Histomorphometric and angiographic analysis of bone healing in the humerus of pigeons.

OBJECTIVE

To evaluate the vascular supply and quantitatively compare the periosteal and endosteal callus formed during fracture healing.

DESIGN

36 pigeons were allotted to 2 groups. In each bird, 1 humerus was surgically osteotomized. The wing with the fractured humerus in birds of the first group was infused with a microparticle barium solution, and the humerus was harvested for angiography. Pigeons of the second group were injected with the labels oxytetracycline and calcein. The fractured humerus in each of these birds was harvested for histomorphometry.

ANIMALS

36 nine-month-old pigeons, consisting of 19 male and 17 female birds.

PROCEDURE

1 humerus from each of the 36 pigeons was osteotomized in the center of the bone by use of an obstetrical wire. All fractured wings were placed in a figure-of-8 bandage after surgery. The specimens harvested for angiography were decalcified, radiographed, and sectioned for H&E-stained tissue slides. Humeruses harvested for histomorphometry were cross-sectioned for tissue slides, which were measured, using a morphometric analyzing system for original and new bone areas.

RESULTS

A continuous intramedullary circulation was not present at any point in the healing process, although 2 of the 42-day-old fractures had a bridging callus. Quantitatively, the periosteal surface formed the largest amount of callus, though the endosteal surface was also active.

CONCLUSIONS

Reformation of the intramedullary circulation may not be imperative for osseous union of the pigeon humerus. Fluorochrome labels cannot be accurately measured at the fracture site. However, subjective evaluation of the endosteal surface indicates it is active during the fracture-healing process even though the periosteal surface provides the largest amount of callus formation.

CLINICAL RELEVANCE

Figure-of-8 coaptation is contra-indicated for humeral fractures. The endosteal surface's contribution to the healing process should be considered when avian humeral fractures are stabilized.