Distal Radioulnar Joint Instability and Galeazzi Fractures

Introduction

The Galeazzi fracture-dislocation is a fracture of the distal one-third of the radial shaft with an associated distal radioulnar joint (DRUJ) dislocation. This injury was described first by Astley Cooper in 1826 and later named after Riccardo Galeazzi who published his series of cases in 1934. ^, The Galeazzi fracture has been given the name the “fracture of necessity,” referring to its need for anatomic reduction and rigid internal fixation in order to achieve optimal results. Galeazzi fracture-dislocations require a high index of suspicion and can frequently go underdiagnosed.

Relevant Anatomy

The forearm rotates about an axis that starts proximally at the center of the radial head and travels through the ulnar fovea distally. The radius, attached carpal bones, and hand rotate around a relatively fixed ulna. The ulna is constrained proximally at the elbow through tight bony and ligamentous constraints, allowing it to function only as a hinge joint. In full supination, the radius and ulna are essentially parallel and in full pronation, the radius rotates across the anterior border of the ulna. To allow rotation of the radius around the straight ulna the radius has a natural bow. This bow is best seen in the sagittal plane on a neutral rotation posteroanterior (PA) radiograph of the forearm.

The radius and ulna have ligamentous connections at the proximal and DRUJs as well as the intervening interosseous membrane. The interosseous membrane is a stout ligamentous complex consisting of proximal, middle, and distal portions. The distal interosseous membrane (DIOM) has been shown by several authors to be a stabilizer of the DRUJ. ^, Within the DIOM is the distal oblique bundle (DOB) which is a thickening of the membrane that runs from the proximal attachment of the pronator quadratus at the ulna to the proximal aspect of the sigmoid notch of the radius with some fibers running dorsal and volar to the DRUJ ligaments. Cadaver studies have shown the DOB to be present to a varying degree within the DIOM, being present in 23%–50% of specimens. Kitamura et al. showed in a cadaver model that specimens with a DOB had increased stability of the DRUJ in the neutral position when compared with specimens without a DOB.

The DRUJ is an inherently unstable joint due to the radius of curvature of the sigmoid notch being greater than that of the ulnar head. This radius of curvature mismatch leads to volar/dorsal translation of the ulna in relation to the sigmoid notch of the radius through a full arc of rotation. The limited congruency of the DRUJ necessitates strong soft tissue support, and the triangular fibrocartilage complex (TFCC) serves as the major soft tissue stabilizer of the DRUJ. The TFCC ( Fig. 65.1 ) is a complex structure, composed of the ulnocarpal meniscus (meniscus homolog), the ulnar collateral ligament, the dorsal radioulnar ligament, the palmar radioulnar ligament, and the subsheath of the extensor carpi ulnaris (ECU). The dorsal and palmar distal radioulnar ligaments are thought to provide the majority of the stability to the DRUJ and are subdivided into superficial and deep portions. ^, They originate at the sigmoid notch of the radius with the deep portion inserting at the fovea and the superficial portion inserting at the base of the ulnar styloid. In full pronation and supination, the deep portion of the TFCC (ligamentum subcruentum) becomes the primary stabilizer of the DRUJ. In full pronation, the dorsal superficial fibers, the dorsal joint capsule, and the deep palmar fibers tighten for stability and prevent dorsal dislocation of the ulna. The reciprocal occurs in supination.

Pathoanatomy

The deforming forces on a fracture of the distal third of the radial shaft cause a typical deformity of shortening and rotation of the radius ( Fig. 65.2 ). Shortening of the fracture is created by pull from the brachioradialis as well as the wrist and finger flexors and extensors which cross the fracture. The pronator quadratus creates a rotational deformity on the distal fragment and the pronator teres creates a rotational deformity of the proximal fragment of the radius.

