Hamate fractures

INTRODUCTION — Hamate fractures are uncommon compared with scaphoid and distal radius fractures but, like these, often occur from a fall onto an outstretched hand.

This topic will review fractures of the hamate in adults. An overview of carpal fractures and reviews of common wrist injuries in adults are presented separately. (See "Evaluation of the adult with acute wrist pain" and "Overview of carpal fractures" and "Scaphoid fractures" and "Distal radius fractures in adults".)

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]. Fractures of bones of the distal carpal row (trapezium, trapezoid, capitate, and hamate) are less frequent than fractures of the scaphoid and other bones in the proximal carpal row.

The hamate is the third most commonly injured carpal bone, representing about 8 percent of all carpal fractures [1-4]. Hamate fractures are found in approximately 10 percent of patients with scaphoid fractures [5].

"Stick and ball" athletes (in sports like baseball, cricket, tennis, and golf) are at highest risk for hook of hamate fractures due to the repetitive impact of the heal of the bat, club, or racquet on the hand when swinging. Hook of hamate fractures were the most common hand and wrist injury requiring surgery among American professional baseball players in a large prospective study and comprised 10.6 percent of injuries overall [6].

CLINICAL ANATOMY — The anatomy of the wrist is discussed in detail separately; aspects relevant to hamate fractures are reviewed briefly below. (See "Anatomy and basic biomechanics of the wrist".)

The body of the hamate articulates distally with the bases of the fourth and fifth metacarpals, radially with the capitate, and proximally with the triquetrum and lunate (image 1 and figure 1 and figure 2 and figure 3 and figure 4). The hook of the hamate (hamulus), which protrudes in a palmar direction, represents the distal border of Guyon's canal (figure 5). This canal contains the ulnar artery and nerve and provides the attachment of the ulnar aspect of the transverse carpal ligament, which forms the roof of the carpal tunnel. Fractures involving the hamate, particularly the hook, can injure branches of the ulnar artery and nerve (image 2), and thus, it is important to ensure that blood flow and sensation is intact in the little and ring fingers. The ulnar nerve also supplies the intrinsic hand muscles, with the distalmost innervation involving the dorsal interosseous muscle of the index finger (index finger abduction). (See 'Symptoms and examination findings' below and 'Complications' below.)

The blood supply to the hook of the hamate is variable and, in some cases, tenuous [7]. Although the incidence of nonunion with fractures involving the hook is not known, the risk is increased in patients with a tenuous blood supply.

The hook of the hamate develops from an ossification center separate from the body of the hamate. In some adults, the hook persists as the os hamulus proprium. This normal variant can present a potential diagnostic pitfall if misinterpreted as a hamate fracture. (See 'Diagnostic imaging' below.)

HISTORY AND MECHANISM OF INJURY — Fractures of the hamate hook are more common than fractures elsewhere in the bone [8,9]. These often result from a fall onto an outstretched hand that puts tension on the transverse carpal ligament and causes avulsion of the hook from the body. In sports, fracture of the hook can occur when the end of a golf club, racquet, or bat is forced into the palm, exerting direct pressure on the hypothenar eminence [10]. The fracture typically occurs in the nondominant hand in golfers and batters but the dominant hand in players of racquet sports (eg, tennis) [8,11]. Hamate hook fractures are prevalent in underwater rugby players due to repeated palming of the ball [12] and can develop in climbers from chronic tension of the finger flexors [13]. Stress fractures of the hamate hook have been reported in participants of climbing, ice hockey, and tennis, and exercisers performing repetitive pushups [14].

Bat grip and bat swing habits likely contribute to the risk of sustaining hook of hamate fractures in baseball players. A grip in which the lowest finger or fingers are placed below the knob of the bat (sometimes called a palmar hamate grip) increases pressure on the hook nearly four times compared with a grip in which all fingers are on the handle shaft [15]. Checking a swing (ie, starting a swing but rapidly stopping prior to ball contact) also leads to markedly increased pressure on the hook [15,16]. These behaviors likely increase the risk of hook fractures.

