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Carpal fractures

Description

There are eight carpal bones at the wrist, situated between the radius and ulna in the forearm and the metacarpals in the hand. The most common (and important) carpal fracture is that of the scaphoid (discussed in its own section).  Among the other carpal bones, only the triquetrum, hamate and pisiform are likely to be fractured  in isolation; other carpal fractures are seen more commonly in conjunction with other injuries. Most isolated carpal fractures are caused by direct trauma.  

Structure and function

There are eight carpal bones, each with its own unique shape and size. The carpal bones articulate with the radius and ulna proximally and the 5 metacarpal joints distally.

There are eight carpal bones arranged in two rows: the proximal row consists of the scaphoid, lunate, triquetrum and pisiform. The distal row consists of the trapezium, trapezoid, capitate and hamate. The proximal row articulates with the distal radius and distal row connects to the metacarpal bones of the hand.

Proximal Row

The scaphoid is located on the radial side of the proximal carpal row.

 

The scaphoid articulates with 4 other carpal bones and is involved with most carpal motions, especially flexion.  The vascular supply of this bone travels from the distal region of the scaphoid back proximally (a so-called “retrograde flow”). Ossification in children also occurs in the distal-to-proximal direction. 

 

The lunate is half-moon shaped and is positioned between the scaphoid and the triquetrum.

 

The lunate is important in flexion/extension and radial/ulnar deviation at the radiocarpal and midcarpal joints.

 

The triquetrum is located on the ulnar side of the proximal carpal row. It is pyramid-shaped with an oval shaped facet on its volar side.

 

 The triquetrum articulates with the pisiform on the volar side, the lunate laterally and the triangular fibrocartilage complex proximally.

The pisiform is a pea shaped sesamoid bone that articulates with the triquetrum.

 

The pisiform is enclosed in the sheath of the flexor carpi ulnaris tendon and is in close proximity to the ulnar nerve.

Distal row

The hamate is a wedge-shaped bone on the ulnar side of the distal carpal row.

 

On the distal volar surface, a hook protrudes out from the ulnar side of the bone. The hamate serves as an attachment site for many ligaments, including the transverse carpal ligament atop the carpal tunnel. The hook of the hamate acts as a pulley for the 4th and 5th finger flexor tendons.

The capitate is the largest carpal bone and is positioned in the central column of the wrist.

 

The capitate articulates with the scaphoid, lunate, hamate and trapezoid, as well as the 2nd, 3rd and 4th metacarpals.

The trapezium is a quadrangular shaped bone located on the radial side of the distal carpal row.

 

The trapezium has a double-saddle facet that articulates with the 1st metacarpal allowing both flexion/extension, abduction/adduction, circumduction and opposition at the joint.

 

The Trapezoid is positioned between the capitate and trapezium.

 

 

 

 

Patient presentation

Patients with acute carpal fractures will typically present with wrist pain and swelling and there will be point tenderness near the fracture. Due to the close proximity of some carpal bones to nearby nerves, some carpal fractures will be associated with neurological injury as well.

  • Triquetral fractures are usually a result of a direct blow to the dorsum of the hand or a fall, forcing the wrist into extreme extension and ulnar deviation.  This position can cause the proximal hamate and distal radius to impinge on the triquetrum and sheer it. Patients typically present with pain and swelling in the wrist with increased tenderness on the ulnar side. The triquetrum lies deep to the pisiform bone, making it difficult to palpate on exam. To expose the bone on exam, the hand must be placed into a position of radial deviation.

  • Hamate fractures are associated with racket sports or sports involving clubs. The injury is often to the hook of the hamate, sparing the body.   Patients will usually have history of a trauma, for example, the accidental strike of the ground with a golf swing. They will have ulnar sided wrist pain, pain in the hypothenar region and decreased grip strength. Because this injury is associated with compression of the ulnar nerve as it crosses Guyon's canal in the wrist, patients may have paresthesias in their ring and small fingers, with weakness of the intrinsic muscles supplied by the  ulnar nerve.  Patients may also have pain with resisted flexion of the 4th and 5th finger.  Hamate body fracture is typically seen in injuries where an axial force was applied to a closed fist. Patients will similarly complain of ulnar sided wrist pain and present with swelling.