The degree of shortening is determined by the severity of the soft tissue injury to the TFCC and DIOM. Cadaver studies in which a radial osteotomy was created have correlated the amount of ulnar positive variance to the degree of injury to the TFCC and/or DIOM. ^, Moore et al. found that following an isolated radius osteotomy, an average of 4.1 mm of ulnar positive variance was noted with a maximum displacement of 7 mm. With release of the TFCC or the DIOM, an additional 2.9 and 1.3 mm, respectively, of shortening was noted. With subsequent release of both structures, 21 mm of shortening was noted. Schneiderman et al. repeated this study and found similar results with 7.7 mm of shortening with a TFCC release, 6.25 mm of shortening with DIOM release, and 15–40 mm of shortening with both structures released. Both studies concluded that the DIOM and TFCC provide stabilization to the DRUJ in fractures of the radius and >10 mm of shortening is indicative of both structures being disrupted. In a retrospective study of diaphyseal radius fractures, Tsismenakis and Tornetta found that an average of 10.9 mm of ulnar positive variance was associated with persistent intraoperative instability of the DRUJ after open reduction and internal fixation (ORIF) of the radius fracture, in comparison with 3.5 mm of ulnar positive variance in a stable DRUJ.

It has been suggested that an intact DOB after anatomic reduction and stable plate fixation can provide sufficient stability to the DRUJ despite a TFCC tear or ulnar styloid fracture. The mechanism for this is thought to be by restoring tension to the DOB with anatomic and stable fixation of the radius fracture; this creates a compressive force in the coronal plane from the ulna towards an intact sigmoid notch of the radius through a tensioned DOB ( Fig. 65.3 ). The heterogeneity in the presence and thickness of the DOB in cadaver specimens may account for the variable incidence of DRUJ instability after ORIF of a distal-third radial shaft fracture. Furthermore, it is not entirely clear if a dislocation of the DRUJ requires both the palmar and dorsal deep fibers of the foveal attachment of the TFCC to be completely injured. It has been described that with forearm pronation, dorsal dislocation of the ulna occurs with isolated sectioning of the palmar radioulnar ligament, dorsal joint capsule, and dorsal superficial fibers, with the reverse found in palmar dislocations of the ulna. This may indicate that there is a varying degree of injury to the TFCC in the context of an acute DRUJ dislocation. Examination of the DRUJ under anesthesia will demonstrate the degree of injury to the TFCC based upon the direction of instability with forearm rotation.

Classifications

There are several classifications used to described Galeazzi fracture-dislocations. The first was adopted from a series of 41 Galeazzi fracture-dislocations in children. In this series, Walsh et al. categorized the fracture pattern into two groups, palmar or dorsal displacement of the distal radius fragment, and then subdivided these groups into fractures within the distal third of the radial shaft or fractures outside of the distal-third border, creating a total of four groups. Walsh Type 1 fractures demonstrate dorsal displacement of the distal radius fragment and palmar displacement of the distal ulna. Type 2 fractures demonstrate palmar displacement of the distal radius fragment and dorsal displacement of the distal ulna.

Bruckner et al. described complex Galeazzi fracture-dislocations in a series of four cases of an irreducible DRUJ. Simple injury described a DRUJ that was easily reduced and maintained. Complex injuries referred to joints that had recurrent subluxation, dislocation, or were irreducible due to interposed soft tissues. Most commonly, the ECU is displaced palmar to the ulna, preventing a closed reduction of the DRUJ. ^, However, the extensor digitorum communis tendons, extensor digiti minimi tendon, dorsal joint capsule, and a displaced ulnar styloid fracture have all been described as structures that can displace palmar to the ulna and become interposed, causing a complex Galeazzi fracture-dislocation. Complex dislocations required an open reduction to remove the interposed tissue from the joint.

Rettig and Raskin categorized 40 adult injuries into two groups: Type I, in which the radial shaft fracture was located <7.5 cm from the articular surface of the radius and Type II in which this distance was >7.5 cm. They found that 12 of the 13 cases that required treatment for a persistently unstable DRUJ after ORIF of the radial shaft fracture were Type I injuries. The authors concluded that Type I injuries should have a high index of suspicion for combined TFCC/DIOM disruption that can cause persistent DRUJ instability after ORIF of the radial shaft fracture.

