Thumb fracture

Definition

The thumb is formed by the metacarpal bone, the proximal and distal phalanges. A thumb fracture can occur in any of these three bones.

Pathology

The distal end of the thumb metacarpal forms a joint with the proximal phalange, which is named the metacarpo-phalangeal (MCP) joint. The proximal end of the thumb metacarpal and the carpal bone (trapezium) form the carpo-metacarpal (CMC) joint. A thumb fracture can occur in any of these anatomical regions but is more frequent at the base of the metacarpal bone. The thumb metacarpal is the broadest tubular metacarpal bone of the hand.  Anatomically it is slightly detached from the other bones of the hand to allow for grasping. Therefore, a thumb fracture can have serious functional implications.

Due to the unique anatomy, a fracture of the thumb metacarpal is quite different compared to other metacarpal bones. Metacarpal fractures can be isolated or combined with injury of the CMC joint and involve the trapezium. These fractures generate instability of the CMC joint producing chronic pain and weakness, commonly requiring surgical reconstruction of the joint surface. A fracture of the thumb metacarpal is also called skier's thumb. In case of fractures to the metacarpal head, the knuckle seems to disappear and its movement triggers pain. When associated with damage to the tendon abductor pollicis longus (APL), it leads to instability of the CMC joint.

Classification

There are different types of thumb fractures that are named based either on their location relative to the joint and take the name of the specialist who first described them. These definitions are:

1. Intra-articular comminuted

2. Extra-articular transverse

3. Extra-articular oblique

4. Intra-articular or Bennett's fracture

5. Intra-articular or Rolando's fracture

Thumb fractures can be stable, non-displaced or minimally displaced, when the bone fragments maintain their anatomical position, or displaced when the bone fragments have moved from their original anatomy. They can also be transverse, oblique, spiral, or comminuted when multiple bone fragments are released.

A Bennett's fracture of the thumb base is the most common type of fracture producing an oblique break of the metacarpal affecting the function of the underlying joint. This requires immediate medical attention.

A Rolando's fracture is a 3-part fracture at the base of the thumb metacarpal generating a T- or Y-fracture pattern. It is located either in the frontal or in the sagittal plane. It is caused by an axial overload along the thumb metacarpal causing a compression fracture of the joint surface. This type of pathology is uncommon but has a worse prognosis than a Bennett's fracture.

Causes

A thumb fracture is the result of an impact and/or torsion energy and is mostly found in men. It is caused by a force pulling the thumb backwards in a flexed position at the metacarpal joint as it happens in:

Falls onto the hand

When catching a ball

Contact sports

Manual work.

Risk factors

The following sports and activities represent the main risk factors for a thumb fracture:

Basketball

Netball

Contact sports (hockey, football, rugby)

Skiing Martial arts

Carpentry work

Symptoms

The symptoms arising from thumb fractures are:

Pain

Swelling

Bruising

Movement restrictions

Thumb deformity

Knuckle asymmetry and/or depression

Instability of the carpo-metacarpal joint

Diagnosis

During the medical examination the patient provides information including the history of previous hand injuries and mechanisms that have caused the current injury to the thumb. Clinical examination of the hand will determine:

Changes in the anatomy of the affected thumb against the healthy thumb

Presence of skin lacerations, bruises

Thumb malrotation

Tenderness at touch

Pain triggered by movement

Reduced range of movement

If a thumb fracture is suspected X-rays are taken under the antero-posterior, lateral, and oblique view to confirm the presence of a fracture and assess its characteristics. CT and MRI scans may be required for a detailed definition of complex fractures.

Treatment

Nonoperative treatment

Management of thumb fractures varies in relation to fracture site and its classification. In case of stable fractures surgery is not required and conservative treatment with a cast is usually sufficient. Sometimes a closed reduction by an orthopaedic/hand surgeon may be necessary to realign the fractured metacarpal. However, surgery is needed if displacement of the abductor pollicis longus (APL) muscle has occurred during the thumb reduction. A special cast named thumb spica cast or a splint are used to hold the bone fracture in place for 4-6 weeks and then replaced with a removable splint if there is sufficient stability with hand movement. Additional thumb fracture management includes:

Rest

Hand elevation

Ice pads

Administration of NSAIDs

Painkillers

Physiotherapy with specific thumb exercises while the hand is in a cast or brace.

Rehabilitation

With or without surgery, the use of a cast or splint is recommended for 6-12 weeks following thumb metacarpal fracture. The prognosis depends on the severity of the fracture. Any physical activities that involve grasping, gripping, pulling and punching should be avoided until a complete fracture healing has been achieved. Once pain has resolved the patient can begin to move the wrist, hand and fingers to prevent stiffness of all joints. Intensive physical therapy usually commences approximately 6-8 weeks after surgery. A physical or occupational therapist will recommend exercises to restore flexibility and strength of the thumb (thumb opposition, extension flexion, etc). The therapist will also advice the patient methods to avoid recurrent injuries. Standard rehabilitative therapy includes:

Massage

Joint mobilisation

Stretches

Electrotherapy

Return to activity plan  

Taping / bracing

Prevention

Preventing thumb fractures is mostly achieved by reducing the risk of falls and protecting the thumb during sports and other professional activities. Common strategies are:

Postural taping

Use of devices to improve elderly patient stability and avoid falls

Wearing protective gear during sport training and carpentry work

Modification of physical activities

Exercise to improve muscle strength, flexibility and posture.