Capitate fractures

INTRODUCTION — The capitate is a major bone of the wrist that may be injured during falls onto an outstretched hand or from other trauma. This topic will review the presentation, diagnosis, and non-operative management of capitate fractures. General overviews of wrist pain and carpal fractures, as well as topics devoted to other specific carpal fractures in adults, are discussed 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" and "Hamate fractures" and "Lunate fractures and perilunate injuries" and "Trapezium and trapezoid fractures".)

EPIDEMIOLOGY — Hand fractures are among the most common of the extremity injuries, accounting for approximately 18 percent of all fractures. Carpal bone fractures comprise between 8 and 19 percent of hand fractures [1]. Fractures to the bones of the distal carpal row (trapezium, trapezoid, capitate, and hamate) are less frequent than fractures of bones in the proximal row (scaphoid, lunate, triquetrum, and pisiform). Capitate fractures account for approximately five percent of all carpal fractures, based primarily on large series in which computed tomography was used for definitive diagnosis [1-4].

CLINICAL ANATOMY — The capitate is the largest carpal bone. Distally, it articulates primarily with the base of the third metacarpal and a small portion of the fourth; radially with the trapezoid; proximally with the scaphoid and lunate; and on its ulnar side with the hamate (image 1 and figure 1 and figure 2 and figure 3). While the capitate receives most of its blood supply from vessels entering the distal pole and flowing retrograde, most capitate bones also receive small vessels that directly supply the proximal pole [5]. The anatomy of the wrist is reviewed in detail separately. (See "Anatomy and basic biomechanics of the wrist".)

MECHANISM OF INJURY — Capitate fractures occur from a number of mechanisms. Falls onto an outstretched hand and motor vehicle crashes are most commonly cited. Cadaver studies suggest that an injury sustained with the wrist in marked extension and radial deviation can cause the dorsal lip of the distal radius to contact the scaphoid, causing a fracture at its waist, and transmitting force to the capitate, which can fracture at its neck [6-8]. The following image depicts this relatively complex mechanism of injury (figure 4). Excessive palmar flexion during trauma may also predispose the capitate to injury [9]. Isolated fractures can occur from a dorsal blow or crush injury. Of note, injuries sustained from excessive palmar or dorsiflexion under a load (eg, falling onto an outstretched hand) may also cause dislocations or fracture dislocations involving additional carpal bones (eg, scaphoid). (See "Scaphoid fractures".)

Isolated capitate fracture is uncommon; concomitant carpal or metacarpal fractures and/or dislocations are much more common. In the largest series reported (53 capitate fractures), only 20 percent of capitate fractures were isolated [10]. The most common injury pattern reported is a "scaphocapitate syndrome." This hyperextension injury involves a force exerted by the radial styloid that causes fractures of both the scaphoid waist and proximal capitate. Depending upon the force, this injury may result in perilunate dislocation, as well as a rotation of the capitate's proximal fracture fragment (figure 4) [11]. Other concomitant injuries can include fractures of the distal radius, hamate, metacarpal, or triquetrum most commonly; and the distal ulna, trapezoid, trapezium, lunate, pisiform, or phalanges less commonly [10]. (See "Evaluation of the adult with acute wrist pain", section on 'Perilunate and lunate dislocations'.)

SYMPTOMS AND EXAMINATION FINDINGS — The patient with a capitate fracture typically presents with pain and swelling on the dorsum of the wrist or proximal hand. There is tenderness dorsally over the area of the capitate (just proximal to the third metacarpal and in line with Lister's tubercle (figure 1)). However, if there is a concomitant soft tissue injury and/or fracture of other parts of the carpus, especially with perilunate dislocations, pain may be more widespread about the wrist and hand. Range of motion of the wrist will likely be diminished due to pain, as will strength of the muscles whose tendons cross the wrist. Neurovascular status in the hand and fingers should be assessed, but compromise in an isolated capitate fracture is unlikely. When associated with a dislocation, however, neurovascular injury is more likely.

