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
- Distal Phalaynx
- Proximal Phalaynx
- 1st Metacarpal
The joints are
- Inter-phalangeal or IP joint between the distal and proximal phalaynx.
- The Metacarpo-phalangeal or MP joint between the 1st Metacarpal and the proximal phalanx.
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.
- Inter-phalangeal or IP joint dislocation
- Metacarpo-phalangeal or MP joint dislocation
IP Joint Dislocation
IP 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 may be used to maintain the reduction. Usually a splint is not required as the joint is stable after re-alignment.
Below are photographs of a patient with IP dislocation before and after re-alignment.
The upper most photo shows a dislocation of the left IP joint of the thumb. The patient unable to flex his IP joint of the left side. The second photo shows the presence of abnormal creasing on the front of the dislocated thumb due to tethering of the skin.
The third photo is after re-alignment. Now he can flex the left thumb. The final photo shows disappearance of the abnormal creasing. Below is a x ray of the same patient.
MP Joint Dislocation
The 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
- Stiffness of the joint
- Chronic pain in the joint
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 22th October 2010.
Causes of finger joint pain...
Swan Neck Deformity
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