Pisiform fractures

INTRODUCTION — While upper extremity fractures are among the most common, and carpal fractures account for approximately 18 percent of hand and wrist fractures and 6 percent of all fractures [1], pisiform fractures account for a relatively small number.

This topic reviews fractures of the pisiform in adults. General overviews 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" and "Hamate fractures" and "Lunate fractures and perilunate injuries" and "Capitate fractures" and "Triquetrum fractures".)

EPIDEMIOLOGY — Of the carpal fractures, injuries to the proximal row are most frequent. However, fractures of the pisiform bone occur less often than fractures of the scaphoid, lunate, or triquetrum, and account for only 1.7 percent of all carpal fractures [2-5]. They usually occur in isolation but can be concomitant with other wrist injuries, especially distal radial fractures [6]

CLINICAL ANATOMY — The pisiform is a sesamoid bone contained within the flexor carpi ulnaris (FCU) tendon (image 1). Ossification occurs between 7 and 10 years of age, and is complete by age 12. It is the last carpus to completely ossify. Segmentation may be present before age 12 and should not be confused with fracture [7].

The pisiform is easily palpable on the volar surface of the wrist directly proximal to the fifth (little finger) metacarpal at the distal wrist crease. Ligamentous attachments travel from the pisiform to the triquetrum, hamate and fifth metacarpal, while the abductor digiti minimi originates at the pisiform. The pisiform marks the ulnar border of Guyon's canal (figure 1). With pisiform fracture there can be concomitant injury to the ulnar nerve, which traverses the canal.

MECHANISM OF INJURY — Most commonly, the pisiform is injured by a fall onto an outstretched hand with the wrist in extension, or when the heel of the hand is used to strike an object. Impact with the handle of a baseball bat, golf club, or racquet while swinging may also produce this injury [8]. These various compressive mechanisms can produce transverse, parasagittal, or comminuted fractures.

When the wrist is forcefully extended against resistance, the flexor carpi ulnaris (FCU) tendon can rupture or cause an avulsion fracture at the distal aspect of the pisiform [9]. This might occur when a heavy object falls and a person attempts to catch it with their hand palm up and wrist flexed, leading to a forceful eccentric contraction of the FCU. Repetitive sub-fracture blows, such as palm strikes in martial arts, may also lead to chondral injury of the pisotriquetral joint [10].

SYMPTOMS AND EXAMINATION FINDINGS — Patients with an isolated pisiform fracture generally present with focal pain and mild swelling at the palmar-ulnar aspect of the wrist. Concomitant ulnar nerve injury may cause fifth (little) and fourth (ring) finger numbness and intrinsic hand muscle weakness (weakness of finger spreading and little finger flexion and abduction).

On examination, tenderness is present directly over the pisiform (picture 1) and over the hypothenar eminence generally. Active wrist flexion and ulnar deviation (actions of the flexor carpi ulnaris) will likely be painful and somewhat limited. The ulnar nerve should be examined carefully for sensory or motor deficits (figure 1). (See "Ulnar neuropathy at the elbow and wrist", section on 'Ulnar neuropathy at the wrist'.)

Ulnar nerve damage near Guyon's canal (in contrast to a more proximal ulnar neuropathy) has been reported as a complication of isolated pisiform fracture [11]. Compression of the nerve at this location causes reduced flexion strength of the little finger at the metacarpophalangeal (MCP) joint, but normal strength at the distal and proximal interphalangeal joints. Such injury causes reduced sensation in the fourth and fifth digits, but sensation of the proximal ulnar palm remains intact.

DIAGNOSTIC IMAGING — Standard wrist radiographs (anterior posterior [AP], lateral, and reverse oblique views) should be obtained to evaluate for suspected pisiform fractures and other carpal injuries (image 2 and image 3 and image 1). The AP view may show a longitudinal (sagittal), transverse, or comminuted fracture. If not visible on standard films, the pisiform can be visualized with a carpal tunnel view (image 4), or a lateral wrist view obtained with 20 to 30 degrees of supination (reverse oblique) (picture 2). However, as the sensitivity of plain radiographs for detecting pisiform fractures is poor [2,3], a computed tomography (CT) scan or magnetic resonance imaging (MRI) may be obtained if necessary when a fracture is not visible but clinical suspicion remains high. CT is useful for evaluating possible fracture or dislocation, while MRI has value in detecting both acute and chronic bony and soft tissue injuries (image 5) [10].