Fractures of the hamate body are less common and can occur from a number of mechanisms, including shear forces exerted on the wrist (which may cause a fracture-dislocation), direct blows to the ulnar aspect of the wrist, and axial loading of the wrist [8,17]. Many such fractures involve significant wrist trauma, and adjacent structures, such as the carpometacarpal joint, may also be injured.

SYMPTOMS AND EXAMINATION FINDINGS — Pain and tenderness from a hamate fracture is usually localized over the hypothenar eminence but may be more diffuse over the volar surface of the wrist or proximal hand; swelling may be minimal or absent. Patients often complain of persistent pain at the base of the hypothenar eminence when gripping objects and possibly pain with flexion of the ring or small finger. Hamate fractures are sometimes misdiagnosed as a wrist sprain due to these relatively mild symptoms [18].

The hamate can be palpated on the palmar side of the hand by placing the tip of your thumb on the prominent pisiform bone located at the ulnar aspect just distal to the wrist crease. From there, slide your thumb 1 to 2 cm toward the space between the index and middle fingers. The hook is appreciated as a small bony prominence. Palpation of the hamate bone is described in the attached picture (picture 1).

The hook of hamate pull test (HHPT) is a method for identifying acute or chronic fractures of the hamulus (figure 6) [19]. To perform the test, the patient's hand is placed palm up on an examination table with the wrist in full active ulnar deviation and the ring and little fingers flexed. The examiner then resists the patient's active flexion (of the digitorum profundus) in these two fingers. During the maneuver, pain focused at the hook of the hamate region (and sometimes radiating into the palm or wrist) suggests fracture of the hamulus. The HHPT has been described in two small series of acute and chronic patients [19,20], and further study is needed to determine its accuracy.

If a hamate fracture has compromised Guyon's canal and injured the ulnar nerve, the patient may complain of paresthesias and manifest impaired sensation in the ring and little fingers and/or impaired motor function of the intrinsic hand muscles supplied by the nerve (hypothenar, interossei, lumbricals of middle and ring fingers, and adductor pollicis). Thus, depending upon which parts of the ulnar nerve are injured, weakness may be noted with little and ring finger flexion, abduction, or adduction, or thumb adduction. (See "Ulnar neuropathy at the elbow and wrist", section on 'Ulnar neuropathy at the wrist'.)

Concomitant arterial injury may cause pallor along the ulnar border of the hand, although this is unlikely as collateral circulation from the palmar arch typically provides flow to this area. The examination should include assessments of capillary refill and ulnar artery patency using the Allen test (picture 2). Embolization or vessel spasm resulting from ulnar artery injury may cause ischemic changes, a phenomenon known as the "hypothenar hammer syndrome." However, this uncommon phenomenon is more often the result of repetitive minor trauma to the hypothenar region [21,22]. (See "Clinical manifestations and diagnosis of Raynaud phenomenon".)

Fractures involving only the hook may be less symptomatic, leading patients to believe that the injury is only a bruised hand, which may delay presentation until chronic pain prompts self-referral. In this case, delayed union is common and close follow-up is needed, generally with a hand surgeon. (See 'Follow-up care' below and 'Indications for surgical referral' below.)

DIAGNOSTIC IMAGING — The initial imaging obtained when a hamate or other wrist fracture is suspected includes standard anteroposterior (AP) and lateral views of the wrist (image 3). If standard views are unrevealing, special views, such as hamate or carpal tunnel views (image 4) or an oblique view (image 5 and picture 3), can be obtained. Advanced imaging is often needed to identify hook fractures.

Fractures of the hamate body may sometimes be seen on standard AP or lateral plain radiographs of the wrist (image 6) or hand, but sensitivity is about 40 percent [2,4]. An AP or oblique view may show small avulsion ("flake") fractures from the distal articular surface just proximal to the base of the fifth metacarpal (image 7).

