Carpal bone fractures
Drawing of the wrist anatomy illustrating the carpal bones

Definition

This is a fracture of one or more of the eight carpal bones of the wrist located between the radius and the ulna bones of the forearm and the metacarpal bones of the hand. This chapter describes the fractures of all carpal bones with the exception of the scaphoid, which is elaborated in a separate chapter.

Examples of various carpal bone fractures

Pathology

The fracture of each carpal bone is the result of different forms of trauma. In the proximal wrist they involve the scaphoid, the lunate, triquetrum and pisiform and in the distal wrist the hamate, capitate, trapezium and trapezoid. Together they comprise 18% of all wrist-hand fractures. The scaphoid fracture is the most common one reaching 70%. The mechanisms leading to these fractures are divided into: direct trauma, indirect trauma and high-energy injuries. The fracture of each carpal bone is described individually in the following sections.

The lunate

The fracture of the lunate can occur as a crash fracture from a traumatic impact onto the heel of the hand or as a consequence of repetitive trauma causing micro-fractures that over time develop into a degenerative condition of the lunate. Due to the particular anatomical structure, the lunate is normally poorly vascularised. Therefore, damage to vessels caused by a fracture can compromise blood supply to the bone. This reduces the success of healing, potentially causing bone necrosis (death) or Kienböck’s disease and wrist osteoarthritis (see separate pathologies). 

The triquetrum

The triquetrum may be fractured by a direct blow to the dorsal hand or by a forced dorsiflexion of the wrist as it happens with a fall. The fractures of the triquetrum are differentiated into fragment or chip fractures and fractures across the entire carpal bone. Such fractures can be complicated by bone displacement requiring surgical treatment.

 The trapezium

The fracture of the trapezium, located below the thumb, is usually the result of an impact to the dorsal side of the hand or the radial deviation of the wrist. These fractures often occur along the bone ridge.

The capitate

The capitate is the central carpal bone situated below the middle finger. Its fracture is usually associated with wrist dislocation or a fracture to the scaphoid. When isolated the capitate fracture is the consequence of a force load to the third metacarpal bone of the hand. The fractures of this bone are less common compared to other carpal bones.

The hamate

The fractures of the hamate are frequently located at the bone hook and occasionally throughout the carpal bone. They are caused by crushing injuries, direct trauma to the outstretched hand as well as stress fractures. Hamate fractures may be associated with the dislocation of the fourth and fifth metacarpal bones (little and ring finger) at the radial side of the wrist. Hook fractures are mostly treated conservatively.

The pisiform

Due to its location at the palmar side of the hand, the fracture of the pisiform occurs with a traumatic impact to the heal of the hand. It is generally treated conservatively.

Example of a minimally displaced fracture of the capitate bone

Classification

Carpal fractures are classified as non-displaced, when the bone fragments maintain their anatomical position, or displaced when the bone fragments have moved from their original anatomy. These characteristics determine the therapeutic approach, with conservative versus operative treatment.

Left: Distal radius intraarticular, displaced fracture; Middle: Older distal radius fracture with callus formation; Right: Distal radius and ulna fracture, extraarticular and displaced

No 2.

Intra-articular fracture extends to the wrist joint (or articulation)

Extra-articular fracture is located outside of the wrist joint

Open fracture when bone fragments perforate the skin

Comminuted fracture when the bone breaks into multiple fragments

Non-displaced when the anatomical alignment of the bone is maintained or displaced when the bone fragments move apart.

Melone’s classification describes the characteristics of intra-articular fractures of the radius:

i    Stable fracture

ii    Unstable "die-punch"

iii   "Spike" fracture

iv Split fracture

v   Explosion injuries

Acetabular fracture of the pelvis

Acetabular fractures

These fractures are divided into:

Anterior pillar (not weight bearing part of joint)

Posterior pillar (often associated with dislocation of the hip including the weight bearing part of joint)

Transverse

Comminuted involving both column type 

Sacral / coccygeal fractures

The sacrum is a triangular-shaped bone formed by 5 fused vertebrae, which provide a posterior wall to the pelvic ring. At each side of the sacrum, the ala structures articulate with the ilium bones forming the sacro-iliac joints. Sacral fractures are usually parallel to the spine and can involve the ala. Less frequently sacral fractures may display an “H” shape, including a transversal fracture uniting both sides of the sacrum. Three zones are described where sacral fractures can occur that are along vertical lines relative to the alignment of the foramina. Sacral fractures may result in sacral instability and require treatment via sacroplasty (injection of bone glue into the fracture). Surgery is necessary in case of associated neurological symptoms.

Fractures of the coccyx involve the tailbone, the terminal portion of the spine situated below the sacrum formed by 3 to 5 fused vertebrae. Coccyx fractures occur when falling on a seated position. They are more common in elderly women and seldom require surgical treatment.