The capitate is palpable on the dorsal wrist at the base of the third metacarpal (MC) but may be difficult to distinguish from the MC. It can be located by palpating the third MC dorsally starting mid-shaft and working toward its base, which is often slightly prominent. Just proximal to this prominence is the capitate. It should lie in the straight line drawn from Lister's tubercle to the third MCP joint with the wrist in neutral deviation (figure 1).

DIAGNOSTIC IMAGING — Capitate fractures often evade detection with plain radiographs, but nevertheless, imaging should begin with standard wrist views, including anteroposterior (AP), lateral, and oblique. These views are helpful for assessing dislocation. In addition, if there is any tenderness of the scaphoid, we suggest obtaining scaphoid and clenched-fist views of the wrist. The following images show examples of capitate fractures (image 2 and image 3 and image 4 and image 5).

Studies using computed tomography (CT) as the gold standard have reported a poor sensitivity of plain radiographs for detecting capitate fractures [2,3]. Therefore, if plain radiographs are unrevealing but clinical suspicion persists, CT or magnetic resonance imaging (MRI) should be obtained. In a series of 53 capitate fractures, CT or MRI was needed for diagnosis in 79 percent of cases, despite plain radiographs being obtained initially in all but one case [10].

CT is highly accurate for identifying fracture or dislocation and for assessing joint surfaces when there is any question of intra-articular fracture with displacement. In addition, CT can delineate the extent of a fracture and any displacement in greater detail [2]. MRI has the additional value of detecting both acute and chronic bony and soft tissue injuries. If significant soft tissue injury (eg, ligament rupture or dislocation) is suspected, MRI should be obtained. MRI is useful for detecting occult fractures and may reveal early vascular problems within the proximal capitate [12].

Capitate fracture patterns can be classified into three groups: body fractures, avulsion tip fractures (dorsal or volar), and shear depression fractures. In addition, bone contusions, or edema of the capitate without apparent fracture, may be seen with MRI [10]. In the case of "scaphocapitate syndrome," fracture occurs in the proximal pole (neck) of the capitate. With such injuries, the proximal portion of the capitate may appear to be seated appropriately in the fossa of the lunate, but the fragment can rotate 90 to 180 degrees, resulting in the proximal articular surface pointing distally.

DIAGNOSIS — The diagnosis of capitate fracture may occasionally be made by plain radiography, in conjunction with a suggestive history and examination findings. However, as plain radiographs demonstrate poor sensitivity for these injuries, computed tomography (CT) or magnetic resonance imaging (MRI) is usually needed when fracture is suspected but initial radiographs are normal and a definitive diagnosis is required. In addition, advanced imaging is useful for detecting the concomitant injuries that are frequently present.

DIFFERENTIAL DIAGNOSIS — Capitate fractures are a heterogeneous group with a high incidence (80 percent) of concomitant injury. Diagnoses that may coincide or be confused with a capitate fracture include those described below. The differential diagnosis for acute wrist pain is discussed in detail separately. (See "Evaluation of the adult with acute wrist pain".)

Fracture of the scaphoid, trapezoid or other carpal bones — Fractures of other carpal bones are a more common cause of acute wrist injury than a capitate fracture. The scaphoid is the most commonly fractured carpal bone. Concomitant scaphoid and capitate fracture is slightly more common than isolated capitate fracture [10]. Carpal fractures may cause diffuse tenderness along the radial aspect of the dorsal wrist. Snuffbox tenderness (picture 1 and picture 2) is suggestive but not diagnostic of scaphoid fracture. 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 "Trapezium and trapezoid fractures".)

Fractures of the third metacarpal — Third metacarpal fracture is suggested by pain, swelling, and tenderness dorsally at the base of the third metacarpal. Standard radiographs of the wrist (AP, lateral, oblique) are typically sufficient for diagnosis, but CT can be useful to determine the position of fragments and full extent of injury. In a series of 53 capitate fractures, 22 percent occurred with concomitant metacarpal fracture [10].