  • Pisiform fractures are usually caused by a fall on the outstretched hand. The chief complaint is ulnar sided wrist pain  and the physical exam is notable for point tenderness over the pisiform.

  • Trapezoid and trapezium fractures are usually not caused by direct trauma, but by a so-called "nutcracker effect", namely, pressure from the second metacarpal when the finger and wrist are hyper-extended.   An index finger injury with tenderness more proximally, towards the wrist, should increase the suspicion of this (rare) fracture.

  • “Fractures” of the lunate seen on x-ray, especially without a history of specific injury, are more likely to represent fragmentation of the bone from osteonecrosis (Kienböck's disease).

  • Capitate fractures in isolation are rare. A ligament injury should be suspected and ruled out when this diagnosis is made (or considered).

Note that many carpal fractures may present as sub-acute or chronic diffuse pain, due to missed diagnosis of a prior injury. In those settings, the presentation is similar to carpometacarpal or radiocarpal arthritis or tendinitis.

 

Objective evidence

The standard wrist radiographs ordered for assessment of the carpal bones include AP, lateral and oblique views. Disruption or widening of the spaces between the bones may indicate carpal instability or damage to the ligaments.

CT scan is the preferred study for diagnosis of hook of hamate fractures (as shown in the figure).


Figure: Hamate fracture as seen on CT (credit http://radiopaedia.org/cases/hook-of-hamate-fracture)

MRI can be a useful modality in not only detecting occult fractures, but also detecting soft tissue injuries such as ligaments or tendon damage.

Interpretation of carpal radiographs is admittedly difficult for the novice, and there is no shame in asking an expert for help.  Two things must be kept in mind: 1) dislocations require urgent attention and 2) the wrist should be immobilized until a definitive diagnosis is obtained.

Epidemiology

Carpal fractures make up nearly one quarter of hand fractures and about 5% of all fractures.  This estimate likely under-represents the true incidence of carpal fractures, as many are presumably not formally diagnosed (and dismissed by the unsuspecting patient as a contusion). As noted, scaphoid fractures account for a majority of  carpal bone fractures.  The second most common carpal fracture is of the triquetrum, which accounts for 14% of all wrist injuries.

Differential diagnosis

All wrist pain due to falls on an outstretched hand should be carefully assessed for the possibility of a carpal fracture. In particular, scaphoid fracture should be kept in mind, due to the high risk of developing a nonunion and, ultimately, post traumatic arthritis if left untreated.

Injuries to the radioulnar joint should also be ruled out when considering carpal fractures.

Carpal dislocations can occur commonly in conjunction with carpal fractures.

Fractures of some carpal bones usually occur in conjunction with other carpal fractures, making it important to rule out fractures to adjacent carpal bones.

Red flags

Marked tenderness over the scaphoid tubercle or the anatomic snuffbox in the setting of normal xrays suggests a non-displaced scaphoid fracture (which must be immobilized).

Finger injuries with wrist tenderness suggest an injury to the carpal bones.

Treatment options and outcomes

The treatment of carpal fractures aims primarily to restore pain-free motion of the wrist. An important secondary aim is to reduce the patient’s risk of developing osteoarthritis of the carpal bones.

Most stable, non-displaced fractures of carpal bones are treated with casting for 6-8 weeks. Non-displaced scaphoid fractures should be immobilized in a thumb spica cast.  In cases of displacement or instability, open reduction with internal fixation is considered.

Most isolated carpal fractures (except the scaphoid, which has a more tenuous blood supply) heal uneventfully.  Because there may be an associated ligament injury with subtle instability, osteoarthritis may develop even if the fractures do heal nicely.   

