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Carpal instability

Description

The eight carpal bones of the wrist (“carpus”) are held together by ligaments. When there is an injury to a ligament (ranging from an isolated sprain to a catastrophic dislocation) the wrist may be rendered unstable.

Carpal ligament injuries can lead to post-traumatic arthritis because the bones of the carpus are normally “intercalated”, that is, tightly tethered to each other. When a carpal ligament is injured, the bones may not move in their normal concerted fashion. This abnormal motion leads to abnormal positioning of the bones and, in turn, overloading of the joint surfaces.   

Structure and function

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. (Please see the previous chapter, Carpal Fractures, for a more detailed description.) The proximal row articulates with the distal radius and distal row connects to the metacarpal bones of the hand.  

 

Figure: The bones of the carpus. The scaphoid is shown in blue; the lunate in orange; trapezium in pink; trapazoid in white; the capitate is green; the  hamate is purple; the triquetrum is yellow and the pisiform is red.

The bones have complex geometry to allow them to remain in contact when the hand is moved in three dimensions.  Yet this complex geometry offers little bony congruity and in turn less inherent stability of the joints (contrasted to what is seen, for exampple, in the hip). As such, a network of ligaments is needed to secure the bone-to-bone connections.

The ligaments of the carpus are categorized as “intrinsic” (for those connecting carpal bone to carpal bone) or “extrinsic” (if they connect either the radius or the ulna to an individual carpal bone).  The nomenclature is simple: a compound word naming the two connecting bones is used, eg, "scapho-lunate" ligament.

When a carpal ligament is injured, the bones will tend to separate and the normal contact points are disrupted. This can lead to focal load bearing and articular cartilage breakdown.  In turn, arthritis may develop, leading to painful and limited motion and radiographic changes.

The carpal bones are said to be “intercalated”. That term technically means “layered”, but the key concept is that the bones are linked to each other via ligaments, and as such, when a ligament is injured the bones do not move in concert, as they should. Two patterns of disruption are common enough to warrant their own name:  

  • dorsal intercalated segmental instability” (DISI), in which the scapholunate ligament is injured, and
     
  • volar intercalated segment instability” (VISI) caused by rupture of the lunotriquetral ligament and dorsal radiocarpal ligament.

 

(The names refer to the abnormal position assumed by the carpal bones because they are not tethered appropriately.)

A third pattern of ligamentous injury, perilunate dislocation, is one of the most severe forms of carpal instability. This is seen when multiple intrinsic and extrinsic ligaments are torn and the lunate completely dissociates from rest of the carpal bones. Because of the high energy associated with this injury, vascularity and neurologic function may be compromised as well.  

 

Patient Presentation

The most common injury mechanism is from a fall on an outstretched hand with wrist extended. Violent trauma such as a motorcycle accident or a contact sports injury is also a frequent cause of carpal instability.  Accordingly, the chief complaint of patients with a carpal  ligament injury is pain, and their primary findings are swelling and tenderness. 

In severe cases of carpal instability, the lunate can be completely displaced (and therefore palpated in an ectopic position).

FIGURE: In this lateral view of a CT of the wrist, a volar dislocation of the lunate is demonstrated  (credit: http://radiopaedia.org/cases/lunate-dislocation-4)

 

Often, the patient’s pain and tenderness will to be too great to allow stress testing of the affected structures and therefore radiographic diagnosis is key. 

In many cases, carpal ligament injuries are associated with fractures of the adjacent bones. For instance, distal radius fractures are commonly seen with scapholunate ligament injury. Therefore, it is important to survey the entire overall spacial relationship of the carpal bones, in addition to assessing the more obvious fracture(s).

Unfortunately, there are no pathognomonic clinical features that are diagnostic of carpal instability. The symptoms are often subtle and unimpressive. Generalized pain especially with wrist motion and axial compression without any obvious deformity or radiographic findings can steer the clinicians to suspect carpal instability.

