Distal-Third Forearm Fractures Workup

Updated: Apr 06, 2021
  • Author: Arvind D Nana, MD; Chief Editor: Harris Gellman, MD  more...
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Workup

Radiography

Initial radiographs of the distal radius should consist of good posteroanterior (PA) and lateral views. A good lateral view demonstrates that the anterior surface of the pisiform lies between the anterior surface of the capitate and the volar surface of the scaphoid tuberosity.

The standard plain radiographs are important because they show the extent and direction of initial displacement, along with information about the distal radioulnar joint (DRUJ). Additional information is obtained later with traction (reduction) radiographs that can help demonstrate whether the distal radius fracture (DRF) is intra-articular or extra-articular, and they can most readily reveal the degree of comminution. In addition to showing the degree of initial displacement, postreduction radiographs are extremely helpful for treatment planning. [2, 13, 14]

Measurements on the reduction radiographs should include the following (see the images below) [15] :

  • Radial inclination (normal, 22°)
  • Radial length (normal, 12 mm)
  • Ulnar variance (normal, 0-1 mm)
  • Volar tilt (normal, 11°)
  • Articular stepoff
  • Articular gap
The normal radial inclination is 22°. The normal radial inclination is 22°.
The normal radial length (RL) is 12 mm, and the ul The normal radial length (RL) is 12 mm, and the ulnar variance (UV) is usually neutral or negative (normal, 0-1 mm).
Lateral radiographic view demonstrates the volar t Lateral radiographic view demonstrates the volar tilt (normal, 11°).

The amount of acceptable articular stepoff is debated, but most authors believe that less than 1-2 mm is desirable. Although long-term functional outcome has not yet been correlated with magnitude of articular stepoff, the development of posttraumatic arthritis certainly has.

Radial length is the measurement along the longitudinal radial axis between the tip of the radial styloid and the articular surface of the ulna styloid. This length is influenced by radial inclination and ulnar variance. [16]  Thus, radial length indicates only the magnitude of longitudinal length discrepancy between the distal radius and ulna, not the specific cause.

Changes in radial inclination and radial shift can result from the multiplanar displacement of the DRF. Pronation or, more commonly, supination of fragments is a frequent deformity that is difficult to measure directly with standard radiographs. Ulnar variance is influenced by metaphyseal comminution and shortening, forearm position, ulnar-head fractures, and/or fracture displacement of the medial aspect of the distal radius. Comparison views of the contralateral uninvolved wrist may assist in the evaluation of complex DRFs.

On plain radiographs, stepoff and gap measurements can be imprecise for various reasons, including nonstandardized radiographic techniques, overlying radiopaque implants, soft-tissue shadows, and/or the complex structure of the distal aspects of the radius and ulna. [17]

Cole et al noted poor interobserver and intraobserver agreement in intra-articular stepoff and gap measurements on plain radiographs of acute DRFs. In the same study, 24% of the plain radiographic values indicated displacement of less than 2 mm, whereas computed tomography (CT) indicated that the displacement was more than 2 mm. Conversely, significant displacement (>2 mm) was noted on 6% of the plain radiographs but not confirmed by the CT readings. [18]

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Plain Tomography and CT

Plain tomography or CT in the sagittal and coronal planes parallel to the longitudinal axis of the radial shaft is extremely helpful in quantifying the displacement and direction of an intra-articular fracture. These techniques are also useful when the fracture pattern is difficult to visualize on plain radiographs. CT is strongly recommended for defining intra-articular fracture patterns, especially those associated with die-punch fractures, volar rim fractures, and fractures involving the scaphoid facet (which can be more difficult to assess on plain radiographs). [15]  The authors routinely obtain CT scans before operating on displaced intra-articular fractures.

