Spectrum of Carpal Dislocations and Fracture-Dislocations: Imaging and Management

Transcription

1 Musculoskeletal Imaging Review Scalcione et al. Carpal Dislocations and Fracture- Dislocations Musculoskeletal Imaging Review FOCUS ON: Luke R. Scalcione 1 Lana H. Gimber 1 nnette M. Ho 1 Stephen S. Johnston 1 Joseph E. Sheppard 2 Mihra S. Taljanovic 1 Scalcione LR, Gimber LH, Ho M, Johnston SS, Sheppard JE, Taljanovic MS Keywords: lunate dislocations, Mayfield classification, perilunate dislocations, perilunate fracture-dislocations, transcapitate, transradial styloid, transscaphoid, transtriquetral, transulnar styloid DOI: /JR Received ugust 4, 2013; accepted after revision January 14, Presented at the 2013 RRS annual meeting, Washington, DC. 1 Department of Medical Imaging, The University of rizona Health Network, 1501 N Campbell ve, PO ox , Tucson, Z ddress correspondence to L. R. Scalcione (lrs@radiology.arizona.edu). 2 Department of Orthopaedic Surgery, The University of rizona Health Network, Tucson, Z. This article is available for credit. JR 2014; 203: X/14/ merican Roentgen Ray Society Spectrum of Carpal Dislocations and Fracture-Dislocations: Imaging and Management OJECTIVE. The objectives of this article are to discuss the imaging of carpal dislocations and fracture-dislocations and to review the ligamentous anatomy of the wrist, mechanisms of injury, and routine management of these injuries. CONCLUSION. Perilunate dislocations, perilunate fracture-dislocations (PLFDs), and lunate dislocations are high-energy wrist injuries that can and should be recognized on radiographs. These injuries are a result of important sequential osseous and ligamentous injuries or failures. Prompt and accurate radiographic diagnosis aids in the management of patients with perilunate dislocations, PLFDs, and lunate dislocations while assisting orthopedic surgeons with subsequent surgical planning. CT may better show the extent of the injury and help in treatment planning particularly in cases of delayed treatment or chronic perilunate dislocation. CT examination with coronal, sagittal, and 3D reformatted images is ordered at our institution in cases in which the extent of the carpal injuries is poorly shown on radiographic examination. P erilunate dislocations and perilunate fracture-dislocations (PLFDs) typically result from high-energy injuries. These injuries are missed clinically and radiographically in up to 25% of cases [1]. Perilunate dislocations and PLFDs typically result from a fall on an outstretched hand in which an axial force is directed on the carpus with the wrist in hyperextension (dorsiflexion), ulnar deviation, and intercarpal supination. Osseous and ligamentous failures occur in a sequential manner as described by Mayfield et al. [2]. Normal ony and Ligamentous natomy of the Wrist and Radiographic ssessment Radiographic Evaluation Posteroanterior, oblique, lateral, and posteroanterior with ulnar deviation (i.e., scaphoid view) radiographs are obtained in the evaluation of wrist injuries. Radiographs are the initial examination, although CT may be performed for further characterization of fractures and of the orientation of fracture fragments in the setting of a perilunate dislocation or PLFD owing to its spatial resolution and ability to reconstruct images in various planes. Posteroanterior radiographs with the patient s wrist in the neutral position should be scrutinized to ensure the continuity of the arcs of Gilula [3] (Fig. 1). The first arc outlines the proximal convexity of the scaphoid, lunate, and triquetrum. The second arc conforms to the distal concave surface of the scaphoid, lunate, and triquetrum. The third arc contours the proximal convex surface of the capitate and hamate [4]. lateral radiograph of the wrist should be obtained to assess the normal colinearity of the distal radial articular surface, lunate, capitate, and middle finger metacarpal base. These structures should align on a lateral radiograph. Scapholunate interosseous ligament injuries are suggested when there is a scapholunate interosseous distance of more than 2 mm on a posteroanterior radiograph [5, 6]. scapholunate interosseous distance of up to 4 mm, however, may be a normal variant in some individuals [7]. When the scapholunate interosseous distance exceeds 4 mm, it is almost certainly abnormal [7]. When the scapholunate interosseous ligament fails, the scaphoid tends to palmar flex whereas the lunate dorsiflexes. The relationship of the scaphoid and lunate can be evaluated by assessing the scapholunate angle; this angle is defined as the angle taken from a line drawn along the long axis of the scaphoid and a line drawn along the short axis of the lunate. normal scapholunate angle measures between 30 and 60 [8] (Fig. 1). scapholunate angle of JR:203, September

2 Scalcione et al. greater than 60 indicates dorsal tilt of the lunate and dorsal intercalated segment instability (DISI), which typically occurs with tears of the scapholunate interosseous and extrinsic dorsal intercarpal ligaments [9]. Conversely, a scapholunate angle of less than 30 indicates volar tilt of the lunate and volar intercalated segment instability (VISI), which is typically associated with lunotriquetral interosseous and extrinsic dorsal radiocarpal ligament tears [10]. On lateral radiographs, perilunate dislocations and PLFDs are characterized by loss of colinearity of the radius, lunate, and capitate. The volar tilt and dislocation of the lunate have been termed the spilled-teacup sign on lateral radiographs and piece-of-pie sign on posteroanterior radiographs. lthough the spilled-teacup and piece-of-pie signs have been classically described in lunate dislocations, the morphology of the lunate in perilunate dislocations may be altered and there may be a loss of the normal