Lunate fractures and perilunate injuries

INTRODUCTION — While not common, lunate fractures and perilunate injuries have important potential consequences. They are most often sustained from a fall onto an extended wrist or some other wrist hyperextension injury.

This topic will review fractures of the lunate and ligamentous injuries of the perilunate region of the wrist, including sprains of the scapholunate and lunotriquetral ligaments, perilunate wrist instability, and perilunate fracture-dislocations. A general overview of wrist pain and carpal fractures, as well as topics devoted to other specific carpal fractures in adults, are presented separately. (See "Evaluation of the adult with acute wrist pain" and "Evaluation of the adult with subacute or chronic wrist pain" and "Overview of carpal fractures" and "Scaphoid fractures".)

EPIDEMIOLOGY — Hand fractures are among the most common of the extremity injuries, accounting for about 18 percent of all fractures. Carpal bone fractures comprise upwards of 8 percent of hand fractures [1,2]. Fractures to bones of the proximal row–comprising the scaphoid, lunate, triquetrum and pisiform–are most frequent. Lunate fractures are relatively uncommon, representing about 4 percent of all carpal bone injuries [1-4].

Perilunate dislocations and fracture-dislocations are relatively uncommon injury patterns in acute wrist trauma. Perilunate instability represents about 7 percent of all injuries to the carpus [5]. When dislocation occurs in the wrist, it is typically perilunate, meaning that the bones surrounding the lunate lose their continuity with the lunate through disruption of the ligaments. Usually this involves the capitate dislocating dorsally. Perilunate dislocations with an associated fracture were twice as prevalent as those without fracture in the largest published series [6].

Perilunate sprains can occur in the absence of fracture or dislocation, and involve partial disruption of ligaments joining the lunate to the scaphoid (most commonly), capitate, or triquetrum. Scapholunate sprains represent about 5 percent of acute wrist injuries [7].

Another reported but uncommon condition is "perilunate injury, not dislocated" (PLIND), in which there is a displaced fracture of the lunate, scaphoid, triquetrum or capitate along with scapholunate and/or lunotriquetral ligament rupture but no dislocation of the capitate from the lunate [8].

CLINICAL ANATOMY AND BIOMECHANICS — The anatomy and mechanics of the wrist are reviewed in detail separately, but aspects of particular relevance to lunate injury are discussed below. (See "Anatomy and basic biomechanics of the wrist".)

The lunate is well protected, as it sits in a sulcus on the distal radius (lunate fossa) between the scaphoid radially and the triquetrum ulnarly (figure 1 and figure 2 and image 1). The lunate is crescent-moon shaped (hence the name) and has a dorsal and a palmar pole. Together, the scaphoid, lunate, and triquetrum lie in the proximal carpal row, as does the pisiform, which has no direct attachment to the lunate. The medial and lateral articular surfaces of the lunate are small compared to the large proximal surface that articulates with the distal radius, and the distal surface that articulates with the capitate in the distal carpal row.

The lunate is attached to its three adjacent carpal bones by intrinsic (or interosseous) ligaments - the scapholunate, capitolunate, and lunotriquetral ligaments (figure 3 and figure 4). It is further stabilized by several dorsal and palmar extrinsic ligaments that connect it to the radius, ulna, and distal carpal row. No muscles or tendons insert directly onto the lunate, or other bones in the proximal carpal row. The distal carpal row is attached firmly to the metacarpal bases, and minimal motion occurs at this interface (ie, carpometacarpal joints), creating a stable segment at the proximal hand, while the distal forearm constitutes a stable segment at the proximal wrist [9]. This leaves the relatively unstable proximal carpal row, often called the intercalated segment, more susceptible to injury.

During wrist flexion, the distal carpal row flexes on the proximal row (midcarpal joints), and the proximal row flexes on the radius. During wrist extension, the distal carpal row extends on the proximal row, which extends on the radius. The extent of flexion or extension is roughly equal at the midcarpal and radiocarpal joints.

