Dislocation - dislocation

Japanese: 脱臼 - だっきゅう（英語表記）dislocation

Dislocation refers to a condition in which the femoral head and the glenoid cavity that make up the joint are not in the normal physiological positional relationship. Dislocations are broadly divided into congenital and acquired depending on the cause, and acquired dislocations include traumatic dislocations and pathological dislocations. Dislocations generally refer to traumatic dislocations, and may also be accompanied by fractures.

[Takashi Nagai]

Congenital dislocations

It is caused by a developmental defect in the bones that make up the joint and can be divided into primary (intrinsic) and secondary (extrinsic) causes. A typical example is congenital dislocation of the hip joint.

[Takashi Nagai]

Traumatic dislocations

Dislocation refers to a condition in which an external force causes a joint to move beyond its physiological range of motion (joint range of motion), causing one of the joint ends to break the joint capsule and lose the normal relative relationship of the joint surfaces. A dislocation in which parts of the joint surfaces are still in contact with each other is called an incomplete dislocation or subluxation, and a dislocation in which the joint surfaces are not in contact at all is called a complete dislocation. A dislocation that easily dislocates repeatedly with minor external forces after the initial reduction is called a habitual dislocation, and also includes voluntary dislocations, which can be caused or reduced by the patient's own will.

The frequency of dislocations is much lower than that of fractures. Approximately 85% of all dislocations occur in the upper limbs, and approximately half of these are shoulder dislocations. The shoulder joint has a wide range of motion, but the glenoid cavity is very small and shallow compared to the size of the humeral head, making it prone to dislocation and habitual dislocation.

In recent years, the number of hip dislocations due to traffic accidents has been increasing. This occurs when a driver strikes the knee joint hard against the dashboard during a collision, causing the femoral head to strike the posterior edge of the acetabulum, fracturing the acetabulum and dislocating the femoral head backwards.

[Takashi Nagai]

Pathologic dislocation

This refers to secondary dislocations caused by arthritis or other joint diseases that result in bone destruction, expansion or relaxation of the joint capsule, relaxation of the ligaments and muscles that stabilize the joint, or paralysis; these are called destructive dislocations and paralytic dislocations, respectively.

[Takashi Nagai]

Treatment of traumatic dislocations

The injury is reduced non-surgically (manual reduction) under general anesthesia as soon as possible after the injury. In general, after reduction, the torn joint capsule is allowed to heal and heal for approximately three weeks, and the patient is kept immobilized and kept at rest. Functional training is then started as soon as possible. In cases where tendons, muscles, joint capsule, or fracture fragments are involved, or where manual reduction is difficult in old cases where the dislocation was left untreated and scarring or adhesions have developed, open reduction surgery is performed. The functional prognosis is good when reduction is performed early and there is little associated damage, but in cases where there is open damage or old cases, joint contracture may occur and movement may remain restricted. It is important to be careful when dislocating the shoulder joint to avoid habitual dislocation.

[Takashi Nagai]

[References] | Shoulder | Hip dislocation | Habitual dislocation | Congenital dislocation of the hip

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

関節を構成する骨頭と関節窩(か)が正常な生理的位置関係にないものをいう。原因により先天性と後天性に大別され、後天性脱臼には外傷性脱臼と病的脱臼が含まれる。一般に脱臼という場合は、外傷性脱臼をさしており、骨折を伴うものもある。

［永井　隆］

先天性脱臼

関節を構成する骨の発育欠陥によるもので、一次性（内因性）と二次性（外因性）に分けられる。代表的なものが先天性股(こ)関節脱臼である。

［永井　隆］

外傷性脱臼

外力によって関節が生理的運動範囲（関節可動域）以上の動きを強制され、関節端の一方が関節包を破って関節面の正常な相対関係を失ったものをいう。関節面の一部が互いにまだ接触しているものを不全脱臼または亜脱臼といい、関節面がまったく接触していないものを完全脱臼とよぶ。また、初回の脱臼整復後に軽微な外力で容易に脱臼を繰り返すものが習慣性脱臼で、自己の意思で脱臼をおこしたり整復もできる随意性脱臼も含む。

　脱臼頻度は、骨折に比べるとはるかに低い。全脱臼の約85％が上肢にみられ、また約半数は肩関節脱臼である。肩関節は関節可動域が広く、しかも上腕骨骨頭の大きさに比べ、関節窩が非常に小さくて浅いために脱臼しやすく、習慣性脱臼もおこしやすい。

　なお、近年は交通事故による股関節脱臼が増えている。これは、衝突事故でドライバーが膝(しつ)関節部をダッシュボード（計器盤）に激しくぶつけ、大腿(だいたい)骨骨頭が寛骨臼後縁に衝撃を与えて寛骨臼を骨折し、骨頭が後方に脱臼する股関節脱臼である。

［永井　隆］

病的脱臼

関節炎をはじめ関節の種々な病変によって骨の破壊、関節包の拡張や弛緩(しかん)、関節を固定する靭帯(じんたい)や筋の弛緩などをきたしたり、あるいは麻痺(まひ)などのため二次的に脱臼するものをいい、それぞれ破壊性脱臼、麻痺性脱臼とよばれる。

［永井　隆］

外傷性脱臼の治療

受傷後できるだけ早く全身麻酔下で非観血的に整復（徒手整復）する。一般には整復後断裂した関節包が癒合修復される約3週間を目安に、固定して安静を保ち、その後なるべく早くから機能訓練を始める。また、腱(けん)や筋肉、関節包、骨折片などが介在したり、脱臼したまま放置されていた陳旧例で瘢痕(はんこん)や癒着を生じて徒手整復が困難な場合には、手術による観血的整復が行われる。早期に整復して合併損傷も少ない場合の機能的予後は良好であるが、開放性損傷があったり陳旧例の場合は関節拘縮をおこし、運動制限が残ることがある。肩関節脱臼では習慣性脱臼をきたさないように留意することが重要である。

［永井　隆］

[参照項目] | 肩 | 股関節脱臼 | 習慣性脱臼 | 先天性股関節脱臼

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