quadrangular appearance of the lunate on posteroanterior radiographs. The capitolunate angle should also be assessed when evaluating the colinearity of the wrist on the lateral view. The capitolunate angle is measured by the angle created by drawing a line along the short axis of the lunate and a line drawn along the long axis of the capitate (Fig. 1). normal capitolunate angle measures less than 30 [8]. capitolunate angle of greater than 30 can be seen in the setting of DISI or VISI as the lunate dorsally and volarly tilts, respectively. n acceptable neutral lateral view is necessary for evaluation of the capitolunate angle because off-lateral views may produce a relative pseudodorsiflexion appearance of the lunate [11]. Fluoroscopic Evaluation of Instability Fluoroscopy can be used in the diagnosis of carpal instability when radiographs show normal findings and clinical examination is indeterminate [12]. Taleisnik [13] introduced the concept of dynamic carpal instability resulting from partial ligamentous injuries that cause wrist pain without changes in carpal alignment on static radiographs. Real-time evaluation of the wrist in a pronated position is performed while the patient moves the wrist from extreme radial deviation to extreme ulnar deviation. The lateral position of the wrist while the patient dorsiflexes and palmar flexes is also assessed. Longitudinal traction and wrist palmar flexion may be used to accentuate capitolunate instability [12, 14]. Dorsal subluxation of the capitate with respect to the lunate will be evident on the lateral view after this maneuver in patients with a capitolunate instability pattern [14]. Normally, when the wrist is in ulnar deviation, the scaphoid is maximally profiled and there is slight widening of the scapholunate interosseous distance [15]. s the patient moves the wrist so it is in radial deviation, the distal pole of the scaphoid rotates into a palmar-flexed position. With the wrist in radial deviation, there is also slight widening of the lunotriquetral interosseous distance [15]. The hamate, capitate, and trapezoid move as a fixed unit in a supple cup formed by the scaphoid, lunate, and triquetrum [15]. With the wrist in a clenched prone position, as the patient moves the wrist from radial deviation to ulnar deviation, the scaphoid may show abnormal tracking in the latter two thirds of the movement with transient widening of the scapholunate interosseous distance and a sudden lurch of the scaphoid as it assumes normal alignment when the wrist moves into extreme ulnar deviation. This altered scaphoid movement can be associated with an audible click [16]. Carpal ones The carpus is formed by the proximal and distal carpal rows in addition to three biomechanically organized columns. The proximal row consists of the scaphoid, lunate, and triquetrum and is more mobile because it adapts to the motions of the distal radius and ulna. The pisiform is a sesamoid within the flexor carpi ulnaris tendon and does not play a significant role in carpal instability owing to its confined location. The distal row consisting of the trapezium, trapezoid, capitate, and hamate is more rigid and conforms to the motion of the metacarpal bases. The three columns of the carpus are divided according to their biomechanical function in the longitudinal plane and include the following: the radioscaphoid column consisting of the scaphoid, trapezium, and trapezoid; the lunate column consisting of the lunate and capitate; and the ulnotriquetral column consisting of the triquetrum and hamate [17]. The radiocarpal joint is formed by the distal biconcave articular surface of the radius and the convex articular surfaces of the scaphoid and lunate bones. The distal articular surface of the radius has a volar tilt of approximately 10 and a radial inclination of approximately 24 [18]. The midcarpal joint is formed by the scaphotrapeziotrapezoidtriscaphe articulation, scaphocapitate articulation, lunocapitate articulation, and triquetral-hamate articulation [19]. Ligaments of the Wrist The wrist ligaments are intracapsular and are categorized into two main subdivisions: the intrinsic wrist ligaments, which have interosseous attachments between carpal bones, and the extrinsic, or capsular, wrist ligaments, which extend beyond the carpal bones. Intrinsic wrist ligaments The two most important intrinsic wrist ligaments are the scapholunate interosseous ligament and lunotriquetral interosseous ligament. The scapholunate interosseous ligament attaches the scaphoid and lunate bones as its name implies and has dorsal, central (proximal), and volar bands. The dorsal band is more robust and more important for wrist stability than the central and volar bands. The central band is triangular-shaped, and the volar band is trapezoidal in shape. The lunotriquetral interosseous ligament is smaller than the scapholunate interosseous ligament and maintains the alignment of the lunate and triquetrum via its osseous attachments. Similar to the scapholunate interosseous ligament, the lunotriquetral interosseous ligament has three bands (dorsal, central or proximal, and volar), with the volar band being the most important for wrist stability. The scapholunate and lunotriquetral interosseous ligaments maintain the stability of the lunate and balance the net forces acting on the lunate. The scaphoid exerts a net volar force on the lunate, and the triquetrum exerts a net dorsal force on the lunate. Thus, disruption of the scapholunate interosseous ligament causes a relatively unopposed dorsal pull on the lunate from the triquetrum via an intact lunotriquetral interosseous ligament, which results in DISI. In contradistinction, disruption of the lunotriquetral interosseous ligament causes a relatively unopposed volar pull on the lunate from the scaphoid via an intact scapholunate interosseous ligament, which results in VISI. Extrinsic wrist ligaments The inconsistency in the nomenclature of the extrinsic wrist ligaments in the radiology and orthopedics literature is often daunting when learning these ligaments. We will address each extrinsic wrist ligament with various supernumerary names in parentheses for ease of referencing these ligaments. The extrinsic ligaments work in concert to oppose the normal tendency of the carpus, which wants to rest in an ulnar and palmar position owing to the radial inclination and a palmar tilt of the distal radius [20]. The palmar extrinsic ligaments are more robust, thicker, and stronger than the dorsal 542 JR:203, September 2014

