Management of Wrist Fractures



Management of Wrist Fractures


Sandeep Jacob Sebastin

Kevin C. Chung



The wrist is one of the most complex joints in the body and links the forearm to the hand. Anatomically the wrist consists of eight carpal bones, but functionally it extends from the distal forearm to the base of the metacarpals and includes the distal ends of the radius and the ulna, eight carpal bones, and the bases of the metacarpals (Figure 76.1). The distal radius and ulna refer to the distal 2 to 3 cm metaphyseal (cancellous) portion of these two bones.1 The carpal bones are arranged in two rows. The proximal row includes the scaphoid, lunate, and the triquetrum and the distal row includes the trapezium, trapezoid, capitate, and the hamate. The pisiform is a sesamoid bone in the tendon of the flexor carpi ulnaris (FCU) and lies palmar to the triquetrum.2 This complex architecture of the wrist is maintained by the inherent geometry of the bones that are held together by numerous extrinsic and intrinsic ligaments (Chapter 81). This joint configuration maintains stability and allows for transfer of loads from the hand, while providing tremendous mobility. This chapter discusses the management of fractures of the wrist with emphasis on the distal radius and the scaphoid with brief mention of avascular necrosis of the lunate (Kienbock disease).


DISTAL RADIUS FRACTURES

A fracture of the distal radius and/or ulna is the most common fracture seen by physicians accounting for 15% to 20% of all fractures. There is a bimodal age distribution, with peaks of incidence occurring in the youth and in the elderly.3,4 In the younger population, these fractures are most often the result of high-energy trauma such as motor vehicle accidents or falls from a height. In the elderly population, however, these fractures frequently result from falls from a standing height and other low-energy trauma.5 Although the overall gender rates are similar, the fractures in men tend to occur in the younger group, whereas there is a preponderance of females in the elderly group due to osteoporosis. In the United States, approximately 280,000 fractures occur in working-age persons and the economic impact of these injuries is considerable, as patients take an average of 12-16 weeks to return to work. Approximately 10% of 65-year-old white women will experience a distal radius fracture in their lifetime and the annual incidence of distal radius fractures in the US population over the age of 65 has been reported to be 57-100 per 100,000. These numbers will rise in the future because the “Baby Boomers” are aging and individuals are living longer and lead healthier and more active lives compared to previous generations.6






FIGURE 76.1. The bones of the wrist as seen from the volar surface.


Anatomy

The ulna articulates proximally with the humerus and represents the stable unit of the forearm. The radius (with the associated carpus and hand) rotates around the ulna at the proximal and distal radioulnar articulations.3 The volar surface of the distal radius is relatively flat, whereas the dorsal surface is convex and closely related to the overlying extensor tendons. The volar cortex of the distal radius is also considerably thicker than the dorsal cortex. The distal ends of the radius and ulna articulate with the proximal carpal row. The distal end of the radius has three articular fossae (Figure 76.2). The most radial is the triangular scaphoid fossa with the radial styloid at its apex. An anteroposterior ridge (interfacet ridge) separates the scaphoid fossa from the lunate fossa. The sigmoid fossa is located along the distal ulnar surface of the radius and articulates with the ulnar head.7 It has a poorly defined proximal margin, but well-defined distal, volar, and dorsal margins.8 The carpus is separated from the distal end of the ulna by the triangular fibrocartilage complex (TFCC). The TFCC originates on the ulnar border of the lunate fossa and inserts onto the base of the ulnar styloid.9


Biomechanics

Approximately 80% of the axial load across the wrist is transmitted through the distal end of the radius and 20% across the TFCC and the distal end of the ulna.3 Most fractures of the radius occur at the metaphysis because it is mostly spongy cancellous bone. Fractures may be either extra-articular or intra-articular involving the radiocarpal and/or distal radioulnar joint/s (DRUJ). Extra-articular fractures often follow a fall on an outstretched, extended hand. Because the dorsal cortex is thinner compared to the volar cortex, it is frequently comminuted and results in the classic dinner fork deformity (dorsal displacement with dorsal tilt [loss of normal volar tilt], radial tilt [loss of radial inclination], and shortening [loss of height]).10 Intra-articular fractures usually result from higher energy trauma and the fracture pattern depends on the magnitude and direction of force and the quality of bone and soft tissues. The lunate can exert pressure on its fossa causing a die-punch fracture. A multifragmentary intra-articular fracture pattern with four large fracture fragments is often seen. These fragments are the radial styloid, the radial shaft, and volar and dorsal lunate fossa fragments.1 Occasionally the articular surface is sheared off to produce a fracture subluxation of the wrist. Other deforming forces around the distal radius include the insertion of the brachioradialis on the radial styloid, associated injuries to the ulnar styloid or the TFCC that can lead to DRUJ instability, and intercarpal injuries that can lead to carpal instability.11






FIGURE 76.2. The distal articular surface of the radius and ulna.







