X-Hand/Fingers

Indication/Technique

X-rays of the hand are requested frequently, particularly at the Emergency Assistance department. They are used primarily to confirm/exclude a fracture, in the diagnostics of (rheumatoid) arthritis, and in functional hand and wrist complaints.

By way of repetition of anatomical terminology: volar/palmar (palm of hand), dorsal (back of hand), ulnar (side of little finger) and radial (side of thumb).
See also figure 1.

Figure 1. Palmar flexion / volar flexion vs. dorsal flexion (dorsiflexion) & radial abduction vs. ulnar abduction.

When asked to confirm or exclude a fracture, the hand/fingers should be imaged in at least two directions, as in any conventional image.

The standard examination of the hand generally consists of a posterior-anterior (PA) image and a PA oblique image (3/4 image).
For a PA image, the hand lies flat on the x-ray plate, at the level of the shoulder with the elbow in 90 degrees flexion. The x-ray beam will pass through the hand from dorsal to palmar (fig. 2).
A PA oblique image is made in similar fashion, however the wrist/hand is now turned about 45° to lateral (fig. 3).

Figure 2. Technique for PA image of the hand.

Figure 3. Technique for oblique image of the hand.

If there are problems with the fingers, a detailed finger image can be made. A standard finger examination includes a PA image and a lateral image. Particularly if a fracture needs to be confirmed, an oblique image is frequently made.
The thumb is imaged in two directions. For the anterior-posterior (AP) image, the arm is rotated internally, with the dorsal side of the thumb flat on the x-ray plate. The x-ray beam will pass through the hand from palmar to dorsal (fig. 4). For the lateral image of the thumb, the other fingers are abducted to ulnar and an attempt is made to get the outside of the thumb as flat as possible on the x-ray plate (fig. 5).

Figure 4. Technique for AP image of the thumb.

Figure 5. Technique for lateral image of the thumb.

Normal anatomy

The human hand consists of 5 fingers. Each finger is designated by a Roman numeral:

  • Digitis-I (dig-I) = the thumb
  • Digitis-II (dig-II) = the forefinger
  • Digitis-III (dig-III) = the middle finger
  • Digitis-IV (dig-IV) = the ring finger
  • Digitis-V (dig-V) = the little finger

The hand/fingers are subdivided over several levels (fig. 6):

  • Carpometacarpal (CMC) joints; articulation between components of the carpus and the metacarpal bones.
  • Metacarpophalangeal (MCP) joints; articulation between the metacarpal bones and the proximal phalanges.
  • Proximal interphalangeal (PIP) joints; articulation between the proximal phalanges and middle phalanges.
  • Distal interphalangeal (PIP) joints; articulation between the proximal phalanges and middle phalanges.

The metacarpal bones and phalanges are small tubular bones and may be subdivided further in base, shaft and head (fig. 6).

 Figure 6. Normal anatomy of the hand. CMC = carpometacarpal joint, MCP = metacarpophalangeal joint, PIP = proximal interphalangeal joint, DIP = distal interphalangeal joint and IP = interphalangeal joint.

Dig II - V consist of 3 phalanges; the proximal phalanx, the middle phalanx and the distal phalanx (fig. 7). The thumb has 2 phalanges (proximal phalanx and distal phalanx).

 Figure 7. PA/lateral/oblique image. Normal anatomy dig II - V. PIP = proximal interphalangeal joint, DIP = distal interphalangeal joint.

Determining the level can be problematic in the physical examination of the hand. The following anatomical outline may be helpful (fig. 8).

 Figure 8. Normal anatomy of the hand. PIP = Proximal interphalangeal joint, DIP = distal interphalangeal joint, MCP = metacarpophalangeal joint, S= scaphoid, L = lunate, Tri = triquetrum, P = pisiform, Tm = trapezium, T = trapezoid, C = capitate, H = hamate.

The carpal bones are formally part of the wrist and are discussed extensively in the wrist x-ray course.

Characteristics of a normal hand/finger x-ray:

  • Symmetrical joints where the bones do not overlap (except the carpal bones and the base of the metacarpal bones).
  • The joint spaces of the CMC joints are equal (average 1 - 2 mm) and form a zigzag configuration (fig. 9).
  • The relatively mobile CMC-I joint (saddle joint) causes variations in the joint space, which can incorrectly be interpreted as a (sub)luxated position.

 Figure 9. Zigzag configuration of CMC joints. The metacarpal bones articulate proximally with the capitate bone, trapezoid bone and trapezium bone.

The hand consists of a large number of bones, muscles, tendons and ligaments. Ligaments/tendons/muscles cannot be evaluated on an x-ray. Nevertheless, it is important to have some knowledge of this. Soft tissue damage can sometimes be observed indirectly on x-rays and impact treatment (see also Pathology section).
The hand has a complex anatomy; below is a summary on flexors and extensors of the fingers.

