Fracture of the Base of the Thumb
Bennett Fracture: A Tiny-Looking Fracture That Can Be Easily Missed
A fall or other injury followed by pain at the base of the thumb should immediately raise suspicion of a Bennett fracture.
The most important clinical clue is point tenderness precisely at the base of the first metacarpal (MC1).
There may be very little swelling, or sometimes no obvious swelling at all. The thumb may still be movable. These findings do not mean that the injury is minor and therefore cannot be ignored.
Pain and point tenderness at the thumb base after an injury require a good-quality, focused X-ray examination.
What is a Bennett fracture?
A Bennett fracture is an intra-articular fracture at the base of the first metacarpal (MC1), extending into the first carpometacarpal (CMC) joint of the thumb. The base has broken into two pieces.
Because the fracture involves the joint surface, accurate assessment and restoration of joint alignment are particularly important to restore smooth and painless thumb movement.
Bennett fractures can be surprisingly easy to miss, especially when attention is focused on another injury.
Why can a Bennett fracture be missed?
A routine whole-hand X-ray may not demonstrate the base of MC1 clearly.
The base of the first metacarpal (MC1) can be obscured by overlapping adjacent bones, particularly the second metacarpal or trapezium. An inadequately positioned or non-magnified image may therefore fail to show the fracture clearly.
Sometimes the patient has another obvious injury, for example, a distal radius fracture, and attention is directed toward that fracture while the tenderness at the base of the thumb is overlooked.
This is why clinical examination must guide the X-ray examination.
If there is precise point tenderness at the base of MC1, a Bennett fracture must be taken seriously even when:
- there is little or no swelling,
- the thumb can still be moved,
- the initial X-ray appears normal, or
- the printed X-ray report states that there is no fracture.
What X-rays are needed?
When a Bennett fracture is suspected, the base of the first metacarpal should be examined with dedicated, properly positioned and magnified X-ray views.
The relevant part should be positioned parallel to the cassette, with appropriate posteroanterior (PA), anteroposterior (AP) and lateral views of the MC1 base.
A specialised Robert's view, which is a hyperpronation AP view, may also be obtained when additional assessment of the thumb CMC joint and the articular surface is required.
Good positioning and magnification can make a significant difference in identifying a small intra-articular fracture.
If there are multiple areas of pain or multiple suspected injuries, additional views may be required.
Each injury must be identified and assessed on its own merit so that appropriate treatment is not overlooked.
What if the X-ray report says "No Fracture"?
This situation deserves particular attention.
A patient may arrive with an X-ray and a printed report stating "no fracture", yet continue to have very well-localised pain and point tenderness at the base of the first metacarpal.
The person reporting the X-ray has not examined the patient, has not felt the exact site of tenderness and may not know that there is point tenderness specifically at the base of MC1.
Therefore, a printed report should not falsely reassure you when the clinical findings strongly suggest a fracture.
A fracture can be missed on the initial X-ray, and a printed report may be erroneous.
If there is persistent, well-localised point tenderness at the base of MC1 despite a report stating "no fracture":
Re-examine the patient → review the actual X-ray images carefully → obtain dedicated, magnified views → repeat the X-ray within a few days if necessary → consider CT if doubt remains.
Do not treat the report alone. Treat the patient and correlate the clinical findings with the actual images.
What should be examined?
The examination should not stop at finding tenderness.
The thumb should be assessed for:
- precise tenderness at the base of MC1,
- CMC joint stability,
- Associated wrist, hand and finger injuries.
The clinical examination helps determine if further imaging is necessary.
Why does the fracture become displaced?
The fracture occurs at the base of the first metacarpal and extends into the CMC joint.
A small medial fragment generally remains held in position by its ligamentous attachments.
The larger metacarpal fragment, however, is subjected to the pull of the robust abductor pollicis longus (APL) tendon.
As a result, the larger fragment can become displaced and migrate proximally, with associated subluxation of the CMC joint.
This explains why a Bennett fracture is unstable most of the time.
Bennett fracture versus Rolando fracture
Both are intra-articular fractures involving the base of the first metacarpal, but their patterns are different.
Bennett fracture
A Bennett fracture is an intra-articular fracture at the base of MC1, typically producing a fracture-dislocation pattern with a relatively larger metacarpal fragment and a smaller fragment maintained by ligamentous attachments.
Rolando fracture
A Rolando fracture is a more complex, usually comminuted intra-articular fracture at the base of MC1, with the fracture dividing the base into more than two pieces.
