A Bennett fracture of the thumb seems like a simple broken bone. However, it has a tendency towards displacement and complications. Since the thumb plays a vital role in gripping, pinching, and overall hand dexterity, a Bennett fracture could cause major problems. Read on to learn more about Bennett fractures, their treatment, and what you can do to help your thumb. Let’s start with anatomy!
The thumb
The thumb is the first digit of the hand. It has 3 main joints which are the carpometacarpal (CMC) joint, metacarpophalangeal (MCP) joint and the interphalangeal (IP) joint. These joints allow the thumb to have significant mobility and the ability to grasp.
The CMC joint is made up of the trapezium (one of the wrist bones) and the first metacarpal bone. This joint is located closer to the wrist. The MCP joint is made up of the articulation of the first metacarpal (long hand bone) and the first phalanx (first bone of the thumb). It is the joint at the base of the thumb. The IP joint is made up of the articulation of the first and second phalanx (bone at tip of thumb).
The CMC and MCP joints have a significant amount of movement. These movements include opposition, flexion, extension, abduction, and abduction. Opposition is the action of touching the thumb to each of the fingers. Thumb extension is moving the thumb away from the index finger and thumb flexion is bending it in toward the palm. Abduction is moving the thumb forward and away from the index finger while adduction is moving it toward the index finger.
The IP joint has less movement. It can only perform flexion and extension. Flexion is bending the thumb while extension is straightening it.
What is a Bennett fracture?
A Bennett fracture is a fracture or break of the first metacarpal at its base near the wrist. It is the most common type of fracture in this area. A Bennett fracture extends into the CMC joint. It occurs when a high force is directed through a partially bent thumb. The injury is usually sustained during contact sports such as football, rugby, or boxing. The prevalence of this fracture is higher among men and usually occurs in the dominant hand.
A Bennett fracture is an intraarticular fracture which means that extends into the CMC joint. It is considered an unstable fracture because the fracture fragment is held in place by a ligament. The rest of the metacarpal bone tends to be moved out of alignment by the pull of the thumb muscles.
What are the symptoms of a Bennett fracture?
There are several symptoms associated with a Bennett fracture. These include:
- Pain and swelling at the base of the thumb
- Limited mobility of the thumb
- Decreased ability to grip or pinch
- Tenderness and warmth at the base of the thumb
Will I need surgery?
The answer is maybe. If the fracture is displaced less than one mm or a closed reduction (putting the bones back in place) is successful in restoring alignment, then a cast is applied for 6 weeks. If the fracture is displaced greater than one mm, a closed reduction is unsuccessful, or if significant instability is present, then surgery would be needed for proper joint alignment and healing.
What are the possible complications with a Bennett fracture?
There are several complications associated with a Bennett fracture. These include:
- Malunion – Malunion is when the bones heal in an abnormal position. It can impair the thumb’s ability to perform different activities.
- Nonunion – Nonunion means that the fracture is not healing and there is little chance of it healing without surgical intervention.
- Arthritis – This is the most common complication with this fracture. Because the fracture is in the joint, it will often result in significant arthritis in the thumb CMC joint. Arthritic symptoms might not be noticed until years after the injury.
- Stiffness – Stiffness of the CMC joint is common after surgery or cast immobilization. It is important to begin gentle motion of the thumb as soon as you are cleared by your physician.
Who should I see?
- Orthopedic hand specialist – If you suspect that you have sustained a Bennett fracture (or some other type of fracture), it is best to go to the emergency room. They will be able to perform imaging, put the thumb in a splint, and recommend an orthopedic hand specialist. Because of the potential complications, this fracture should be treated quickly.
- Physical or occupational therapist – Hand therapy will be needed to regain mobility and strength in the hand. This will be true whether or not surgery was needed. Because of the extended time in the cast, the thumb will be stiff and sore when trying to move or use it. Your PT or OT can evaluate you to determine the extent of your mobility and strength deficits and use manual therapy, as well as, stretching and strengthening to help address all problems in and around the wrist.
What can I do?
- Relative rest – Resting the area to decrease further pain and damage from occurring is one of the best ways to allow the bones to heal. If you are not able to participate in your activity or sport, then you can supplement with non-irritating activities such as walking or jogging while your wrist is healing.
- Ice – Ice can help decrease pain and symptoms at the thumb. Ice the painful area for 15 to 20 minutes at a time. I would recommend using an ice pack several times per day if the pain is constant or is preventing you from participating in an activity. Ice immediately after activity.
- The following are activities that you can do after the cast is removed or you are cleared by your surgeon.
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- Thumb active range of motion – These are a series of exercises designed to move the thumb in all of its different directions. The thumb will likely be stiff after surgery or an extended time in a cast. See the video below for how to perform these exercises.
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- Thumb strengthening
- It is important to strengthen the muscles that control the thumb in order to be able to return to all previous activities. These are exercises designed to strengthen the muscles around the thumb CMC joint. You can use finger exercisers or thick rubber bands to provide resistance. See the videos below.
- Thumb strengthening
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- Gripping and pinching
- The thumb plays a vital role in the actions of gripping and pinching. Your grip and pinch will be weak after the injury. These exercises are designed to strengthen grip and pinching. You can use a towel, stress ball, or grip trainers to add resistance and strength. See the videos below.
- Gripping and pinching
In review
- The thumb is the first digit of the hand.
- It has 3 main joints which are the carpometacarpal (CMC) joint, metacarpophalangeal (MCP) joint and the interphalangeal (IP) joint.
- The CMC joint is made up of the trapezium (one of the wrist bones) and the first metacarpal bone.
- This joint is located closer to the wrist.
- The CMC and MCP joints have a significant amount of movement.
- These movements include opposition, flexion, extension, abduction, and abduction.
- A Bennett fracture is a fracture or break of the first metacarpal at its base near the wrist.
- A Bennett fracture is an intraarticular fracture which means that extends into the CMC joint.
- It is considered an unstable fracture.
- Symptoms of a Bennett fracture include pain and swelling at the base of the thumb.
- It could require surgery because of its tendency toward displacement.
- You should see a hand specialist to determine the best course of action.
- Hand therapy will be needed after surgery or once the cast is removed.
- There are things that you can do.
- Relative rest
- Icing
- Thumb exercises
- Active range of motion
- Thumb strengthening
- Grip and pinch strengthening
As always, If you have questions about the content of this post or any other musculoskeletal questions, please e-mail me.
Additional resources
https://www.ncbi.nlm.nih.gov/books/NBK500035/
https://www.physio-pedia.com/Bennett%27s_fracture