Flexors:

The collateral ligaments (= parallel connective tissue bands) and volar plate provide much of the stabilization of the MCP joints and IP joints.
The volar plate is a fibrous ligamentous structure located at the palmar side of the hand. It separates the bone from the flexor tendons and prevents hyperextension of the finger.
Flexion of dig II - V is mediated by the superficial digital flexor and the deep digital flexor. The superficial digital flexor inserts on the base of the middle phalanx and mediates flexion of the PIP joint. The deep digital flexor is located deeper, inserts on the distal phalanx and mediates flexion of the PIP joint (fig. 10).
The thumb is a unique joint where the long pollicis flexor mediates flexion.

Figure 10. Flexors and collateral ligaments of dig II - V. 

Extensors:

Thumb extension is mediated by the long abductor pollicis muscle tendon (insertion: base of MC-I), short extensor pollicis (insertion: base of proximal phalanx) and the long extensor pollicis muscle (insertion: base of the distal phalanx). The anatomical snuff box is formed by the long extensor pollicis at the ulnar side and the short extensor pollicis/long abductor pollicis at the radial side (fig. 11).

Figure 11. Extensors of the thumb. Anatomical snuff box (*). 

The primary extensor tendon of the other fingers is the tendon of the common digital extensor muscle. The tendon separates into three bands. The central bands insert on the base of the middle phalanx. The two lateral bands join distally of the PIP joint and together insert on the base of the distal phalanx (fig. 12).

Figure 12. Common digital extensor.

Checklist

The following points may be used as a guide to assess hand X-rays.

  1. Has everything been imaged? 
  2. Is there soft tissue swelling? Foreign body?
  3. General impression of the bone; osteoporosis?  Ossal lesions?
  4. Examine all joints. What is their position? Do the joint spaces have equal dimensions everywhere? 
  5. Position of the CMC joints; is there interruption of the zigzag configuration? 
  6. Check the full length of the cortex. Is there an interruption or asymmetry anywhere?
  7. In the event of fracture; orientation of the fracture line? intra- or extra-articular? extent and position (dislocation/angulation/rotation/shortening)?
  8. Changes versus previous examinations?

Pathology

  • Luxation

  • Fracture (tuft fracture, boxer’s fracture, spiral fracture, CMC-I fracture)

  • Skier’s thumb

  • Volar avulsion fracture

  • Extensor tendon damage

  • Osteoarthritis

Luxation

Luxation of the metacarpophalangeal (MCP's) and the interphalangeal joints (PIP’s & DIP’s) are easily identified (fig. 13).

 Figure 13. Lateral image and PA image of dig-V in the left hand. Dorsal luxation of the PIP joint. Lateral image; note the overlap of the proximal phalanx and the middle phalanx.

Contrarily, a luxation of the carpometacarpal joints (CMC’s) may be subtle on x-ray. CMC luxations are uncommon, are often the result of high-energy impact and are regularly associated with fractures. A CT scan is recommended for more detailed evaluation of associated fractures.

Be alert for a CMC luxation when (fig. 14):

  • The joint space at the base of the metacarpal bones is poorly visible.
  • There is asymmetry in the joint space of the CMC joints.
  • There are fractures around the CMC joints (base of MC & carpal bones).
  • Hamate fracture at the dorsal side (see oblique hand image in particular) is associated with CMC-V luxation.
      

 Figure 14. PA image of left hand. Interruption of the zigzag configuration in a luxation of the CMC-V joint.

Fracture

The position of the hand and the direction of force determine the fracture type. The direction of the fracture line, joint involvement (intra- vs extra-articular) and the degree of dislocation/angulation should be assessed for each fracture. See the Fracture General Principles  under Basic Knowledge.
Most hand fractures are extra-articular shaft fractures of the phalanges and metacarpal bones. Extra-articular fractures with little to no dislocation are generally stable and have a good prognosis.
Knowledge of the insertions of ligaments and tendons is essential in the assessment of fractures. Tendon/ligament involvement may impact prognosis and treatment. 
Ligament type, degree of dislocation, tendon/ligament involvement and general factors such as age, desired functional level etc. are important factors in the decision to opt for conservative or surgical treatment.

A number of common fractures are summarized below.

Tuft fracture (figure 15):

A tuft fracture is a comminuted fracture of the distal phalanx and usually results from a crush injury (e.g. finger caught between the door). Tuft fractures are associated with subungal hematomas (= hematoma under the nail bed). Additionally, be alert for damage of the flexor/extensor tendons.