The lunate receives its blood supply along both its volar and dorsal surfaces from nutrient arteries derived from the palmar and dorsal arches between the radial and ulnar arteries (figure 5) [4]. In 80 percent of individuals, the source of this supply involves two arteries, but the other 20 percent have a single arterial source leading to a high incidence of ischemic bone injury following fracture.

MECHANISM OF INJURY — Acute lunate fractures most often occur as the result of a fall onto an extended wrist or some other wrist hyperextension injury, or from a direct blow. The five major fracture types include the volar pole (most common), which may be associated with volar subluxation of the carpus [5], followed by chip fractures and dorsal pole fractures, with transverse body and sagittal body fractures being least common [10]. A dorsal lip avulsion fracture can occur from a translational injury, in which force is applied to the heel of the hand [11].

Associated risk factors for fracture include occupations or sports involving repetitive pressure to the base of the hand with the wrist in extension (eg, gymnast, jack hammer operator), and with a short ulna relative to the length of the radius, a condition referred to as "ulna minus variance" [12]. (See "Distal radius fractures in adults", section on 'Anatomic landmarks and measurements'.)

Perilunate fracture-dislocations usually occur from high-energy trauma, most commonly a fall onto an extended wrist, such as during skateboarding, downhill skiing, or falls from a ladder. The trans-scaphoid perilunate fracture dislocation is the most common of this type of injury, in which the scaphoid fractures and the distal carpal row dislocates dorsally. Other combinations of carpal fracture-dislocations have been reported but are less common. Perilunate dislocations can also occur with trans-capitate or trans-triquetral fractures, or any combination of the above, but these too are less common [6,13]. Perilunate sprains can occur with similar mechanism but usually involving less force.

When progressively greater loads are placed on an extended wrist, a predictable sequence of ligamentous disruptions (moving from radial to ulnar structures) and carpal instability occur. The standard scheme describing these injuries involves four stages (figure 6) [9,14]. In stage 1, the scapholunate ligament ruptures. While this causes instability between the scaphoid and lunate, dislocation rarely occurs. In stage 2, the capitolunate ligament ruptures and the capitate sometimes dislocates; when dislocation occurs, 95 percent are dorsal. In stage 3, the lunotriquetral ligament ruptures and the lunate dislocates dorsally, but the lunate remains aligned with the radius when seen on an anteroposterior radiograph. Further loading leads to stage 4 injury, which involves volar dislocation of the lunate into the carpal tunnel.

As described above, the scope of perilunate injuries includes fracture-dislocations, pure dislocations without fracture, pure ligamentous sprains without dislocation, and fractures associated with ligamentous injury but no dislocation.

SYMPTOMS AND EXAMINATION FINDINGS — Given the wide range of lunate and perilunate injuries, findings can range from the subtle to the dramatic. The patient with a lunate fracture or perilunate injury typically presents with a history of significant wrist trauma and complains of pain in the middle of the wrist that is aggravated by wrist motion or gripping, though pain may be widespread both dorsally and volarly with dislocations. Because of the intracapsular location of the lunate, swelling may be minimal with isolated scapholunate sprains or small lunate fractures, and the amount of swelling does not correlate with the severity of injury. Tenderness is generally present at the dorsum of the wrist just distal to Lister's tubercle.

The lunate can be appreciated by palpation of the dorsum of the wrist, just distal to the radius and in line with the middle finger (picture 1). A useful landmark is Lister's tubercle (figure 2 and picture 2), a longitudinal bony prominence of the distal radius that is located just proximal and radial to the lunate. The scapholunate joint and dorsal scapholunate ligament are palpable dorsally just distal to Lister’s tubercle, which lies less than a centimeter away towards the ulna. The lunate becomes more prominent in this location with volar flexion of the wrist. To locate the lunotriquetral joint and ligament, move your finger distally from the ulnar styloid dorsally to palpate the triquetrum, then move less than a centimeter radially.