Astute examiners can localize tender spots over the scapholunate and lunotriquetral ligaments based on anatomic landmarks.

Provocative maneuvers such as the Watson test and scaphoid ballottement test are helpful. The Watson test (also known as the scaphoid shift test) is perhaps the most important exam maneuver when there is suspicion for carpal instability.  The Watson test is used to identify scapholunate ligament tears. In order to perform this test, the clinician’s thumb presses on the scaphoid tuberosity. As the examiner passively deviates the wrist from ulnar to radial direction, pain and clunking signifies a positive test. This "clunk" results from subluxation of  ths proximal scaphoid over the dorsal lip of the radius.  Although the Watson test is sensitive for the detection of scapholunate ligament tears, its specificity is low. 

Clinical evidence

After a thorough history and physical examination, posteroanterior, oblique and lateral radiographs of the wrist  (the so-called "three-views") should be obtained.

Full thickness tears or chronic injuries to the scapholunate and lunotriquetral ligaments are often detected due to widened intervals of the proximal carpal bones.

Carpal instability can be demonstrated on imaging studies, either by detecting the carpal bones out of their normal place, suggesting laxity, or by demonstrating arthritic damage to the articular surfaces.

When assessing for carpal instability, the bone worthy of particular attention on imaging studies is the lunate. The lunate is tethered to scaphoid and triquetrum. 

The key point to recall is that if the carpal bones were not connected, the scaphoid would flex (move in a volar direction) and the triquetrum would extend (move in a dorsal direction). The lunate, connected to both the scaphoid and the triquetrum, stabilizes these bones accordingly. Critically, the position of the lunate can therefore indicate the status of the ligaments:  

  • when scapholunate ligament is injured, the uninjured lunotriquetral ligament drags the lunate into extension; and 
  • when the lunotriquetral ligament is injured, the intact scapholunate ligament pulls the lunate into flexion.

With a complete tear of the scapholunate ligament, abnormal extension of the lunate is visible on the lateral view of the wrist. This, as noted above, is known as dorsal intercalated segment instability or DISI.

 

 

Figure: Lateral view of the wrist on MRI, showing the lunate extended, ie tilted towards the dorsal surface. (Some have suggested that this looks like a tea cup that has been tipped over.) This "tilted tea cup" is indicative of complete disruption of the scapholunate ligament.

A complete tear of the lunotriquetral ligament will allow the scaphoid to drag the lunate into flexion, indicating volar intercalated segment instability (VISI)

Partial tears of the scapholunate and lunotriquetral ligaments are more challenging to identify on static radiographs, which tend to appear normal.

Stress views (for example the "clenched fist" view) can reveal carpal instability.  

In cases where multiple views including stress radiographs do not show any abnormality, MRI may prove to be helpful. However, the sensitivity of MRI for scapholunate ligament tear is only approximately 60-70%. 

The current gold standard for diagnosing carpal instability is wrist arthroscopy.The direct visualization of the carpal ligaments with the use of a camera and blunt probing instruments, can definitively diagnose or rule out subtle or radiographically negative ligament tears.

Epidemiology

Carpal instability is an injury of young and middle aged populations.  The exact incidence of carpal instability is unknown, as the diagnosis is not often apparent.

Instability can be subtle: severe symptoms can be found in the setting of fairly benign-appearing radiographs. It has been shown that carpal instability can be detected (if sought) in approximately 30% of patients with displaced intra-articular distal radius or scaphoid fractures.

Differential diagnosis

Major carpal instabilities and frank dislocations are readily visualized on radiographs. Clinical findings of partial tears or attenuation of scapholunate and lunotriquetral ligaments are subtle and symptoms are nonspecific. More common clinical entities should be entertained prior to diagnosing carpal instability. 

