of the metacarpal.

When this manipulation fails, the volar accessory ligament should be
divided longitudinally through a puncture made with a tenotomy knife
on the dorsal aspect of the joint, so as to separate the sesamoid
bones and permit the passage of the head between them. An open
operation is seldom necessary.

Dislocation _forward_ is rare. It results from forced flexion of the
thumb with abduction, tearing the posterior and medial collateral
ligaments. The deformity is characteristic: the rounded head of the
metacarpal projecting behind the level of the joint, while the base of
the phalanx forms a prominence among the muscles of the thenar
eminence.

Reduction is easily effected by making traction on the phalanges and
carrying out movements of flexion and extension. The deformity,
however, is liable to be reproduced unless a retentive apparatus is
securely applied.

Dislocation of the thumb to one or other side is rare.

Dislocations of the _metacarpo-phalangeal joint of the fingers_ may be
backward or forward. They are less common than those of the thumb, but
present the same general characters. In the backward variety the same
difficulty in reduction occurs as is met with in the corresponding
dislocation of the thumb, and is to be dealt with on the same lines.

_Inter-phalangeal Dislocation._--The second and the ungual phalanges
may be displaced backwards, forwards, or to the side. The clinical
features are characteristic, and the diagnosis, as well as reduction,
is easy. These dislocations are frequently the result of machinery
accidents, and being compound and difficult to render aseptic, often
necessitate amputation.

_Persistent flexion of the terminal phalanx_ of the thumb or fingers
(_drop_ or _mallet finger_) may result from violence applied to the
end of the digit when in the extended position--as, for example, in
attempting to catch a cricket-ball. The terminal phalanx is flexed
towards the palm, and the patient is unable to extend it voluntarily.
A palmar splint is applied securing extension of the distal joint for
three or four weeks. If the deformity has been allowed to occur it can
only be corrected by an open operation, suturing or tightening the
extensor tendon at its insertion into the base of the terminal
phalanx.

CHAPTER VI

INJURIES IN THE REGION OF THE PELVIS, HIP-JOINT, AND THIGH

FRACTURES OF PELVIS: _Varieties_--INJURIES IN REGION OF HIP: Surgical
anatomy; _Fr