Risk factors and prevention

The use of wrist guards when rollerblading (or when participating any other activity with a high rate of falls on the outstretched hand) may be helpful.

Miscellany

The mnemonic for recalling the names of the carpal bones in medial-to-lateral order,  "Some Lovers Try Positions That They Can't Handle", is somewhat self-referential as weight-bearing on the palm is painful for people with injured or arthritic carpal bones.  (ed: The vivacity of the mental image is worth the risk of offending the Bluenose readers) 

Key terms

anatomic snuffbox; wrist fracture; avascular necrosis; non-union;  Scaphoid; Lunate; Triquetrum; Pisiform; Trapezium; Trapezoid; Capitate; Hamate

Skills

recognize and name a carpal fracture;

perform a physical exam to detect and define carpal injury

 

Content

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  1. Mar 25, 2014

    I'm going section by section, copying and pasting the text as is, inserting a note where I have a comment, and giving details of the comment below.

    Description

    [g1] The most common (and important) carpal fracture is that of the scaphoid (and is [g2] discussed in its own section).  [g3] Among the other carpal bones, only the triquetrum, hamate and pisiform are likely to be fractured  in isolation; other carpal fractures are seen more commonly in conjunction with other injuries. Most isolated carpal fractures are caused by direct trauma.  Many lay people are not even aware that they have carpal bones,[g4]  until they break (or get arthritic).


     [g1]Would consider a broader intro sentence to set the scene, e.g. “The carpus is a set of eight bones lying in the anatomic wrist that connects the radius and ulna in the forearm to the metacarpals in the hand”

     [g2]Would remove “and is” – sounds awkward

     [g3]Extremely nit-picky, but half of sentence breaks have 2 spaces in between and half only have one. I’d be happy to go through and make it uniform if your OCD is as bad as mine.

     [g4]Can remove comma. (Also, this sentence is interesting but maybe not 100% necessary for high yield fact purposes)

  2. Mar 25, 2014

    Structure and function

    There are eight carpal bones [g1] each with its own unique shape and size. This variation creates a complex arrangement of the bones,  [g2] making interpretation of radiographs and examination difficult. The carpal bones articulate with the radius and ulna proximally and the 5 metacarpal joints[g3]  distally.

    There are eight carpal bones arranged in two rows: the proximal row consists of scaphoid, lunate, triquetrum and pisiform. The distal row consists of trapezium, trapezoid, capitate and hamate. The proximal row articulates with the distal radius and distal row connects to the metacarpal bones of the hand.

     [g4] The scaphoid is a[g5]  located on the radial side of the proximal carpal row. It articulates with 4 other carpal bones and is involved with most carpal motions, especially volar flexion.  The vascular supply is unusual,[g6]  in that it travels from the distal region of the scaphoid proximally (“retrograde”)[g7] . Ossification in children also occurs in the distal-to-proximal direction.  [g8] 

    The lunate is half-moon shaped and is positioned between the scaphoid and [g9] triquetrum. The lunate is important in flexion/extension and radial/ulnar deviation at the radiocarpal and midcarpal joints.

    The triquetrum[g10]  is located on the ulnar side of the proximal carpal row. It is pyramid shaped with an oval shaped facet on is[g11]  volar side. It articulates with the pisiform on the volar side, the lunate laterally and [g12] triangular fibrocartilage complex proximally.

    The pisiform is a pea shaped sesamoid bone that articulates with the triquetrum. It is enclosed in the sheath of the flexor carpi ulnaris tendon and is in close proximity to the ulnar nerve.

    Distal row

    The hamate is a wedge-shaped bone on the ulnar side of the distal carpal row. On the distal region of the volar surface [g13] a hook protrudes out directed laterally. The hamate serves as an attachment site for many ligaments including the transverse carpal ligament. The hook of the hamate acts as a pulley for the 4th and 5th flexor tendons.