With dorsal dislocations of the wrist, there is prominence of the capitate dorsally, and possible fullness in the carpal tunnel volarly if the lunate has dislocated. Findings associated with a scapholunate ligament rupture can be subtle. Tenderness is present over the scapholunate joint dorsally, just distal to Lister's tubercle. Joint instability may be detectable and should be assessed using the Scaphoid Shift (or Watson) Test. This test is summarized in the following photographs (picture 3 and picture 4 and picture 5 and picture 6) but described in greater detail separately. (See "Evaluation of the adult with subacute or chronic wrist pain", section on 'Special tests'.)

Injury to the lunotriquetral ligament may produce tenderness at the lunotriquetral joint dorsally, just distal to and about one centimeter radially from the ulnar styloid. Instability of the joint can be assessed using the Lunotriquetral test [15]. This is performed by grasping the lunate with thumb dorsally and fingers volarly with one hand, and grasping the triquetrum with the other hand, and manipulating the bones in alternating dorsal and palmar directions to produce shear at the joint. However, one cross-sectional study showed the test to be of little or no value (positive likelihood ratio 1.03) compared to arthroscopy [16].

Injury to the extrinsic dorsal carpal ligaments after a reduced wrist dislocation produces tenderness diffusely at the dorsal wrist. Instability of the carpus between the proximal and distal carpal rows should be assessed using the Midcarpal Shift test [17]. To perform the test, the examiner grasps the patient's distal radius and ulna with one hand and with the other grasps the distal capitate, then produces a palmar-directed shear force at the metacarpal base, and finally deviates the hand in an ulnar direction while maintaining the palmar force. A positive test is noted by a painful clunk as the hand is being ulnarly deviated. One cross-sectional study showed the positive likelihood ratio of this test to be 2.67 ("mildly useful") compared to arthroscopy [16].

Examination should include careful assessment of the neurovascular structures. While vascular injuries are rare, median nerve injury is common if the lunate dislocates volarly into the carpal tunnel. Findings can include prominence (eg, due to swelling or deformity) of the volar wrist; reduced sensation in the thumb, index and middle fingers, and radial half of the ring finger; and decreased strength of thumb flexion, opposition, and abduction. (See "Carpal tunnel syndrome: Clinical manifestations and diagnosis".)

DIAGNOSTIC IMAGING — Lunate fractures and perilunate injuries often evade detection with plain radiographs; obtaining advanced imaging is advised if these injuries are clinically suspected but radiographs are unremarkable. Computed tomography (CT) is probably best for detecting fractures, while CT-arthrography is probably best for detecting ligamentous injury. Nevertheless, when lunate or perilunate injuries are suspected, imaging typically begins with standard plain radiographs of the wrist.

The five major types of lunate fracture to look for on radiographs include the volar pole most commonly (which may be associated with volar subluxation of the carpus [5]), followed by chip fractures and dorsal pole fractures, with transverse body and sagittal body fractures being least common [10].

Plain radiographs — Imaging should begin with standard wrist radiograph views, including anteroposterior (AP), lateral, and both radial and ulnar obliques. A lunate fracture line is often difficult to detect, but may appear as a thin, lucent, typically transverse line (image 2).

Perilunate injuries are sometimes suggested by radiograph findings (image 3). With complete scapholunate ligament ruptures, static instability can result, with rotatory subluxation of scaphoid producing the "signet ring sign" on the AP view. This sign is produced when the tubercle of the scaphoid is superimposed on the waist. In addition, the radioscaphoid angle may be increased (normal range 30 to 60 degrees), and there may be widening of the scapholunate space greater than 3 mm (image 4) [18].

With lunotriquetral ligament rupture, there may be an increase in the space between the two bones on the AP view, though this is uncommon. On lateral view, the scapholunate angle may be less than 30 degrees, and the capitolunate angle may be greater than 30 degrees. If the dislocated lunate is rotated significantly, as it often is, on lateral view the normally concave-up lunate may be rotated 90 to 180 degrees, changing the orientation of the concavity, which has been described as a "spilled teacup" (image 5) [18].

Stress radiographs — Stress radiographs such as the "clenched fist view" have been used to detect perilunate injuries when plain radiographs are normal, but studies supporting this approach are scant and it is limited by the wide variability in normal ligament laxity in the general population. Widening of the scapholunate interval greater than 3 mm on an AP clenched fist view (image 6), or a difference of greater than 1 mm compared to the uninjured side, suggests ligamentous rupture or laxity (image 7) [18].

