11. Most of the symptoms formerly mentioned (5 and 6) as accompanying a
fracture of the clavicle, are evidently the result of a displacement of
its broken ends. Yet this phenomenon, taken notice of by all authors,
and considered by them as a necessary effect of the disease, does not
occur in every case (8). There are instances, in cases of transverse
fractures, where the extremity attached to the shoulder, has retained
its natural position. Three examples of this kind occurred in the
Hotel-Dieu in the course of the year 1787.
12. Instances have also been known, in which the sternal fragment, when
fractured obliquely upwards, has supported the end of the humeral in
such a manner as to prevent any derangement. Desault was accustomed
to relate several cases, where similar occurrences took place; but,
in general, this state of things is rare, in comparison with that in
which the fragments lose their natural level.
Almost always, then, there is more or less of a perceptible overlapping
(_chevauchement_) produced, either, by the elevation (a circumstance
which is very rare) of the external fragment over the internal; or, (as
commonly occurs) by the depression of the former beneath the latter.
13. Of the first of these modes of displacement (a mode but rarely
mentioned by authors) a few examples are to be found among the
observations of Desault, one of which he has recorded in his journal.
Hippocrates speaks of the phenomenon as a thing that was familiar to
him.
14. The second kind of displacement, that which we constantly find
in practice, and which the laws of muscular action render almost
inevitable, takes place in such a manner that the shoulder appears
to obey the impulse of two powers, one of which draws it downwards,
and along with it the external fragment of the clavicle, which is
displaced by this power in the direction of its transverse diameter, or
thickness. The other power approximates the shoulder to the breast, and
draws it forward, carrying along with it the same fragment, which is by
this means displaced in a longitudinal direction.
That we may the better understand them and their effects, let us, in
our minds, separate these two powers, although they are perfectly
simultaneous in their action. A knowledge of them will lead us to a
knowledge of the resistances which ought to be opposed to them. But let
us first remark, that the humeral fragment, being drawn downward and
inward, takes sometimes such a direction, that its internal extremity
passes backward under the sternal fragment, its external end continuing
to point forward: this disposition can be understood from its natural
direction.
15. The first of these powers, namely, that which depresses the point
of the shoulder, appears to have escaped the notice of the ancient
physicians of Greece, who attributed the apparent depression of this
part, to the elevation of the sternal fragment, and, accordingly,
endeavoured by making compression on the latter, to restore it to
a level with the other. Hippocrates, more judicious than those who
had preceded him, demonstrated that their doctrine, false in its
principles, was still more dangerous in its consequences, and that
the sternal fragment being immoveable, lost its relative position
with respect to the humeral, only because the latter was depressed
by the weight of the arm. This doctrine of the father of physic is
satisfactorily proved, by a comparison of the sound shoulder with
the diseased one, and has since been admitted by all practitioners.
Indeed, the mere recollection that one of the uses of the clavicle is
to support the shoulder at that level necessary for the performance of
its functions, is alone sufficient to convince us, that, in case of its
ceasing to fulfil that office, the shoulder must obey the laws of its
own gravity, increased by that of the hand and arm.
16. The illustrious Petit, and with him Duverney, in acknowledging this
cause of displacement, have added to it as another the action of the
deltoid muscle on the external end of the bone; in this action, the
end of the clavicle is the moveable point, while the humerus affords
the fixed point. But how can we admit this cause, when the humeral
fragment, in passing under the sternal, moves in a backward direction?
So far is the deltoid muscle from drawing the bone downward, that here
the bone rather draws the muscle in part backward, and yet, in such a
case, the displacement is as perceptible as in any other. Besides, when
the sternal fragment, broken obliquely upwards, supports the humeral
and prevents a displacement, why does not the deltoid produce this
displacement?
It is then in the weight of the arm and shoulder alone, that we must
look for the passive power, which depresses them, and which produces a
displacement in the direction of the transverse diameter or thickness
of the clavicle.
17. A second power, highly active, co-operates with this. I allude to
the permanent contraction of the muscles, that extend from the breast
to the clavicle and shoulder: from this cause arises the displacement
in the longitudinal direction of the bone.
The pectoralis major, the pectoralis minor, the subclavius, the
serratus major, and the trapezius, unite their efforts in producing
this displacement. These muscles are, in certain respects, antagonists
to each other, but they all unite in drawing the shoulder forward
and inward. None of them appears to act with more effect than the
pectoralis major. To this, in particular, is to be attributed the
displacement in a forward direction.
Except in the instances stated above, the action of the muscles is not
immediate. They act only secondarily on the external fragment, which,
being stedfastly attached to the scapula and humerus, is obedient to
the motions impressed by the muscles on these two bones; motions which,
in a sound state, the clavicle has a power of controlling.
18. To the weight of the lower extremity (15 and 16), and the
spontaneous action of the muscles (17) must be added, as another cause
of displacement, the motions which are communicated to the arm by
external bodies, and which, being imparted ultimately to the clavicle,
derange the fragments, by separating them, approximating them, or
making them overlap each other, according to the direction in which
they act.
19. When a fracture occurs at the extremity next the shoulder, no
displacement of the fragments in general takes place. This circumstance
is attributed to the action of the trapezius, which draws each fragment
upwards with equal force. However this may be, it is doubtless to such
cases that we must refer the complete cures, obtained without any
retentive apparatus, by Gasparetti, Brown, and other writers. Hence
also, without doubt, arise the difficulties experienced by certain
practitioners, such as Duverney, with respect to the diagnosis of this
disease. These fractures may be mistaken for fractures of the acromion,
being situated so immediately in its vicinity.
§ VI.