    The capitate is the largest carpal bone and is positioned in the central column of the wrist. It articulates with the scaphoid, lunate, hamate, [g14] trapezoid, and[g15]  the 2nd, 3rd and 4th metacarpals.

    The trapezium is a quadrangular shaped bone located on the radial side of the distal carpal row. It has a double-saddle facet that articulates with the 1st metacarpal [g16] allowing both flexion/extension and abduction/adduction at the joint. 

    The Trapezoid[g17]  is positioned between the capitate and trapezium.[g18] 


     [g1]Insert comma

     [g2]Delete extra space

     [g3]Replace with “bones”

     [g4]Would insert heading of “Proximal Row” since there is a heading below for the distal row.

     [g5]Delete “a”

     [g6]Can delete comma

     [g7]I think this sentence is fine, but may consider rephrasing, e.g. “in that it enters from the distal region of the scaphoid and travels proximally”

     [g8]Comment on figures – may consider labeling the bone of interest in the figures directly or referencing them in the text (e.g. “see image below”), only because in the PDF version the images sometimes get separated from the sentence referencing them.

     [g9]Insert “the”

     [g10]Make bold (scaphoid and lunate intros are bolded above)

     [g11]Should say “its”, not “is”

     [g12]Insert “the”

     [g13]Insert comma

     [g14]Insert “and”

     [g15]Change to “as well as” (these two edits not necessary, but the double ands made the sentence a little tough to read)

     [g16]Insert comma

     [g17]Other names of bones not capitalized)

     [g18]If want to make it more precise, can say “between the capitate medially, the trapezium laterally, the scaphoid proximally and the 2nd metacarpal distally” or something to that effect.

  3. Mar 25, 2014

    I am not able to edit the already submitted comments, but in the structure and function section commented on above, each bone (pisiform, hamate, capitate, trapezium and trapezoid) should be bolded when initially introduced to stay consistent. I forgot to add that comment for each new bone mentioned. 

  4. Mar 25, 2014

    Patient presentation

    In general [g1] patients with carpal fractures will present with wrist pain and swelling. There will be point tenderness in the anatomic region of fracture. Carpal fractures are commonly misdiagnosed --[g2] which means patients may often [g3] present with chronic pain. Due to the close proximity of some carpal bones to nerves nearby[g4] , some carpal fractures will be associated with neurological [g5] injury as well.

    Triquetral fractures are usually a result of a direct blow to the dorsum of the hand or a fall, forcing the wrist into extreme dorsiflexion and ulnar deviation.  This position applies a sheer stress on the triquetrum,[g6]  from impingement of[g7]  the proximal hamate and distal radius. Patients typically present with pain and swelling in the wrist with increased tenderness on the ulnar side.

    The triquetrum lies under[g8]  the pisiform bone, making it difficult to palpate on exam. To expose the bone on exam, the hand must be placed into a position of radial deviation.

    Figure of triquetrum fx xray

    Hamate fractures are associated with racket sports or sports involving clubs. The injury is often to the hook of the hamate, sparing the body.   

    Patients will usually have history of a trauma similar [g9] to an accidental strike of the ground with a golf swing. They will have ulnar sided wrist pain, pain in the hypothenar region and decreased grip strength. Because this injury is associated with ulnar nerve compression as it crosses [g10] Guyon's canal in the wrist, patients may have paresthesias in their ring and small fingers, with weakness of the intrinsic muscles supplied by the  ulnar nerve.  Patients may also have pain with resisted flexion of the 4th and 5th finger.  Hamate body fracture is typically seen in injuries where an axial force was applied to a closed fist. Patients will similarly complain of ulnar sided wrist pain and present with swelling.

    Figure of Hamate xray

    Pisiform fractures are usually caused by a fall on the outstretched hand. The chief complaint is ulnar sided wrist pain  and the physical exam is notable for point tenderness over the pisiform.