 Figure 15. PA image of dig-V in the right hand. Tuft fracture.

Spiral fracture (fig. 16)

The spiral fracture of the phalanges/metacarpal bones is infamous for the rotation and shortening that may occur. Particularly in the event of dislocation, beware of instability.

 Figure 16. PA image and PA oblique image of the left hand. Spiral fracture of MC-II.

Boxer’s fracture 

A boxer’s fracture is a transversal metacarpal fracture of the neck (= subcapital) and is most common in the 5th metacarpal. The classical mechanism is a fist blow against a person or hard surface (e.g. a wall). The axial force in the flexed hand causes a boxer’s fracture, frequently with dislocation of the distal part (= the head) to palmar (fig. 17). Contrary to what its name suggests, the boxer’s fracture is not more common among boxers.

 Figure 17. PA oblique image and PA image of the left hand. Subcapital fracture of MC-V (= boxer’s fracture).

Thumb fracture

Metacarpal fractures in metacarpal II - V are usually located in the shaft and neck. This is contrary to the thumb, where mostly the base is affected. 
An extra-articular fracture of MC-I is generally transversal or oblique (fig. 18/19).

Figure 18. Transversal & oblique extra-articular fracture of the base of metacarpal I (lateral view).

 Figure 19. Lateral image and AP image of the left hand. Extra-articular transversal fracture of the base of MC-I.

The intra-articular fractures of MC-I can be subdivided into a two-part (Bennett fracture), three-part (Rolando fracture) and a comminuted fracture (fig. 20).
A Rolando fracture is a three-part intra-articular fracture of the base of MC-I and typically has a T or Y configuration.  

Figure 20. Intra-articular MC-I fractures. Above: lateral view of Bennett fracture (two-part), Rolando fracture (three-part) and comminuted fracture. Below: anteroposterior view of a Rolando fracture type Y and T.

Bennett fracture

A Bennett fracture is an intra-articular fracture of the ulnar side of the base of MC-I. A prevalent mechanism is an axial force where the thumb is in flexion, as in a blow with the fist.
In a Bennett fracture, the adductor pollicis/long abductor pollicis muscles contribute significantly to the associated dislocation/rotation (fig. 21).
The adductor pollicis muscle is a two-headed fan-shaped muscle at the palmar side of the hand and mediates the adduction of the thumb. The adductor pollicis muscle inserts on the medial side of the base of the phalanx of the thumb. 
The long abductor pollicis muscle mediates the abduction and flexion of the thumb and inserts on the base of MC I (radial side). The little fragment at the palmo-ulnar side in a Bennett fracture retains its anatomical position thanks to the local ligaments. The distal part of the MC-I, however, will undergo adduction and supination (by the adductor pollicis muscle). Additionally, the MC-I will be moved to proximal in its entirety (by the long abductor pollicis muscle).

 Figure 21. Lateral image of dig-I of the left hand. Bennett fracture.

Rolando fracture

A Rolando fracture may be regarded as a comminuted version of the Bennett fracture (fig. 22). Dislocation/rotation may develop as a result of involvement of the adductor pollicis/long abductor pollicis muscles.
Compared to a Bennett fracture, a Rolando fracture has poorer prognosis.

  Figure 22. AP image (a) and CT scan (b) of the right hand (a) Rolando fracture, type Y.

Skier’s thumb 

In a skier’s thumb, there is ligament damage (twist/rupture) of the ulnar collateral ligament of the MCP-I joint. The ligament damage results from forced abduction of the thumb and may eventually cause instability. This can be caused either by acute injury (getting caught in ski pole/ball sports) or due to chronic injury (repeated stretching of the joint ligament).
Skier’s thumb is also known as gamekeeper’s thumb. In the 18th and 19th century, English gamekeepers had to break the necks of rabbits, causing chronic stress on the ulnar collateral ligament.
A rupture of the ulnar collateral ligament may be associated with an avulsion fragment. With sufficient force, the avulsion fragment may penetrate the adductor aponeurosis (aponeurosis = tendinous membrane). The adductor aponeurosis is then located between the avulsion fragment and the insertion site. This is termed a Stener lesion. A Stener lesion will not heal spontaneously and surgical intervention is indicated.

 Figure 23. Skier’s thumb & Stener lesion. UCL = ulnar collateral ligament.

Volar avulsion fracture

An avulsion fracture is a fracture at the level of a tendon insertion. The bone of the insertion site is ripped loose by the tendon/muscle (excessive traction on the bone).
A volar avulsion fracture develops as a result of forced hyperextension of the finger. 
The loose fragment is generally visible on the lateral image only and frequently involves the PIP joint (fig. 24). However, an avulsion fracture need not always be present in volar plate injury; there may also be partial/full tendon injury (clinically reduced/absent flexor function).
The joint has lost its stability. Eventually, the extensor tendon (without the resistance of the flexor tendon) may cause a hyperextension deformity of the finger.

