These findings lead to the following conclusions:
All procedures which jeopardize the superior group of arteries must be avoided.
Prostheses with a stem as narrow as possible must be used, in order to spare as many intra-osseons vessels as possible.
Reaming and shaping of the neck is a dangerous operative procedure which may result in a weakening of the area which supports the prosthesis.
Too early weight-bearing must be proscribed.
For the past twenty-eight months, we have used a new design for the prosthesis, which was made essentially for a better redistribution of pressure on the cervical stumpt; however, it has several advantages as far as vascularization is concerned:
1. The diameter of the stem is smaller.
2. The collar has been given up; therefore, shaping the neck by means of a reamer is unnecessary. Reoperations performed in earlier cases had demonstrated frequent necrosis of the area covered by acrylic.
See Image in the PDF File
3. During oblique resection of the head, the inferior medial group of arteries is left intact; its contribution to the vascular supply of both the inferior cortex and the cancellous hone of the neck has been mentioned above.
All of these factors may improve the postoperative course in the future.
FRACTIRES OF THE NECK
In fractures of the neck, the prognosis does not rest on vascular factors alone. This problem has been studied by many authors1,7,10,15, 16, 17. Most of these authors have attempted to establish more precisely the contribution of the ligamentum teres artery to the vascular supply. Their main concern was the fate of the head which has been deprived of its mail1 arterial group. The importance of the vascularization of the head should not be overlooked, but we believe that the vascular condition of the stump must also be considered.
It is now an accepted fact, confirmed by our experiments, that the blood supply through the ligamentum teres does not decrease with age; Nordenson even thinks it increases.
It is also an accepted fact that the degree of vascular damage is in proportion to the displacement of the fracture fragments. A slight forward displacement of the fractured surface certainly leaves unchanged the majority of posterior and superior vessels. The displacement itself is related to the obliquity of the fracture line. When the angle made by the fracture line with the axis of the diaphysis is4 is acute (less than 40 degrees), the displacement may be significant. When this angle is wide, the displacement is always moderate. The latter type of fracture heals more easily than the former. Thus, we are brought back to the theories developed by Pauwels, which are based upon mechanical considerations.
In all types of fractures with marked displacement, whatever the site and the direction of the fracture line, the capital fragment is deprived of most of its vascular supply and what remains is insufficient to maintain viability of bone tissue. Therefore, for nutrition and for healing, the head fragment needs vessels coming from the neck.
However, the vascularization of the neck can also be affected by the very site of the fracture.
We have pointed out that in a number of cases (20 per cent. of the specimens examined) the main arterial group of the neck issued from a bifurcation of the cervicocapital arteries; this bifurcation may even be found in the head in some cases. If such a neck is fractured—that is, if there is a subcapital fracture or a transcervical fracture close to the head—the main part of the superior arterial group, as well as the medial inferior group, is destroyed. The only arteries remaining are the two or three belonging to the superior group which penerate the neck proximal to the trochanter, coursing toward the diaphysis.
Thus, a major part of the neck will be lacking in normal vascularization and, when the fracture has been reduced and nailed, both contacting fragments will be poorly vascularized (Fig. 18). In such a case, it is evident that, if the reduction of the fracture is not perfect, if immobilization is not complete, and if weight-bearing is started too early, all of these factors will result in a pseudarthrosis with resorption of the neck.
However, sometimes such fractures do heal, because of revascularization, first of the neck, and then of the head. This involves two processes: First, creeping substitution, described by Phemister and recently demonstrated experimentally by Tovee. This, however, requires perfect reduction and strict and prolonged immobilization. The second process is that of peripheral vascularization. This may occur even with an imperfect reduction, but vascularization remains abnormal; such abnormal vascularization results in deformities of the head, which remains poorly nourished in its center and is unexpectedly bordered by hypervascularized osteophytes (Figs. 19-A and 19-B).
Such factors might be the explanation for certain cases of shortening of the neck and for some pseudarthroses which occur even after proper treatment.
Finally, the case of fractures at the base of the neck, in which the fracture line follows the capsular insertion, is different. Such fractures heal badly, probably because they interrupt most of the arterial supply of the neck which will have to re-form later.