--- under construction---Introduction
|I once overheard a colleague say "a finger injury isn't important until it's yours". The same could be said of finger radiography. There are some common mistakes in finger radiography technique that can be easily avoided.|
| The hand is a human being's most exquisite organ of direct interaction with the surrounding universe |
Skeletal trauma: basic science, management, and reconstruction Bruce D. Browner, Alan M. Levine, Jesse B. Jupiter, Peter G. Trafton, Christian Krettek
- PIP joint consists of medial and lateral condyles on the proximal phalanx, with matching concavities on the associated distal phalanx.
- IP joints have flexion and extension movements , but they are relatively rigid in abduction and adduction
- IP joints are hinge (ginglymus) joints functionally ( Greek gínglymos - hinge )
- Interphalangeal joints are supported by similar soft-tissue structures on all 4 sides
- the volar plate (+ flexor tendons) on the palmar side
- extensor complex (central slip, lateral bands, and hood) dorsally. These structures attach to and reinforce the joint capsule.
- collateral ligaments on the radial and ulnar sides
- For a dislocation to occur, at least 1, often 2, and sometimes 3 of these structures must be significantly injured.
The Flexor Tendons
The Extensor Tendons
Lateral Finger Technique
|Lateral finger radiography is often executed quite poorly. Hyperextension and hyperflexion avulsion fractures can be very subtle and can be obscured by poor technique. The patient's finger must be positioned at ninety degrees to the central ray to achieve a true lateral position.|
|This position will result in a malposiitoned lateral finger image.|
|This commonly employed technique of forced extension of the finger can mask tendon injuries such as mallet finger, swan-neck deformity and boutonniere deformity.||Similarly, forced extension of the finger using the contralateral finger will not only mask tendon injuries, but will also irradiate the normal hand.||This is a third technique for forced extension which fails for the same reasons.|
|The labelling of the fingers is somewhat controversial. There are two methods of labelling;|
- the number method
- the descriptor method
Advocates of the various methods will espouse the benefits of their preferred method and dismiss any suggestion of alternative methods. The one area of agreement is that the term 3rd finger etc is to be avoided at all costs given that the thumb is not a finger.
The Number Method
“The digits are described by numbers and names; however, description by number is the more correct practice.” (Merrills Atlas of radiographic projections and radiological procedures, Vol 1, 10th ed, 1999, p 91). Confusion arises in patients with digits on one hand numbering other than 5 (trauma, congenital). In addition, if you are not familiar with the number system, it may not be clear whether the numbers start at the thumb or the little finger (junior doctors have asked me whether you start the numbering at the thumb or the little finger, but I have never been asked which is the ring finger!).The Descriptor Method
One advantage of the number system is that it correlates well with the descriptions of the metacarpals- it is almost universal to describe a boxer's fracture as a fracture of the head of the 5th metacarpal.
It is also noteworthy that the number system correlates well with the way we describe the toes- there are no index or ring toes!
“The numbering system should not be used with digits because of confusion in patients with amputated fingers” (personal communication). The difficulty with this descriptor system is that it is somewhat ethnocentric- would the term ring finger be equally meaningful in all cultures?Another Method
In addition, the pinky is a bit of a problem- pinky, little finger and small finger all sound a bit silly.
I prefer the method that is least likely to cause ambiguity in a given situation. This might mean following the established protocol in your institution. Where there is no established system, the number method is easily understood once you know that you start the numbering at the thumb. In patients with digits on one hand numbering other than 5, make it clear which finger you are referring to (thought required).