Conditions that may present with complaints similar to those of mild carpal instability include:

 

  • DeQuervain’s tenosynovitis
  • Extensor tendonitis
  • Carpal tunnel syndrome
  • Distal radioulnar joint instability
  • Triangular fibrocartilage complex injury
  • Wartenberg syndrome (radial sensory neuritis)
  • Intersection syndrome (inflammation at the point where the abductor pollicis longus and extensor pollicis brevis “intersect” the extensor carpi radialis longus and the extensor carpi radialis brevis in the forearm.
  • Nondisplaced scaphoid fractures.

Red flags


  • A history of high energy trauma. Due to complex geometry of the bones and their overlap on lateral views, the radiographs of carpal bones are very difficult to evaluate.  As such the best means to detecting ligament injuries and carpal instability is to maintain vigilance, especially with higher-energy trauma. Loss of the normal symmetrical spaces normal seen radiographs can be a clue that ligament injury is present.  

 

Figures: Top: normal scapholunate interval (modified from wikipedia); bottom, the scapholunate interval is wide modified from wikiradiography

 

  • Presence of a displaced, intra-articular distal radius fracture. Scapholunate ligament tears are commonly associated with distal radius fractures. Persistent wrist pain despite fracture fixation suggests a diagnosis of a ligament injury. 

  • Sudden onset of neurologic symptoms such as numbness, tingling, and radiating pain along the thumb, index and middle finger distribution suggest median nerve compression (an acute carpal tunnel syndrome) and may require urgent decompression. 

Treatment options and outcomes

Partial tears of scapholunate and lunotriquetral ligaments without positive radiographic findings are initially treated nonoperatively with a short course of immobilization, followed by therapy.  In persistently symptomatic cases, wrist arthroscopy is the next phase of treatment. Partial tears can be confirmed and the ligament remnant may be debrided. Arthroscopically-assisted and percutaneous pinning of the injured interval can provide further stabilization to promote healing.

Complete tears of scapholunate and lunotriquetral ligaments (and with that, loss of ligament integrity) allow the carpal intervals to widen. The goal of treatment for this condition is to restore and maintain carpal alignment. Many operative techniques have been described; no single technique has proved superior to the others. An open approach (contrasted to arthroscopy) allows for better visualization of the wrist bones at the cost of more surgical trauma.  

Regardless of the operative approach, screws and pins are ultimately used to hold the proximal carpal in an anatomic position.  

Primary repair is feasible in certain cases, but more frequently wrist capsule and other ligaments are “borrowed” to augment the injured interval.

Figure Fixation can be attained with screws, pins or suture anchors- or all three!

In cases of perilunate dislocation,closed reduction with sedation can be attempted in the emergency department, but it is often unsuccessful as a long-term solution. These injuries are treated surgically with nerve decompression (i.e. carpal tunnel release) and open reduction of the lunate.  

High level medical evidence (ie prospective trials) regarding treatment outcome does not exist, and case reports may be misleading because of bias. Still, in general it can be observed that an injury severe enough to be easily detected is severe enough to lead to a less than desirable outcome, regardless of how it was treated. Similarly, mild ligament injuries treated with the immobilization often do well though some loss of motion  may be expected. In severe or chronic cases, post-traumatic arthritis is expected.

Risk factors and prevention

Any activity that increases the risk of falls or high energy trauma theoretically increases the risk of carpal instability. In general, there are no specific preventative steps to avoid this condition.

Miscellany

One of the most common injuries in orthopaedics is a distal radius fracture. When describing a distal radius fracture, make it a habit to mentally assess the  scapholunate interval to detect concomitant injuries there.

Key terms

  • carpal instability
  • scapholunate ligament
  • lunotriquetral ligament 
  • perilunate dislocation 
  • dorsal intercalated segment instability (DISI)
  • volar intercalated segment instability (VISI)

Skills

  • Identify the surface anatomy distal edge of radius, scaphoid, lunate and triquetrum on an uninjured wrist.
  • Perform a Watson test during clinical exam.
  • Name and identify the proximal carpal bones, and recognize, if present, any widened intervals between them on AP radiographs and any lunate (“tea cup”) tilt on lateral radiograph.

