5. The superficial situation of the tendo Achillis, always renders
the diagnosis of its division easy. It can be rendered difficult
only by the occurrence of a considerable swelling, an accident that
rarely happens. If there be an external wound, the depth to which the
instrument has penetrated, and the possibility of sometimes feeling
the ends of the tendon between the edges of the wound, are the first
evidences of its division. If, on the other hand, the tendon be only
ruptured, then at the moment when the rupture happens, a report is
heard by the patient, not sharp, and like the crack of a whip, as is
said to take place when the plantaris muscle is ruptured, but more dull
and flat, according to the account given to Desault by a patient, whom
he interrogated on the subject.
6. In either case, there occurs suddenly, if not an entire inability,
at least, an extreme difficulty in either standing or walking: hence
the patient falls, and is unable to rise again; but, in divisions that
are only partial or incomplete (4), this sign does not occur. Between
the divided ends of the tendon there exists a depression sensible to
the touch. This depression is increased by the flexion of the foot, but
diminished and even entirely removed by its extension.
7. The patient can spontaneously flex the foot, none of the flexor
muscles being affected, and this flexion may be carried even beyond
what is natural, because the divided tendon forms no obstacle to it
behind. Spontaneous extension is also practicable, in as much as the
peroneus longus, tibialis posticus, &c. which remain uninjured, are
capable of producing that motion. Some have alleged that the calf of
the leg must be increased in size by the swelling of the gastrocnemii
and soleus muscles, in consequence of their state of contraction; but
modern experience has shown, that there is but little reliance to be
placed on that appearance.
§ III.