FIGURE 76.3. Standard PA radiograph of wrist. A. Positioning for a wrist PA radiograph. B. A correctly positioned PA view showing the ECU groove radial to the ulnar styloid.






FIGURE 76.4. Standard lateral radiograph of wrist. A. Positioning for a wrist lateral radiograph. B. A correctly positioned lateral view showing the pisiform (white dotted lines) overlying the distal scaphoid (green dotted lines) and the capitate (red dotted lines).




Radiographic Evaluation

The posteroanterior (PA) and lateral radiographs are routine. The PA view is obtained with the shoulder in 90° abduction, the elbow in 90° flexion, and the wrist and forearm in neutral rotation (Figure 76.3A).13 In a true standard PA view, the groove for the tendon of the extensor carpi ulnaris should be at the level or radial to the base of the ulnar styloid (Figure 76.3B).9 The lateral view is obtained with the shoulder in 90° adduction, elbow in 90° flexion, and the hand positioned in the same plane as the humerus (Figure 76.4A). In a true lateral view, the palmar cortex of the pisiform should overlie the central third of the interval between the palmar cortices of the distal scaphoid and the head of the capitate (Figure 76.4B).






FIGURE 76.5. Measurement of radiographic parameters of the distal end of the radius [Radial height (red dotted lines), radial inclination (white dotted lines), and volar tilt (green dotted lines)].

Three radiographic measurements on standard PA and lateral views correlate with patient outcome: radial height, radial inclination, and volar tilt (Figure 76.5).9,11,13 The radial height is measured on a PA radiograph as the distance between a line perpendicular to the long axis of the radius passing through the distal tip of the sigmoid notch at the distal ulnar articular surface of the radius and a second perpendicular line at the tip of the radial styloid. Normal radial height averages 10 to 14 mm. The articular surface of the radius has a radial to ulnar slope (radial inclination) and a dorsal to volar slope (volar tilt).

The radial inclination is also measured on a PA radiograph and represents the angle between one line connecting the tip of the radial styloid and the ulnar aspect of the distal radius and the second line perpendicular to the longitudinal axis of the radius. The normal radial inclination ranges between 20° and 25°. The volar tilt is measured on a lateral radiograph and represents the angle between the line along the distal articular surface of the radius and a line perpendicular to the longitudinal axis of the radius. The normal volar tilt averages 11° and has a range of 5° to 15°. An additional radiographic parameter that is useful is ulnar variance. Ulnar variance refers to the distance between the articular surface of the ulnar head and the ulnar border of the lunate fossa. It is described as neutral when both are at the same level: ulnar plus, when the ulna is longer; and ulnar minus, when the ulna is shorter (Figure 76.6). Normal ulnar variance can range from 0 ± 2 mm.







FIGURE 76.6. Measurement of ulnar variance.

Plain radiography may be insufficient in the assessment of the comminuted, grossly displaced, and complex intra-articular fractures. Computed tomography (CT) is performed in such cases (Figure 76.7). CT should also be considered when a detailed evaluation of an articular step or gap is required. Magnetic resonance imaging (MRI) is useful when concomitant ligamentous injuries are suspected or fractures are suspected but not visualized on routine radiographs (Chapter 81). A dynamic fluoroscopic examination is also useful for detecting carpal instability.


Classification

Many eponyms and classification systems have been used to describe distal radius fractures. A list of common eponyms has been provided because they are frequently used in clinical practice (Figure 76.8). The commonly used classification systems include the Frykman,14 Melone,15 Fernandez,16 Mayo Clinic,17 and the AO18 (Association for the Study of Internal Fixation) classifications. The Frykman, Melone, Mayo clinic, and the AO classifications focus on the fracture pattern, whereas the Fernandez classification is based on the mechanism of injury. We use the AO classification in our practice. It divides the fractures into three broad groups (A. Extra-articular; B. Partial involvement of articular surface; and C. Involvement of entire articular surface). These are then subdivided into 9 subtypes or 27 distinct fracture patterns (Figure 76.9).






FIGURE 76.7. CT images of a comminuted intra-articular distal radius fracture demonstrate the comminuted and impacted “die-punched” articular fragments.

Jun 26, 2016 | Posted by in General Surgery | Comments Off on Management of Wrist Fractures
Premium Wordpress Themes by UFO Themes