Highlights
- •The progression of periosteal callus formation was quantified from weekly radiographs of long bone healing in a sheep model.
- •Under controlled fixation, bony callus had formed adjacent to the osteotomy site by two weeks, and grew outwards.
- •Although contrary to a common view of healing patterns, this is consistent with a role for bony callus in reducing interfragmentary strain.
Abstract
Long bone fractures typically heal via formation of an external callus, which helps
stabilise the bone fragments. Callus composition and morphology influence the mechanical
environment, which in turn regulates the progression of healing. Therefore characterising
callus development over time is crucial in understanding this mechanobiological regulation.
Although bony callus is often assumed to grow towards the fracture from either side,
this is not consistent with observations from large animal studies and clinical cases.
Therefore, we sought to quantify the morphology of bony callus over time in a large
animal model.
Sheep tibiae were x-rayed weekly over eight weeks following an osteotomy (n=5), with fixation allowing up to 10% axial displacement under normal weight-bearing.
After scaling radiographs by known landmarks and normalising greyscales, bony callus
boundaries were defined by manual segmentation. The lateral callus area and coordinates
of its centroid were calculated from each image.
The external callus initially formed adjacent to the osteotomy site. Over the first
four weeks, callus growth from its outer surfaces was characterised by its centre
of area moving outwards and away from the osteotomy, on both proximal and distal fragments.
Subsequent weeks showed consolidation and resorption from the outer surface of the
callus.
Our approach allowed bony callus development to be tracked in individuals throughout
healing. Contrary to the view that periosteal bone formation originates distant from
the fracture, our data showed bony callus adjacent to the defect from early stages,
followed by approximately concentric growth. This discrepancy highlights the need
for data specific to experimental conditions, and particularly early stages of healing,
for evaluating theoretical models of mechanical regulation.
Keywords
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Article Info
Publication History
Published online: October 18, 2020
Accepted:
October 17,
2020
Received in revised form:
October 9,
2020
Received:
August 1,
2020
Identification
Copyright
© 2020 Elsevier Ltd. All rights reserved.
