
Using cadaveric rat femurs stabilised with the external fixator, day 0 mechanical assessment of construct stiffness was calculated on materials testing machine displacement vs load output. The construct stiffness for the 1.0, 1.5 and 2.0 mm gaps was 32.6 ± 5.4, 32.5 ± 2.4, and 32.4 ± 8.3 N/mm (p = 0.779). Interfragmentary strain (IFS) was calculated using the change in osteotomy gap displacement as measured using microstrain miniature differential reluctance transducer spanning the osteotomy gap. Increasing the gap size significantly reduced the IFS (p = 0.013). The mean ‘day 0’ IFS for the 1.0, 1.5 and 2.0 mm gaps were 11.2 ± 1.3, 8.4 ± 1.5 and 6.1 ± 1.2% respectively.
A 1.5 mm gap resulted in a delayed fracture healing by 5 weeks and may represent a useful test environment for fracture healing therapy. Increasing gap size did not affect construct stiffness, but did reduce the ‘day 0’ IFS, with a doubling of non-union and halving of bone volume measured between 1.0 and 2.0 mm gaps.
Meeson, R. L., Moazen, M., Sanghani-Keri, A., Osagie-Clouard, L., Coathup, M., & Blunn, G. (2019). The influence of gap size on the development of fracture union with a micro external fixator. Journal of the Mechanical Behavior of Biomedical Materials, 99, 161-168. https://doi.org/10.1016/j.jmbbm.2019.07.015
|Journal Article Type||Article|
|Acceptance Date||Jul 18, 2019|
|Publication Date||Jul 19, 2019|
|Deposit Date||Jul 25, 2019|
|Publicly Available Date||Nov 20, 2020|
|Journal||Journal of the Mechanical Behavior of Biomedical Materials|
|Peer Reviewed||Peer Reviewed|
You might also like
Traumatic physeal fractures in cats: a review of 36 cases (2010–2020)