Scapholunate ligament sprain and instability — A fall onto an outstretched hand with the wrist extended can disrupt the scapholunate ligament. Patients complain of swelling and pain over the dorsal wrist, grip weakness, and painful or decreased wrist motion. Tenderness at the scapholunate junction is common. This can be palpated just distal to Lister's tubercle (figure 1). The scaphoid shift test can help detect ligamentous instability; it is described in detail separately. (See "Evaluation of the adult with subacute or chronic wrist pain", section on 'Special tests'.)

Plain radiographs should be obtained if scapholunate injury is suspected, including the "clenched fist" view, which may show widening between the scaphoid and lunate (image 6). Advanced imaging should be obtained if clinical suspicion is high, as early surgical management is optimal. (See "Evaluation of the adult with subacute or chronic wrist pain", section on 'Scapholunate instability'.)

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. Approximately one quarter of capitate fractures have a concomitant distal radius fracture [10]. (See "Distal radius fractures in adults".)

Wrist sprain — In the absence of fracture or dislocation, sprain of any of the many wrist ligaments or the capsule is likely after acute trauma. Examination typically reveals wrist tenderness and often swelling, but plain radiographs are negative. Advanced imaging may be needed to definitively rule out a fracture. (See "Evaluation of the adult with acute wrist pain", section on 'Wrist sprain'.)

INDICATIONS FOR SURGICAL REFERRAL — All patients with persistent vascular or neurologic deficits associated with a capitate fracture should be referred immediately to a hand surgeon. Open fractures also require immediate surgical referral.

Patients with displaced capitate fractures (displacement >2 mm), delayed diagnosis of nondisplaced fractures, and concomitant carpal fractures or ligamentous instability should be seen by a hand surgeon for definitive care within three to seven days [6].

INITIAL TREATMENT — Since capitate fractures are usually accompanied by other significant wrist injuries, referral to a hand surgeon is strongly suggested. However, primary care clinicians with experience managing fractures may elect to manage the patient with an isolated, nondisplaced capitate body or a dorsal (volar) avulsion fracture without associated dislocation or scapholunate ligament instability.

Icing and elevation of the wrist above the level of the heart should be stressed. Basic fracture care is described separately. (See "General principles of acute fracture management" and "General principles of definitive fracture management".)

If there is marked wrist swelling at presentation, a sugar-tong splint (figure 5) can be used for initial immobilization. Subsequently, a short arm cast is placed once swelling subsides. If swelling is minimal at presentation, a short arm cast can be placed without delay. (See "Basic techniques for splinting of musculoskeletal injuries" and "General principles of definitive fracture management", section on 'Casting'.)

If initial radiographs are negative (as they usually are), but suspicion for a fracture remains, immobilize as usual for a known capitate fracture and obtain CT or MRI within about seven days.

Treatment of capitate fractures is based on expert opinion, as these fractures are rare and the literature is limited to case series and reports. It is reasonable to treat isolated, nondisplaced capitate fractures with cast immobilization for four to six weeks [13].

FOLLOW-UP CARE — The patient being managed nonoperatively should be assessed for cast integrity after approximately three weeks, or as needed should symptoms of poor cast fit develop. Biweekly cast checks may be prudent in very active patients.

Casting should be continued for four to six weeks for isolated capitate fractures with ≤2 mm displacement. When the cast is removed after this interval, healing should be confirmed both clinically by the absence of point tenderness and radiographically by callus formation. If there is a question about proper healing, a CT scan can identify crossing trabeculae at the site of union [13]. If nonunion is encountered after six weeks of casting, the patient should be referred to a hand surgeon. (See "General principles of acute fracture management", section on 'Initial radiologic assessment'.)

COMPLICATIONS — In a series of 53 capitate fractures, posttraumatic degenerative arthrosis was the most common complication, occurring in 7.5 percent of patients [10]. In "scaphocapitate syndrome," rotational displacement of the capitate fracture fragment can lead to avascular necrosis (AVN). Fractures of the head and neck may also be complicated by AVN [6,14]. However, such complications are uncommon, and in the above series, there were no cases of AVN [10]. The authors surmised that this low rate, relative to the higher rates reported in older and smaller case series [14,15], may have been due to earlier treatment stemming from more frequent use of computed tomography (CT) or magnetic resonance imaging (MRI) for diagnosis [10]. Clinical signs consistent with AVN include chronic pain and tenderness of the capitate; radiographic evidence includes partial collapse and increased density of the affected portion of the bone. Any of these findings should prompt advanced imaging (CT or MRI) and referral to a hand surgeon.