CT and MRI — Studies using CT as the gold standard report that plain radiographs show poor sensitivity for detecting lunate fractures, while CT and MRI (image 8 and image 9) demonstrate high sensitivity [2,3]. Therefore, if plain radiographs are unrevealing but clinical suspicion of fracture persists, CT or MRI should be obtained.

If ligament injury or carpal instability are suspected, clinicians should have a low threshold for obtaining advanced imaging, as suspected "wrist sprains" with negative radiographs have a high incidence of ligamentous injuries [19]. Two systematic reviews have concluded that MRI provides only a "moderate diagnostic performance" for detection of scapholunate and lunotriquetral ligament injury, with sensitivities ranging from 65 to 89 percent [18,20]. CT is not sensitive for ligamentous injury. Surgical arthroscopy is considered the gold standard, but arthrography performed with CT or MRI is often performed.

Ultrasonography — Based on the limited research available, the role of ultrasonography in diagnosing lunate and perilunate injuries remains unclear. The reported sensitivity of ultrasonography in diagnosis of a dorsal scapholunate ligament injury ranges from 46 to 100 percent in four small observational studies [21-24]. The sensitivity of ultrasound for detecting lunotriquetral tears is even lower, ranging from 25 to 50 percent in the same studies. Specificity appears to be better, and ranged from 90 to 100 percent. (See "Musculoskeletal ultrasound of the wrist", section on 'Dorsal wrist and hand'.)

Arthrography — Numerous direct-comparison studies show increased sensitivity of MR-arthrography (MRA) and CT-arthrography (CTA) compared to standard MRI for detecting ligamentous wrist injury [18]. The sensitivity of direct MRA, in which contrast is first injected into the wrist joint, is reported to range from 85 to 100 percent compared to arthroscopy for scapholunate and lunotriquetral ligament tears. CTA shows similar sensitivity for detecting complete ligament ruptures and is more sensitive than MRA for detecting incomplete tears. The sensitivity of indirect 1.5-Tesla MRA using IV contrast is significantly lower than MRA done with intraarticular contrast; however, 3-Tesla MR may be as useful as MRA for complete ligament tears.

DIAGNOSIS — Lunate fracture is suspected on clinical grounds, but the definitive diagnosis is made with imaging studies. Following a fall onto an extended wrist or some other wrist hyperextension injury, patients typically present with pain in the wrist area that is aggravated by wrist motion or gripping. Tenderness is generally present on the dorsum of the wrist just distal to Lister's tubercle. Lunate fractures can be difficult to see on plain radiographs, and CT or MRI may be necessary to establish the diagnosis. Maintaining a high index of suspicion is important as about 25 percent of these injuries are misdiagnosed initially [8,25].

Perilunate ligamentous injury is suspected on clinical grounds but the definitive diagnosis is usually made with advanced imaging studies. A patient with a history of wrist trauma–usually involving hyperextension–may have tenderness at the scapholunate, lunocapitate, and/or lunotriquetral joint spaces, and may have signs of clinical instability with provocative maneuvers. With severe cases involving dislocation, wrist deformity is present, and if the lunate is dislocated volarly, as it usually is, acute carpal tunnel syndrome may be present. This can cause numbness in the first four digits and weakness of the thumb flexors, opposers, and abductors.

DIFFERENTIAL DIAGNOSIS — Lunate fractures and perilunate injuries are a heterogeneous group, and high-energy wrist injuries have a high incidence of concomitant injury. Diagnoses that may coincide or be confused with these injuries include those described below. The differential diagnosis for acute and subacute wrist pain is discussed in detail separately. (See "Evaluation of the adult with acute wrist pain", section on 'Differential diagnosis by regions of the wrist' and "Evaluation of the adult with subacute or chronic wrist pain", section on 'Differential diagnosis by regions of the wrist'.)

