Fig. 54.—A. Splint applied as used by Bennett. B. Poroplastic Moulded Splint for Bennett's Fracture.
Fractures of phalanges usually result from direct violence, and on account of the superficial position of the bones, are often compound, and attended with much bruising of soft parts. Force applied to the distal end of the finger may also fracture a phalanx. The proximal phalanges are broken oftener than the others. The deformity is usually angular, with the apex towards the palm, and if union takes place in this position, the power of grasping is interfered with. Unnatural mobility and crepitus can usually be recognised, but, on account of the swelling and tenderness, the fracture is apt to be overlooked. Firm union takes place in two or three weeks. In oblique and comminuted fractures, union may take place with overlapping, producing a deformity which may prevent the wearing of a glove or of rings. In compound fractures, non-union sometimes occurs, and causes persistent disability. In doubtful cases radioscopy renders valuable aid, as the parts are readily seen with the screen.
Treatment.—Early movement and massage are all-important. The contiguous fingers may be utilised as side splints, and a long palmar splint projecting beyond the fingers is applied. In oblique and comminuted fractures it may be necessary to anæsthetise the patient to effect reduction. When it is particularly desirable to avoid deformity, an open operation may be advisable.
Dislocation.—Dislocation of the Metacarpo-phalangeal Joint of the Thumb.—The commonest dislocation at this joint is a backward displacement of the proximal phalanx, which may be complete or incomplete. Its special clinical importance lies in the fact that much difficulty is often experienced in effecting reduction.
This dislocation is usually produced by extreme dorsiflexion of the thumb, whereby the volar accessory (palmar) and the collateral ligaments are torn from their metacarpal attachments, the phalanx carrying with it the volar accessory ligament and sesamoid bones. The head of the metacarpal passes forward between the two heads of the short flexor of the thumb, and the tendon of the long flexor slips to the ulnar side. The phalanx passes on to the dorsum of the metacarpal, where it is held erect by the tension of the abductor and adductor muscles.
The attitude of the thumb is characteristic. The metacarpal is adducted, its head forming a marked prominence on the front of the thenar eminence, and the phalanges are displaced backwards, the proximal being dorsiflexed and the distal flexed towards the palm.
Many explanations of the difficulty so often experienced in reducing this variety of dislocation have been offered, but the consensus of opinion seems to be that it is due to the interposition of the volar accessory ligament and the sesamoid bones between the phalanx and the metacarpal, and that this is most frequently the result of ill-advised efforts at reduction. In some cases the tension of the long flexor tendon may be a factor in preventing reduction, but the “button-holing” by the short flexor is probably of no importance.
Reduction is to be effected by flexing and abducting the metacarpal while the phalanx is hyper-extended and pushed down towards the joint and levered over the head 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.