    Figure of Pisiform fracture xray

    Trapezoid and trapezium fractures are usually not caused by direct trauma, but by a so-called nutcracker effect on[g11]  the second[g12]  metacarpal when the finger and wrist are hyper-extended.   A finger injury with tenderness more proximally, towards the wrist, should increase the suspicion of this (rare) fracture.

    “Fractures” of the lunate, especially without a history of specific injury, are more likely to be changes from osteonecrosis (Kienböck's disease).

    Capitate fractures in isolation are rare. A ligament injury should be suspected and ruled out when this diagnosis is made (or considered).

    Note that many carpal fractures may present as sub-acute or chronic [g13] diffuse pain,[g14]  due to missed diagnosis of a prior injury. In those settings, the presentation is similar to carpometacarpal or radiocarpal arthritis or tendinitis.


     [g1]Insert comma

     [g2]Change “—“ to a comma

     [g3]Remove “often” (or can remove “may”, but I wouldn’t say “may often” as it implies that the often-ness is what may vary as opposed to the presenting with chronic pain or not)

     [g4]Would change to “nerves nearby” to “nearby nerves”

     [g5]Fun fact: I looked it up and the American Academy of Neurology prefers that “neurologic” be used preferentially over “neurological” as an adjective, but it appears they are used interchangeably in the literature. So no change necessary :)

     [g6]Delete comma

     [g7]Change “of” to “by” or “between”—“of” implies that the hamate or radius is what is being impinged, whereas I believe they are doing the impinging.

     [g8]I think “under” may be unclear. Consider changing to “deep to”?

     [g9]Insert comma, change “similar to” to “for example”

     [g10]Change “ulnar nerve compression as it crosses” to “compression of the ulnar nerve as it crosses” to clarify that “it” is the ulnar nerve

     [g11]Change “on” to “of”; I think this makes it more clear that the 2nd metacarpal is the nutcracker and the carpals are the nuts.

     [g12]Again SUPER nit-picky, but everywhere else we’ve been using numbers instead of words, so I would change "second" to "2nd".

     [g13]Insert comma

     [g14]Delete comma

  5. Mar 25, 2014

    Clinical evidence

    The standard wrist radiographs ordered for assessment of the carpal bones include AP, lateral and oblique views. On a PA view [g1] three arcuate lines [g2] can be drawn along the carpal surfaces [g3] if there is disruption or widening of the spaces [g4] it may indicate carpal instability or damage to the ligaments.

    CT scan is the preferred study for diagnosis of hook of hamate fractures (?add this).

    MRI can be a useful modality in not only[g5]  determining[g6]  occult fractures [g7] but also [g8] detecting soft tissue injuries such as ligaments or tendon damage.

    Interpretation of carpal radiographs is admittedly difficult for the novice, and there is no shame [g9] asking an expert for help.  Two things must be kept in mind: 1) dislocations require urgent attention and 2) the wrist should be immobilized until a definitive diagnosis is obtained.


     [g1]Insert comma

     [g2]A picture of an XR with these lines drawn would be very helpful here.

     [g3]Insert period after “surfaces”. Capitalize “If” and start new sentence.

     [g4]Insert comma

     [g5]Change “in not only” to “not only in”

     [g6]Change “determining” to “diagnosing” ("Determining a fracture" sounds funny to me, I would use "diagnosing" or even "determining the existence of")

     [g7]Insert comma

     [g8]Insert “in”

     [g9]Insert “in”

  6. Mar 25, 2014

    Epidemiology

    Carpal fractures make up nearly one quarter of hand fractures and about 5% of all fractures.  This estimate likely under-represents the true incidence of carpal fractures, as many are presumably not formally diagnosed (and dismissed by the unsuspecting patient as a contusion or the like). As noted, scaphoid fractures account for a majority of  [g1] carpal bone fractures.  The second most common carpal fracture is of the triquetrum [g2] which accounts for 14% of all wrist injuries.


