Bennett’s dislocation is an uncommon injury that affects the first metacarpal. It usually occurs in males aged between 15 and 45 and is caused by the fist impacting an object with the thumb bent, a fall on the radial edge of the hand or car and cycling accidents.
Its treatment is highly complicated due to the various complications that can occur: instability, stiffness, malunion, tendon adhesions and significant functional limitation, among others.
Treatment of Bennett’s dislocation
A direct blow to a flexed thumb can cause Bennett’s dislocation. This leads to severe pain, weakness of the thumb, lack of alignment and movement difficulties. In addition, the base of the thumb and back of the hand often become inflamed and bruises appear.
Bennett’s dislocation treatment is complicated because of its location: the trapeziometacarpal joint. This is where the thumb makes its most important movements.
When a Bennett’s fracture occurs, oblique at the base of the first metacarpal, it breaks into two fragments. One small, wedge-shaped and intraarticular, which remains in place as it is attached to the trapezium. The other fragment is the remainder of the metacarpal and moves backwards, upwards and outwards.
Since it is an intraarticular injury, it is very unstable. This instability is what makes Bennett’s dislocation complicated to treat. It cannot be reduced conservatively because, when the fracture occurs, a space forms between the fragments which usually fills with a callus. This causes a number of abnormalities that make injuries easily appear in the area. In addition, the deformity that appears leads to osteoporosis.
Techniques for reducing Bennett’s fracture
There are several techniques for reducing Bennett’s fracture. One of them is use of an orthosis, such as Orliman’s wrist immobilisation splint (in dorsiflexion) with thumb support. This orthosis enables metacarpophalangeal immobilisation of the thumb, while the rest of the fingers remain free. This reduces pain and oedema and prevents tendon retraction.
Orthoses immobilise the area of the Bennett’s dislocation.
If the orthosis does not work, it is necessary to resort to surgery or osteosynthesis. Osteosynthesis is a surgical procedure for treating fractures, in which they are reduced and fixed in a stable way. In the case of Bennett’s dislocation, screws or Kirschner wires are used.
In either case, orthosis or surgery, the joint needs to be immobilised for between four and six weeks for correct recovery from Bennett’s dislocation and to prevent possible after-effects, such as early osteoarthritis, weakness in grasping movements and chronic pain. In addition, stretching and strengthening exercises are necessary to improve the strength of the muscles of the hand and re-educate the muscles to recover the use of the thumb and hand.