Distal radius fracture — This most common fracture of the wrist and hand is usually sustained from a fall onto an outstretched hand. Tenderness is present at the distal radius, sometimes accompanied by deformity and ecchymosis. Diagnosis is generally made with plain radiographs. (See "Distal radius fractures in adults".)

Fracture of the scaphoid, triquetrum, capitate, or other carpal bones — Fractures of other carpal bones are a more common cause of acute wrist injury than a lunate fracture. The scaphoid is the most commonly fractured carpal bone. Some carpal fractures cause diffuse tenderness along the radial aspect of the dorsal wrist. Snuffbox tenderness is suggestive but not diagnostic of scaphoid fracture (picture 7). Diagnostic imaging to identify such fractures should include standard wrist and scaphoid views, but advanced imaging with CT or MRI may be required. (See "Overview of carpal fractures" and "Scaphoid fractures" and "Triquetrum fractures" and "Capitate fractures".)

Kienböck's disease of the lunate — This is a progressive collapse of the lunate that is a chronic condition but can have acute exacerbations. The mechanism remains unclear but appears to involve disruption of the blood supply, possibly related to undiagnosed fractures of the lunate, repetitive trauma, or abnormal biomechanical loading patterns at the radiocarpal joint. The most common symptoms are dorsal wrist pain with mild swelling. (See "Evaluation of the adult with subacute or chronic wrist pain", section on 'Kienböck disease (avascular necrosis) of the lunate'.)

Wrist sprain — A sprained wrist involves injury to the supporting ligaments of the radiocarpal joint. They can occur with hyperflexion or hyperextension mechanisms, and range from mild to severe. Those involving intrinsic ligaments such as the scapholunate and lunotriquetral ligaments are more concerning because of the resulting instability and penchant for producing degenerative arthritis. However, most wrist sprains involve only extrinsic ligaments, which cause little or no instability and generally heal well without sequelae. Uncomplicated sprains are associated with mild wrist pain or stiffness and slightly reduced motion. The majority resolve within two weeks with conservative therapy (ie, ice, immobilization, gentle passive stretching exercises).

INDICATIONS FOR SURGICAL REFERRAL — Any open injuries, irreducible dislocations, and injuries associated with neurovascular compromise require immediate emergency referral to a hand or orthopedic surgeon. Because of the frequent incidence of concurrent bony and ligamentous carpal injuries, and the considerable potential for lunate non-union, osteonecrosis, and risk for osteoarthritis if not treated aggressively, all patients with lunate fractures, perilunate sprains, or carpal instability should be referred to a hand surgeon. All such injuries should be referred within 72 hours.

INITIAL TREATMENT — When a wrist dislocation is present, immediate reduction is paramount to prevent further cartilage damage and to relieve pressure on the median nerve in the case of acute carpal tunnel syndrome, which is seen in up to 46 percent of dislocations [5]. Initial closed reduction usually requires procedural sedation performed in an emergency department [9,26]. (See "Procedural sedation in adults in the emergency department: General considerations, preparation, monitoring, and mitigating complications" and "Procedural sedation in children: Approach" and "Carpal tunnel syndrome: Clinical manifestations and diagnosis".)

For fractures and other injuries not involving a dislocation, application of a short-arm wrist splint and ice, and elevation of the wrist above the level of the heart, should be performed. Basic fracture care is described separately. (See "General principles of acute fracture management".)

Perilunate injuries, including dislocations, fracture-dislocations, and fractures without dislocation but with wrist instability, require surgical management. This restores anatomic relationships and normal wrist biomechanics and probably reduces the risk of complications. Referral should be made within approximately one week, and a short-arm wrist splint should remain in place until the patient is seen by the surgeon. (See 'Indications for surgical referral' above and 'Complications' below.)

The best treatment for scapholunate and lunotriquetral ligament sprains remains unclear due in part to a paucity of research. These injuries are frequently missed if patients present acutely, and delayed presentation is also common. Experts generally agree that for significant injuries operative management using wrist arthroscopy is best, so referral to a hand surgeon is strongly recommended [5,27-29].