 

 

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  1. Mar 06, 2013

    This article was written by Michael S. Murphy MD, and Jaehon M. Kim MD.  I have edited it. Anything good is due to them; errors are mine

  2. Mar 14, 2014

    Edits for clarity and phrasing are made below; Where something in the original text needed to be deleted (ie spelling or pluralization mistakes), I added a margin comment so it could be easily noted. I also added a margin comment to flag edits that might not be easy to pick up skimming through (ie adding a comma or period). Finally I added a margin comment to discuss larger editorial, extra-grammatical issues (ie issues of clarification). The margin comments seem like they will appear at the bottom of the comment box.

     

    Description

    The eight carpal bones of the wrist (“carpus”) are held together by ligaments. When there is an injury to a ligament (ranging from an isolated sprain[JLM1]  to a catastrophic dislocation) the wrist may be rendered unstable. The main source of difficulty when a ligament is injured in the carpus is that ordinarily the ligaments tether the carpal bones to each other (rendering them “intercalated”). When a ligament is injured, the bones will not move in unison, leading to abnormal positioning in the range of motion and along with that, overloading. Ultimately this overloading can lead to post-traumatic arthritis. 

     

     

    Structure and function[JLM2] 

    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. (Please see the previous chapter, Carpal Fractures, for a more detailed description.) The proximal row articulates with the distal radius and distal row connects to the metacarpal bones of the hand.

    The bones have complex geometry to allow them to remain in contact when the hand is moved in three dimensions.  Yet this complex geometry precludes stability from bony congruity (as seen, say, in the hip joint) and, as such[JLM3] , a network of ligaments is needed to secure the bone-to-bone connections.

    The ligaments of the carpus are categorized as “intrinsic” (for those connecting carpal bone to carpal bone) or “extrinsic” (if they connect either the radius or the ulna to an individual carpal bone).  The nomenclature is simple: a compound word naming the two connecting bones is used, eg, "scapho-lunate" ligament, and so on.

    When a carpal ligament is injured, the contact between the carpal bones is altered. This can lead to focal load bearing and articular cartilage breakdown.  In turn, arthritis may develop, leading to painful and limited motion and radiographic changes.

    The carpal bones are said to be “intercalated”. That term technically means “layered”, but the key concept is that the bones are linked to each other via ligaments, and as such, when a ligament is injured the bones do not move in unison, as they should. Two patterns of disruption are common enough to warrant their own name[JLM4] :

    (a)   dorsal intercalated segmental instability (DISI), in which the scapholunate ligament is injured, and

    (b)   volar intercalated segment instability (VISI) caused by rupture of the lunotriquetral ligament.

    The names refer to the abnormal position assumed by the carpal bones because they are not tethered appropriately.

    A third pattern of ligamentous injury, perilunate dislocation, is one of the most severe form of carpal instability. This is seen when multiple intrinsic and extrinsic ligaments are torn and the lunate completely dissociates from rest of the carpal bones. Because of the high energy associated with this injury, vascularity and neurologic function may be compromised as well.  

     

     

    Patient Presentation

    The most common injury mechanism is from a fall on an outstretched hand with wrist extended. Violent trauma such as a motorcycle accident or a contact sports injury is also a[JLM5]  frequent cause of carpal instability.  Accordingly, the chief complaint of acute carpal ligament injury is pain and the primary findings are swelling and tenderness. 

    In severe cases of carpal instability, the lunate can be completely displaced (and therefore palpated in an ectopic position).

     

    FIGURE: A volar dislocation is demonstrated (left), a normal alignment is shown for contrast[JLM6] 

     

    Often, the patient’s pain and tenderness will to be too great to allow stress testing of the affected structures and therefore radiographic diagnosis is key. 

    In many cases, carpal ligament injuries are associated with fractures of the adjacent bones. For instance, distal radius fractures are commonly seen with scapholunate ligament injury. Therefore, it is important to survey the overall spatial alignment of all of the carpal bones in addition to assessing the more obvious fracture(s).