Both injuries require careful assessment of:
- the joint surface,
- fracture displacement,
- CMC joint alignment, and
- stability.
Does a displaced Bennett fracture require surgery?
Yes. A displaced Bennett fracture requires reduction and fixation.
Because the fracture involves the thumb CMC joint, the displaced fragments need to be restored to proper alignment and held securely while healing occurs.
If a displaced fracture is left untreated, it can result in:
- persistent joint incongruity,
- CMC subluxation or instability,
- loss of grip and pinch strength,
- persistent pain, and
- post-traumatic arthritis.
The objective of treatment is to restore the joint surface and functional alignment of the thumb.
How soon should surgery be performed?
Reduction and fixation should be performed as early as reasonably possible, generally within a few days..
However, the timing of surgery must take into account the patient's overall condition and any associated injuries.
Before proceeding with surgery, factors such as:
- breathing and circulation,
- chest or other associated injuries,
- medical comorbidities,
- general fitness for anaesthesia, and
- other injuries requiring treatment
must be considered.
If other injuries also require surgery, procedures may sometimes be coordinated under the same anaesthetic when medically appropriate.
How is a Bennett fracture fixed?
Kirshner wires (K-wire) fixation is commonly used.
The fracture fragments are reduced into their proper position and stabilised with K-wires using an image intensifier or C-arm.
In addition, K-wires are inserted across the CMC joint for added stability.
The purpose of this additional CMC fixation is to maintain the correct relationship between the first metacarpal and the trapezium while the fracture heals.
Typical K-wire removal
- K-wires stabilising the CMC joint: generally removed at around 4 weeks.
- K-wires holding the fracture fragments: generally removed at around 6 weeks.
The exact timing depends on the fracture pattern, fixation, healing, clinical examination and follow-up X-rays.
What happens after fixation?
Post-reduction X-rays should confirm:
- satisfactory fracture reduction,
- restoration of CMC alignment,
- appropriate position of the fixation wires, and
- maintenance of reduction during follow-up X-rays.
Follow-up X-rays are important because they confirm that the fracture has not displaced again and that healing is progressing appropriately.
They also allow the surgeon to identify any problem with the fixation, such as a wire bending, breaking, loosening or migrating.
Can a stable Bennett fracture be treated without surgery?
A truly undisplaced and stable fracture may occasionally be treated without surgery.
However, this requires very close radiographic monitoring, because displacement can develop during the healing period.
A fracture that is well aligned today may not necessarily remain well aligned during healing.
For this reason, if a fracture is treated non-operatively, follow-up X-rays may be required every 5-7 days initially and continued for up to 6 weeks, depending on the fracture pattern and clinical situation.
The purpose is to identify any secondary displacement early, when treatment can still be appropriately modified.
Is delayed presentation or a malunited Bennett fracture hopeless?
No. Delayed presentation or a malunited Bennett fracture is not the end of the world.
If the fracture has healed in an unacceptable position, selected patients can undergo corrective surgery.
The malunited fracture site can be exposed and carefully osteotomised.
A fine osteotome with a 4-6 mm thin blade can be used to osteotomise the healed bone. The newly formed bone and dense callus are removed sufficiently to recreate and mobilise the original fracture site.
The fracture can then be reduced.
The first metacarpal is repositioned over the trapezium, restoring the CMC relationship, and the CMC joint and base of MC1 are stabilised with K-wires.
Additional K-wires across the CMC joint provide added stability.
Typically:
- CMC-spanning K-wires are removed at around 4 weeks.
- Fracture-holding K-wires are removed at around 6 weeks.
The exact timing is individualised according to healing and stability.
The objective of corrective surgery is to restore:
- joint alignment,
- CMC stability,
- the functional position of the thumb, and
- useful thumb function.
What if the patient presents very late with arthritis?
If the patient presents very late and the CMC joint has developed established painful post-traumatic arthritis that significantly affects activities of daily living, reconstruction of the old fracture may no longer be appropriate.
In appropriately selected patients, the painful arthritic CMC joint may instead be treated with trapeziectomy.
The principle in a very late, painful and function-limiting case is to relieve pain and restore useful thumb function, rather than attempting simply to recreate the original Bennett fracture.
Important
Radiographic arthritis alone is not an indication for surgery.
Treatment is considered when arthritis is symptomatic and function-limiting, particularly when pain interferes with activities of daily living.
When is a CT scan useful?