3 Carpal Dislocations and Fracture-Dislocations extrinsic wrist ligaments and are important in wrist stabilization [21, 22]. The palmar extrinsic ligaments include the radioscaphocapitate (also known as radiocapitate), long radiolunate (also known as radiolunotriquetral, radiotriquetral, and lunotriquetral), radioscapholunate (also known as the ligament of Testut and Kuenz), short radiolunate (also known as radiolunate), ulnocapitate (also known as ulnotriquetrocapitate), palmar ulnolunate, palmar ulnotriquetral, and palmar scaphotriquetral (also known as triquetrocapitoscaphoidal and triquetroscaphoidal) (Fig. 2). The radioscaphocapitate ligament originates from the volar radial aspect of the radial styloid, courses about the scaphoid waist, and inserts onto the palmar aspect of the capitate [23, 24]. The radioscaphocapitate ligament is a major stabilizer of the scaphoid and has been likened to a seat belt around the scaphoid waist that maintains the anatomic position of the scaphoid [21]. The long radiolunate ligament is the longest palmar extrinsic wrist ligament; it originates just ulnar to the radioscaphocapitate ligament from the radial styloid and courses obliquely along the palmar aspect of the lunate to insert onto the triquetrum [23, 24]. The long radiolunate ligament may be interrupted along its course, typically around the lunate [21]. The radioscapholunate ligament is a not a true ligament and does not contain ligamentous fibers; instead, it is a synovial fold with an associated neurovascular bundle and may represent an embryologic remnant of vascular ingrowth [20, 21]. The deep fibers of the radioscapholunate ligament are intimate with the palmar aspect of the scapholunate interosseous ligament. The short radiolunate ligament represents the capsular thickening that stabilizes the lunate. The short radiolunate ligament originates from the volar aspect of the distal radius and spans the entire lunate fossa and attaches to the radial half of the lunate [23, 24]. The palmar ulnolunate and palmar ulnotriquetral ligaments originate from the volar radioulnar ligament [22]. These ligaments help stabilize the lunate. Superficial to the palmar ulnolunate and palmar ulnotriquetral ligaments is the ulnocapitate ligament; the ulnocapitate ligament originates from the ulnar head and courses obliquely distally over the volar aspect of the interosseous lunotriquetral ligament, extends into the midcarpal joint space, and then extends toward the radius to attach to the capitate body. The palmar scaphotriquetral ligament extends between the scaphoid and triquetrum superficial to the radioscaphocapitate and ulnocapitate ligaments. The radioscaphocapitate, lunocapitate, and palmar scaphotriquetral ligaments form the arcuate ligament [25]. The dorsal extrinsic ligaments are less robust than the palmar extrinsic ligaments and are biomechanically less important [21]. The dorsal extrinsic ligaments include the dorsal radiocarpal (also known as radiotriquetral and radiolunotriquetral), dorsal intercarpal (also known as triquetroscaphoidal and triquetrotrapezoidotrapezial), and dorsal ulnotriquetral (also referred to as capsular thickening ) ligaments (Fig. 2). The dorsal extrinsic ligaments contribute to stabilization of the proximal carpal row. The dorsal radiocarpal ligament in conjunction with the lunotriquetral interosseous ligament are responsible for maintaining lunate stability, and failure of these ligaments results in VISI. The dorsal intercarpal ligament in conjunction with the scapholunate interosseous ligament are responsible for maintaining lunate stability; the failure of these ligaments results in DISI. The collateral extrinsic, or capsular, wrist ligaments include the radial collateral and ulnar collateral ligaments at the radial and ulnar aspects of the wrist, respectively, and do not contribute significantly to carpal stability. The radial collateral ligament extends between the radial styloid and scaphoid bones, and the ulnar collateral ligament extends between the ulnar styloid and triquetrum. Normal Wrist Kinematics complete discussion of the nuances of wrist kinematics is beyond the scope of this article and there is much debate in the literature about the precise wrist kinematics and intracarpal motions. We will focus our discussion on the kinematics of ulnar and radial deviations as well as dorsiflexion and palmar flexion as they relate to perilunate dislocations and PLFDs. In ulnar deviation, the proximal carpal row slides toward the radius, whereas in radial deviation, the proximal carpal row slides toward the ulna [2, 26]. The distal carpal row including the trapezium, trapezoid, capitate, and hamate form a stable platform for the metacarpals with very little motion occurring at these bones [27]. Dorsiflexion is primarily a function of the midcarpal joint with the radiocarpal joint contributing slight movement [2]. Palmar flexion occurs primarily at the radiocarpal joint. screw-vice phenomenon occurs as the wrist is fully extended (dorsiflexed) [28]. The palmar extrinsic wrist ligaments become taut and