Fractures of the hook can be difficult to see on standard plain radiographs, and special views are generally needed. These include a 20-degree supinated lateral view and a carpal tunnel view (image 8), in which the wrist is maximally extended and the x-ray tube angled 25 degrees inferiorly from the plane of the palm [8,11,17,18]. The sensitivity of plain radiographs for hook fractures is only 53 to 90 percent, using computed tomography (CT) as the reference standard [23].

If suspicion is high and plain film radiographs are inconclusive, a CT scan of the wrist should be obtained for definitive diagnosis [24]. Although studies are limited by small numbers, CT appears to be highly sensitive and specific and can be especially helpful in visualizing the base of the hook when the patient cannot adequately extend the wrist because of pain (image 9 and image 10A-B) [25,26].

Magnetic resonance imaging (MRI) is considered sensitive for hamate body and hook fractures (image 11) and has the advantage of detecting concomitant soft tissue injuries, but it is more expensive than other modalities [27].

As noted above, the hamate hook ossifies independently from the body of the hamate. A separate bone known as the os hamulus proprium may be present in some adults [11]. When the hamate is bipartite, the radiolucent region separating the hook from the body is typically smooth and the margins are uniformly calcified. In contrast, in the case of a hamate fracture, the edges of the fragments are typically linear or jagged and the cortical or subchondral bone is disrupted. If there is any doubt, views of the uninjured wrist may be valuable for comparison, or thin-cut CT or MRI can be used to assess further.

DIAGNOSIS — A hamate fracture is definitively diagnosed by diagnostic imaging. A presumptive diagnosis is made based upon a history of trauma to the ulnar or hypothenar region of the wrist and hand and the presence of focal tenderness in the area of the hamate. Fractures involving only the hook may be less symptomatic, leading patients to believe the injury is only a bruised hand, which may delay presentation until chronic pain prompts self-referral. Plain radiographs are insensitive, so computed tomography (CT) may be needed if radiographs are negative and clinical suspicion persists, or if a hook fracture is present.

DIFFERENTIAL DIAGNOSIS — Diagnoses that may coincide or be confused with a hamate 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 other carpal bones — Ulnar-sided wrist pain following trauma may be due to a fracture of the pisiform, triquetrum, lunate, capitate, or any combination of these bones. Approximately 10 percent of scaphoid fractures have concomitant hamate hook fractures [5]. Tenderness may be diffuse at the ulnar aspect of the wrist. Diagnostic imaging to identify such fractures should include standard and carpal tunnel wrist views, and advanced imaging may be required. (See "Overview of carpal fractures".)

Fracture-dislocations of carpal bones — These potentially catastrophic injuries may be sustained from trauma, generally involving significant force, and must be diagnosed quickly to avoid possible neurovascular injury and osteoarthritis. Examination often but not always reveals wrist deformity; definitive diagnosis is made with radiographs. Depending upon the extent of injury, immediate or urgent orthopedic consultation is required. (See "Evaluation of the adult with acute wrist pain", section on 'Perilunate and lunate dislocations'.)

Distal radius fractures — Hamate fractures accompany 1 to 2 percent of distal radius fractures [28,29]. Such injuries are suspected on the basis of the history (usually a fall onto an outstretched hand) and examination findings (focal tenderness and deformity of the distal forearm or wrist). Imaging studies, beginning with anteroposterior (AP) and lateral views of the wrist, establish the diagnosis in most cases. (See "Distal radius fractures in adults".)

Metacarpal fractures — Injuries sustained from punching an object or person can fracture both the metacarpals and the hamate or result in complex hamate-metacarpal fracture-dislocations or isolated metacarpal fractures [30]. Fractures of the bases of the fourth and/or fifth metacarpals can present as ulnar-sided wrist and hand pain. Tenderness is typically present along the dorsal and palmar hand in the region of the injury. Diagnosis is confirmed with plain radiographs. Treatment usually requires operative intervention, so orthopedic consultation is advised. (See "Overview of metacarpal fractures".)