CT can be particularly useful when:
- the fracture is complex,
- the fracture is comminuted,
- the joint surface is difficult to define on X-ray,
- the fracture is old or malunited,
- plain X-rays do not adequately explain the clinical findings, or
- exact joint anatomy needs clarification before treatment.
CT should complement clinical examination and appropriate plain X-rays rather than replace them.
What are the possible complications?
Possible complications include:
- loss of fracture reduction,
- CMC instability or subluxation,
- stiffness,
- pin-site infection,
- persistent pain,
- weakness of grip or pinch, and
- post-traumatic arthritis.
Accurate reduction, stable fixation and appropriate follow-up help minimise these problems.
When should you see a Hand Surgeon?
You should seek specialist assessment after a thumb injury if there is:
- point tenderness at the base of the thumb or first metacarpal,
- pain with pinch or gripping,
- difficulty moving or opposing the thumb,
- persistent pain despite an X-ray reported as normal,
- a suspected fracture-dislocation or multiple injuries, or
- a fracture that is displaced, unstable or difficult to define on X-ray.
Early assessment is particularly important because a displaced Bennett fracture requires reduction and fixation.
What should you avoid?
Do not rely only on a printed X-ray report when the clinical findings strongly suggest a fracture.
Do not continue prolonged sling use unnecessarily.
Do not assume that a fracture which is well aligned initially will remain aligned without appropriate follow-up X-rays.
What should I do immediately after the injury?
In the early period after injury or surgery:
Keep the hand elevated
The hand should be kept above the level of the heart whenever possible to help minimise swelling and oedema.
Use a sling only when necessary
A sling may be useful for comfort immediately after an injury or surgery, but it should not be used routinely or continuously for prolonged periods.
Prolonged sling use can lead to stiffness of the elbow and shoulder.
If a sling is required, it should generally be used for the shortest appropriate period, sometimes only a few hours at a time.
Move the uninvolved fingers
Any fingers that are not immobilised should be moved fully and regularly from the beginning.
Early movement helps prevent stiffness and swelling.
A simple exercise is to count 1-2-3-4 with the fingertips, gently flexing and extending the fingers through their available range without stressing the fracture or fixation.
What about thumb movement?
Thumb movement depends on the stability of the fracture and the method of fixation.
After plaster immobilisation is removed, once X-rays show that the reduction has been maintained and there is evidence of healing, thumb movement can be started .
The exact timing should be individualised according to the fracture, fixation and follow-up X-rays.
Frequently Asked Questions
1. What is a Bennett fracture?
A Bennett fracture is an intra-articular fracture at the base of the first metacarpal involving the thumb CMC joint.
2. How does a Bennett fracture usually occur?
It commonly occurs after a fall or blow in which the thumb is forced into an abnormal position, particularly extension or abduction.
3. When should I suspect a Bennett fracture?
After an injury, point tenderness precisely at the base of the first metacarpal should raise strong suspicion, even if swelling is minimal and the thumb can still move.
4. Can a Bennett fracture be missed on an ordinary X-ray?
Yes. The base of MC1 may be obscured by overlapping bones, particularly the second metacarpal or trapezium. Dedicated, properly positioned and magnified views may be necessary.
5. What X-rays are required?
Dedicated, magnified views of the base of MC1, with the relevant part properly positioned parallel to the cassette, including appropriate PA, AP and lateral views. A specialised Robert's view (hyperpronation AP view) may also be obtained when additional assessment of the thumb CMC joint is required.
6. What if my X-ray report says there is no fracture?
Do not rely on the report alone if there is persistent, well-localised tenderness at the base of MC1.
The actual images should be reviewed, dedicated views obtained, and the X-ray repeated within a few days if necessary. CT may be considered when doubt remains.
A printed report may be erroneous. Clinical findings and the actual images must be correlated.
7. Does a displaced Bennett fracture require surgery?
Yes. A displaced Bennett fracture requires reduction and fixation.
8. How soon should surgery be performed?
As early as reasonably possible, generally within a few days, and sometimes on the same day when appropriate, after considering the patient's overall condition and associated injuries.
9. Can a stable Bennett fracture be treated without surgery?
A truly undisplaced and stable fracture may occasionally be treated without surgery, but it requires close serial radiographic monitoring.
10. Why are repeated X-rays necessary?
A fracture that is well aligned initially may displace during healing. Repeated X-rays detect secondary displacement early and also help identify problems with fixation such as wire bending, breakage, loosening or migration.
11. How often are X-rays required when treatment is non-operative?
Typically every 5-7 days initially and continued for up to 6 weeks, depending on the fracture pattern and clinical situation.
