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Four Corner Fusion

Four corner fusion is for the treatment for SLAC or SNAC wrist arthritis(ref). It is essentially making the wrist into a ball and socket joint. It is a partial wrist fusion and is an operation for significant wrist pain. Instead of making the wrist totally stiff as one would do with a total wrist fusion by performing a partial or four corner wrist fusion this enables some range of movement. It is likely that the operation will leave 50% of normal wrist range of movement. It does rely on the integrity of the cartilage on part of the surface of the end of the distal radius (which is the long bone on the thumb side of the forearm) and this operation is therefore quite often preceded by a wrist arthroscopy to ascertain this information. It involves removing the scaphoid bone and fusing four of the remaining bones of the wrist, capitate, lunate, triquetral and hamate.

ANAESTHETIC

General or regional anaesthetic.

OPERATIVE PROCEDURE

There is a 10cm incision made over the middle of the back of the wrist. The wrist joint is opened, the scaphoid is excised. Generally it is quite difficult to remove the scaphoid and it has to be removed piece meal, rather than excising it as one bone. A dental bur is then used to decorticate (remove hard bone down to marrow bone) the joints between the capitate and the hamate, the capitate and the lunate, triquetrum and the lunate. A bone graft is then taken from the radius bone and also often using the scaphoid remnants, placed in the joints that have been previously burred out and a form of screw fixation is used to hold the four bones. This can done by using simple wire or blue cross screws, or there are round screws that can be used on the back of a joint. The skin is closed with nylon. If there is not enough bone cartilage then bone may need to be taken from the hip (this is not the hip joint itself it is from the part of your pelvis on which you hang your trousers).

POST OPERATIVELY

There is a half cast applied and the hand is elevated over night and the patient is given antibiotics as a prophylactic against infection. The patient goes home in a high arm sling and seen at two weeks for removal of the half plaster and removal of stitches and then a further plaster applied for a period of eight to twelve weeks.

COMPLICATIONS

  1. Infection - the chances of this are 1 - 2%
  2. Failure of fusion, possible in 5% of cases in which case a further operation may be necessary.
  3. Restricted range of movement. Generally the operation results in 50% loss of range of movement but it may be more.
  4. Bad reaction to surgery. This occurs in between 1% and 5% of cases. This is called complex regional pain syndrome, or complex regional pain syndrome type 1 or algodystrophy