The rare lunate fracture that is non-displaced and not associated with perilunate dislocation or disruption of the scapholunate or lunotriquetral ligaments can be treated with a short arm cast for three to six weeks [5,29]. (See "General principles of acute fracture management" and "Basic techniques for splinting of musculoskeletal injuries" and "Patient education: Cast and splint care (Beyond the Basics)".)

Displaced fractures and those associated with any perilunate ligamentous injury or dislocation should be referred for surgical management. The timing is generally within one to several weeks, although in general the sooner referral is made the better [9]. However, the patient with progressive numbness in the distribution of the median nerve despite successful closed reduction, requires urgent open reduction within 24 hours [26].

FOLLOW-UP CARE — The patient with an isolated, nondisplaced lunate fracture without perilunate injury (ie, without ligament injury of any kind), who is treated with casting, should be assessed for cast integrity after about three weeks or as needed for symptoms of poor cast fit. Biweekly cast checks may be prudent in very active patients.

After three weeks, the cast should be removed and healing should be assessed by checking for lunate tenderness. If significant tenderness persists, casting should be continued for one to three weeks. If early cast removal is a priority for the patient, weekly cast removals and examinations can be performed, with the cast reapplied as needed (eg, in cases of persistent tenderness).

Plain radiographs should be repeated after cast removal. If at any point there are signs of nonunion or lunate osteonecrosis, a hand surgeon should be consulted.

After several weeks of casting the wrist will have lost strength and mobility. Depending on the clinical circumstances, formal physical therapy or a home exercise program can be used to help the patient regain full function. The patient can stop the program once full mobility and strength are regained.

A basic home exercise program might consist of the following:

●Perform passive stretches twice daily, holding each stretch for 30 seconds. Stretch the wrist in flexion, extension, ulnar deviation, and radial deviation. The hand and wrist can be soaked in very warm water for 5 minutes prior to stretching to facilitate motion.

●Perform motion and strength exercises after stretching. Exercises should include active wrist circles 10 times in each direction, followed by two sets of 15 repetitions using appropriate resistance (eg, elastic band, dumbbell) for each of the following: wrist flexion, wrist extension, ulnar deviation, and radial deviation.

The patient's pain, motion and function should be assessed about two weeks after cast removal. Those who are having persistent, significant pain and/or functional impairment may benefit from a referral to physical therapy.

COMPLICATIONS — Early surgical treatment (within seven days of injury), when indicated, gives the best results for these injuries. Treatment later than six weeks after injury results in worse clinical outcomes [30]. Wrist osteoarthritis, usually at the radioscaphoid or lunocapitate joints (or both), is a common long-term complication after lunate and perilunate injuries due to the chondral injury sustained from trauma [30-34]. In small observational studies, the incidence of osteoarthritis was 70 percent at 3.3 years [31] and 79 percent at 10 years [32]. Persistent carpal instability is common in those not treated surgically. Even with operative management, most patients experience significant reductions in wrist mobility and function, variable reductions in grip strength, and greater pain as a result of their injuries [31,32,35,36].

Uncommon complications of perilunate injuries include complex regional pain syndrome, rupture of weakened tendons [9], and avascular necrosis of the lunate. Avascular necrosis from perilunate fractures and fracture-dislocations occurs in only 3 percent of cases, and transient ischemia occurs in about 2 percent [37]. (See "Complex regional pain syndrome in adults: Treatment, prognosis, and prevention" and "Evaluation of the adult with subacute or chronic wrist pain", section on 'Kienböck disease (avascular necrosis) of the lunate'.)

RECOMMENDATIONS FOR RETURN TO SPORT OR WORK — For patients with uncomplicated lunate fractures being treated with immobilization, activities including some sports can be resumed during cast treatment. Sports and labor requiring wrist flexion should be avoided during cast treatment. After casting, return to these activities is permitted once the patient has regained full wrist motion and at least 80 percent strength in all wrist planes of motion, compared to the uninjured side. This may occur one to three weeks after cast removal, but additional time may be needed in some cases. Rigid bracing of the wrist during activities should be continued until strength and range of motion are essentially equal to that of the contralateral side.