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Ultrasonography

Bedside ultrasonography (US) has been shown to be effective in the diagnosis of nonangulated distal forearm fractures in children and may develop into a more portable diagnostic tool helpful in emergency departments (EDs). [19]

Douma-den Hamer et al performed a systematic review and meta-analysis aimed at determining the diagnostic accuracy of US for detecting distal forearm fractures. [20] They found US to have a sensitivity of 97%, a specificity of 95%, a positive likelihood ratio (LR) of 20.0, a negative LR of 0.03, and a pooled diagnostic odds ratio (DOR) of 667, with the six-view method yielding higher specificity, positive LR, and DOR than the four-view method. The authors concluded that US is highly accurate for diagnosing distal forearm fractures in children when the proper viewing method is used and that it could be considered a reliable alternative to radiography in this setting.

Others have found point-of-care US (POCUS) to be useful for diagnosing distal forearm fractures in pediatric EDs. [21, 22]

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Classification

Burstein stated that a classification system must suggest a method of treatment and provide a reasonably precise estimation of the outcome of that fracture. Furthermore, a classification system must have intraobserver repeatability and interobserver reliability. [23]

Although the Frykman system for classification of DRFs has been used extensively in the medical literature, this classification fails to identify the direction and extent of fracture displacement. [24]  As a result, other classification tools have been developed, such as the Association for the Study of Internal Fixation (AO/ASIF), Melone, and Mayo systems. These systems classify the fractures on the basis of the following four distinguishing characteristics [24] :

  • Extent of comminution
  • Radiographic appearance or magnitude of displacement
  • Articular joint involvement
  • Mechanism of injury

Andersen et al compared the Frykman, Melone, Mayo, and AO/ASIF classification systems and concluded that each of the four systems is characterized by a low degree of intraobserver and interobserver agreement. [25]  Consequently, the use of any of these classifications as the primary method to determine treatment and outcome of treatment is not warranted.

Andersen et al also stated, "Some orthopaedists have expressed concern, especially in training programs, that more effort is spent trying to memorize classification systems for a number of fractures, rather than truly understanding the fracture mechanics or the factors that have significant bearing on prognosis or treatment." [25]

Despite the negative aspects of the various tools for classifying DRFs, the AO/ASIF system reached the "substantial level" for both interobserver and intraobserver agreement when these tools were reduced to the following three broad fracture categories [25] :

  • Extra-articular
  • Partial articular
  • Complete articular

These three general fracture categories are incorporated in the classification system that the authors prefer (see Table 1 below).

Table 1. Classification and Treatment Guidelines for Distal Radius Fractures (Open Table in a new window)

Fracture

Treatment*

A: Extra-articular

Stable (nondisplaced or reduced)

CR, splinting

Unstable (displaced)

Dorsal displacement

Large dorsal metaphyseal fragments

Small dorsal metaphyseal fragments (comminuted)

Volar displacement

Large volar metaphyseal fragments

Small volar metaphyseal fragments (comminuted)

CR, PP, splinting

Limited dorsal OR, BG, external fixation

CR, PP, splinting

Volar plating with or without BG

B: Intra-articular

Stable (nondisplaced or reduced)

CR, splinting

Unstable (displaced)

Dorsal fragments

Large dorsal metaphyseal fragments

Small dorsal metaphyseal fragments (comminuted)

Volar fragments (large and small volar metaphyseal fragments)

Dorsal and volar fragments

Large dorsal metaphyseal fragments

Small dorsal metaphyseal fragments (comminuted)

Radial styloid fracture

Large metaphyseal fragments

Small metaphyseal fragments (comminuted)

Central depression fracture

CR, PP, splinting

Limited dorsal OR, BG, external fixation

Volar plating with or without BG

Volar plating, dorsal PP

Volar plating, limited dorsal OR, BG, external fixation

CR, PP, splinting

CR, PP vs OR, volar radial plating

Limited dorsal OR vs AR, BG, PP

Source.—Adapted from Beaty. [26]

* AR indicates arthroscopic reduction; BG, bone grafting of void (eg, iliac crest bone graft, allograft, bone graft substitute); CR, closed reduction; OR, open reduction; PP, percutaneous pinning.

