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The fractures of the metacarpals that are unstable tend to be spiral or oblique fractures. When they are unstable they either cause shortening bone and therefore shortening of the respective digits and they may also cause rotation. If there is rotation of the bone then it may cause overlapping of the fingers when the patient makes a fist and this can be very debilitating and irritating.
General or regional anaesthetic.
An incision is made over the metacarpal in the line of the bone and the tendons. The tendons are retracted and the bone is exposed. We try to take as little of the periosteum (the membrane covering the bone), away as possible but we have to clear the membrane from the fracture site itself. When the fracture site itself is clean we can then put the two ends of the bone together and these should fit accurately very similar to a jigsaw. When the bone ends have been aligned these are generally held with a clamp of sort and the bone is held with some form of internal fixation.
There are three types of internal fixation:
- Intermedullary wires - the metacarpals are the long bones of the hand and as with any long bones such as a femur (thigh bone) or tibia (shin bones) these bones are like long tubes with a hard outer core and in the middle is the bone marrow which is called the medullary cavity. The medullary cavity is full of soft bone and it is very easy to introduce a pin well under the bone and pass it all the way along the bone across the fracture to hold the fracture as an internal splint. The insertions of these pins can be either at the base of the bone or at the knuckle end of the bone. Generally it is advantageous to have two pins rather than one if feasible.
- Simple screw fixation - this involves passing a screw at 90° to the fracture site in order to hold it rigid, usually 2 or 3 of these are used and a fairly rigid fixation is performed and this involves very little metal work and this has huge advantages in that firstly doesn't need to be removed and secondly tendons and soft tissues don't get stuck to the screws as much as they do to plates.
- Plate fixation - normally these are tiny plates that are placed over the fracture site and screws are inserted into the bone either side of the fracture generally two screws are used in the hand. They are placed over the periosteum and the plate is used as a form of internal splint to hold the fracture. The wound is then closed hopefully getting some of the periosteum over the plate or screws if at all possible to reduce the adhesions or sticking of the tendons. The skin is closed.
The patient has a plaster of Paris in the position of function for two weeks and is sent home in a high arm sling for a week. At two weeks the plaster is removed and the stitches are removed and physiotherapy commences. Time off work 2- 4 weeks.
- Infection. The operation has a chance of infection but if metal work is inserted into the wound then the infection rate rises. Although infection rate in the hand is small probably less than 1%.
- Tendon adhesions. Which means that the fingers may end up a little stiff and sometimes the joints will not completely move because the tendons are stuck and this may warrant further surgery in the form of a tenolysis (which is an operation to free the tendons).
- Metal work removal. If a plate is inserted it doesn't have to be removed but if it causes trouble or becomes very subcutaneous and the patient knocks it they become painful and the patient may want it removed.
- Complex regional pain syndrome. A rare complication
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