After surgical treatment of perilunate dislocation, fracture-dislocation, fracture with ligamentous instability, or scapholunate or lunotriquetral ligament ruptures, treatment with casting and splinting continue for 8 to 12 weeks, and surgical wires usually remain in place for the same duration. Rehabilitation after immobilization is discontinued requires additional time. Return to high-level athletics can take several months, and athletes should be counseled that such injuries could end their career [5]. Laborers, especially those in manual labor, may have difficulty returning to the same type of work due to pain and stiffness. The proportion requiring a change in jobs or cessation or prior jobs ranges from 4 to 55 percent in various studies [31].

ADDITIONAL INFORMATION — Several UpToDate topics provide additional information about fractures, including the physiology of fracture healing, how to describe radiographs of fractures to consultants, acute and definitive fracture care (including how to make a cast), and the complications associated with fractures. These topics can be accessed using the links below:

●(See "General principles of fracture management: Bone healing and fracture description".)

●(See "General principles of fracture management: Fracture patterns and description in children".)

●(See "General principles of acute fracture management".)

●(See "General principles of definitive fracture management".)

●(See "General principles of fracture management: Early and late complications".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Fractures of the skull, face, and upper extremity in adults" and "Society guideline links: Acute pain management".)

SUMMARY AND RECOMMENDATIONS

●Mechanism of injury – Acute lunate fractures and perilunate ligament injuries are relatively uncommon. The usual mechanism for both involves a fall onto an extended wrist. Perilunate fracture-dislocations usually occur from high-energy trauma, most commonly a fall onto an extended wrist, such as during skateboarding, downhill skiing, or falls from a ladder. (See 'Clinical anatomy and biomechanics' above and 'Mechanism of injury' above.)

●Clinical presentation and examination – The severity of lunate and perilunate injuries can vary widely, as can their associated clinical findings. Patients typically present with wrist pain that is aggravated by motion or gripping. Swelling and deformity may be minimal even with significant injury. Tenderness is generally present on the dorsum of the wrist just distal and ulnar to Lister's tubercle (picture 1 and figure 2). Provocative maneuvers used to help identify particular injuries are described in the text. (See 'Symptoms and examination findings' above.)

●Imaging – Lunate fractures and perilunate injuries often evade detection with plain radiographs; advanced imaging is advised if injury is clinically suspected but plain radiographs are unremarkable. Computed tomography (CT) is probably best for detecting fractures; CT-arthrography is probably best for detecting ligamentous injury. Nevertheless, imaging typically begins with standard plain radiographs of the wrist. Look carefully for widening of the scapholunate space, abnormal position of the capitate and lunate, and dorsal lip avulsion fracture. (See 'Diagnostic imaging' above.)

●Differential diagnosis – Lunate and perilunate injuries are heterogeneous, and wrist injuries from high-energy trauma have a high incidence of concomitant injury. Diagnoses that may coincide or be confused with these injuries include distal radius fracture, fractures of other carpal bones (eg, scaphoid, triquetrum, capitate), osteonecrosis of the lunate, and wrist sprain. (See 'Differential diagnosis' above.)

●Indications for hand surgery referral – Concurrent bony and ligamentous carpal injuries are common, and there is a risk of lunate non-union, osteonecrosis, and risk for osteoarthritis if the initial injury is not treated aggressively. Therefore, all patients with lunate fractures, perilunate sprains, or carpal instability should be referred to a hand surgeon within 72 hours. (See 'Indications for surgical referral' above.)

●Management – Immediate reduction of a wrist (radio-carpal) dislocation is paramount to prevent further cartilage damage and relieve pressure on the median nerve. For injuries not involving a dislocation, basic fracture care and a short-arm wrist splint are appropriate. The rare lunate fracture that is non-displaced and not associated with perilunate dislocation or disruption of the scapholunate or lunotriquetral ligaments can be treated with a short arm cast for three to six weeks. (See 'Initial treatment' above and 'Follow-up care' above and 'Recommendations for return to sport or work' above.)

●Complications – Complications such as decreased mobility and pain are common. Other complications may include osteoarthritis, transient ischemia, and osteonecrosis. (See 'Complications' above.)