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.

Pathology

The fracture of each carpal bone is the result of different forms of trauma. In the proximal wrist they involve the scaphoid, 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.

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.

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

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.

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

Treatment

Nonoperative 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

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