12. What is a Rolando fracture?
A Rolando fracture is a more complex, usually comminuted intra-articular fracture at the base of the first metacarpal, with the fracture dividing the base into more than two pieces.
13. Why should the hand be elevated?
Elevation above heart level helps reduce swelling and oedema.
14. Why should prolonged sling use be avoided?
Prolonged sling use can cause stiffness of the elbow and shoulder. A sling should generally be used for the shortest appropriate period and primarily for comfort.
15. Should the other fingers be moved?
Yes. Fingers that are not immobilised should be moved fully and regularly from the beginning to reduce stiffness and swelling.
16. When can I start moving the thumb?
Thumb movement depends on fracture stability and fixation. It is generally started at the appropriate stage after immobilisation is removed and follow-up X-rays confirm maintained reduction and evidence of healing.
17. When are the K-wires removed?
CMC-spanning K-wires are generally removed at around 4 weeks, while K-wires holding the fracture fragments are generally removed at around 6 weeks, depending on healing and stability.
18. Is a delayed or malunited Bennett fracture hopeless?
No. Selected patients can undergo corrective surgery to recreate and mobilise the old fracture site, restore the first metacarpal, trapezium relationship and stabilise the CMC joint.
19. What can be done if the fracture has healed in the wrong position?
A corrective osteotomy can be performed in selected cases. The healed fracture can be carefully reopened using a fine osteotome, dense callus removed, the fracture reduced and the first metacarpal repositioned over the trapezium, followed by appropriate fixation.
20. What if the patient presents very late with painful arthritis?
If there is established, painful post-traumatic CMC arthritis that significantly affects daily activities, reconstruction of the old fracture may no longer be appropriate. Trapeziectomy may be considered in appropriately selected patients.
21. Is arthritis visible on an X-ray alone an indication for surgery?
No. Treatment is based on the patient's symptoms and functional limitation. Radiographic arthritis alone does not automatically require surgery.
22. Why might a CT scan be required?
CT can clarify complex, comminuted, old or malunited fractures and can define the joint surface when plain X-rays do not provide sufficient information.
23. What complications can occur?
Complications may include loss of reduction, CMC instability, stiffness, pin-site infection, persistent pain, grip or pinch weakness and post-traumatic arthritis.
Key Message
A Bennett fracture may look small on an X-ray, but it involves the thumb CMC joint and can have important consequences for thumb function.
Remember:
Injury + point tenderness at the base of the first metacarpal = think Bennett fracture.
If the first X-ray does not explain the clinical findings:
Look again → obtain dedicated magnified views → repeat the X-ray within a few days if necessary → consider CT when doubt remains.
Do not be falsely reassured by the absence of swelling or by a printed report stating that there is no fracture when the clinical findings strongly suggest otherwise.
A displaced Bennett fracture requires reduction and fixation.
A delayed or malunited fracture is not necessarily the end of the road. Selected patients can undergo corrective surgery to restore joint alignment and thumb function.
In very late cases with painful, function-limiting post-traumatic CMC arthritis, treatment may instead focus on the arthritic joint, including trapeziectomy in appropriately selected patients.
Early recognition, accurate assessment, timely fixation when displaced, appropriate management of delayed cases and vigilant follow-up can help preserve thumb function, strength and long-term joint health.
About the Author
Dr. Pankaj Jindal (MS Orthopaedics & Reconstructive Microsurgeon) is a Specialist Hand Surgeon at Jindal Hand Surgery, Pune, Maharashtra, India, with extensive experience in hand surgery, reconstruction and peripheral nerve surgery.
He practises through Jindal Hand Surgery, Pune.
His clinical interests include hand trauma, fractures and fracture-dislocations of the hand and wrist, tendon and nerve injuries, microsurgery, reconstruction and restoration of hand function.
This article is intended for patient education and reflects clinical principles used in the assessment and treatment of Bennett fractures.
References and Further Reading
- Green's Operative Hand Surgery, David P. Green and colleagues. A major reference text in hand surgery covering operative management of fractures, reconstruction and disorders of the hand and wrist.
- The Journal of Hand Surgery (American), the official journal of the American Society for Surgery of the Hand (ASSH).
These resources provide further reading on the diagnosis, treatment and surgical management of hand and wrist conditions, including fractures involving the thumb CMC joint.
Medical Information
This article is intended for general patient education and does not replace an examination by a qualified doctor. The appropriate investigation and treatment depend on the individual injury, examination findings and imaging.