Although fractures in the distal third of the radius are the most likely to cause dislocations of the DRUJ, not all distal-third fractures of the radius are associated with dislocations of the DRUJ. Several studies have found that the location of the fracture alone is insufficient to determine if the DRUJ is stable. ^{, ,} Ring et al. reviewed a series of 36 diaphyseal radius fractures, 8 of which were distal-third diaphyseal fractures. Using 5 mm of ulnar positive variance as a measure of DRUJ dislocation, they found nine DRUJ injuries. Of the nine injuries, five were located in the distal third of the radius. Tsismenakis and Tornetta reviewed a series of 66 isolated diaphyseal radius fractures. Intraoperative assessment of DRUJ stability after radial shaft fixation was used as the definition for a fracture-dislocation of the DRUJ. Of the 66 radial shaft fractures, 29 were in the distal third of the radial shaft and 7 were fracture-dislocations. Of the 26 fractures occurring within 7.5 cm of the radiolunate joint, only 5 were associated with DRUJ instability. There is a large discrepancy between the incidence of DRUJ instability with distal-third radial shaft fracture between the studies by Ring (63%) and Tsismenakis (19%). Thus the index of suspicion for a combined injury should remain high.

Galeazzi equivalent lesions refer to injuries that occur in children with concomitant fracture of the distal ulna. This can consist most commonly of an ulnar styloid fracture in adults or a transphyseal fracture of the distal ulna in a child with an open distal ulna physis. The latter injury pattern leaves the distal radioulnar ligaments intact, remaining attached to the ulna epiphysis. The ulnar styloid fracture in an adult will have variable amounts of attached soft tissues depending on the size of the fragment.

Presentation and Evaluation

Patients typically present with characteristic swelling and deformity due to prominence of the ulna from a dislocated DRUJ and shortened radius ( Fig. 65.3 ). With less displaced radial shaft fractures, palpation of the DRUJ should be performed to identify tenderness that could indicate DRUJ disruption. A thorough neurovascular examination should be performed as rare injuries to the median and ulnar nerve have been reported. ^, Skin should be fully assessed to evaluate for an open fracture. History obtained from the patient typically reveals a high-energy fall or mechanism of injury such as a motor vehicle accident. While a fall onto an outstretched arm with forced pronation or supination of the forearm is the typically described mechanism, the characteristic Galeazzi fracture-dislocation has not been reproduced in a biomechanics laboratory.

Radiographs of the wrist, forearm, and elbow should be obtained and should include PA and lateral views ( Fig. 65.4 ). On the PA view, characteristic shortening and rotation of the radius is noted ( Fig. 65.2 ) as well as widening of the space between the sigmoid notch of the radius and the distal ulna. A lateral radiograph ( Fig. 65.4B ) will demonstrate either dorsal or palmar displacement of the radius; this should be noted as it may help the surgeon identify the direction of instability after reduction of the radius. The majority of these injuries will be Walsh Type 2 injuries. While not diagnostic for DRUJ instability, specific attention should be made to the level of the radius fracture and amount of ulnar positive variance due to proximal displacement of the radius, as a radius fracture <7.5 cm away from the articular surface of the radius and with >10 mm ulnar positive variance have been associated with DRUJ instability after radial shaft ORIF ( Table 65.1 ). Radiographs should also be scrutinized for the presence of an ulnar styloid fracture. Contralateral wrist radiographs or a computerized tomography (CT) scan of the wrist and forearm can be performed to assess the DRUJ if radiographs are not clear and suspicion is high for a DRUJ injury, but these are not routinely obtained. The use of magnetic resonance imaging has not been studied in the context of Galeazzi fracture-dislocations and is not a part of routine evaluation.