Thumb Dislocation: Types, Diagnosis, Treatment
Thumb dislocations can involve both the joints of the thumb. Before we know more about this injury it is essential to know a little about the thumb anatomy. Each thumb is made of three bones and two joints. The bones are
The joints are
The joints of the thumb are held stable by tough fibrous structures called ligaments and joint capsule. These are attached to the bones on either side of the joint. When a joint dislocates then these structures are torn. As the thumb has two joints so there can be two types of thumb dislocations.
IP Joint DislocationIP joint dislocations are less common than MP joint dislocations. Usually these dislocations are associated with a fracture. This fracture dislocation can be a mallet type with the extensor tendon taking away a bone chip and the remaining bone dislocating towards the palmer (finger print) surface. The other fracture dislocation occurs when the flexor tendon pulls a bone chip away and the remaining bone dislocates towards the dorsal (finger nail) surface. This condition requires surgical intervention or else active flexion of the thumb will be lost. Mallet type of thumb fracture dislocations are treated in the same way as mallet finger. Mallet fracture dislocation is most common type of thumb dislocation. Pure IP dislocation with out a fracture is a rare injury. It is caused by a fall on the thumb. The skin can be torn and bone exposed. These dislocations are usually towards the dorsal (finger nail) surface. In pure IP dislocations the thumb remains extended and there is inability to flex the joint. Diagnosis can be confirmed by x rays.Treatment is by re-alignment of the joint. Re-alignment can be done by traction and flexion. A splint is used to maintain the reduction. 
This is a photo of a patient with a pure IP joint dislocation of the right thumb. He sustained this injury when his motorcycle slipped. You can see that he is unable to flex his IP joint. On the left side the IP joint is flexed. Below is a x ray of the same. 
MP Joint DislocationThe MP joint most commonly dislocates backwards or posteriorly. This type of injury is usually caused by a force that tends to hyper-extend the joint. These dislocations are of two types
Simple dislocations can be easily corrected by manipulation alone. After dislocation the proximal phalaynx lies at 90 degrees to the metacarpal. Re-location is done by moving the phalaynx back over the metacarpal head. 
Complex dislocations can not be reduced by manipulation alone. They require surgery. Surgery is required because a part of the joint capsule called the volar plate gets entrapped within the joint. This prevents reduction. During surgery the capsule between the bones is removed and the joint re-located. At times complex dislocations may reduce by manipulation. So before surgery the surgeon attempts relocation by manipulation after the patient has been anaesthetised. After surgery the joint is usually stable. Movement can be started as soon as pain decreases. At times splinting of the thumb may be required. Common complications seen after this dislocation are
This below is a x ray of a young lady who sustained a complex thumb dislocation during a martial arts tournament when her opponent slammed a kick on her thumb. Surgery was required to correct it. 
I hope the information provided was helpful. If you have any query you can ask me at the contact me page. This page was last updated on 26th August 2009. Causes of finger joint pain... Go back from Thumb Dislocation to Finger Pain
|