    Unfortunately, there are no pathognomonic clinical features that are diagnostic of carpal instability. The symptoms are often subtle and unimpressive. Generalized pain especially with wrist motion and axial compression without any obvious deformity or radiographic findings can steer the clinicians to suspect carpal instability.

    Astute examiners can localize tender spots over the scapholunate and lunotriquetral ligaments based on anatomic landmarks.

    Provocative maneuvers such as the Watson test and scaphoid ballottement test are helpful. The Watson test, also known as the scaphoid shift test,[JLM7]  is perhaps the most important exam mane[JLM8] uver when there is suspicion for carpal instability. It is used to identify scapholunate ligament tears. In order to perform this test, the clinician’s thumb is placed on scaphoid tuberosity with pressure. As the wrist is deviated from ulnar to radial direction, pain and clunking signifies a positive test. This is a result of subluxation of the proximal scaphoid over the dorsal lip of the radius.

     

    While the Watson test is a useful tool in the setting of clinical suspicion for carpal instability, the clinician must bear in mind that the specificity[JLM9]  of the test is low.

     

     

     

     

    Clinical evidence

    After a thorough history and physical examination, a standard three-view radiograph (posteroanterior, oblique and lateral) of the wrist is the first study to obtain. Full thickness tears or chronic injuries to the scapholunate and lunotriquetral ligaments are often detected due to widened intervals of the proximal carpal bones[JLM10] .

    Carpal instability can be demonstrated on imaging studies, either by detecting the carpal bones out of their normal place, suggesting laxity, or by demonstrating arthritic damage to the articular surfaces. The latter suggests abnormal loading that laxity would allow (though is of course non-specific[JLM11] ).

    The[JLM12]  bone worthy of particular attention on imaging studies assessing for carpal instability is the lunate. The lunate is tethered to the scaphoid and the triquetrum.  During wrist motion[JLM13] , the scaphoid is pulled in a flexion direction and the triquetrum in the opposite direction. The lunate, connected to both, stabilizes these bones accordingly.  Thus, when the scapholunate ligament is injured, the uninjured lunotriquetral ligament can drag the lunate into extension; and when the lunotriquetral ligament is injured, the intact scapholunate ligament pulls the lunate into flexion.

    With a complete tear of the scapholunate ligament, abnormal extension of the lunate is visible on the lateral view of the wrist. This, as noted above, is known as dorsal intercalated segment instability (DISI[JLM14] ).

     

     

     

    Figure: Lateral view of the wrist on MRI. The lunate appears extended which is indicative of complete disruption of the scapholunate ligament[JLM15] .

     

    A complete tear of the lunotriquetral ligament will allow the scaphoid to drag the lunate into flexion, indicating volar intercalated segment instability (VISI[JLM16] ).

     

    Partial tears of the scapholunate and lunotriquetral ligaments are more challenging to identify on static radiographs, which tend to appear normal. Stress views, such as clenched fist or pencil clenched views,[JLM17]  can reveal carpal instability.  

     

    In cases where multiple views including stress radiographs do not show any abnormality, MRI may prove to be helpful. However, the sensitivity of MRI for scapholunate ligament tear is only approximately 60-70%.

     

    The current gold standard for diagnosing carpal instability is wrist arthroscopy. The direct visualization of the carpal ligaments with the use of a camera and blunt probing instruments, can definitively diagnose or rule out subtle or radiographically negative ligament tears.

     

     

    Epidemiology

    Carpal instability is an injury of young and middle aged populations.  The exact incidence of carpal instability is unknown, as the diagnosis is not often apparent. Instability can be subtle: severe symptoms can be found in the setting of fairly benign-appearing radiographs. Importantly[JLM18] , it has been shown that carpal instability can be detected (if sought) in approximately 30% of displaced intra-articular distal radius fractures and acute scaphoid wrist[JLM19]  fractures (Geissler 1996 and Weber 1980).

