I.
Distal Radius Fracture
In the elderly FOOH is the most common cause of distal radius fractures.
Younger patients may have these fractures but occur in a high energy impact trauma.
When evaluating the AP and lateral views of the wrist it is important to assess for radial height,
radial inclination,
volar tilt,
and intra articular involvement.
If there is wrist dislocation a pre and post reduction films are needed for complete evaluation and to determine definitive treatment 18.
Colles Fracture Fig. 3
Is a transverse fracture of the distal radial metaphyseal area with dorsal angulation and displacement of the distal fragment.
This occurs more frequent on elderly women as the result of a FOOH with a dorsiflexed wrist 8.
Smith Fracture Fig. 4
Is a transverse fracture of the distal radial metaphyseal area with volar angulation and displacement of the distal fragment.
This is seen more often in younger patients as the result of high energy trauma on a palmar flexed wrist 8.
II.
Ulnar Styloid Fracture Fig. 5
Ulnar styloid fracture can be an isolated fracture or with other wrist fractures.
Normally occurs when FOOH.
Patients present with limited range of motion,
weak grip and pain on the ulnar side of the wrist 3.
Many of the ulnar styloid fractures progress to nonunion fractures,
resulting in chronic ulnar sided wrist pain 3.
Ulnar styloid fractures can be easily diagnosed with a plain film.
III.
Scaphoid Fracture Fig. 6 Fig. 7
The scaphoid bone fractures accounts for an 80% of carpal fractures 3.
The mechanism of injury includes FOOH on a dorsiflexed position.
Fractures are described by their obliquity to the long axis,
comminution and displacement.
The fractured scaphoid bone is at increased risk of osteonecrosis due to its single artery supply (from distal to proximal) and due to extensive coverage of of articular cartilage (80% of the scaphoid surface) 11.
Scaphoid fractures can can be missed on initial plain films in a 30% of cases 11,
for this reason additional imaging modalities should be used if there is clinical suspicion for a scaphoid fracture despite negative initial films.
A delay in the diagnosis of a scaphoid fracture may result in progressive fragment displacement,
malunion,
delayed union,
nonunion or avascular necrosis.
IV.
Avascular Necrosis of the Scaphoid Fig. 8
Avascular necrosis (AVN) occurs in a 13-50% of scaphoid fractures; the proximal third of the scaphoid is at an increased risk.
Patients present with a chronic radial sided wrist pain and a history of wrist trauma.
On plain films the AVN scaphoid fragment demonstrates increased density when compared to the rest of the scaphoid or other carpal bone 14.
On MR imaging the double line sign is characteristic of osteonecrosis.
V.
Scaphoid Nonunion Advanced Collapse (SNAC) Fig. 9 Fig. 10 Fig. 11
SNAC is a possible complication of scaphoid fractures,
most commonly nonunion fractures.
It consists of the development of osteoarthritis starting with the scapho-radial-styloid articulation,
then affects the scaphocapitate and capitolunate joints 8.
The arthritis is the result of an abnormal contact at the radioscaphoid compartment by the distal fragment of the scaphoid which is no longer connected to the proximal fragment and the lunate.
VI.
Scapholunate Dissociation Fig. 12
Scapholunate dissociation results from injury to the scapholunate ligament (SLL) by trauma on a hyperextended wrist.
The SLL has three components: the dorsal segment which has the most important role on stability,
the intermediate segment which is composed mainly of fibrocartilage,
and the volar segment.
There are secondary stabilizers (palmar radioscaphocapitate,
radiolunotriquetral and dorsal intercarpal ligaments) that prevent a permanent scapholunate dissociation.
If secondary stabilizers are injured injury may progress to Dorsal Intercalated Segment Instability (DISI)
Scapholunate ligament injuries can be classified as static,
static reducible,
dynamic,
predynamic depending on the radiographic features 3.
On MR imaging a partial tear appears as a focal thinning,
irregularity or increased signal intensity.
A complete tear appears as a discontinuation or nonvisualization of the scapholunate ligament 3.
VII.