lock the lunate to the radius at the lunate fossa with subsequent tightening of the palmar ligaments locking the distal carpal row to the proximal carpal row. Mechanism of Injury Perilunate dislocations, PLFDs, and lunate dislocations occur from a fall on an outstretched hand that involves a summation of forces. The carpus is hyperextended and supinates on a fixed pronated forearm. The term zone of vulnerability describes a mechanism of wrist injuries that follow a sequential pattern around the carpus [29]. The zone of vulnerability outlines the direction of the major volar wrist ligaments in the region of the greater carpal arc and is a more simplistic approach than the more complex Mayfield classification [2]. Failure can involve ligamentous or osseous structures (or both) around the carpus (Fig. 3). Starting at the radial aspect of the wrist, failure may occur at the radial styloid, scaphoid waist, proximal pole of the scaphoid, or scapholunate joint. Failure at the capitate, which may manifest as a fracture of the capitate body or disruption of the capitolunate joint, occurs next. Then, the base of the hamate, the triquetrum, or the lunotriquetral joint fails. Last, a fracture of the ulnar styloid may occur (Fig. 3). Mayfield et al. [2] reported that a rapid application of forces (axial loading with dorsiflexion, ulnar deviation, and supination of the carpus) produced purely ligamentous injuries involving the so-called lesser arc, which outlines the radial, distal, and ulnar aspects of the lunate. slower application of forces results in mixed osseous and ligamentous failures causing PLFDs involving the greater arc of the carpus (Fig. 3). Perilunate dislocations are primarily ligamentous injuries and involve the lesser arc of the carpus (Fig. 3). Mayfield et al. [2, 26, 30] classified perilunate injuries in cadaveric specimens and showed the sequential failures (progressive perilunate instability) of the intrinsic and extrinsic ligaments around the carpus and resulting dislocation of the carpus (Table 1). The pattern of failure begins at the radius and traverses the lesser arc of the carpus (Fig. 3). s the radial-sided force moves in an ulnar direction, the first stage of failure (stage I) involves the scapholunate joint with failure of the scapholunate interosseous ligament and the radioscaphocapitate ligament (Fig. 4, solid yellow line). Disruption of the scapholunate interosseous ligament allows rotary subluxation of the scaphoid. lternatively, the force may tra- JR:203, September

4 Scalcione et al. TLE 1: Classification of Perilunate Injuries ccording to Mayfield et al. [2] Classification Joint Failure Ligament Failure lternate Osseous Failure Stage I Scapholunate joint or triscaphe joint Scapholunate interosseous ligament or radioscaphocapitate ligament Radial styloid Stage II Capitolunate joint Radial collateral ligament Capitate Stage III Lunotriquetral or Lunotriquetral interosseous Triquetrum triquetrohamate joint ligament, long radiolunate ligament, or palmar ulnotriquetral ligament Stage IV Dorsal radiocarpal ligament verse the triscaphe joint (scaphotrapeziotrapezoid joint) [1] (Fig. 4, dashed yellow line) for which the radiographic findings are not described in the literature to date. Stage II injuries disrupt the capitolunate joint with failure of the radial collateral ligament (Fig. 4, orange line). The third stage of failure (stage III) is disruption of the lunotriquetral joint by means of tearing the lunotriquetral interosseous ligament, long radiolunate ligament, and palmar ulnotriquetral ligament (Fig. 4, solid red line). The entire carpus with the exception of the lunate is now mobilized and dislocates dorsally with respect to the long axis of the radius and lunate. lthough exceedingly rare, the carpus can dislocate volarly. lternatively, the force may disrupt the triquetrohamate joint and spare the lunotriquetral joint (Fig. 4, dashed red line) [31]. The final stage, stage IV, involves failure of the dorsal radiocarpal ligament with resultant palmar dislocation of the lunate (Fig. 4, blue line; Fig. 5). The short radiolunate ligament, which maintains a vascular supply to the lunate and allows closed reduction, is usually intact [31]. fter the sequential ligamentous disruption described, the lunate traverses the space of Poirier, which is a relatively weak zone in the central palmar aspect of the carpus in which no ligamentous structures reside. The space of Poirier is between the lesser and greater carpal arcs between the capitate and lunate. The lunate may dislocate into the carpal tunnel and may potentially cause injury of the median nerve; reported rates of median nerve injury range from 24% to 45% [32]. PLFDs involve both ligamentous and osseous failure. PLFDs fail in a similar sequence as purely ligamentous perilunate dislocations. Unlike the purely ligamentous perilunate dislocations that involve the lesser arc of the carpus, PLFDs involve the greater arc of the carpus. Greater arc injuries are designated by the prefix trans- (transradial styloid, transscaphoid, transcapitate, transtriquetral, transulnar styloid) (Fig. 4). These subcategories of PLFDs represent a number of variants and can be seen in combinations. If one adheres to the Mayfield et al. [2] progression of ligamentous injuries from a wrist sprain or a partial scapholunate ligament injury to an isolated complete scapholunate disruption followed by perilunate dislocation and subsequent volar lunate dislocation, one can easily imagine an injury that results in a near progression from stage II (isolated scapholunate ligament disruption) to stage III (perilunate dislocation), which might result in an incomplete transition that returns to an isolated injury of the scapholunate ligament if the force either terminates or dissipates through a fracture