A dislocated thumb is a common injury, especially in sports or after a fall. These injuries usually happen at either the metacarpophalangeal (MCP) joint (at the base of your thumb) or the interphalangeal (IP) joint (the joint in the middle of your thumb).
Getting a quick, accurate diagnosis and getting the thumb put back in place (a “reduction”) is critical. This helps prevent long-term issues and get your thumb working again.
This article will cover how doctors evaluate and treat thumb dislocations, potential problems that can arise, and practical ways to ensure a successful reduction.
Anatomy and mechanism of injury
To understand how a thumb dislocation happens, it’s helpful to know a little about the anatomy of the thumb.
Relevant anatomy
The metacarpophalangeal (MCP) joint connects the thumb metacarpal to the proximal phalanx. Key anatomical structures in this area include the volar plate, the sesamoid bones, and the collateral ligaments, especially the ulnar collateral ligament (UCL).
The interphalangeal (IP) joint connects the proximal and distal phalanges of the thumb. It’s a hinge joint, which means it allows for flexion and extension.
Tendons in the thumb include the flexor pollicis longus (FPL) and the flexor pollicis brevis (FPB).
Common mechanisms of injury
Dorsal dislocations often happen because of hyperextension injuries, in which the thumb bends backward too far.
Volar dislocations are less common, and they typically involve axial loading and rotational forces.
Axial load injuries are more likely to cause Bennett or Rolando fractures.
Diagnosis and evaluation
If you think you’ve dislocated your thumb, a doctor will need to examine it to confirm the diagnosis and rule out other injuries.
History and physical examination
The doctor will want to know how the injury happened, since that can help them assess the likelihood of other injuries. They’ll check the location and severity of your pain and swelling. They’ll also be looking for any obvious deformities, such as bending or angling of the thumb.
It’s important to check the nerve and artery function in your thumb and fingers, since those can be damaged with a dislocation. The doctor will check how well you can move your thumb, both on your own and with assistance. If you dislocated the joint at the base of your thumb (MCP), the doctor will check the ligaments around that joint.
Imaging
X-rays are essential for confirming a dislocation and looking for any fractures or avulsion injuries. The doctor will likely order anteroposterior (AP), lateral, and oblique views of the thumb.
It’s also important to get X-rays after the dislocation has been reduced, or put back into place.
If your injury was caused by a force pushing straight down on your thumb, you’re more likely to have a Bennett or Rolando fracture, so the doctor will pay special attention to the X-rays to look for those.
Reduction techniques
A dislocated thumb needs to be put back in place, and there are several things doctors need to keep in mind as they attempt to reduce the dislocation.
Approach considerations
- Make sure you’ve had adequate pain relief. A local anesthetic, hematoma block, or procedural sedation can minimize pain and muscle spasms.
- Consider taking a low dose of an anti-anxiety medication to help you relax.
- Your doctor should avoid repeated, forceful attempts at reduction.
- Closed reduction may be impossible in certain cases (e.g., significant delay, severe swelling, residual instability).
- If needed, the doctor may need to reposition you or change the way they’re holding your hand.
- The doctor should never increase the amount of force they’re using during reduction attempts.
Reduction of dorsal dislocation
- The doctor shouldn’t use traction during attempts to reduce dorsal dislocations.
- Keeping the MCP joint flexed and adducted may help with successful reduction.
- The doctor will apply pressure to the distal aspect of the proximal phalanx while applying pressure to the metacarpal head.
- After the reduction, the doctor will check the joint’s stability and range of motion.
Reduction of volar dislocation
- Reduction of volar MCP and IP dislocations of the thumb is less successful and leads to more complications than reduction of dorsal dislocations does.
- The doctor will hold the joint in extreme flexion.
- The doctor will apply traction and direct pressure to disengage the volar plate.
- The doctor will slowly extend the joint while maintaining traction.
Special considerations
- Stener lesion. With a Stener lesion, the ulnar collateral ligament (UCL) is displaced. If there is persistent instability after reduction, the doctor may suspect a Stener lesion. These cases require urgent orthopedic consultation and surgical repair.
- Irreducible dislocations. If the dislocation can’t be reduced after a few tries, it’s considered irreducible. This can happen if soft tissues or bone fragments are in the way. Irreducible dislocations require open reduction.
After the thumb is back in place
Once your thumb has been relocated, there are a few important steps to take to make sure it heals properly.
Immobilization
After the reduction, your thumb will need to be kept still so the joint can heal. Doctors usually use a short arm thumb spica splint for this purpose. When they apply the splint, they’ll position your wrist in a slightly extended position (between 20 and 30 degrees).
If the dislocation happened at the MCP joint, the splint will also include the IP joint.
The splint itself is usually made up of eight layers of 3-inch plaster roll.
Post-reduction assessment
After the splint is applied, your doctor will check the nerves and blood vessels in your thumb and hand. They’ll also assess your range of motion.
It’s vital that they carefully check and document the stability of the collateral ligaments after the reduction.
Follow-up care
Your healthcare team will likely refer you to an orthopedic surgeon or hand specialist for follow-up care.
Be sure to follow the instructions you’re given about how to care for the splint.
Keep an eye out for any signs of complications, like pain, swelling, or nerve compression, and let your doctor know right away if you spot anything unusual.
What complications can arise with a dislocated thumb?
As with any injury, there are some possible complications that can arise with a dislocated thumb.
Early complications
Attempts to reduce the dislocation can sometimes lead to a neurovascular injury or even a fracture. It’s also possible that the thumb will dislocate again after it’s been reset, or that the joint will remain unstable.
Late complications
If the thumb is immobilized for too long, it can become stiff. If the ligaments remain loose, the thumb can become chronically unstable. Damage to the joint can lead to arthritis later in life.
Surgical considerations
Some fractures, such as Bennett fractures, may require open reduction and internal fixation (ORIF). Stener lesions usually require surgical repair within 10 days of the injury.
To Conclude
A dislocated thumb requires careful diagnosis and treatment. Quick realignment, appropriate immobilization, and follow-up care are key to a good outcome.
It’s also important to be aware of possible problems, like Stener lesions or fractures, to avoid long-term issues.