Scapholunate Advanced Collapse (SLAC) Fig. 13
SLAC is the most common osteoarthritic pattern of the wrist.
SLAC is the result of an injury to the SLL which leads to a misalignment between the radius,
lunate and scaphoid resulting in more stress to the radioscaphoid and capitolunate joint.
It has a progressive pattern that begins at the radial styloid and progresses to involve the entire radioscaphoid joint and eventually the capitolunate joint.
The radiolunate joint is involved very late in the disease progression24.
Eventually there is enough separation between the proximal scaphoid and the lunate bone,
causing a potential space for the capitate to migrate proximally 24.
VIII.
Triquetral Fractures Fig. 14
The triquetrum is the second most common fractured carpal bone.
Fractures are the result of FOOH on ulnar deviation or a direct blow; commonly occur on the dorsal surface of the triquetrum by ulnar styloid impingement,
avulsion injuries or shear force 8.
On imaging we can see a fragment of the triquetrum dorsally displaced creating the pooping duck sign.
IX.
Lunate Fractures Fig. 15
Lunate fracture are a 3.9% of all carpal fractures 11 and occur as the result of a FOOH or by a compression force 8.
Lunate fractures may be undiagnosed due to the overlapping of the carpal bones on plain film.
If left unrecognized lunate fractures can lead to carpal instability,
nonunion and avascular necrosis.
On imaging all of the margins of the lunate should be observed to assess for possible fractures.
On the lateral view of the radiograph a break on the lunate cortex on either the volar or dorsal aspects suggests a possible fracture 8.
X.
Kienbock's Disease Fig. 16
Kienböck's disease is AVN of the lunate due to blood supply disruption to the lunate.
Prior trauma to the wrist may be a cause.
Patients present with: swollen wrist,
limited range of motion,
pain localized over the bone,
and motor deficits.
X-rays and magnetic resonance imaging (MRI) scans,
are used to confirm the diagnosis.
XI.
Hook of Hamate Fractures Fig. 17
Fractures of the hook of the hamate occur most commonly among golfers and racket sports.
It is the result of direct trauma or an avulsion of the transverse carpal ligament 8.
Patients present clinically with pain at direct palpation.
On imaging there is absence of the hook in an acutely displaced fracture 11.
An accessory ossicle may mimic a fracture of the hook of the hamate but it will be much larger than an avulsion of the hamate hook.
XII.
Perilunate Dislocation Fig. 18
Perilunate dislocation refers to the dislocation of the carpal bones from the lunate,
while the lunate remains articulating with the distal radius.
Results from a high energy wrist hyperextension,
as can be seen with a fall from height,
motor vehicle accident or sports related injury 11.
It is the result of a progressive failure of ligaments in a radial to ulnar direction.
XIII.
Lunate Dislocation Fig. 19
Results from a high energy impact caused by FOOH in which the wrist is extended and with ulnar deviation.
Lunate dislocations are commonly preceded by a perilunate dislocation; a pattern has been described in which the instability progresses from the scapholunate joint,
to the lunocapitate joint,
to the lunotriquetral joint and ends with the volar displacement of the lunate due to disruption of the dorsal radiocarpal ligaments 11,20.
On the contrary to perilunate dislocation where the radiolunate articulation is preserved,
when a lunate dislocation occurs the lunate is displaced volarly while the remaining carpus stay aligned with the radius.
On imaging on a lateral radiograph a “spilled tea cup sign” can be seen as the lunate is no longer articulating with the radius.
XIV.
Lunotriquetral Instability Fig. 20
Results from injury to the lunotriquetral ligament by FOOH.
Patients present with ulnar sided wrist pain and weakness.
On plain films an increase in the lunotriquetral joint space.
On MRI a complete tear results in the communication of the radiocarpal and midcarpal joints,
better demonstrated with MR arthrography 3.
Injury to the lunotriquetral ligament can lead to Volar Intercalated Segment Instability (VISI),
due to an unopposed volar tilt of the lunate (caused by an intact scapholunate interosseous ligament) leading to a scapholunate angle of <30 and a capitolunate angle >30 20.