elsewhere. Herzberg [31] reported that spontaneous reduction can occur with any perilunate dislocation or PLFD. This spontaneous reduction might result in a radiographic malalignment of the carpus that underestimates the full extent of the original injury. The radiographs obtained after any injury represent only the manifestations of the extent of the injury after the dissipation or termination of forces and not the extent of the radiographic abnormalities during the injury. This likely could be said about many traumatic radiographic abnormalities. We believe that the utility of the Mayfield classification system [2] may be more from an academic rather than a clinical standpoint. The specifics of each stage are not as important as an understanding of the propagation of forces and of the mechanism of injury that aids radiologists in heightening their awareness to potential radiographic findings given the stage the propagating force has reached. Transradial Styloid Perilunate Fracture-Dislocations Transradial styloid PLFDs may occur in stage I or II injuries. Transradial styloid PLFDs are sequelae of the ulnar deviation forces acting on the wrist during a fall on the outstretched hand (Fig. 6). Intense strain is placed on the radial aspect of the carpus. Radial styloid body fractures occur secondary to an avulsive injury of the radioscaphocapitate ligament (stage I injury) [2]. n avulsive injury of the radial collateral ligament (stage II injuries), however, results in a fracture of the radial styloid tip [2]. Transscaphoid Perilunate Fracture-Dislocations Transscaphoid fracture-dislocations are the most common greater arc injuries associated with PLFDs (Fig. 7). They account for approximately 95% of PLFDs [1]. Most transscaphoid fractures involve the middle portion of the scaphoid and scaphoid waist [1]. The proximal pole of the scaphoid typically maintains its alignment with the lunate. The distal fracture fragment dislocates dorsally with the capitate [33]. Transcapitate Perilunate Fracture-Dislocations During hyperextension of the wrist (dorsiflexion), as the lunate rotates dorsally, the dorsal lip of the lunate impinges on the body of the capitate, which can result in a transcapitate PLFD. Some authors believe that the dorsal lip of the radius causes the transcapitate PLFD [34]. transcapitate fracture is typically transversely oriented with respect to the long axis of the capitate [35] (Fig. 8). Transcapitate fractures have a high incidence of nonunion and osteonecrosis because, like the scaphoid, the capitate has a tenuous blood supply. Transtriquetral Perilunate Fracture-Dislocations vulsion fractures of the long radiolunate ligament or palmar ulnotriquetral ligament result in transtriquetral PLFDs. These fractures occur in stage III injuries. Triquetral fractures associated with perilunate dislocations more often involve the triquetral body rather than the more common isolated triquetral fracture of the dorsal ridge [35] (Fig. 9). Transulnar Styloid Perilunate Fracture-Dislocations Transulnar styloid PLFDs occur as an accompanying fracture in PLFDs [1] (Figs. 3 and 6). Midcarpal or Central Carpal Dislocations Midcarpal or central carpal dislocations are a variation of stage III perilunate dislocations and PLFDs. Midcarpal dislocations are characterized by dorsal perilunate subluxation of the capitate with slight volar subluxation and tilt of the lunate (Fig. 10). There is loss of the normal colinearity of the radius and lunate as well as of the lunate and capi- 544 JR:203, September 2014

5 Carpal Dislocations and Fracture-Dislocations tate. It is conceivable that partially reduced lunate dislocation or perilunate dislocation could have an appearance of a midcarpal dislocation, although no additional supporting information is in the literature to date. Lunate Dislocations Lunate dislocations occur in stage IV perilunate dislocations and PLFDs. In order for the lunate to dislocate volarly, the dorsal restraints of the lunate must be injured. Failure of the dorsal radiocarpal ligament in stage IV injuries disrupts the dorsal restraint of the lunate and leaves the lunate entirely without ligamentous attachment, thus allowing the lunate to dislocate volarly (Fig. 10). Herzberg et al. [1] classified perilunate and lunate dislocations into two stages (Table 2): Stage I injuries included perilunate dislocations and fracture-dislocations (Mayfield stages I III), and stage II injuries included lunate dislocations (Mayfield stage IV). Lunate dislocations, stage II injuries, were further subdivided into two substages: Stage II lunate dislocations occur when the lunate is volarly dislocated and rotated less than 90 [1]. Stage II injuries are characterized by a lunate that has dislocated volarly and has rotated more than 90 [1] (Table 2). lunate that is rotated greater than 90 has a higher probability of soft-tissue interposition, which could preclude closed reduction [1]. Treatment When acute perilunate dislocations, PLFDs, and lunate dislocations are identified radiographically, immediate closed reduction is attempted with the patient under IV sedation. Longitudinal traction is applied to the hand with the wrist in dorsiflexion for perilunate dislocations and PLFDs. The wrist is slowly brought into flexion (palmar flexion), thus allowing the carpus to return to anatomic alignment, typically with an audible clunk. Stage II lunate dislocations are reduced with the patient s wrist in flexion initially to loosen tension on the palmar extrinsic ligaments. The clinician s thumb applies a dorsally directed force to the lunate in an attempt to reduce the lunate into the lunate fossa. Longitudinal traction is applied to the hand and the wrist is extended (dorsiflexed). The clinician maintains a volar buttress around the lunate with his or her