Wrist sprain — In the absence of fracture or dislocation, sprain of any of the many wrist ligaments and 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. Treatment involves a period of immobilization and rehabilitation once healing is adequate. (See "Evaluation of the adult with acute wrist pain", section on 'Wrist sprain'.)

Hypothenar hammer syndrome — Repetitive stress injury to the hypothenar eminence from biking, handball, martial arts, and other activities can lead to chronic injury to the ulnar artery in the region of Guyon's canal. Such chronic stress results in arterial constriction and thickening, and possibly thrombosis or aneurysm. Symptoms can include pain in the palm or ulnar digits and cold intolerance. The Allen test may show absent or delayed filling from the ulnar artery. Surgical treatment may be needed. (See "Surgical and endovascular techniques for aortic arch branch and upper extremity revascularization".)

INDICATIONS FOR SURGICAL REFERRAL — Indications for surgical referral of fractures involving the hamate body or hook include the following [8,17,31-33]:

●Injuries associated with neurovascular deficits

●Fracture-dislocations

●Displaced body fractures

●Acute hook fractures in persons requiring rapid return to work or play

●Acute hook fractures that fail to improve with several weeks of immobilization

●Delayed diagnosis (greater than six weeks since time of injury)

●Fractures associated with ruptures of the flexor digiti minimi tendon

All patients with persistent vascular or neurologic deficits associated with a hamate fracture should be referred immediately to a hand surgeon. Evaluation of the ulnar nerve and artery are particularly important in this regard. In addition, if there is any evidence of flexor tendon injury associated with an acute fracture during the initial evaluation, the patient should be referred. (See 'Symptoms and examination findings' above.)

Acute hamate hook fractures in those with need for rapid return to work or play often require surgical consultation. Conservative treatment requires prolonged immobilization, and some persons may not tolerate this for comfort or financial reasons. Optimal management of an acute hamate hook fracture is uncertain. Some authors recommend excision or mini-screw fixation, while others recommend at least a trial of immobilization [11,34-36]. Competitive athletes and those in occupations requiring grip strength often proceed with surgical excision at the outset because of pressure to return to full activity as soon as possible (ie, not waiting for four to six weeks to see if they will heal with immobilization).

Although clear guidelines are lacking, hamate hook fractures that present after a delay in diagnosis (greater than six weeks) may be at increased risk for nonunion, and referral to a hand surgeon is reasonable. Unfortunately, this is a common occurrence; the average delay to diagnosis for hook fractures is over five months [23].

Patients who have been managed appropriately with immobilization but fail to heal should be referred for excision.

INITIAL TREATMENT

Basic care — Patients with hamate hook fractures or displaced hamate body fractures that are being referred for operative consideration can be protected in a volar splint until reassessed by the surgeon (figure 7). Basic fracture care, which is reviewed separately, should be implemented, including rest, ice, elevation, and analgesia. (See "Basic techniques for splinting of musculoskeletal injuries" and "Patient education: Cast and splint care (Beyond the Basics)" and "General principles of acute fracture management" and "General principles of definitive fracture management".)

Cast placement and positioning — Nondisplaced hamate body fractures, avulsion fractures, and fractures of the hook being treated nonoperatively can typically be placed immediately in a definitive short arm cast, unless swelling is too great, in which case the cast is placed within several days at the first follow-up visit. (See 'Indications for surgical referral' above.)

The short arm cast should be properly positioned and should include the metacarpophalangeal (MCP) joints of the ring and little fingers [11]. The wrist should be placed in slight flexion to reduce tension on the hook from the small and ring fingers. The MCP joints should be placed in flexion (close to 90 degrees) to prevent shortening of the collateral ligaments (figure 8) and thus minimize the loss of motion that can result from prolonged immobilization of the MCP.

FOLLOW-UP CARE — Nonoperatively managed patients should be immobilized in a short arm cast for a minimum of four to six weeks. Some hook fractures take up to 12 weeks to heal [32,34]. Radiographs can be repeated at two- to three-week intervals to assess the progress of healing. The absence of tenderness and radiographic signs of healing (eg, callus formation) are used to determine whether the fracture has healed.

