Imaging Scaphoid Fractures

Introduction

The scaphoid fracture is the most common carpal bone fracture (60 - 70% of carpal bone fractures). Scaphoid fractures suffer from being both potentially difficult to demonstrate, and troublesome for the patient if undiagnosed and untreated. This page examines the radiographic techniques for demonstrating scaphoid fractures.

Anatomy

The carpal bones can be thought of as being arranged in two rows- a proximal row and a distal row. The lunate and scaphoid occupy the proximal row and articulate with the radius. The row theory is based on the fact that the proximal and distal rows work as 2 separate functional units. This model has been challenged/modified by the proposition that the two rows are stabilized by the scaphoid which could be considered to be part of both rows. There is also an alternate column theory.

Surface Anatomy

<a class="external" href="http://www.aafp.org/afp/20040901/879.html" rel="nofollow" target="_blank">http://www.aafp.org/afp/20040901/879.html</a>

The scaphoid position is most easily determined by locating the surface anatomy feature known as the anatomical snuff box. This is a void at the base of the thumb best demonstrated when the thumb is abducted (hitch-hiking position). This triangular depression is defined by the extensor and abductor tendons of the thumb, and is easily visible when the wrist is partially ulnar deviated and the thumb abducted and extended.<a class="external" href="http://www.aafp.org/afp/20040901/879.html" rel="nofollow" target="_blank">http://www.aafp.org/afp/20040901/879.html</a>

Mechanism of Injury

source: <a class="external" href="http://www.handuniversity.com/topics.asp?Topic_ID=30" rel="nofollow" target="_blank">Hand University</a>

Scaphoid fractures are almost invariably caused by a fall onto an outstretched hand. This is useful for the radiographer to know. It is good practice to ask the patient about their mechanism of injury in cases of acute injury to help assess the likelihood that the patient may have sustained a scaphoid fracture. A history of a fall onto an outstretched hand and acute localised pain in the anatomical snuff box suggests a high probability of a scaphoid fracture (base of thumb fractures - Bennett, Rolando, other- are common clinical misdiagnoses). Scaphoid fractures are most common in males 15 to 30 years of age and are rare in young children and infants.<a class="external" href="http://www.aafp.org/afp/20040901/879.html" rel="nofollow" target="_blank">http://www.aafp.org/afp/20040901/879.html</a>

Radiography

PA with Ulnar Deviation and Tube angulation

This is the commonly performed "scaphoid view" that is an essential inclusion in any scaphoid series. This view provides an elongated image of the scaphoid that can reveal a fracture that is not evident in any of the other views. The elongation of the scaphoid should perhaps be better described as a reduction in the foreshortening which is evident in a conventional PA wrist view. This effect is due to two factors- one purely anatomical and the other positional.

Zero Degree Tube Angle	20 Degrees Tube Angle modified from <a class="external" href="http://www.aafp.org/afp/20040901/879.html" rel="nofollow" target="_blank">http://www.aafp.org/afp/20040901/879.html</a>	30 Degrees Tube Angle
This is a scaphoid position with no tube angle. It is essentially a PA wrist position with ulnar deviation.	The wrist is positioned for a PA wrist view then moved into an ulnar deviated position. A tube angle of 20 degrees is applied as shown above. The tube angle is an approximation of the angle of the scaphoid to achieve an en face image of the scaphoid. The perfect angle will vary between patients and with the degree of ulnar deviation. This photograph shows a position that needs more ulnar deviation- a good guide is when the first metacarpal lines up with the longaxis of the radius.	The 30 degree tube angle produces some elongation of the scaphoid in most patients.

1. Anatomical

The scaphoid is positioned at an angle of approximately 30 - 60 degrees to the coronal plane (and the lunate). This angle is widely variable between individuals and also changes with the ulnar/radial deviation of the wrist as explained below.