 Closed reduction with manipulation should be attempted on all displaced fractures, and surgery should be considered only in cases of inadequate closed reduction or loss of reduction with splint immobilization.

 Can be considered separately or in combination with other intra-articular fractures.

With regard to the radiographic characteristics of intra-articular fractures, the Melone four-part pattern seems to be fairly reproducible. The basic fragments of this pattern consist of the radial styloid, the dorsal lunate facet die-punch fragment, the palmar lunate facet die-punch fragment, and the radial shaft (see the image below). Various combinations of these basic fragments are manifested consistently in intra-articular DRFs. In addition to variability of fragment displacement, variability of comminution of each individual component fragment also exists.

The basic fragments of the Melone 4-part pattern c The basic fragments of the Melone 4-part pattern consist of the radial styloid, dorsal lunate facet die-punch fragment, volar lunate facet die-punch fragment, and radial shaft. Note that displacement of the dorsal and/or volar lunate facet die-punch fragments also alters the anatomy of the sigmoid notch articular surface; thus, it has important consequences for forearm pronation and supination.

Of historical interest, the Melone four-part pattern can be viewed as the summation of the eponymous Colles, Smith, Barton, and chauffeur fractures. [27]

The volar and dorsal vertical shear fractures (Smith II/volar Barton fracture and dorsal Barton fracture, respectively) have classically been described as partial articular injuries involving the lunate facet of the distal radius. These injuries include volar or dorsal carpal displacement because of the important extrinsic radiocarpal ligaments that attach to the lunate facet. Accordingly, displaced volar and dorsal vertical shear fractures (Barton/Smith fractures) have the same biomechanical implications and treatment methods as displacement of Melone palmar and dorsal lunate facet die-punch fragments, respectively.

The authors' selection of treatment is based consistently on the particular configuration and displacement of the Melone fracture components. Because the goal of a good classification system is to define reproducible clinical characteristics that can guide treatment selection, the authors believe that their treatment algorithm can also serve as a practical classification system for DRFs. (See Table 1 above and Treatment.)

If a dorsal lunate facet die-punch component does not have significant dorsal metaphyseal comminution, it can be reduced against the intact volar surface and stabilized by transfixing percutaneous pins.

Inherent stability is restored with good dorsal cortical apposition. In highly comminuted dorsal fractures in which contact with the dorsal metaphyseal cortex is lost, inherent dorsal stability is established by using bone grafts as void fillers, in combination with external fixation, to maintain neutral tension in the dorsal aspect.

In the presence of unstable volar fragments, the anterior cortex cannot serve as an adequate anterior buttress against which the dorsal fragments can be reduced. In these instances, the authors routinely add a volar plate to stabilize the volar distal cortex (see the image below). Thus, in cases with combined dorsal and volar instability, the dorsal fragments are treated as outlined above, but the volar cortex is reconstructed first with a volar buttress plate.

Postsurgical lateral radiograph shows a good reduc Postsurgical lateral radiograph shows a good reduction of the fracture with a volar buttress plate.

If a displaced radial styloid component is present, it is reduced manually and, if required, stabilized with two parallel radial styloid pins. Open reduction of the radial styloid may be necessary if closed reduction is not successful, and, in the presence of comminution and instability, volar radial plating of the radial styloid is an effective treatment option. Other treatment modalities, such as the use of small lateral buttress plates and clips are currently being investigated. Pronation or, more commonly, supination deformity of the radial styloid must be corrected. The use of intra-operative fluoroscopy is helpful in identifying rotation of the styloid fragment.

Thus, the classification system the authors prefer is a modification of the AO/ASIF and Melone systems that incorporates the various treatment principles described above. The classification system is derived from rational treatment-based options that the authors believe reflect the physiologic differences in each fracture pattern. Table 1 (see above) represents the authors' classification system and a practical guide for treatment of DRFs.

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