Radiocarpal Dislocations and Fracture Dislocation

Introduction

Radiocarpal dislocations are rare injuries that occur as a result of a high-energy mechanism. The initial descriptions of this injury were prior to the advent of radiographs, at which time the clinical deformity of a distal radius fracture was presumed to be a dislocation of the joint. The advent of radiography naturally elucidated the bony injuries underlying clinical deformities and allowed better comprehension of the spectrum of distal radial injuries. In fact, true radiocarpal dislocation was not confirmed until the postmortem examinations by Malle in 1838. Subsequent published series have documented these injuries, with a reported incidence of 0.2% of all wrist injuries.

Since the original documentation of these injuries in 1838, we have come to appreciate that radiocarpal dislocations are, in fact, a spectrum of injuries involving the bony and ligamentous structures which allow “internal disarticulation of the wrist joint.” This can be associated with intercarpal instability, multiplanar instability of the radiocarpal joint, progressive ulnar translation of the carpus, as well as posttraumatic arthritis.

The most common causes of radiocarpal dislocation include falls from height, motor vehicle collisions, and industrial accidents. These are typically polytrauma patients with high-energy mechanisms. In one series, all patients had injury to another organ system, highlighting the importance of looking beyond the distracting extremity injury to focus on the whole patient. Given the energy imparted to create these injuries, associated traumatic neurovascular insults are not uncommon and demand scrutiny in the workup and evaluation of these patients. Arterial occlusion can occur secondary to the deformity of the dislocation and is often remedied with reduction by longitudinal traction. ^, Neurologic injuries may occur, especially in open fracture-dislocations, with the median nerve more often affected than the ulnar nerve. ^,

The radiographs of these injuries are often dramatic, with obvious dislocation at the radiocarpal joint. In contrast, the appearance postreduction can be deceivingly benign, with limited or even no fractures appreciated. Films should be scrutinized for joint diastasis suggestive of intercarpal ligament injury in addition to radial and ulnar styloid fractures. Gilula’s lines may be disrupted in severe carpal instability or fracture to the carpal bones. Evaluation of these lines is an imperative tool in any examination of traumatic wrist films. The films should also be interrogated for dorsal or volar rim fractures. The inclusion of a 10-degree lateral radiograph allows the best appreciation of the volar aspect of the lunate facet to visualize subtle fractures that can be hidden in a standard lateral film. With regard to advanced imaging, computed tomography (CT) is the most sensitive for evaluation of bony injuries. Likewise, magnetic resonance imaging (MRI) is the most sensitive modality for ligamentous injuries, though this is rarely required in the acute setting. These injuries are almost uniformly treated with open reduction, at which point the ligamentous structures are directly identified, obviating the need for advanced imaging. Careful evaluation of plain radiographs with an understanding of the underlying bony and ligamentous anatomy is typically sufficient to identify these injuries and guide appropriate treatment strategies.

Relevant Anatomy

The bony anatomy of the radiocarpal joint is composed of the biconcave articular surface of the radius composed of the lunate and scaphoid facets, as well as the bony buttress of the radial styloid. The extrinsic radiocarpal ligaments, joint capsule, and bony congruity confer stability to the radiocarpal joint.

The volar ligaments take their origin from the volar ridge of the radius. The short radiolunate ligament originates from the most ulnar aspect of the lunate facet and inserts on the volar surface of the lunate. This ligament represents the primary restraint to volar translation of the carpus. The long radiolunate (LRL), radioscaphocapitate (RSC), and radioscapholunate (RSL) ligaments originate more radially along the volar ridge. The RSC is a robust ligamentous structure that is the primary restraint to ulnar translation of the carpus. The radial collateral ligament is an extracapsular ligament that originates from the palmar tip of the radial styloid spanning to the base of the thumb metacarpal and can be confluent with the RSC. ^,

The dorsal radiocarpal (DRC) ligaments originate from the most dorsal and distal edge of the radius. ^, The DRC ligament originates 15 mm from the tip of the radial styloid, between the scaphoid and lunate facet. Along with the dorsal intercarpal (DIC) ligament, the DRC acts as a dorsal stabilizer for the radioscaphoid joint.