A STUDY ON THE HEALING OF FRACTURE

-A Tracing Study Performed by Utilizing Tetracycline Labelling, Microradiography and Microangiography-

Abstract

Purpose : Although fractures of bones have been studied extensively and actively, there is as yet no definite view concerning their mechanism of healing and opinions are conflicting in this regard. In view of this the author conducted an experiment on 2 groups of rats with experimental fracture of the femur and both comparison of healing process between the groups and the follow-up study mainly of ossification process by the use of tetracycline (Achromycin®) as a bone seeker were performed.
Method : Adult female rats with manually produced subcutaneous fracture of the femur were either left untreated (Group 1) or subjected to intramedullary fixation with kirschner wire (Group 2) and subsequently observed for the time course of healing of the fracture over a 8-week period. In each group five animals were assigned to examine every week, the animals used thus numbering 80. After being sacrificed they were performed on microangiography (after Ogawa) . Three animals of each of the five were pretreated with, 50 mg/kg TC i, p. 24 hours prior to their sacrifice ; after they received the angiography as mentioned above, bone specimens were taken from them and, were subject upon grinding, to both fluorescence microscopy and contact-microradiography.
Results ; In Group 1, excessive callus formation was noted at the site of displacement on the 4 th to 5 th week ; on the 6 th week and thereafter, its resorption was prominent and predominated, giving thus the appearance of pseudoarthrosis. In Group 2 there was an excessive callus formation noted at the fractured site for the period from the 4 th to 5 th week similarly as in Group 1, which, however, was followed by both resorption and consolidation leading to an earlier healing. The difference in the healing process noted between both groups was related to biophysical factors (i. e., the degree of rest and immobilization achieved of the affected part) . Despite serious destruction of bone marrow tissues, involving blood vessels supplying them, caused by the insertion of a solid wire into the marrow space, the fact that cure was attained earlier in Group 1 provides evidence, both angiological and histological, in support of the theory claiming that the mesenchyma which has long been believed to play an important role in the healing of fracture originates from the periosteum.
The present study utilizing TC labelling and microradiography demonstrated that bony callus derives from the deeper layer of the periosteum and that TC is incorporated in ossifying tissues (though failed to clarify the mechanism whereby this is accomplished), confirming thus the necessity of employing both procedures concurrently.
The performance of angiography, in addition to the aforementioned 2 procedures, permitted to investigate more closely the utilization by bone tissues of TC as a bone seeker and thereby to obtain valuable informations on the formation and absorption of a bony substance. This combination of investigative procedures, being entirely safe unlike the conventional methods utilizing radioisotope or alizarin red, easy to use and moreover inexpensive, will certainly find a wide clinical use.