finger and the wrist is slowly brought into flexion (palmar flexion), allowing the capitate to realign with the lunate. displaced volar capsule or palmar extrinsic ligaments adjacent to the radiocarpal joint and lunate fossa may preclude a closed reduction [36]. Some authors do TLE 2: Classification of Perilunate and Lunate Dislocations ccording to Herzberg et al. [1] Classification not advocate closed reduction for stage II lunate dislocations owing to the risk of injuring the short radiolunate ligament and compromising its vascular contribution [1, 32]. Historically, closed reductions have been the definitive treatment of perilunate and lunate dislocations and fracture-dislocations [37]. The current practice, however, entails operative management of these injuries because the complex intercarpal relationship is difficult to maintain with closed reduction and immobilization alone. Inadequate realignment of the carpus can result in carpal instability, posttraumatic osteoarthritis, scapholunate advanced collapse, and loss of range of motion [36]. Intraoperative volar, dorsal, or combined volar-dorsal surgical approaches can be used for repair after closed reduction by 3 5 days to allow the swelling around the carpus to subside. Successful open reduction involves realignment of the scaphoid and lunate and correcting the intercalated segment instability. The remaining carpus (lunotriquetral alignment and midcarpal alignment) typically falls into alignment with correction of lunate dorsiflexion and scaphoid palmar flexion. Ligamentous repair, particularly scapholunate interosseous ligament repair, is important for maintaining carpal stability. Some authors will repair the lunotriquetral interosseous ligament and the dorsal radiocarpal ligament [32]. Percutaneous fixation with Kirschner wire maintains alignment of the scaphoid and capitate (preventing scaphoid palmar flexion), scaphoid and lunate (maintaining the scapholunate interosseous distance), and lunate and triquetrum (maintaining the lunotriquetral interosseous distance) [36]. Most authors support carpal tunnel release in patients with median nerve neurapraxia. Greater arc bony injuries are transfixed with headless screws (scaphoid and capitate). Missed or chronic injuries are often treated with proximal row carpectomy or scaphoidectomy and four-corner fusion ( lunotriquetrocapitohamate fusion ). Description a Stage I Mayfield stages I III Stage II Mayfield stage IV Stage II Mayfield stage IV and lunate is volarly dislocated and rotated < 90 Stage II Mayfield stage IV and lunate is volarly dislocated and rotated > 90 a Mayfield stages are from Mayfield et al. [2] and are defined in Table 1. Conclusion Perilunate dislocations, PLFDs, and lunate dislocations are high-energy wrist injuries that can and should be recognized on radiographs. These injuries are a result of sequential osseous and ligamentous injuries or failures. Prompt and accurate radiographic diagnosis aids in the management of patients with perilunate dislocations, PLFDs, and lunate dislocations and assists orthopedic surgeons with surgical planning. CT examination may better show the extent of injury and help in treatment planning particularly in cases of delayed treatment or chronic perilunate dislocation [1]. CT examination with coronal, sagittal, and 3D reformed images is ordered at our institution in cases in which the extent of the carpal injuries is poorly shown on radiographic examinations. References 1. Herzberg G, Comtet JJ, Linscheid RL, et al. Perilunate dislocations and fracture-dislocations: a multicenter study. J Hand Surg m 1993; 18: Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: pathomechanics and progressive perilunar instability. J Hand Surg m 1980; 5: Peh WC, Gilula L. Normal disruption of carpal arcs. J Hand Surg m 1996; 21: Gilula L. Carpal injuries: analytic approach and case exercises. JR 1979; 133: Taljanovic MS, Sheppard JE, Jones MD, et al. Sonography and sonoarthrography of the scapholunate and lunotriquetral ligaments and triangular fibrocartilage disk. J Ultrasound Med 2008; 27: Jacobson J, Oh E, Propeck T, Jebson PJ, Jamadar D, Hayes CW. Sonography of the scapholunate ligament in four cadaveric wrists: correlation with MR arthrography and anatomy. JR 2002; 179: Griffith JF, Chan DP, Ho PC, et al. Sonography of the normal scapholunate ligament and scapholunate joint space. J Clin Ultrasound 2001; 29: Walsh JJ, erger R, Cononey WP. Current status of scapholunate interosseous ligament injuries. J m cad Orthop Surg 2002; 10: Mitsuyasu H, Patterson RM, Shah M, et al. The JR:203, September

6 Scalcione et al. role of the dorsal intercarpal ligament in dynamic and static scapholunate instability. J Hand Surg m 2004; 29: Viegas SF, Patterson RM, Peterson PD, et al. Ulnarsided perilunate instability: an anatomic and biomechanic study. J Hand Surg m 1990; 15: Yang Z, Mann F, Gilula L, Haerr C, Larsen CF. Scaphopisocapitate alignment: criterion to establish a neutral lateral view of the wrist. Radiology 1997; 205: raunstein EM, Louis DS, Greene TL, Hankin FM. Fluoroscopic and arthrographic evaluation of carpal instability. JR 1985; 144: Taleisnik J. The wrist. New York, NY: Churchill Livingstone, 1985: White SJ, Louis DS, raunstein EM, Hankin FM, Greene TL. Capitate-lunate instability: recognition by manipulation under fluoroscopy. JR 1984; 143: rkless. Cineradiography in normal and abnormal wrists. m J Roentgenol Radium Ther Nucl Med 1966; 96: Protas JM, Jackson WT. Evaluating carpal instabilities with fluoroscopy. JR 1980; 135: Craigen M, Stanley JK. Wrist kinematics: row, column or both? J Hand Surg r 1995; 20: Schuind F, Linscheid RL, n KN, Chao EY. normal database of posteroanterior roentgenographic measurements of the wrist. J one Joint Surg m 1992; 74: Moritomo H, pergis E, Herzberg G, et