Other fracture complications are described separately but are uncommon with isolated capitate fractures. (See "General principles of fracture management: Early and late complications".)

After four to six weeks of casting, the wrist will have lost strength and mobility. Depending on the clinical circumstances, formal physical or occupational 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.

RECOMMENDATIONS FOR RETURN TO SPORT OR WORK — Once any acute pain has resolved, patients with isolated, nondisplaced fractures treated with casting can likely return to full activity, including sports, while casted (assuming this is permitted in their sport). After definitive casting for four to six weeks, the patient can use a semi-rigid brace to support the wrist while performing exercises to regain full range of motion and strength. We suggest that athletes continue to use protective splinting for three months or until the wrist has regained full strength and range of motion.

Patients with other associated injuries–especially those requiring surgery–have a much more prolonged recovery and may not be capable of resuming their highest level of athletic competition due to the common sequelae of wrist stiffness [13].

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

●Isolated capitate fractures are relatively rare. Other carpal and metacarpal fractures and fracture-dislocations commonly occur in association with capitate fractures. (See 'Epidemiology' above.)

●Capitate fractures are caused by several mechanisms, most commonly falls onto an outstretched hand and motor vehicle crashes. Falls with the wrist in marked flexion or extension may be involved. (See 'Clinical anatomy' above and 'Mechanism of injury' above.)

●The patient with a capitate fracture typically presents with pain and swelling along the dorsum of the hand. Tenderness is present dorsally over the area of the capitate (just proximal to the third metacarpal and in line with Lister's tubercle (figure 1)). With concomitant soft tissue injury and/or fracture of other parts of the carpus, especially perilunate dislocations, pain may be more widespread about the wrist and hand. Wrist motion is often diminished due to pain, as is the strength of the muscles whose tendons cross the wrist. (See 'Symptoms and examination findings' above.)

●Although the sensitivity of plain radiographs for diagnosing capitate fractures is limited, imaging should begin with standard wrist views, including anteroposterior (AP), lateral, and oblique. These views may reveal fractures and are helpful for assessing dislocation. If any scaphoid tenderness is present, we suggest obtaining scaphoid and clenched-fist views of the wrist. If radiographs are negative but suspicion persists, advanced imaging with computed tomography (CT) or magnetic resonance imaging (MRI) is indicated. (See 'Diagnostic imaging' above.)

●The differential diagnosis for capitate fracture includes fracture of the scaphoid, trapezoid, and other carpal bones, fracture of the third metacarpal, scapholunate ligament injury, distal radius fracture, and wrist sprain. (See 'Differential diagnosis' above.)

●Indications for immediate surgical referral include open fracture, persistent neurovascular deficit, and carpal dislocation. Patients with displaced capitate fractures (displacement >2 mm), delayed diagnosis of nondisplaced fractures, and concomitant carpal fractures or ligamentous instability should be seen by a hand surgeon for definitive care within three to seven days. (See 'Indications for surgical referral' above.)

●Nondisplaced capitate fractures without comminution or significant associated injury can be managed by primary care clinicians, and are treated with a short arm cast for four to six weeks. Healing should be confirmed both clinically by the absence of point tenderness and radiographically by callus formation. (See 'Initial treatment' above and 'Follow-up care' above.)

●Following four to six weeks of casting, a semi-rigid brace is useful to support the wrist while performing exercises to regain full range of motion and strength. We suggest that athletes continue to use protective splinting for three months or until the wrist has regained full strength and range of motion. (See 'Recommendations for return to sport or work' above.)

●Posttraumatic degenerative arthrosis is the most common complication of capitate fracture. There is a risk of avascular necrosis of the proximal pole as a delayed sequela, but this complication is uncommon. (See 'Complications' above.)