#MiniTeach: A Perilous Spending Spree
“An otherwise well 42-year-old lady presents having fallen over in town three days previously whilst carrying heavy shopping.”
She is complaining of pain around her right thumb and wrist. She initially used NSAIDs and ice as treatment but the thumb remains painful and bruised and she is struggling to drive or grip.
On initial inspection she has a swollen left thumb with bruising to the thenar eminence.
Her wrist is not swollen, bruised or deformed.
Wrist has full range of movement with pain on extreme flexion. No bony tenderness. There is some mild discomfort on palpation of the anatomical snuff box.
She is exquisitely tender over the base of the first metacarpal. She has less than 5 degrees of movement in flexion, extension, abduction, adduction and opposition of the thumb. You think you can feel some bony crepitus.
You give her paracetamol and ibuprofen and send her round for x-rays of her thumb.
1. Describe the fracture
There is an intra-articular two part fracture at the base of the first metacarpal bone.
2. What is the name of this type of fracture?
This is a Bennett’s fracture. Named after Irish surgeon Edward Hallaran Bennett in 1882. If there were three parts to the fracture then it would be called a Rolando fracture which is managed in the same way from an emergency department perspective but has a worse prognosis.
3. What are the ligaments likely involved in this type of fracture?
The Anterior oblique ligament (or beak ligament) inserts into the base of the base of the first metacarpal and opposes the action of the abductor pollicis longus. When the fracture occurs this unattached fragment is pulled away by the volar oblique and the then unopposed strong abductor pollicis longus dislocates the remaining base of the thumb metacarpal.
AOL – Anterior Oblique Ligament (beak ligament)
APL – Abductor Pollicis Longus
4. What should you do next?
Enquire if the patient requires any further analgesia.
The important issue in this unstable fracture is to obtain and maintain good fracture reduction to ensure healing in anatomical position.
As such Bennett fractures should always be discussed at the time of presentation and referred to the on-call orthopaedic team for review and on-going treatment.
The consequences of inadequate reduction include weakness and pain in the short term and long term recurrent dislocation/subluxation and osteoarthritis.
Patients should be plastered in a Bennett’s cast.
5. What is the definitive treatment?
You explain to the patient that this can be quite a difficult injury to treat. The treatment will depend on her specific fracture and other considerations but will involve an operation which may be done under local, regional or general anaesthesia. She may require the bones manipulating under x-ray with or without wires inserted into the bone to stabilise it or a small incision to fix the fracture directly.
