Dislocation refers to a displacement of one articular surface relative to another, resulting in an interruption of joint continuity. Although it is often caused by a traumait can also result from a ligament hyperlaxity. Typically, dislocation causes pain and limits movement usual joint. It’s what a dislocation? Is a dislocation severe ? How to treat it?

Definition: what is a dislocation?

dislocation means a displacement of one articular surface vis-à-vis another, thus operating a break in joint continuity. Often caused by trauma, it can also result from ligament hyperlaxity, which does not hold the joint properly or allows too much joint play. The dislocation usually causes pain, and prevents normal joint movement. She is sometimes accompanied by a torn ligament. Both articular surfaces must be quickly put back in place. The dislocations of shoulder, elbow, patella, hip, finger or even of the jaw are quite common. The dislocation can take on an impressive character depending on its seat, in particular the shoulder.

What is the difference between dislocation and subluxation?

A subluxation East an incomplete dislocation characterized by the displacement of only one of the two bones composing a joint. “In the event of a subluxation, the joint is no longer correctly aligned and the loss of contact between the articular surfaces is only partial (unlike a dislocation), the joint returning without outside help to the correct position.“, explains Dr. Michael Mangin, orthopedic surgeon. Subluxations are frequent in hypermobile people because their ligaments do not perform their joint maintenance function well. Subluxations can involve any joint whether it is the jaw, fingers, elbow, hip, knee or ankle for example.

What are the types of dislocation?

The most frequent dislocations are those of the shoulder and the knee, but the hip, fingers, jaw and elbow are also areas often affected.

► The shoulder dislocation is damage to the shoulder joint. “It corresponds to the exit of the head of the humerus outside its cavity at the level of the scapula resulting in ligament lesions which risk causing new dislocations: this is called chronic shoulder instability“, continues our interlocutor. Here nerve and vascular lesions are rare but possible, causing an impact on the entire upper limb.

► Posterior dislocations of the elbow are frequent; it is the second most common joint dislocation after shoulder dislocation. It can be associated with fractures, lesion of the ulnar or median nerves and rarely lesion of the brachial artery. The joint is usually flexed about 45°, and the olecranon is prominent posterior to the humeral epicondyle. “Classically, patients with elbow dislocation have a shortened forearm and a very prominent olecranon with total functional impotence“recalls the doctor.

► Dislocation of the knee is rare but serious. It can be reduced to the complete dislocation of the joint. It almost always leads to ligament tears (cruciate ligaments and/or peripheral ligament of the knee) but its prognosis depends on vascular (popliteal vessels) and nerve (sciatic nerve) lesions.

► To achieve a dislocation of hip, you have to be the victim of a particularly violent shock given the great stability of this joint. Also referred to as hip dislocation in neonates with joint instability coxo-femoral. It’s about a congenital hip dislocation due to dysplasia (morphological abnormality of the bone) femoral or acetabular (articular part of the pelvis). In this case, early detection allows preventive treatment of hip dislocations with very satisfactory results.

► One jaw dislocation (mandibular dislocation) is usually a very painful dental emergency that requires prompt consultation with a doctor or dentist. It leads to a inability to close the mouth and sometimes a lateral deviation of the jaw. A mandibular dislocation is sometimes caused by trauma, but is usually caused by excessive opening of the mouth (such as when yawning, when biting into a thick sandwich, when vomiting or during a dental procedure).

► Most of the finger dislocations occur at the central joint. They usually occur when the finger is bent back, as may be the case when a basketball or baseball hits the end of an outstretched finger. But, they can occur when the finger is bent to the side or forward. The ligaments that hold the finger bones together can be torn.

The symptoms are quite revealing, in a context of trauma or traction mainly on a limb:

• painsometimes significant;
• difficulty or inability to use of the joint;
• deformation sometimes visible.

In the event of complications and vascular or nerve damage:

• Limb cold and bluish or white
• Tingling (paresthesia)
• Shock (dysesthesia)

Which examination for a dislocation?

The diagnosis is often obvious from the context, and in the case where the deformity is directly visible. “In any case, a x-ray can make it possible to eliminate an associated fracture, and to confirm the dislocation as well as to direct the doctor towards the best reduction maneuver to perform“, specifies Dr. Mangin.

“The first step in treatment is to relieve pain with immobilization of the limb preventing friction between the 2 bone pieces and then usingclassic analgesics or anti-inflammatories, and sometimes stronger molecules in case of painful dislocation of large joints“, adds the specialist. In some casesthe reduction of the dislocation can be operated immediately. It is preferable to have been previously trained to perform this type of gesture, so as not to aggravate the lesions. Reduction of a dislocation is usually painful, and can be done under painkillers, relaxing gas often in children, or even general anesthesia in the event of major dislocation of a large joint. Complete immobilization of the joint is often necessary afterwards.

► Note a case children’s classic : painful pronation. It is, in the small child generally aged a few years, often less than 3 or 4 years, of a subluxation of the head of the radius, the lateral bone of the forearm, at the level of the elbow. This dislocation is made possible by the fact that a ligament located at this level is not yet “wide” enough and that during an arm traction mechanism, the radial head comes out of its location and cannot recover. spontaneously. This engenders in the child a characteristic attitude: he no longer uses his hand to grab things, and cries when his arm is moved. The classic context of occurrence is the child held by the hand who stumbles, held by the arm by reflex, or a child pulled a little too harshly by the arm. In this case, a simple medical technique allows the head of the radius to be returned to its correct location ; in a few minutes, the child plays normally again, without any sequelae.

Thanks to Dr. Michael Mangin, orthopedic surgeon at the Rhéna clinic in Strasbourg.