Carpal Fractures 

This article addresses carpal fractures in the hand. Because treatment varies depending on the carpal element involved, fractures of the various bones are discussed individually. This article addresses carpal fractures in the hand. Because treatment varies depending on the carpal element involved, fractures of the various bones are discussed individually.

Wilhelm Conrad Roentgen's discovery of x-rays, for which he was later awarded the Nobel Prize in Physics, was a major turning point in the understanding and categorization of wrist fractures. One year after Roentgen obtained the first radiograph of the hand in 1895, Sir Robert Jones published the first report on the clinical use of a radiograph to locate a bullet in the wrist. By the early 20th century, the radiograph allowed for the description of almost every currently known wrist fracture (see example in image below).

Radiographs provided insights into fracture fixation that proved particularly valuable by the mid-20th century. Treatment of war injuries has always played a significant role in the development and refinement of surgical principles and procedures. The knowledge obtained from treating casualties during World War I played an important role in the treatment of fracture fixation during World War II, when military surgeons developed a number of fixation procedures with the intent of expediting the return of soldiers to the battlefield.

Martin Kirschner was a German surgeon known for his fixation methods, particularly the development of the Kirschner wire (K-wire) fixation technique. Contemporary surgeons continue to favor this fixation method in the treatment of unstable fractures. The K-wire fixation method is technically easy to perform and probably the least traumatic method of fixing bones.

In the years following the war, advances in the treatment of carpal fractures included refinements in surgical techniques and improvements in prosthetic implants available for reconstruction. Wrist arthroscopy is a minimally invasive technique that has an established role in the diagnosis and staging of wrist pathology. Diagnostic wrist arthroscopy is becoming the standard against which other diagnostic techniques are being compared. Similarly, staging arthroscopy has found an appealing role in evaluating and documenting the progression of disease and in tailoring treatment options accordingly.^[1]

The latter half of the 20th century also witnessed the development of new devices for rigid internal fixation. The Herbert bone screw has been a useful device. It provides highly secure internal fixation that allows for early mobilization. Originally designed to treat scaphoid fractures, this method of fixation has expanded to include fixation of other small osseous fractures as well. The Acutrak bone screw is a fully threaded, conically shaped implant with variable pitch threads.

More recently, the bone screw has been developed for use in cancellous applications in which good compression and a headless design are desired. The unique combination of variable thread pitch, along with a fully threaded and tapered profile, provides excellent compression and holding power. In addition, bioresorbable implants are now being evaluated for fracture fixation. Studies to refine and improve the torsional strength and rigidity of such materials continue and may perhaps play a role in improving the treatment of unstable carpal fractures.

Frequency

Upper-extremity fractures are among the most common fractures of the skeletal system.^[2] Carpal bone fractures account for 18% of hand fractures. Of the carpal elements, bones in the proximal row are the most frequently fractured. The scaphoid is by far the most common carpal bone fractured, representing 70% of fractures in the carpal group and 10% of all hand fractures.^{[3, 4]} Triquetral fractures are the second most common, accounting for 14% of wrist injuries. The incidence of isolated fractures of any of the remaining carpal bones is comparatively low, in the range of 0.2-5%.^[5]

Carpal injury is usually a result of direct or indirect trauma. In general, mechanisms that cause carpal fractures are injuries of moderately high energy. If the diagnosis is not established early or if a displaced fracture displacement is not recognized, disability may result.

Scaphoid fractures

Two thirds of scaphoid fractures occur at the wrist, an area of the bone that can be impinged upon by the styloid process of the radius during a radial deviation maneuver. This fracture is usually associated with a force applied to the distal pole of the scaphoid, often with the wrist hyperextended. The radiostyloid essentially functions as a fulcrum against the center of the scaphoid, resulting in the predominance of fractures at the wrist level. The mechanism of injury usually consists of a fall on the palm of an outstretched hand. On clinical examination, pain is elicited when pressure is exerted on the distal pole or on the scaphoid at the anatomic snuffbox on the radial aspect of the wrist.

Triquetral fractures

The mechanism of triquetral injury usually consists of either a direct blow to the dorsum of the hand or extreme dorsiflexion of the hand. The fracture is thought to result either from the hamate being forced against the triquetrum or from the ulnar styloid creating a volar compressive force on the dorsal aspect of the triquetrum. On clinical examination, palpation of the triquetrum is facilitated by radial deviation of the hand. This maneuver allows direct palpation of the triquetrum as it moves away from the ulnar styloid process. Point tenderness is usually elicited directly over the triquetrum.