|It is good practice to label the image 'post reduction' to indicate that the image is post-treatment. It may also be necessary to label images post reduction 1, post reduction 2 etc where multiple attempts have been made to effect a reduction of the dislocation.|
Buddy Taping Splint
Buddy Taping Splint
|Patients will present for finger radiography with two fingers taped together. There are a number of radiographic options to consider|
- remove the tape splint (don't do this unless the patient routinely removes the splint at home, or you have the express permission of the referring doctor)
- don't perform a lateral view
- perform a lateral view knowing that the anatomy will be partly obscured by the splinting finger
- perform an off-lateral view to ensure some separation of the two fingers
- check your departmental policy re splint removal
|This patient presented from fracture clinic with budding taping of the middle and ring fingers. The volar plate fracture is demonstrated on the lateral projection image despite the overlapping finger.|
Fixed Flexion Deformity
Finger or hand radiography
|Generally speaking, hand radiography is not a good substitute for finger radiography. Some injuries (particularly avulsion fractures) can be very subtle and difficult to demonstrate radiographically. Poor radiographic technique can mask the subtle fractures. Despite this limitation, there may be cases where the patient cannot give a history and a lateral hand to demonstrate the digits may be warranted.|
Case Study 1
|This 25 year year old male presented to the Emergency Department after injuring his left index finger in a fight. He was referred for left index finger radiography. The PA finger position does not take into consideration the inability of the patient to fully extend the finger joints. An AP projection of the finger could have been employed to good effect. Equally, isolation of teh injury to a single joint would allow the finger to be positioned in all projections to profile the joint of interest.|
The oblique and lateral projections of the finger demonstrates that the finger was not at right angles to the central ray in both cases.
Case Study 2What Went Wrong?
|Radiographer 1||Radiographer 1|
|This is a PA hand view taken at followup orthopedic clinic in a patient with a K-wire internal fixation of a middle phalanx fracture of the ring finger. The flexion of the fingers resulted in a very distorted view of the anatomy of interest. ||This is an oblique hand view of the ring finger fracture. The overlapping of the middle finger may have been unavoidable because of splinting. |
|Radiographer 2||Radiographer 2|
|On the second follow-up clinic appointment the radiographer reviewed the previous imaging and performed a Brewertons-like view of the fingers. Compared with the conventional PA hand view shown above, this is a vast improvement in the demonstration of the fracture.||Similarly, the radiographer reviewed the previous imaging of this patient's fracture and performed an AP oblique view of the finger/hand. This projection provides a vastly improved demonstration of the fracture compared to the original conventional PA oblique hand view' shown above.|
Radiographer 1 has approached this examination with a 'photographic' rather than a 'clinical' focus. Radiographer 1 has performed the routine views for this patient without further thought. Radiographer 2 has taken a clinical approach to this case and asked the question ..."what does the surgeon want from this imaging?" The answer is undistorted and unobstructed views of the fracture. On review of the previous imaging, this was not achieved at the last clinic visit. Radiographer 2 has not only supplied the referring doctor with high quality imaging, he/she has achieved a high level of professional and personal satisfaction.
|The finger is not labelled- which finger is it? It is also considered good practice to include the adjacent finger/fingers on the PA and/or oblique projections.|
|There is overlap of adjacent images. |
|Raytek gauze (arrowed) overlying thumb on PA projection image. Unless you are familiar with radiopaque sponges, you may not realise that the sponge/gauze has a 'wire' though it.|
|It can be very easy to forget the orientation of the cassette!|
Pathological AppearancesFinger Fractures
|This 29 year old female presented to the Emergency Department after injuring the 5th digit of her left hand. There is an oblique fracture of the left middle phalanx of the 5th digit of the left hand. The fracture does not appear to extend into either joint.|
The radiographer has not labelled the digits, but it is clear (in this projection) that these are the 4th and 5th digits of the left hand.
|fracture arrowed||The fracture is not demonstrated on the oblique projection image. Minimally displaced finger fractures may only be demonstrated on one projection.||The fracture is not demonstrated on the lateral projection image.|
Mallet Finger- DP- lateral slip injuryVolar Plate Injury
Middle Phalanx Hyperflexion Avulsion Fracture
|Mallet finger (or drop finger) is a flexion deformity that is caused by detachment or stretching of the extensor tendon from the base of the distal phalanx||There are 3 possible causes of mallet finger|
- elongated tendon
- ruptured tendon
- avulsion fracture
|If you use one of these 3 popular lateral finger positioning techniques, you risk masking the extensor tendon injury.|
|This 17 year old male was kicked in the hand while playing soccer. He was examined and found to have pain and swelling around the PIP joint of his right ring finger. He was referred for radiography of his right ring finger. The PA projection image reveals no displaced fracture.||The oblique projection image reveals no displaced fracture.||The lateral projection image reveals a fracture of the dorsal aspect of the base of the middle phalanx on the right ring finger||Fracture arrowed.|
|One of the traps with volar plate injuries is that they are not always revealed on the lateral projection image as might be expected. This patient has some irregularity of the volar aspect of the proximal middle phalax (suspicious of a volar plate injury). The fracture is most conclusively demonstrated on the PA projection image. This fracture could be easily missed.|
| The Volar plate is a dense fibrous band that forms the palmar aspect of the capsule of the thumb metacarpophalangeal joints and finger PIP joints. Distally , the volar plate is fibrocartilaginous at its insertion on the volar margin of the base of the adjacent phalanx. Volar plate injuries, regardless of their anatomical location, are the result of hyperextension. In hyperextension, the volar plate itself may rupture. Volar plate fractures, unless appropriately recognised and treated, may lead to joint instability.|
Plain film demonstration of volar plate fracture Lateral- 65% PA + obl- 35%
Harris and Harris
The Radiology of Emergency Medicine 3rd Ed.