     

     

    Differential diagnosis

    Major carpal instabilities and frank dislocations are readily visualized on radiographs. Clinical findings of partial tears or attenuation of scapholunate and lunotriquetral ligaments are subtle and symptoms are nonspecific. More common clinical entities should be entertained prior to diagnosing carpal instability. Conditions that may present with complaints similar to those of mild carpal instability include:

     

    • DeQuervain’s tenosynovitis
    • Extensor tendonitis
    • Carpal tunnel syndrome
    • Distal radioulnar joint instability
    • Triangular fibrocartilage complex injury
    • Wartenberg syndrome (radial sensory neuritis)
    • Intersection syndrome (inflammation at the point where the[JLM20]  abductor pollicis longus and extensor pollicis brevis “inters[JLM21] ect” the extensor carpi radialis longus and the extensor carpi radialis brevis in the forearm.
    • Nondisplaced scaphoid fractures.

     

     

     

    Red flags[JLM22] 

    Due to complex geometry of the bones and their overlap on lateral views, the radiographs of carpal bones are very difficult to evaluate.  As such the best means to detecting ligament injuries and carpal instability is to maintain vigilance, especially with higher-energy trauma.

    Loss of the normal symmetrical spaces normal seen radiographs can be a clue that ligament injury is present.  

     

    Figure: widened scapholunate interval is shown[JLM23] 

    Also, scapholunate ligament tears are commonly associated with distal radius fractures. Persistent wrist pain despite fracture fixation suggests a diagnosis of a ligament injury. 

    Sudden onset of neurologic symptoms such as numbness, tingling, and radiating pain along the thumb, index and middle finger distribution suggest median nerve compression (an acute carpal tunnel syndrome) and may require urgent decompression[JLM24] . 

     

     

     

    Treatment options and outcomes

    Partial tears of scapholunate and lunotriquetral ligaments without positive radiographic findings are initially treated nonoperatively with a short course of {blank[JLM25] }, followed by physical therapy.  In persistently symptomatic cases, wrist arthroscopy is the next phase of treatment. Partial tears can be confirmed and the ligament remnant may be debrided. Arthroscopically-assisted and percutaneous pinning of the injured interval can provide further stabilization to promote healing.

    A complete tear of the scapholunate and lunotriquetral ligaments (and with that loss of ligament integrity) allow the carpal intervals to widen. The goal of treatment for this condition is to restore and maintain carpal alignment. Many operative techniques have been described; no single technique has proved superior to the others. An open approach allows for full visualization of the wrist bones, making the procedure easier, but[JLM26]  arthroscopy also has its advocates.

    Regardless of the operative approach, screws and pins are ultimately used to hold the proximal carpal in an anatomic position. Primary repair is feasible in certain cases, but more frequently wrist capsule and other ligaments are “borrowed” to augment the injured interval.

     

    Figure Fixation can be attained with screws, pins or suture anchors- or all three!

    In cases of perilunate dislocation, closed reduction with sedation can be attempted in the emergency department, but it is often unsuccessful as a long-term solution. These injuries are treated surgically with nerve decompression (i.e. carpal tunnel release) and open reduction of the lunate.  

    Good[JLM27]  long-term level I evidence regarding treatment outcome does not exist. Moreover, many reported cases may be misleading because of bias. In general, if the injury is severe enough to be easily detected, it is severe enough to lead to a less than desirable outcome. Similarly, mild injuries that occur in the setting of overt fractures can be successfully treated with the immobilization offered for the fracture. Here, the outcome from the ligament injury is good.  Case series have shown that some loss of motion after injury and repair is a universal finding. In severe or chronic cases, post-traumatic arthritis can develop in the course of a[JLM28]  few years.

    Risk factors and prevention

    Any activity that increases the risk of falls or high energy trauma theoretically increases the risk of carpal instability. In general, there are no specific preventative steps to avoid this condition.