2. Positional

Ulnar Deviation	Radial Deviation	The difference in appearance of the carpal bones between the two images, particularly evident in the change in appearance of the scaphoid, suggests that there is a flexion/extension movement of the carpal bones associated with radial/ulnar deviation. During radial deviation, the proximal carpal row rotates in a palmar direction/flexes. Conversely, during ulnar deviation the proximal carpal row (including the scaphoid) rotates in a dorsal direction.
Ulnar Deviation <a class="external" href="http://books.google.com.au/books?id=67UjC6sFy04C&pg=PA120&lpg=PA120&dq=meniscus+homologue&source=bl&ots=LbhEMWnz-M&sig=yf1l2Js5wqLx8XAzBncGuRnz6Ds&hl=en&ei=D8ETSp6pKtGUkAW0p4T9Dg&sa=X&oi=book_result&ct=result&resnum=11#PPA129,M1" rel="nofollow" target="_blank">Ulrich Lanz, Rainer Schmitt, Wolfgang Buchberger. Diagnostic Imaging of the Hand. 2008</a> The scaphoid rotates in a dorsal direction during ulnar deviation. This movement is used to advantage in the common PA scaphoid view with ulnar deviation.	Radial Deviation <a class="external" href="http://books.google.com.au/books?id=67UjC6sFy04C&pg=PA120&lpg=PA120&dq=meniscus+homologue&source=bl&ots=LbhEMWnz-M&sig=yf1l2Js5wqLx8XAzBncGuRnz6Ds&hl=en&ei=D8ETSp6pKtGUkAW0p4T9Dg&sa=X&oi=book_result&ct=result&resnum=11#PPA129,M1" rel="nofollow" target="_blank">Ulrich Lanz, Rainer Schmitt, Wolfgang Buchberger. Diagnostic Imaging of the Hand. 2008</a> The scaphoid seen here on CT imaging moves in a palmar direction during radial deviation.	These saggital CT images demonstrate the position of the scaphoid in ulnar deviation and radial deviation. The scaphoid clearly rotates in a dorsal direction during ulnar deviation. Importantly, this movement mitigates toward a more en face imaging of the scaphoid when undertaking a dedicated scaphoid view.

This video demonstrates the movement of the proximal carpal row (scaphoid, lunate triquetrum) in ulnar and radial deviation. <embed allowfullscreen="true" height="350" src="http://widget.wetpaintserv.us/wiki/wikiradiography/widget/youtubevideo/d878862db6973300fa2f6c5cf41934350072bf02" type="application/x-shockwave-flash" width="425" wmode="transparent"/> source: <a class="external" href="http://www.eatonhand.com/img/img00085.htm" rel="nofollow" target="_blank">e-hand.com</a> (Note: Youtube videos are displayed at lower resolution when 'hot-linked'. Click on the bottom right corner of the video and it will open at full resolution.)

This video demonstrates the movement of the carpus in ulnar and radial deviation. <embed allowfullscreen="true" height="350" src="http://widget.wetpaintserv.us/wiki/wikiradiography/widget/youtubevideo/0e39f2a0c3f16cabe5f64166a13d96a21eeaedf5" type="application/x-shockwave-flash" width="425" wmode="transparent"/> (Note: Youtube videos are displayed at lower resolution when 'hot-linked'. Click on the bottom right corner of the video and it will open at full resolution.)

Scaphoid Acute Series

This is a typical approach to a wrist and scaphoid series in an acute setting. This approach takes account of the possibility that the patient could have a radial fracture or metacarpal fracture when the clinical diagnosis is "fractured scaphoid". A 24 x 30 cm (12 x 10 inch) cassette is usually employed for this series. Note that the radiographer has not used lead rubber to reduce scatter radiation fog.

Scaphoid Follow-up Series

This is a typical scaphoid follow-up series. The view are as follows (clockwise from top left) PA wrist with ulnar deviation oblique wrist lateral wrist pa wrist with ulnar deviation and 20 degrees tube angulation The radiographer has used lead rubber shielding to minimise the scatter radiation fog. This approach is theoretically sound, but is untidy and can produce some undesirable confusing artifacts (arrowed). You could argue that the scatter radiation fog is preferable to the confusing artifacts! Compare with the image above that does not use lead rubber to reduce scatter fog. An 18 x 24cm (10 x 8 inch) cassette is usually employed for this series. This approach can cause algorithm problems in digital radiography. It is arguably better in digital systems to use one image per "film"- this approach is however slow, and the benefits may not always be clinically significant.

How Much Tube Angle do I use for the Scaphoid View?

The first question is what are you trying to achieve with this view? If your answer is an en face projection of the scaphoid (i.e. without distortion/elongation), the 20 degree angle (as proposed in some textbooks) appears reasonable in a patient who can achieve good ulnar deviation. This is based on the fact that the scaphoid rotates dorsally during ulnar deviation and is likely to be positioned at about 20 degrees to the coronal plane of the wrist (see CT images above). If you are aiming to demonstrate fractures of the scaphoid by producing an elongated image of the scaphoid, 30 degrees of tube angle would achieve that objective in most patients who adequately ulnar deviate their wrists. More than 30 degrees tube angulation tends to elongate the scaphoid excessively, and also increases the chances of superimposing the scaphoid over other adjacent bony anatomy.