Falling on the hand heel may lead to a carpal bone fracture

Causes

The causes leading to carpal fractures include:

Fall on the outstretched hand

Blow to the dorsal or the palmar side of the hand/wrist

Repetitive traumas causing stress fractures (hamate hook)

Crush injury

Dislocation caused by hyperflexion or hyperextension of the wrist

Lateral dislocation

The use of bat in ice hockey is a risk factor for carpal bone fracture

Risk factors

Possible risks factors leading to carpal bone fractures include:

Sports using racquets, clubs and bats (tennis, baseball, hockey) (hamate fractures)

High risk of falls in the elderly

Workers with frequent repetitive grabbing, gripping or lifting activities.

Swelling is a characteristic of a carpal bone fracture

Symptoms

The symptoms arising from a carpal bone fracture are:

Sharp pain at the carpal region of the wrist affected

Pain at the ulnar aspect of the palm or dorso-ulnar aspect of the wrist

Central dorsal wrist pain

Tenderness at touch

Pain exacerbated with wrist movement

Swelling

Reduced pinch grip strength

Diminished wrist movement

Wrist instability

Kirk Watson test is used to assess particularly the scapho-lunate instability

Diagnosis

The medical specialist will review the medical history of the patient including the occurrence of previous wrist dislocations, injuries or predisposing activities. Clinical examination will determine:

Changes in the anatomy of the injured wrist against the healthy wrist

Tenderness when applying gentle pressure on the fractured carpal bone (acute fracture)

Pain when applying pressure to the wrist or when extending the wrist

Testing for grip strength

X-rays usually confirm the presence of a carpal bone fracture. Images are taken under different views: antero-posterior and lateral planes to visualise the complexity of the carpal bone arrangement in the wrist. This increases the chance to detecting a fracture that could be overseen. A CT scan or MRI allow for a superior characterisation of carpal fractures and thus provide a guide towards suitable treatment.

Treatment

Conservative treatment of a carpal bone fracture with a brace

Non-operative treatment

The management of the carpal fractures varies in relation to the fracture site and whether or not the fracture is displaced or comminuted. Uncomplicated fractures are usually managed conservatively. Rest and immobilisation with a short-arm cast for up to 6-8 weeks is the treatment of choice. Additional treatments include:

Ice pads

Administration of NSAIDs

Pain killers

Left: intercarpal fixation; Right: necrosis of the lunate months after fracture

Surgical treatment

Surgery is required in significantly displaced fractures of the carpal bones or following the diagnosis of a non-union from an older untreated fracture.

Internal fixation is done in displaced fractures using special screws and wires after an incision is made either on the back or the frontal side of the wrist. The size of the incision varies depending on the level of fracture. This fixation will accelerate the healing process and allow a faster return to sports and other daily activities. A graft may be used if the bone is comminuted in several parts.

Complications

In case of complications e.g. non-unions, following a carpal bone fracture, surgery will involve the removal of the necrotic bone followed by the replacement with a bone graft taken from the wrist or the pelvis region. This procedure also includes the vessels of the grafted bone to ensure optimal blood supply and healing. The recovery time after a bone graft can last several months of cast treatment. Ultrasound and electromagnetic waves can support the bone healing process. Other complications after carpal bone fracture include:

Non-union of the carpal bone if fracture was untreated immediately after injury

Non-union combined with an injury to the radial artery causing avascular necrosis of the bone. This is often detected with X-rays months after injury and requires surgical treatment

Lunate bone is at particular risk to develop avascular necrosis after a fracture

Nerve injury (ulnar nerve after hamate fracture)

Wrist arthritis involving chronic pain and restricted wrist movement

Infection

Strengthening exercise of the wrist is recommended after a carpal bone fracture

Rehabilitation

Regardless of the treatment type following a carpal bone fracture, a cast or splint is normally worn for 9-12 weeks or up to 6 months. Any physical activities that increase the risk of a fall or stress to the wrist should be avoided until the carpal fracture has completely healed. To prevent stiffness, it is critical to maintain finger movement and begin physical therapy soon after the fracture has repaired, approximately 6-8 weeks after surgery.

A physical or occupational therapist will recommend exercises to restore flexibility and strength of the wrist including fine movement of the fingers. Education will inform the patient how to modify activities to avoid future carpal injuries. Standard rehabilitative therapy includes:

Massage

Joint mobilisation

Stretches

Electrotherapy

Return to activity plan

Taping / bracing

Wrist protection used by a gymnast

Prevention

The main preventative measures aim at reducing the risk of falls and protect the wrist during sport or working activities that are known to increase the risk of carpal bone fracture. Common preventive strategies are: 

Postural taping

Devices to improve elderly patient stability

Modification of physical activities

Exercise to improve muscle strength, flexibility, balance and posture