DIAGNOSIS — The diagnosis of pisiform fracture may be made by positive radiography in conjunction with suggestive history and examination findings. However, as the sensitivity of plain radiographs poor, computed tomography (CT) or magnetic resonance imaging (MRI) may be needed should a definitive diagnosis be required.

DIFFERENTIAL DIAGNOSIS — Diagnoses that may coincide or be confused with a pisiform 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 hamate, triquetrum, lunate, capitate, or any combination of these bones. 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".)

Dislocation of the pisiform — Pisotriquetral dislocation or subluxation can occur in the absence of fracture. Dislocation is usually in the distal direction. Examination reveals ulnar-palm tenderness and swelling with absence of the pisiform prominence at its usual location near the wrist crease. Wrist flexion and ulnar deviation are painful. Radiographic detection may require a special oblique view with the forearm in 30 degrees of supination or computed tomography (CT). Reduction should be performed urgently and is likely best done under anesthesia [12]. If this fails, open reduction may be required [13].

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 — Distal radius fractures are the most common in the wrist. If a pisiform fracture is seen, a careful search for concomitant radial injury should be undertaken. Tenderness over the radius is typical, often accompanied by ecchymosis and deformity. Diagnosis is confirmed with radiographs, computed tomography (CT), or magnetic resonance imaging (MRI). (See "Distal radius fractures in adults".)

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 complete. (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. (See "Surgical and endovascular techniques for aortic arch branch and upper extremity revascularization".)

Pisotriquetral osteoarthritis — Chronic pisiform-related pain may be caused by pisotriquetral chondromalacia or osteoarthritis. A careful history reveals pre-injury pain at this location, but acute injury could cause a significant increase in pain.

Flexor carpi ulnaris tendinopathy — The pisiform is a sesamoid within the flexor carpi ulnaris (FCU) tendon, and overuse can lead to tendonitis or tendinopathy. These conditions present with focal volar and ulnar sided wrist pain reproduced with wrist flexion and ulnar deviation. The diagnosis is clinical, but diagnostic ultrasound may be useful to ascertain the extent of pathology, and MRI may be helpful to rule out concurrent pathology.

INDICATIONS FOR SURGICAL REFERRAL — A widely displaced or comminuted fracture, or one associated with decreased flexor carpi ulnaris (FCU) function, in a person desiring a quick return to work or sport is best treated with resection of the pisiform, and surgical referral is appropriate [8,9]. If symptomatic nonunion or malunion develop after appropriate conservative care, or if there is symptomatic post-traumatic osteoarthritis of the pisotriquetral joint, referral for surgical excision is warranted. Patients with associated ulnar neuropathy should be referred for possible surgical management of the fracture and decompression of the ulnar nerve [11]. Referral may be necessary for patients with other concomitant injuries that warrant treatment by a specialist.

INITIAL TREATMENT — Isolated, nondisplaced pisiform fractures generally heal well when treated with immobilization for four to six weeks, typically in a short arm cast placed in 30 degrees of flexion with slight ulnar deviation [14]. Motion at the metacarpophalangeal joints should not be restricted by the cast to prevent the development of joint stiffness. If swelling is marked or there is concern that swelling may progress, pisiform fractures can be immobilized initially in a volar (figure 2) or dorsal splint (figure 3). If swelling is minimal or absent, definitive immobilization with a cast is appropriate. When a splint is used initially, it should be replaced with a cast at the first follow-up visit, generally five to seven days after the injury was sustained.

FOLLOW-UP CARE — The integrity of the short arm cast should be assessed after about three weeks or as needed for symptoms of poor cast fit. Biweekly cast checks may be prudent in highly active patients. After four to six weeks, the cast should be removed. Healing should be confirmed clinically by the absence of point tenderness or pain with resisted wrist flexion. Repeat imaging studies are unnecessary if the patient is healed clinically. If tenderness persists after six weeks of immobilization, referral should be made for possible surgical management. (See 'Indications for surgical referral' above.)