al IFSSH Committee report of wrist biomechanics committee: biomechanics of the so-called dartthrowing motion of the wrist. J Hand Surg m 2007; 32: Theumann NH, Pfirrmann CW, ntonio GE, et al. Extrinsic carpal ligaments: normal MR arthrographic appearance in cadavers. Radiology 2003; 226: Shahabpour M, Demaeseneer M, Pouders C, et al. MR imaging of normal extrinsic wrist ligaments using thick slices with clinical and surgical correlation. Eur J Radiol 2011; 77: Taljanovic MS, Malan JJ, Sheppard JE. Normal anatomy of the extrinsic capsular wrist ligaments by 3-T MRI and high-resolution ultrasonography. Semin Musculoskelet Radiol 2012; 16: erger R. The ligaments of the wrist: a current overview of anatomy with considerations of their potential functions. Hand Clin 1997; 13: erger R. The anatomy of the ligaments of the wrist and distal radioulnar joints. Clin Orthop Relat Res 2001; 383: Taljanovic MS, Goldberg MR, Sheppard JE, Rogers LF. US of the intrinsic and extrinsic wrist ligaments and triangular fibrocartilage complex: normal anatomy and imaging technique. Radio- Graphics 2011; 31:e Mayfield JK. Mechanism of carpal injuries. Clin Orthop Relat Res 1980; 149: Stanley JK, Trail I. Carpal instability. J one Joint Surg r 1994; 76: Macconaill M. The mechanical anatomy of the carpus and its bearing on some surgical problems. J nat 1941; 75: Johnson RP. The acutely injured wrist and its residuals. Clin Orthop Relat Res 1980; 149: Mayfield JK, Johnson RP, Kilcoyne RF. The ligaments of the human wrist and their functional significance. nat Rec 1976; 186: Herzberg G. Perilunate and axial carpal dislocations and fracture-dislocations. J Hand Surg m 2008; 33: Stanbury SJ, Elfar JC. Perilunate dislocation and perilunate fracture-dislocation. J m cad Orthop Surg 2011; 19: Yeager, Dalinka MK. Radiology of trauma to the wrist: dislocations, fracture-dislocations, and instability patterns. Skeletal Radiol 1985; 13: E1-Khoury GY, Usta HY, lair WF. Naviculocapitate fracture-dislocation. JR 1982; 139: Kaewlai R, very LL, srani V, et al. Multidetector CT of carpal injuries: anatomy, fractures, and fracture-dislocations. RadioGraphics 2008; 28: Najarian R, Nourbakhsh, Capo J, et al. Perilunate injuries. Hand (N Y) 2011; 6: dkison JW, Chapman MW. Treatment of acute lunate and perilunate dislocations. Clin Orthop Relat Res 1982; 164: Fig. 1 Radiographic assessment of normal wrists in 36-year-old-man., Posteroanterior radiograph of wrist of shows three Gilula s arcs. First arc (1, solid white line) outlines proximal convexity of scaphoid, lunate, and triquetrum. Second arc (2, dashed white line) conforms to distal concave surface of scaphoid, lunate, and triquetrum. Third arc (3, black line) contours proximal convex surface of capitate and hamate., Lateral radiograph of wrist of shows normal scapholunate angle (black arc) of measured from line drawn along long axis of scaphoid (white line) and line drawn along short axis of lunate (black line). NL = normal. C, Lateral radiograph of wrist of shows normal capitolunate angle (black arc) that measures less than 30. ngle is measured from line along short axis of lunate (black line) and line drawn along long axis of capitate (white line). NL = normal C 546 JR:203, September 2014

7 Carpal Dislocations and Fracture-Dislocations Fig. 2 Extrinsic wrist ligaments in healthy 36-year-old male (same patient as in Fig. 1)., Drawing of palmar extrinsic wrist ligaments superimposed on posteroanterior radiograph of normal wrist. 1 = radioscaphocapitate (also known as radiocapitate), 2 = long radiolunate (also known as radiolunotriquetral, radiotriquetral, and lunotriquetral), 3 = radioscapholunate (also known as ligament of Testut and Kuenz), 4 = short radiolunate (also known as radiolunate), 5 = palmar ulnolunate, 6 = palmar ulnotriquetral, 7 = lunocapitate (also known as ulnotriquetrocapitate), 8 = palmar scaphotriquetral (also known as triquetrocapitoscaphoidal and triquetroscaphoidal)., Drawing of dorsal extrinsic wrist ligaments superimposed on posteroanterior radiograph of normal wrist. 1 = dorsal radiocarpal (also known as radiotriquetral and radiolunotriquetral), 2 = dorsal intercarpal (also known as triquetroscaphoidal and triquetrotrapezoidotrapezial), 3 = ulnar collateral, 4 = radial collateral, 5 = dorsal ulnotriquetral (also referred to as capsular thickening ). Fig. 4 Ligamentous and osseous failures seen in perilunate fracture-dislocations (PLFDs) and lunate fracturedislocations. Images obtained in healthy 36-year-old man (same patient as in Fig. 1)., Drawing shows pathways of ligamentous failures in perilunate dislocations according to Mayfield classification [2] superimposed on posteroanterior radiograph of normal wrist. Stage I injuries involve disruption of scapholunate joint (solid yellow line) with failure of scapholunate interosseous ligament and radioscaphocapitate ligament or failure at triscaphe joint (dashed yellow line). Stage II injuries disrupt capitolunate joint (orange line). Stage III injuries disrupt lunotriquetral joint (solid red line) with failure of lunotriquetral interosseous ligament, long radiolunate ligament, and palmar ulnotriquetral ligament or disrupt triquetrohamate joint (dashed red line). Finally, stage IV injuries completely mobilize lunate with failure of short radiolunate ligament and dorsal radiocarpal ligament (blue line and arrow)., Drawing shows alternate osseous pathways involved in PLFDs involving greater arc injuries of carpus superimposed on posteroanterior radiograph of normal wrist. Stage I injuries can take transscaphoid or transradial styloid course from avulsive injuries of radioscaphocapitate ligament or radial collateral ligament (dashed yellow lines). Stage II injuries follow transcapitate course (dashed orange line). Stage III injuries follow transtriquetral course (dashed red line) with failure of ulnotriquetral ligament or long radiolunate ligament. Finally, ulnar styloid fractures (dashed white line) can occur in conjunction with PLFD. Solid yellow line = scapholunate interosseous ligament, solid orange line = capitolunate, solid red line = lunotriquetral interosseous ligament, blue line and arrow = dorsal radiocarpal ligament. Fig. 3 Zone of vulnerability and greater and lesser arcs. Drawing of zone of vulnerability and greater and lesser arcs superimposed on posteroanterior radiograph of normal wrist of 36-year-old healthy man (same patient as in Fig. 1). Greater arc (dashed black line) outlines osseous failure in perilunate fracturedislocations. Lesser arc (dashed white line) outlines lunate and represents purely ligamentous failure in perilunate dislocations or lunate dislocations. 