Lunate fractures

The mechanism of lunate fracture involves either chronic repetitive trauma leading to multiple microfractures or a direct traumatic blow resulting in a primary fracture. The etiology of avascular necrosis of the lunate or Kienböck disease has long been debated.^{[6, 7]} The arterial blood supply of the lunate is variable, and it may be predominately derived from a single vessel. Other evidence, however, suggests that venous stasis may be more of an etiologic factor than an inadequate arterial supply. The diagnosis should be suspected in the patient who reports central dorsal wrist pain, loss of motion at the wrist, and diminished grip strength. Tenderness is demonstrated with direct palpation of the dorsal aspect of the lunate.

Pisiform fractures

Pisiform fractures usually involve either a direct blow to the ulnar aspect of the wrist or forceful hyperextension, as in a fall on an outstretched hand. On clinical examination, the diagnosis is suggested by pain and tenderness with direct palpation of the pisiform.

Trapezial fractures

Trapezial fractures usually result from a direct blow to the dorsum of the hand or from a fall on a radially deviated closed fist. Patients usually complain of a painful and weak pinch. On clinical examination, point tenderness is present on direct palpation of the trapezium.

Hamate fractures

The mechanism of hamate injury usually involves direct trauma to the volar aspect of the hand. It is not an uncommon injury in athletes who sustain a direct blow against the hamate while gripping the handle of a tennis racquet, golf club, or baseball bat. The end of the handle strikes the hamate during an unorthodox swing, resulting in a fracture. Pain elicited with the gripping of objects is a common complaint. On clinical examination, tenderness is localized to either the volar or dorsal ulnar aspect of the wrist.^[8]

Capitate fractures

Because of its protected position, isolated fractures of the capitate are rare. Capitate injury usually involves a direct axial load transmitted down the shaft of the third metacarpal with the wrist in dorsiflexion and slight radial deviation. Tenderness is demonstrated with direct palpation immediately proximal to the base of the third metacarpal.

A complete history should be obtained from each patient being evaluated for a potential wrist injury. A thorough physical examination and extensive radiographic evaluation should be complimented with basic knowledge of wrist anatomy and common fracture patterns. This vastly improves the accuracy of the diagnosis and thereby directs the treatment of carpal fractures.^{[9, 10, 11, 12]}

Once the diagnosis is established, the cardinal objective is to obtain and maintain normal anatomic alignment, because nonanatomic positioning may lead to functionally disabling results. Thereafter, treatment revolves around protective immobilization followed by thorough rehabilitation of the injured hand. These established principles provide clinical guidelines for the management of carpal injuries, and they are critical steps to a successful outcome in the treatment of carpal fractures.

The accepted indications for surgical intervention in the treatment of carpal fractures include the presence of an unstable or displaced fracture, an open fracture, and failure of nonoperative treatment with established nonunion.

Located between the forearm and hand, the wrist extends from the insertion of the pronator quadratus on the radius and ulna proximally to the carpometacarpal joints distally. The wrist contains 8 carpal bones, all of which are associated with a network of tightly interwoven ligamentous connections.

The vascular supply to the wrist begins with the radial and ulnar arteries, as well as the anterior and posterior interosseous arteries. These vessels contribute to the formation of palmar and dorsal vascular arches that provide circulation to the carpal bones. The pattern of blood flow to the scaphoid is of particular importance. The scaphoid receives its blood supply through 2 small branches that primarily arise from the radial artery. The palmar scaphoid branch enters the cortex at the distal pole of the scaphoid and the dorsal scaphoid branch enters along the dorsal ridge. Circulation to the proximal pole is maintained in a retrograde fashion by the intraosseous vessels.

Because the vascular supply of the proximal pole primarily relies on vessels entering the scaphoid, more distal injuries to the wrist of the scaphoid may disrupt the blood flow, thereby making the proximal pole particularly susceptible to ischemic changes. A fracture of the wrist may interfere with the proximal flow, placing the scaphoid at risk for avascular necrosis.^[13]

The treatment of carpal fractures has no absolute contraindications. The key to treatment is to obtain and maintain anatomic alignment with the most appropriate method.