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Dr Constantin SOKOLOW/F.I.H.S
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What is thumb dislocation ?


The term dislocation refers to complete or partial rupture of a ligament.

Ligaments are fibrous structures that keep joints stable and allow their use without undergoing deformations. In case of a serious dislocation (complete rupture of a ligament), the joint becomes unstable, and the function of the thumb is definitely altered.

The joint of the thumb, between the metacarpal and the first phalanx, has two major ligaments (ulnar collateral ligament and dorsal collateral ligament) which may suffer from trauma and even rupture. Affection of the ulnar collateral ligament (towards the second finger) is the most common one, and will be described below.

When rupture of the ulnar collateral ligament occurs, the pinch and grip function between the index and the thumb is becomes difficult and unstable. This is due to the loss of stabilisation of the metacrapophalangeal thumb joint.
Complete ruptures of the internal lateral ligament should be surgically repaired.

Which are the clinical signs ?

Ulnar collateral ligament dislocations result from trauma which abruptly tears the thumb open. It is most frequently caused by falls while skiing. A fall on the snow -with or without the poles- causes dislocation. Pain and slight swelling occur in the thumb. The examination performed by a doctor seeks collateral instability of the thumb joint. The doctor grabs the first phalanx of the thumb and performs vulgus motions (the second finger is opened). In the case of serious dislocation, the thumb may be opened abnormally with some pain.
This tests confirms ligamentous rupture; therefore, surgery is required. Owing to the pain and swelling, this test is sometimes difficult to be applied; it is the doctor's expertise that will help interpret this examination. After a few days with immobilisation, a second examination may be needed to confirm diagnosis.


Which complementary examinations are helpful ?

An AP radiograph is made, no significant fracture is observed, but sometimes there may be some minimum bone rupture at the base of the thumb which confirms the dislocation.
Radioscopy confirms lateral laxity.

How is it treated ?

1 - Non surgical treatment.

Not all dislocations need to be surgically treated. In fact, rupture of a ligament may partial, which does not destabilise the joint. In such case, orthopaedic treatment is indicated: immobilisation with a fixed plaster cast or resin to block the metacarpophalangeal joint of the thumb, with the wrist released. This immobilisation should be kept for three weeks. After removal of the immobilisation, the patient will gradually regain thumb motion, and should take care for two months. Provided motion is not spontaneously regained, a few rehabilitation sessions will be needed.



2 - Surgical treatment.

Serious dislocations (complete rupture of the ulnar collateral ligament) should be surgically treated. It does not pose an emergency situation; the patient may be temporarily immobilised . If the doctor agrees (to end his/her stay or return home) to be operated on, it is required that the operation is performed within six days to be successful.

Operative protocol :

regional anaesthesia,
ambulatory hospitalisation,
incision on the inside part of the joint, and reinsertion of the torn ligament : this reinsertion is possible as long as it is recent
immobilisation of the thumb in the postoperative period for 3-6 weeks, according to the surgeon's procedures.
rehabilitation sessions are usually required to regain fill motion of the thumb.
it is advised not to practise any sports or male any efforts with the thumb for 4 months.



Which are the risks during the development of the injury ?

Presence of the injury is ignored :

This is likely to happen due to reasons we will not death with. The patient presents difficulty using the thumb, which he/she is used to (sometimes for years). Pains are rare. When pinch and grip function is attempted, the patient cannot actually grab at the moment of grip motion.
Surgical intervention may be indicated -if it is the patient's will- to stabilise the thumb.

Two possibilities :

reconstruction of the ligament will be proposed provided the radiograph indicated that the joint is not altered. The result of this procedure is generally satisfactory.
if radiographs are indicative of an altered joint (sings of arthrosis) ; a joint block is indicated (arthrodesis) This block is definitive and the function of the hand will be perfect despite the block.

Failure of the initial treatment due to :

incorrect choice of initial therapy : immobilisation of an injury that actually required surgical treatment.
Failure to reinsert a ligament,
the protocol described above will be proposed.


Complications.
Complications may arise after any of the treatments ; thumb stiffness, algodystrophy, etc. This will require a specific treatment.

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