Distal-Third Forearm Fractures

Updated: Feb 19, 2019
  • Author: Arvind D Nana, MD; Chief Editor: Harris Gellman, MD  more...
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Overview

Background

Distal radius fractures (DRFs) account for approximately 15% of all fractures in adults. A thorough understanding of the pathophysiology and treatment of DRFs is important because these injuries are not limited to 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

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 DRF requires that this biomechanical relation be reestablished. Accordingly, the volar buttress must be addressed first in unstable volar fractures (eg, volar Barton fracture, DRF 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 DRFs 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 DRFs, 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]

DRFs 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 DRFs 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 DRF. [9]

In general, the authors do not treat carpal ligament injuries (including TFCC injuries) occurring in association with DRFs 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.

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Etiology

The typical mechanism of a dorsally displaced DRF 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, DRFs 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 (DRUJ), 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; accordingly, 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 (BMD) and the severity of DRFs. [11] In patients with osteoporosis, the probability of early instability was 43%; that of late carpal malalignment, 39%; and that of malunion, 66%. In patients with osteopenia, the probability of early instability was 35%; that of late carpal malalignment, 31%; and that 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 BMD.

Koenig et al evaluated whether early internal fixation or nonoperative treatment is preferred for displaced, potentially unstable DRFs with initial adequate reduction. [12] 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.

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

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