Dr Patrick HOUVET/F.I.H.S

What does a serious carpal dislocation involve ?

The osteo-articular complex of the wrist involves :

the radial cavity,
The carpal group made up of eight bones which may be classified in two rows: proximal and distal.

The 33 ligaments of the articular carpal complex may be grouped into :
intracapsular ligaments, which can be divided into two groups :
palmar intracapsular ligaments.
dorsal intracapsular ligaments, relatively thin.
interosseous ligaments, among them, they link the bones of one same row : the scapholunate and perilunate interosseous ligaments are powerful ligaments that have a close relationship among these three bones. Therefore, movements will always be performed in one direction, even though they are not always the same degree

Mobility of the carpal bones is coherent and co-ordinated :

in dorsal flexion, the semilunate and the capitate move backwards, and the scaphoid moves upwards. The opposite movements occur in palmar flexion.

in radial inclination, the scaphoid moves horizontally ; inversely, in cubital, it moves vertically.

the carpal bones of the first row move together backwards and forwards. However, an additional shear flow is produced at the scapholunate space.

the loss of the scapholunate coupling occurs due to a palmar swing of the scaphoid, which moves horizontally, together with a swing of the dorsal lunate in flexion.

Ligament injuries may be isolated, but they are often accompanied by oseoarticular injuries. The impaction component with cartilage involvement aggravates the prognosis. (styloid radial impaction, fracture-depression isolated from the surface of the radius (dye punch fracture).

Which are the clinical signs ?

L'histoire clinique est celle d'un adulte jeune, victime d'une chute violente au cours d'un exercice sportif, poignet en hyper-extension. Apres une période douloureuse de durée variable en fonction de l'éventuelle immobilisation, le poignet reprend sa fonction... pour une durée variable.
C'est donc souvent un traumatisme négligé par le patient ou son interlocuteur médical et l'interrogatoire ultérieur retrouvera la notion d' "entorse".

Le diagnostic est alors difficile devant un poignet douloureux chronique pour lequel les exercices de force et la pratique sportive sont devenus progressivement impossibles.
La douleur est postéro-externe, retrouvée à l'examen au niveau de l'interligne scapho- lunaire avec parfois un oedème et une tuméfaction synoviale localisée.

There are two helpful manoeuvres that may be performed :

the ballottement test
Watson's manoeuvre, which involves application of pressure on the scaphoid at the level its tuberosity, and performs cubital to radial deviation of the wrist
Dans le mouvement physiologique le scaphoïde se couche réguliérement et progressivement.

During physiological movements, the scaphoid moves down regularly and progressively. In the case of a scapholunate injury, the lunate moves progressively, but the scaphoid remains straightened as a result of the application of pressure performed by the examiner.

Besides a certain radial position, the scaphoid, -under the pressure of the trapezium and trapezoid- cannot remains straightened and moves down abruptly. This rough flexion causes abrupt and painful avulsion. This pathological instability, found by means of the Watson's test, is responsible for the spurs and pains exhibited by the patient.

Progressively patients will complain about pain in the wrist, together with the feeling of bony spurs when the wrist is used for a long time.
Mobility may be reduced when an interval -between movements- lasts quite long. After several years, the complaint is due to painful stiffness.

Which complementary examinations are helpful ?

Both dynamic or standard radiographs are not indicative of any abnormality, the carpal position is not disrupted.

Complementary examinations involve invasive imaging :

arthrography may reveal a tuberosity at the level of the scapholunate ligament.
arthroscanner is very effective, as it allows to measure the significance of the sprain, observe the presence of ligamentous stumps, and eventually find an associated osteochondral fracture.



IRM is not helpful at the time.
arthroscopy is helpful as injuries are clearly visible. Later, the scaphoid is no longer capable of cubital positioning and extension. The lunate takes its physiological position, that is dorsal inclination, where the thinnest posterior cornea lies.
Therefore, there is anterior displacement of the scaphoid , and inverse dorsal displacement of the lunate. This aspect -DISI deformity- may be observed in a strict anterior view.
At this stage, the complete dissociation between the scaphoid and the lunate results in a scapholunate diastasis superior to 3mm (Terry Thomas sign)
The scaphoid remains laid down and shows its distal base, this is the Ring-sign or "le signe de l'anneau".



This scapholunate instability -functionally uncomfortable- develops in a relatively long time into radio-scaphoid and later intercarpal arthrosis : this is Watson's SLAC Wrist.
The radiolunate interval remains intact for a long time, but injuries at the head of the capitate occur.
If untreated, development leads pan-carpal arthrosis. In this case the diagnosis is established upon plain anterior/posterior radiographs. Performance of complicated examinations is not helpful for the diagnosis. It should only be observed that the intervals remain healthy to recommend an adequate treatment as we will see below.

Which are the possible treatments ?

At an early stage, when the diagnosis is established in an emergency, it is possible to prescribe an effective and conservative treatment.
The ligament is torn away from the scaphoid removing also cartilage fragment or leaving a stump attached.
The ligament may be reinserted through transosseous suture or an anchor graft.
Suture should be protected by screwing and a plaster cast for two months.
In the late stages, in case of an symptomatic chronically painful wrist, indications are given according to the significance of the symptomatology and the field. In case of discrete dynamic instability, conservative treatment may be indicated. Arthrostopy may be suggested which, apart for lavage and drebidement, allows to observe the ligamentous conditions as well as the joint surfaces. Surgery is imperative in case asymptomatic patients require it, or due to major instability.

anatomical repair provides reduction of instability is possible, and the ligamentous stump may still be sutured.

ligamentoplasties require meticulous performance, and they fail with time.

transposition of a free fragment, bone-ligament-bone, according to the A-P Weiss or Cueno, are technically difficult, but probably the most helpful. At a terminal stage or arthrosis, therapeutic indication depends on the cartilage joint surfaces still intact.

if the radio ulnar interval remains always intact, and if the head of the capitate is satisfactory, resection of the first row of carpal bones allows to have a painless wrist, keeping postoperative mobility and considerable strength.

in case of injury of the capitate head, the only possibility is arthrodesis of the 4 internal bones, with ablation of the scaphoid.

in case of developed arthrosis, involving all the wrist intervals, only pan-carpal arthordesis will allow to eliminate pain.

Which are the risks during recovery ?

Natural history of scapholunate ligament rupture is currently well known.
After a difficult initial period, things stabilise but then, they gradually aggravate leading, in a relatively long time, to radioscaphoid and later intercarpal arthrodesis : this is Watson's SLAC wrist.

Early diagnosis is imperative, for it is ensures the best result.

Surgical interventions often leave a little bit of stiffness on flexion-extension.
It should be considered that there is risk of re-rupture after anatomical reparation of the ligament, above all is it is performed at a late stage, with trauma of a low quality stump.