     [g1]Delete second space in text

     [g2]Insert comma

  7. Mar 25, 2014

    Differential diagnosis

    All wrist pain due to falls on outstretched hands [g1] should be carefully assessed for the possibility of a carpal fracture. Particularly [g2] scaphoid fracture should be thoroughly ruled out due to the high risk of developing avascular necrosis in displaced scaphoid fractures.

    Injuries to the radioulnar joint and distal radius and ulnar fractures [g3] should also be ruled out when considering carpal fractures.

    Carpal dislocations can occur commonly in conjunction with carpal fractures. It is also possible that carpal fracture will occur secondary to carpal dislocations[g4] . Radiographic imaging is needed to distinguish between a dislocation and fracture.

    Fractures of some carpal bones usually occur in conjunction with other carpal fractures [g5] making it important to rule out fractures to adjacent carpal bones.


     [g1]“a fall on an outstretched hand” may sound better than the plural, but that’s just a preference thing

     [g2]Insert comma

     [g3]This sounds a bit funny. Maybe change to “Injury to the radioulnar joint and fracture of the distal radius and/or ulna” or “Injuries to the distal radius, distal ulna or radioulnar joint”

     [g4]Would make this singular since “fracture” (earlier in the sentence) is singular

     [g5]Insert comma

  8. Mar 25, 2014

    Red flags

    Marked tenderness and[g1]  over the scaphoid tubercle or the anatomic snuffbox in the setting of normal xrays suggests a non-displaced scaphoid fracture (which must be immobilized) [g2] 

    Finger injuries with wrist tenderness suggest an injury to the carpal bones.


     [g1]Delete “and”

     [g2]Insert period

  9. Mar 25, 2014

    Treatment options and outcome [g1] 

    The treatment of carpal fractures aims primarily to restore pain-free motion of the wrist. An important secondary aim is to reduce the patient’s risk of developing osteoarthritis of the carpal bones.

    Most stable, non-displaced fractures of carpal bones are treated with casting for 6-8 weeks. Non-displaced scaphoid fractures should be immobilized in a thumb spica cast.  In cases of displacement or instability [g2] open reduction with internal fixation is considered.

    Most isolated carpal fractures (except the scaphoid, which has a more tenuous blood supply) heal uneventfully.  Because there may be an associated ligament injury with subtle instability [g3] osteoarthritis may develop even if the fractures do [g4] heal nicely.   


     [g1]Change “outcome” to “outcomes”

     [g2]Insert comma

     [g3]Insert comma

     [g4]I would change “fractures do” to “fracture does”, but this is mostly just personal preference. 

  10. Mar 25, 2014

    Risk factors and prevention

    The use of wrist guards when roller blading [g1] (or [g2] any other activity with a high rate of falls on the outstretched hand) may be helpful [g3] 


     [g1]Can make rollerblading one word

     [g2]Insert “participating in”

     [g3]Insert period

  11. Mar 25, 2014

    Miscellany

    The mnemonic [g1] for recalling the names of the carpal bones in order -- [g2] "Some Lovers Try Positions That They Can't Handle" – is somewhat self-referential as weight-bearing on the palm is painful for people with injured or arthritic carpal bones.  (ed: The vivacity of the mental image is worth the risk of offending the Bluenose readers) 


     [g1]I’m really glad we included this; I was going to suggest it!

     [g2]May want to specify “in order, moving lateral to medial, starting with the proximal row and then the distal” (or something to clarify what order we’re going in) 

  12. Mar 25, 2014

    Key terms

    anatomic snuffbox; wrist fracture; avascular necrosis; non-union;  [g1] Scaphoid; Lunate; Triquetrum; Pisiform; Trapezium; Trapezoid; Capitate; Hamate [g2] 


     [g1]Remove second space

     [g2]Just a note: we didn’t capitalize these elsewhere

  13. Mar 25, 2014

    Skills

    be[g1]  able to read an xray to diagnose a carpal [g2] ; perform a physical exam to detect and define carpal injury

     


     [g1]Capitalize “Be” (unless this is intentionally formatted to match other chapters)

     [g2]Insert “fracture”