1 = fracture of radial styloid, scaphoid waist, or proximal pole and failure of scapholunate joint (scapholunate interosseous ligament); 2 = fracture of capitate body or failure of capitolunate joint; 3 = fracture of base of hamate, fracture of triquetrum, or failure of lunotriquetral joint (lunotriquetral interosseous ligament); 4 = fracture of ulnar styloid. JR:203, September

8 Scalcione et al. D Fig. 5 Perilunate and lunate dislocations overview. Drawings show lateral view of wrist. Normal wrist maintains colinearity (dashed lines) of radius, lunate (Lun), capitate (Cap), and third metacarpal and middle finger (3). Perilunate dislocations maintain colinearity of radius and lunate while capitate and middle finger metacarpal are dorsally dislocated. Midcarpal dislocations disrupt colinearity of radius and lunate with volar tilt and volar subluxation of lunate and dorsal subluxation of capitate and middle finger metacarpal. Late lunate dislocations will show loss of colinearity of lunate and radius with lunate volarly tilted and dislocated, but colinearity of radius, capitate, and middle finger metacarpal is maintained. E Fig. 6 Perilunate fracture-dislocations (PLFDs)., Transradial styloid, transscaphoid transulnar styloid, dorsal perilunate fracture-dislocation (PLFD) in 50-yearold woman who fell. Posteroanterior radiograph of wrist shows mildly displaced fracture of radial styloid (solid arrow), minimally displaced fracture of proximal pole of scaphoid (arrowhead), and mildly displaced fracture of ulnar styloid (dashed arrow). There is disruption of scapholunate and lunotriquetral joints characterized by loss of Gilula s first and second arcs., Lateral radiograph of same patient shown in shows dorsal dislocation of triquetrum (Trq) and capitate (Cap) (arrow). Sc = scaphoid, Lun = lunate. C E, Transradial styloid, transulnar styloid PLFD in 40-year-old man who sustained acute right wrist injury. Coronal CT images (C and D) and 3D surface-rendered reconstructed image viewed dorsally (E) show there are minimally displaced fractures of radial styloid (solid white arrow) and ulnar styloid (dashed white arrow, D and E). There is disruption of scapholunate joint with avulsed fracture fragment from scaphoid at attachment of scapholunate interosseous ligament (dashed black arrow, C). Small avulsed fracture fragment is seen about dorsal aspect of capitate that is likely from avulsive injury of dorsal intercarpal ligament (solid black arrow, E). ll these findings are consistent with transradial styloid, transulnar styloid PLFD. C 548 JR:203, September 2014

9 Carpal Dislocations and Fracture-Dislocations Fig. 7 Transscaphoid dorsal perilunate fracturedislocation., Coronal reformatted CT image shows distal pole of scaphoid (dashed arrow) and rotated proximal scaphoid pole (solid arrow) fragments after scaphoid waist fracture. Lunate remains aligned with distal radius., Sagittal reformatted CT image shows dorsally dislocated capitate (arrow) with respect to distal radius. Fig. 8 Transscaphoid transcapitate volar perilunate fracture-dislocation (PLFD) in 23-year-old woman., Posteroanterior radiograph of wrist shows mildly displaced transversely oriented fracture of distal pole of scaphoid (solid arrow). There is transversely oriented fracture of capitate (dashed arrow)., Lateral radiograph shows capitate fracture fragments (dashed lines). Lunate remains aligned with distal radius and fractured capitate is volarly dislocated. JR:203, September

10 Fig. 9 Transtriquetral perilunate fracturedislocation (PLFD)., Posteroanterior radiograph of wrist shows fracture of triquetral body (arrow) with disruption of Gilula s arcs., Lateral radiograph shows dorsal dislocation of carpus (arrow) with preserved colinearity of lunate and distal radius. Scalcione et al. Fig. 10 Midcarpal and lunate dislocations., Posteroanterior view of wrist shows abnormal configuration of lunate (dashed lines), which is referred to as piece-of-pie sign., Lateral radiograph of wrist shows loss of colinearity of radius, lunate, and capitate (dashed line). Lunate (solid arrow) is volarly tilted and volarly subluxed. Capitate (dotted arrow) is dorsally subluxed. ll these findings are consistent with midcarpal and central carpal dislocation. C, Lunate dislocation. Posteroanterior view of wrist shows abnormal configuration of lunate (dashed lines) known as piece-of-pie sign. D, Lateral radiograph of wrist in same patient as C shows loss of colinearity of radius and lunate and preserved colinearity of radius and capitate. Lunate (arrow) is volarly dislocated and rotated less than 90 ; these findings are consistent with Herzberg stage II injury [1]. C D FOR YOUR INFORMTION This article is available for CME and Self-ssessment (S-CME) credit that satisfies Part II requirements for maintenance of certification (MOC). To access the examination for this article, follow the prompts associated with the online version of the article. 550 JR:203, September 2014