    Miscellany

    One of the most common injuries in orthopaedics is a distal radius fracture. When describing a distal radius fracture, make it a habit to mentally assess the scapholunate interval. It should be less than 5 mm.

    Key terms[JLM29] 

    • Carpal instability 
    • Scapholunate ligament 
    • Lunotriquetral ligament 
    • Perilunate dislocation 
    • Dorsal intercalated segment instability (DISI) 
    • Volar intercalate segment instability (VISI)

    Skills

    • Identify the surface anatomy distal edge of radius, scaphoid, lunate and triquetrum on an uninjured wrist.
    • Perform a Watson test during clinical exam.
    • Name and identify the proximal carpal bones, and recognize, if present, any widened intervals between them on AP radiographs and any lunate (“tea cup”) [JLM30] tilt on lateral radiograph.

     

     


     [JLM1]Removed plural from “sprains”

     [JLM2]If there is not an easily accessible figure showing the carpal bones in the previous chapter, this would be a good place for a clear illustration of normal anatomy.

     [JLM3]Added offsetting commas

     [JLM4]Added some formatting here to underline the two key patterns of injury. I find it helpful when textbooks use formatting like this, especially for key terms/ concepts.

     [JLM5]Many small edits here: “an” outstretched; “a” motorcycle; “a” contact; “injury” instead of injuries; “is” instead of are; “a” frequent.

     [JLM6]I find it helpful when textbooks consistently include a description of the image: e.g. “lateral radiograph of R wrist”

     [JLM7]Added comma

     [JLM8]Added “e”

     [JLM9]Is it just specificity that is low or is sensitivity low, too? The mechanism of the positive test seems that it would be fairly unique to carpal instability.

     [JLM10]Several small edits: “a” thorough; “a” standard; deleted “s” in radiographs; “the” scapholunate; widen”ed”; “the” proximal;

     [JLM11]Added period

     [JLM12]Deleted “key”

     [JLM13]Is this both flexion and extension or just flexion? It is hard to visualize the physics of the movement without knowing this.

     [JLM14]Added italics and clarified that the chapter had dealt with this concept before.

     [JLM15]I personally find it helpful when there is a normal study for comparison, if not on the same page then at least in an easily identifiable other section.

     

    Also, in the key terms section at the back of the chapter, you mention a “tea cup” appearance in conjunction with the lunate; if you don’t go into this in another chapter, it should be at least mentioned here so it’s not a non-sequitir at the back of the chapter.

     [JLM16]Again, added italics and clarified that we’d seen this term before. I also added “complete” tear; is this right? It seems from the context of the following paragraphs that you are addressing complete tears in this one

     [JLM17]Added offsetting commas

     [JLM18]I find it helpful when textbooks sign-post important clinical information like this

     [JLM19]Changed “waist” to “wrist”

     [JLM20]Deleted second “the

     [JLM21]“intersect”

     [JLM22]On first read-through it wasn’t entirely clear what this section was supposed to impart. Maybe a different section title like “clinical pearls” or “clinical caveats” or “important clinical considerations” would make it a bit clearer

     [JLM23]Again I like it when textbooks include: “on this PA radiograph of wrist”; also, potentially include normal PA radiograph to compare intervals

     [JLM24]Does this represent “worst case” carpal instability? It’s not entirely clear how this surgical urgency is related to carpal instability.

     [JLM25]This was left blank: is it short course of immobilization, NSAIDs?

     [JLM26]This sentence was just a little unclear, justification for the detail about open visualization of the bones seemed necessary.

     [JLM27]This first section of the paragraph is a little unclear. It seems that it is both trying to illustrate the bias of case reporting, but also to comment on the outcomes of the injuries. Is it that the more severe cases are the ones that are reported, leading to exaggeratedly bad outcomes data?

     [JLM28]Added “a”

     [JLM29]Removed the semi-colons and the period after the terms and capitalized

     [JLM30]Again, if another chapter doesn't go into this,  the “tea cup” appearance of the lunate should be mentioned in the radiology section of this chapter.