Distal-Third Forearm Fractures

Updated: Sep 28, 2016
  • Author: Arvind D Nana, MD; Chief Editor: Harris Gellman, MD  more...
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Overview

Background

Distal radius fractures account for approximately 15% of all fractures in adults. A thorough understanding of the pathophysiology and treatment of distal radius fractures is important because these injuries are not limited to just the elderly population. High-energy trauma to the distal radius in younger adults is becoming more prevalent, [1] and long-term functional results are unclear. With an aging patient population that is increasingly active, these common injuries must be evaluated thoroughly and treated adequately. [2, 3, 4, 5, 6, 7]

For patient education resources, see the First Aid and Injuries Center, as well as Broken Arm.

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Pathophysiology

Mechanisms and relevant anatomy

The dorsal metaphysis of the distal radius is subject to tensile and compressive forces during routine forearm activities. The volar surface transmits higher compressive forces. Stable reduction of the distal radius fracture requires that this biomechanical relation be reestablished. Accordingly, the volar buttress must be addressed first in unstable volar fractures (eg, volar Barton fracture, distal radius fracture with significant volar comminution).

In the presence of volar comminution or inherently unstable volar vertical shear fractures, the key to stable fracture reduction is to create a solid volar buttress either by accurate reduction of large volar metaphyseal fragments or by placement of a volar buttress plate. Once volar stability is restored, the dorsal metaphyseal fragments can be reduced against the stable volar buttress.

Restoration of volar stability also has important radiocarpal implications because the stout radiocarpal ligaments are attached to the volar surface. Therefore, volar integrity is critical for the following reasons: (1) it allows reduction of dorsal metaphyseal fragments against a stable volar buttress and (2) it prevents possible radiocarpal instability.

Studies have shown that distal radius fractures often are associated with tears of the triangular fibrocartilage complex (TFCC), scapholunate ligament, and lunotriquetral ligament. [8, 9] Geissler et al found that intracarpal soft-tissue injuries occurred most frequently with fractures involving the lunate facet. [8] The lunate facet and its strong ligamentous attachments with the proximal carpal row and ulnar styloid form the medial complex of the distal radius as described by Melone (see the image below). [10] The carpus almost always is displaced with the palmar and/or dorsal lunate facet die-punch fragment of the distal radius because of the exceptionally strong ligaments of the medial complex.

The medial complex, as described by Melone, consis The medial complex, as described by Melone, consists of the lunate facet and its ligamentous attachments, especially the strong volar ligaments. Displacement of the medial complex has important functional implications.

Scapholunate dissociation can occur with severely displaced distal radius fractures, and the lunate displaces with the medial complex (lunate fossa), while the scaphoid remains with the radial styloid. The scapholunate diastasis usually corrects with reduction of the medial complex. Most of the disrupted soft tissues of the scapholunate articulation can heal with a period of immobilization, and Melone had no cases of subsequent chronic carpal instability. [10]

Scapholunate and lunotriquetral ligament injuries can occur in minimally displaced extra-articular fractures and in severely comminuted intra-articular fractures. The presence of central perforations of the scapholunate ligament and tears of the short radiolunate ligaments has important implications. Although these injuries do not result in scapholunate instability, Richards et al found false findings on arthrograms in 8% of patients in whom arthrography rather than arthroscopy was used for diagnosis. [9]

With arthroscopy, it is difficult to evaluate injury to the volar extrinsic ligaments, including the radioscaphocapitate and long radiolunate ligaments, because these ligaments may be pulled taut with the longitudinal traction necessary for entry of the arthroscope. [8]

Distal radius fractures characterized by shortening and dorsal angulation are more likely to have a TFCC disruption, but preoperative radiographs have no predictive value in identifying specific interosseus ligament injuries. Intra-articular and extra-articular distal radius fractures commonly are associated with ligamentous injuries and tears of the radial aspect of the TFCC; however, disruption of the ulnar insertion of the TFCC is uncommon. That certain intra-articular fracture patterns are associated with fewer TFCC injuries emphasizes the role played by the TFCC in force dissipation and stability after a distal radius fracture. [9]

In general, the authors do not treat carpal ligament injuries (including TFCC injuries) that are associated with distal radius fractures that do not show visible deformities on plain radiographs. The authors believe that with accurate fracture reduction, the ligaments heal during the postoperative or postreduction immobilization period. However, whenever an external fixator is applied, it must be used for neutralization only because excessive traction can displace or complete undiagnosed partial carpal ligament tears.

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. [11]

Although the Frykman system for classification of distal radius fractures has been used extensively in the medical literature, this classification fails to identify the direction and extent of fracture displacement. [12] 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 [12] :

  • 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. [13] 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." [13]

Despite the negative aspects of the various tools for classifying distal radius fractures, 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 [13] :

  • 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. [14]



* 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 distal radius fractures. 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. [15]

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 distal radius fractures. (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 distal radius fractures.

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Etiology

The typical mechanism of a dorsally displaced distal radius fracture is a fall on an outstretched hand. This type of injury results in tensile forces across the volar surface (compression side), compressive forces on the dorsal surface (tension side), and supination of the distal fracture fragment. In the young adult, distal radius fractures are often caused by high-energy trauma. In the elderly patient, low-energy trauma, such as a fall from a standing height, can result in this injury.

Compression and torsion across the articular surface can cause various patterns of intra-articular displacement. Dorsal and palmar shear fractures of the medial complex are examples of compression applied to specific locations. Radial styloid fractures can be due to compression and/or torsion.

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Prognosis

Fractures of the distal radius are not simple injuries and, thus, require careful evaluation of the radiocarpal joint, the distal radioulnar joint, and the carpal bones. However, educated decision making based on objective data and patient profile can lead to optimal outcomes of these challenging fractures.

The prognosis is dependent on the functional expectations of the patient, and as such, anatomic restoration of the distal radius and early radiocarpal joint mobilization are important for patients with high functional demands.

In a study by Clayton et al, a high correlation was identified between bone mineral density and the severity of distal radius fractures. In patients with osteoporosis, the probability of early instability was 43%; the probability of late carpal malalignment, 39%; and the probability of malunion, 66%. In patients with osteopenia, the probability of early instability was 35%; the probability of late carpal malalignment, 31%; and the probability of malunion, 56%. These findings compared with a 28% probability of early instability, a 25% probability of late carpal malalignment, and a 48% probability of malunion in patients with normal bone mineral density. [16]

Koenig et al evaluated whether early internal fixation or nonoperative treatment is preferred for displaced, potentially unstable distal radial fractures with initial adequate reduction. They found that internal fixation with a volar plate provided a higher probability of painless union for potentially unstable distal radius fractures. In most cases, long-term gain in quality-adjusted life years outweighed the short-term risks of surgical complications, making early internal fixation the preferred treatment. In patients older than 64 years, however, nonoperative treatment may be preferred because of lower disutility for malunion and painful malunion outcome states. [17]

In postmenopausal women, detailed bone structure and strength measurements provide insight into the pathogenesis of forearm fracture, but femoral neck area bone mineral density (BMD) provides adequate measurement for routine clinical risk assessment, according to Melton et al. Fracture cases had inferior bone density, geometry, microstructure, and strength. The factor-of-risk was 15% worse in patients with forearm fracture. [7]  See also the Fracture Index WITH known Bone Mineral Density (BMD) calculator.

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