The Journal of Bone and Joint Surgery, Vol 62, Issue 6 964-973, Copyright © 1980 by Journal of Bone and Joint Surgery, Inc
Changes in tissue morphology and collagen composition during the repair of cortical bone in the adult chicken
MJ Glimcher, F Shapiro, RD Ellis and DR Eyre
An animal model was developed to study the histology and collagen chemistry
of healing cortical bone. A hole was cut through the cortex of the
mid-shaft of the humerus of the adult chicken, which allowed for repair at
a mechanically stable site. After one to two weeks the collagen of the
repair tissue, which consisted principally of woven bone, contained almost
three times as much hydroxylysine as the collagen of normal adult bone and
thus resembled the collagen of embryonic long bones. By eight weeks, when
lamellar one predominated, the hydroxylysine content had fallen to normal
levels. Type I was the major genetic type of collagen present throughout.
No type-II collagen, characteristic of cartilage, was detected; this was
consistent with the histological findings. The results established that
hydroxylysine-rich type-I collagen can be made by osteoblasts of adult
animals as well as by those of embryos and early postnates. Clinical
relevance: In order to understand the biological characteristics of
fracture healing, it is vital to study not only the macroscopic
organization of the repair tissue but also the chemical properties of its
molecular components. The strength of healing fractured bone, and indeed of
normal bone, depends largely on the properties of the structural protein
collagen. To date, it is not known whether the collagen in healing
fractures is the same as that in normal bone, or whether it has distinct
chemical features that may suit it for bone repair.