After four to six 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 — The great majority of isolated pisiform fractures heal uneventfully. Malunion and nonunion are rare complications. Post-traumatic pisotriquetral osteoarthritis may be a late sequela [10]. Should any of these three complications develop, they are treated by excising the pisiform. Ulnar nerve injury can occur from the initial trauma or from chronic irritation by fracture fragments [11]. Malunion of a transverse fracture may lead to chronic dysfunction of the flexor carpi ulnaris tendon.

RETURN TO SPORT OR WORK — Activities, including sports, can be resumed with cast protection as soon as the acute pain subsides. Baseball, golf, and racquet sports, or heavy labor involving wrist flexion, are not advised during cast treatment. After casting, return to these activities is permitted once the patient has achieved full wrist range of 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.

In the rare case of a nonunion, an athlete can continue to play, with the wrist protected from contusion as desired, until excision can be performed at the end of the season. After pisiform excision, athletes can return to play typically within four to six weeks [15].

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 definitive fracture management".)

●(See "General principles of acute 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 anatomy – The pisiform is a sesamoid bone contained within the flexor carpi ulnaris (FCU) tendon (image 1). Pisiform fractures are uncommon and often uncomplicated. However, concomitant injury, such as distal radius fracture, can occur, particularly when the mechanism involves substantial force. (See 'Epidemiology' above and 'Clinical anatomy' above.)

●Mechanism and physical examination – Most commonly, the pisiform is injured by a fall onto an outstretched hand with the wrist in extension, or when the heel of the hand is used to strike an object. Impact with the handle of a baseball bat, golf club, or racquet while swinging may produce this injury, as may a sudden, forceful eccentric contraction of the wrist. A common finding is focal pain and tenderness over the pisiform, which is relatively superficial and located proximal to the fifth metacarpal at the distal palmar crease (picture 1). Active wrist flexion and ulnar deviation (actions of the flexor carpi ulnaris) will likely be painful and somewhat limited. The ulnar nerve should be examined carefully for sensory or motor deficits. (See 'Mechanism of injury' above and 'Symptoms and examination findings' above.)

●Diagnostic imaging – The sensitivity of standard plain radiographs for identifying pisiform fractures is limited , but the injury may be identified using a carpal tunnel view or a lateral wrist view with an additional 20 degrees of supination. Computed tomography (CT) scan or magnetic resonance imaging (MRI) can be used if plain radiograph is not diagnostic, but clinical concern persists and a definitive diagnosis is required. (See 'Diagnostic imaging' above.)

●Differential diagnosis – The differential diagnosis for pisiform fracture includes fracture of other carpal bones, fracture-dislocation of carpal bones, and distal radius fracture. Diagnostic imaging is needed to distinguish among these injuries. (See 'Differential diagnosis' above.)

●Indications for surgical referral – Indications for surgical referral include a widely displaced or comminuted fracture, symptomatic nonunion or malunion, symptomatic post-traumatic osteoarthritis of the pisotriquetral joint, and associated ulnar neuropathy that fails to improve with 12 weeks of observation. (See 'Indications for surgical referral' above.)

●Treatment – Isolated, nondisplaced pisiform fractures generally heal well when treated with immobilization for four to six weeks, typically in a short arm cast placed in 30 degrees of flexion with slight ulnar deviation. If swelling is marked or there is concern that swelling may progress, pisiform fractures can be immobilized initially in a volar or dorsal splint. In persons desiring a quick return to work or sport, or in cases where complications arise or are likely to arise, referral to a hand surgeon for possible pisiform excision is recommended. Follow-up care is straight-forward and described in the text. (See 'Initial treatment' above and 'Follow-up care' above.)

●Complications and return to activity – Complications are uncommon, but may include malunion, nonunion, post-traumatic osteoarthritis, ulnar nerve injury, and flexor carpi ulnaris tendon dysfunction. After casting, a return to strenuous activities involving the wrist is permitted once the patient has achieved full wrist range of motion and at least 80 percent strength in all wrist planes of motion, compared to the uninjured side. (See 'Complications' above and 'Return to sport or work' above.)