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 five 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 — Hamate fractures are rarely accompanied by complications. A retrospective study of 1120 hamate fractures managed nonoperatively reported nonunion in 2 percent, ulnar neuropathy in 1.7 percent, and flexor tendon rupture in 0.2 percent [37]. (See "General principles of fracture management: Early and late complications".)

According to small case reports, delayed union and nonunion of hamate hook fractures have been successfully treated with low-intensity pulsed ultrasound and without immobilization, but reported times to healing were 8, 12, and 36 months [38,39]. Further study of this technique is needed before it can be recommended.

RETURN TO SPORT OR WORK — Patients with hamate fractures that are managed nonoperatively can return to work or sports immediately with casting if the cast does not interfere with performing their activities [31,35]. Manual laborers and athletes who have undergone operative intervention should be restricted from active participation until after four to six weeks of immobilization [35].

Following excision of the hook of the hamate, most patients can return to full activities in four to seven weeks [11,35,40-43]. High-level amateur athletes [41] and competitive baseball players and golfers [10,42,43] treated with surgical hook excision return to full participation in sports an average of six to seven weeks after surgery [41,44,45]. However, the time required for return ranges from 1 to 36 weeks, and in one large series, 14 percent of athletes needed over 12 weeks [42]. In a case series of 261 professional baseball players, 16 percent did not return to sport after excision, whereas 81 percent returned to the same level of competition [43]. Complications, most often transient ulnar nerve dysfunction, occur in up to 25 percent of patients.

Exercises to increase wrist motion should begin as soon as casting is removed and pain has subsided. (See 'Follow-up care' above.)

Protective splinting should be continued for three months (and possibly longer) until full pain-free motion and strength have been regained.

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

●Epidemiology and mechanism – Fractures of the hook of the hamate are more common than fractures of the hamate body. Hook fractures often result from a fall on the outstretched hand or, in sports, can occur when the end of a golf club, racquet, or bat is forced into the palm. (See 'Clinical anatomy' above and 'History and mechanism of injury' above.)

●Clinical presentation and examination – Pain and tenderness from a hamate fracture are usually localized over the hypothenar eminence; swelling may be minimal or absent. Patients often complain of persistent pain at the base of the hypothenar eminence when gripping objects. Hamate fractures are sometimes misdiagnosed as a wrist sprain. (See 'Symptoms and examination findings' above.)

Examination of the hamate includes direct palpation (picture 1) and the hook of hamate pull test. Guyon's Canal is adjacent to the hook, and thus the examination must include an assessment for damage to the ulnar artery or nerve when a hook fracture occurs. This includes performing the Allen test (picture 2) and assessing little and ring finger strength and sensation.

●Diagnostic imaging – A hamate fracture is definitively diagnosed by radiograph. Body fractures can typically be seen with standard anteroposterior and lateral plain radiographs of the hand and wrist (image 7), but the hook is best visualized with a carpal tunnel view (image 8) or a lateral view with the wrist in 20 degrees of supination. Computed tomography (CT) may be needed if radiographs are negative but clinical suspicion persists. (See 'Diagnostic imaging' above.)

●Differential diagnosis – Fracture of other carpal bones, especially the scaphoid or the distal radius, is more common in acute wrist injury than a hamate fracture. (See 'Differential diagnosis' above.)

●Indications for surgical referral – All displaced fractures of the body, fractures involving subluxation or dislocations, and hook fractures where the patient cannot tolerate prolonged immobilization should be referred for operative intervention. Other indications for surgical referral are described in the text. (See 'Indications for surgical referral' above.)

●Treatment of nonoperative injuries – Nondisplaced and avulsion fractures of the body and certain cases of hook fracture are treated with a short arm cast (with ring and little fingers included) for four to six weeks, or possibly longer with hook fractures. Protection during sports using some type of splint continues for three months afterward. (See 'Initial treatment' above and 'Follow-up care' above and 'Return to sport or work' above.)