|This 62 year old male presented to the Emergency Department after a fall. He was examined and found to have a painful left index finger. He was referred for left index finger radiography. There is a volar plate fracture of the left index finger middle phalanx (arrowed)|
|This 12 year old girl presented to the Emergency Department following a fall in which she suffered a hyperextension injury to her left ring finger. She was examined and was found to have a painful swollen proximal IP joint. She was referred for left ring finger radiography. There is a volar plate fracture (arrowed) of the base of the left ring finger middle phalanx best demonstrated on the PA projection image.|
Swan neck Deformity
|There is only one tendon that is responsible for extending both of the finger joints. This is in contrast to the flexor tendons that are two in number. This extensor tendon divides into three slips (branches). The central one extends the proximal joint and the remaining two (one on each side of the finger) join up and extend the distal joint||The boutonniere deformity may not occur right away. It is the imbalance in the extensor hood that results from the torn tendon that eventually causes the deformity. Because the middle phalanx no longer is pulled by the central slip, the flexor tendon on the other side begins to bend the PIP joint without resistance. The lateral bands begin to slide down along the side of the finger where they continue to straighten the DIP joint. Eventually the finger becomes stiff in this position.|
|This 52 year old lady has developed a boutonniere deformity following an extensor tendon injury.||Self explanatory video|
|Index finger distal phalax posterior dislocation with volar avulsion fracture.||Posterior DIP joint dislocation in a 15 year old male following sports injury.||Posterior dislocations of the DIP and PIP joints of the 5th digit in a 63 year old male.|
Avulsion fracture of the volar aspect of the distal phalanx
|Posterior dislocation 2nd MP joint in a 21 year old male following fall.|
DP Crush Injury
|It is good practice to label the image post reduction to indicate that the image is post-treatment. It may also be necessary to label images post reduction 1, post reduction 2 etc where multiple attempts have been made to effect a reduction of the dislocation.|
|Crush injury in a 61 year old female. There is a comminuted fracture of the terminal tuft of the distal phalanx of the right ring finger. If the fingernail is broken, this is an open fracture- antibiotic therapy is required.|
Imaging Amputated Digits
|The mechanism of injury resulting in amputated digits is varied. Industrial accidents and home use of circular saws are common mechanisms.|
The affected hand and amputated anatomy should all be imaged. These digits have been kept in their specimen containers when imaged. Care should be taken to keep the amputated anatomy clean and moist to maximise chances of successful re-attachment.
The amputated digits should be labelled for side and digit. Whilst it might appear that the identification of the digit is obvious in cases of single digit amputation, confusion with subsequent amputations could occur.
''Enchondromas are benign cartilaginous neoplasms that are usually solitary lesions in intramedullary bone. The primary significant factors of enchondromas are related to their complications, most notably pathologic fracture, and a small incidence of malignant transformation, which may be associated with pathologic fracture.
The lesions replace normal bone with mineralized or unmineralized hyaline cartilage, thereby generating a lytic pattern on radiographs or, more commonly, a lytic area containing rings and arcs of chondroid calcifications. The lesions likely arise from cartilaginous rests that are displaced from the growth plate.''
Enchondroma and Enchondromatosis Imaging, Felix S Chew, Catherine Maldjian, MD
|This 32 year old female presented to the ED with finger pain following trivial trauma. There is a sharply marginated lucent lesion sited at the proximal third of the middle phalanx of the 5th digit of the left hand. This is likely to be a enchondroma. There is a transverse pathological frature with a moderate degree of dorsal angulation.|
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