 Figure 24. Lateral image of dig-V of the left hand. Volar avulsion fracture of the PIP joint with marked proximal dislocation. FDS = flexor digitorum superficialis or superficial digital flexor.

Extensor tendon injuries

Mallet finger

A Mallet finger involves an avulsion of the extensor tendon on the distal phalanx (fig. 25). The tendon rupture prevents active extension, possibly causing the distal phalanx to assume a position of flexion.
This may be a purely ligamentous avulsion (= tendinous Mallet), which may or may not be combined with an ossal avulsion (= ossal Mallet).
Note: the absence of a fracture therefore does not exclude a Mallet finger. The extension function of the DIP joint requires clinical evaluation in this setting.

 Figure 25. Lateral image of dig-V of the right hand. The position of flexion of the DIP joint and the inability to induce extension are signs of a tendinous Mallet finger.

In about one third of the cases, there is ossal avulsion (fig. 26).
Mallet finger can also be termed dropped finger or baseball finger. The trauma mechanism frequently involves a ball trauma where the DIP joint makes a forced hyperflexion movement.

 Figure 26. Lateral image of dig-V of the right hand. Ossal Mallet finger with dislocation to dorsal.

Boutonniere deformity

A Boutonniere deformity is also termed buttonhole deformity.
This is an abnormal position characterized by flexion of the PIP joint and hyperextension of the DIP joint. This deformity typically develops after a rupture of the central band of the extensor tendon, e.g. due to a fracture or volar luxation). Other causes include osteoarthritis and rheumatoid arthritis. 
A rupture of the central band causes the PIP joint to assume a position of slight flexion. The lateral bands will migrate in palmar direction of the original axis and eventually cause the DIP joint to assume a position of hyperextension (fig. 27).

 Figure 27. Boutonniere deformity in a rupture of the central band of the extensor tendon.

Osteoarthritis

Osteoarthritis is wear and tear on the cartilage. It is associated with a diversity of symptoms. Patients may complain about progressive load-dependent pain and/or reduced function.
The osteoarthritis may be primary with no obvious identifiable cause. Secondary osteoarthritis may develop after e.g. a fracture. Persistent instability symptoms and altered transfer of force over the joints after fractures may lead to long-term degenerative changes.  
Radiological characteristics of osteoarthritis:

  • Narrowing of the joint space (secondary to loss of cartilage).
  • Subchondral sclerosis (increased bone production secondary to increased pressure with cartilage loss).
  • Osteophyte formation (bone exostoses attempting to increase the joint surface).
  • Subchondral cysts (secondary to microfractures of the subchondral bone and pressure of the synovial fluid).

Primary osteoarthritis in the hand develops particularly in the interphalangeal joints (PIP’s & DIP’s), the CMC-I joint and the scaphoid-trapezium-trapezoid joint (STT joint). Particularly in the initial stage, the MCP joints are less frequently affected.

There is also an erosive form of osteoarthritis, with erosive changes in the joint. This can be rapidly progressive. This type of osteoarthritis occurs mostly in the DIP joints (as opposed to rheumatoid arthritis) in elderly women.

 Figure 28. Osteoarthritis of the DIP joints and to a lesser degree also of the PIP joints (left) versus normal PIP/DIP joints (right).

 Figure 29. Osteoarthritis of the CMC-I joint and scaphoid-trapezium-trapezoid joint (STT joint). At right a normal CMC-I and STT joint.

Sources

  • B.J. Manaster et al. The Requisites – Musculoskeletal Imaging. 2007.
  • N. Raby et al. Accident & Emergency Radiology – A Survival Guide. 2005.
  • R.W.Bucholz Rockwood & Green’s Fracturen in Adults. 2006.
  • Prof.dr. J.A.N. Verhaar, dr. J.B.A. van Mourik. Orthopedie. 2008.
  • K.L. Bontrager, J.P. Lampignano. Textbook of Radiographic Positioning and Related Anatomy. 2014 (8th edition).

Author

  • Annelies van der Plas, MSK radiologist Maastricht UMC+

  • Prof. dr. J.L. Bloem, radiologist LUMC

With special thanks to S. Challiui (Advanced Practioner Radiology LUMC) & A. Bubberman (Advanced Practioner Radiology LUMC) 

20/07/2014 (translated 05/08/2016)

Copyright
All the work (text, illustrations, visual elements) seen on this website is copyright by Annelies van der Plas.
It may not be used without written permission of Annelies van der Plas.

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