Another technique consideration is how much your technique is superimposing the scaphoid over the adjacent bony structures.

Yet another consideration is whether you perform a series of tube angles in patients who have convincing clinical evidence of a scaphoid fracture but no radiographic evidence on routine views. This is arguably reasonable if there are good diagnostic yields in patients who would otherwise be referred for MRI imaging.

Scaphoid Series

A patient referred for a scaphoid series in an Emergency Department (or other acute care setting) might typically be subject to 4 exposures as follows

1. PA wrist with ulnar deviation
2. Lateral wrist
3. Oblique Wrist
4. Scaphoid View (20 - 30 degrees tube angle)

It should be borne in mind that the clinical diagnosis of scaphoid fracture could easily be incorrect- it is a provisional diagnosis only. It is important therefore to include as much of the metacarpals and forearm as would be indicated by the particular case. This would typically extend as far as inclusion of all of the metacarpals, and the distal 1/3 of the radius and ulna.

1. PA with Ulnar Deviation	2. Lateral	3. Oblique	4. Scaphoid View
This is over-coned for an acute injury case. There is good ulnar deviation		The oblique view will superimpose the scaphoid in part over the distal radius, capitate and lunate. Despite this limitation, the oblique position does afford good visualisation of the scaphoid and can be the best view for demonstrating scaphoid tubercle fractures.	This is a 30 degree tube angle which results in some elongation of the scaphoid.

Avascular Necrosis

Fractures of the waist of the scaphoid have a high probability of disrupting the blood supply to the middle and proximal poles of the scaphoid. Non-displaced scaphoid waist fractures can cause avascular necrosis (AVN) of the proximal scaphoid pole in as many as 50% of patients. Displaced fractures of the scaphoid waist cause proximal pole AVN in more like 100% of patients. <a class="external" href="http://books.google.com.au/books?id=iJZyb0s7dhgC&pg=RA3-PA401&lpg=RA3-PA401&dq=scaphoid+fracture+avascular&source=bl&ots=VlMghkZnp9&sig=_Z9KRij0Z3Z2CSvu_btgbM4l1uc&hl=en&ei=S-AbSu2JMI3W6gPztYHVBg&sa=X&oi=book_result&ct=result&resnum=12#PRA3-PA409,M1" rel="nofollow" target="_blank">John H. HarrisThe radiology of emergency medicine. Edition: 4, 2000</a> This patient has a displaced fracture of the waist of the scaphoid. This follow-up image demonstrates sclerosis of the proximal pole suggesting AVN.

Case 1

This elderly man was hit by a car. He presented to the Emergency Department with a sore left wrist and was referred for wrist radiography including scaphoid view(s).

The PA wrist image demonstrates no clear fracture. The scaphoid fat pad is not seen which can indicate a scaphoid injury.	There is a fracture of the scaphoid tubercle (arrowed).	The lateral wrist image demonstrates no abnormality. The pronator fat pad is not clearly demonstrated but is not obviously abnormal
The scaphoid view demonstrates the scaphoid tubercle fracture (arrowed). The wrist is not ulnar deviated which is likely to be a reflection of the patient's inability to move the wrist

Case 2

This 24 year old male suffered ongoing wrist pain after a fall. Follow-up scaphoid views revealed a sclerotic appearance to the lunate consistent with Kienbock's disease. Kienbock's disease should be considered in patients who are being investigated for undiagnosed scaphoid fracture. This case demonstrates the disadvantage of coning the X-ray beam too tightly when performing follow-up imaging of the scaphoid.

Sclerotic lunate demonstrated on scaphoid view (arrowed)

Case 3

This 16 year old male presented to the Emergency Department after falling onto an outstretched hand. He was referred for wrist radiography including scaphoid views.

The scaphoid view demonstrates a radial metaphysis fracture (arrowed). This case supports the argument for not coning the X-ray beam too tightly when performing the scaphoid view. Interestingly, the fracture of the distal radius was demonstrated most convincingly on this view.

MRI Imaging of Wrist Trauma

MRI imaging of the wrist can be useful in patients who are suspected to have sustained a scaphoid fracture which is not revealed on plain film imaging