Fractures and dislocations of
the carpus
By Gatobu
6A
Scope
• Introduction
• Anatomy
• Imaging of carpal bones
• Lunate fractures/lunate dislocation
• Perilunate dislocation
Introduction
• Carpus is a complex unit of bony articulations that transfers the forces
of the hand to the supporting forearm and upper extremity
• Allows wide range of motion in 2 planes
• Carpal bones are 8 in number arranged in 2 rows
• Main motions
• Extension
• Flexion
• Radial and ulnar deviation
• The primary axis of motion resides within the head of carpitate.
General, surgical and applied anatomy
• Bones and joints
• Composed of 8 bones in 2 rows
• The 8 bones are influenced by
• Shape of distal radius
• The distal ulnar
• Triangular fibrocartilage complex
Anatomy of the Wrist
• Carpal bones tightly linked by capsular and interosseous ligaments.
• Capsular (extrinsic) ligaments originate from the radius and insert
onto the carpus.
• Interosseous (intrinsic) ligaments traverse the carpal bones.
• The lunate is the key to carpal stability.
Extrinsic ligaments
Extrinsic ligaments link the carpal bones to the radius, ulna, and
metacarpals.
Intrinsic ligaments
The intra-articular intrinsic ligaments connect adjacent
carpal bones.
Lunate
• Connected to both scaphoid and triquetrum by strong interosseous
ligaments.
• Injury to the scapholunate or lunotriquetral ligaments leads to
asynchronous motion of the lunate and leads to dissociative carpal
instability.
Intercarpal Ligaments
• Injury to these ligaments leads to
abnormal motion between the
two rows, and non-dissociative
wrist instability patterns.
Neurovascular anatomy
Circulation of the wrist is obtained through the radial, ulnar,
and anterior interosseous arteries and the deep palmar arch
Neurovascular anatomy
• The scaphoid, capitate, and about 20% of all lunates are supplied by a
single vessel and thus are at risk for avascular necrosis.
• The trapezium, triquetrum, pisiform, and 80% of lunates receive
nutrient arteries through two nonarticular surfaces and have
consistent intraosseous anastomoses. AVN is therefore rare.
• The trapezoid and hamate lack an intraosseous anastomosis and,
after fracture, can have avascular fragments.
Mechanism of injury
• Most common is an axial compression force applied with the wrist in
hyperextension
• Most common injury is a fall on the outstretched hand
• Other mechanisms
• Palmer flexion,twisting injuries
Mechanism of injury
• High energy forces
• Results in carpal bone fractures or ligamentous disruption of both extrinsic
and extrinsic ligaments and perilunate dislocation
• Low energy forces results in minor injuries such as sprains
Imaging
• Plain radiographs: multiple views necessary:
•
•
•
•
•
Anteroposterior
Lateral
Oblique
Clenched-fist AP
Radial and ulnar deviation
Imaging
Gilula's lines. A. AP views show three smooth Gilula arcs in a
normal wrist. These arcs outline proximal and distal surfaces of
the proximal carpal row and the proximal cortical margins of
capitate and hamate. B. Arc I is broken, which indicates an
abnormal lunotriquetral joint due to a perilunate dislocation. .
Imaging
• Standard scaphoid views detect most carpal injuries
• PA x-ray with wrist neutral and in ulnar deviation
• elongates scaphoid to better visualize
• MRI scans are useful in detecting occult fractures, AVN of the carpal
bones, and ligamentous injuries.
• Perilunate dislocations are easily missed if the continuity of Gilula's
line is not assessed.
General Principles of Treatment
• Carefully evaluate x-rays for subtle fractures and/or evidence of
carpal instability.
• Reduce and immobilize scaphoid fractures or perilunate injuries
pending definitive treatment.
• Diagnose and appropriately treat ligament and bony injuries.
Lunate fractures
• Rare
• <1% of all carpal fractures
• Isolated fractures of lunate often missed
Lunate anatomy
• Sits like a keystone in the proximal row
• Well protected in concavity of the lunate fossa of the radius
• Vascular supply-proximal carpal arcade dorsally,palmarly
• 7-26% of lunates have single volar or dorsal blood supply
Mechanism of injury
• Hyperextension injury
• Others:
• repetitive stresses of the wrist
• Strenuous push
• Avulsion of the dorsal pole( S-L tension)
Classification of lunate fractures
• Acute fractures are classified in 5 groups:
•
•
•
•
•
Frontal fracture of palmer pole
Osteochondral fractures of the proximal articular surface
Frontal fracture of the dorsal pole
Transverse fracture of the body
Trans articular fracture of the body
Imaging
• Plain radiographs
• Technetium 99m bone scan
• CT scan
• Arthroscopic exam
Lunate fractures
• MRI
Management of lunate fractures
• Undisplaced-cast immobilization for 4wks
• ORIF
• Displaced fractures
• Associated carpal instability
• Non-union
Perilunate dislocation
• Triquetral and scaphoid malrotation
• Result of a fall on an outstretched, hyperextended hand
• Relatively rare
• Occurs when the lunate maintains normal position with respect to the
distal radius while all other carpal bones are dislocated posteriorly
Perilunate dislocation
• Very commonly associated with a scaphoid waist fracture
• Sometimes ulnar styloid as well
• Lunate appears triangular in shape on PA view
• Lunate rotates forward slightly on lateral view
• In lateral view, all other carpal bones are dislocated posterior with
respect to lunate
Perilunate dislocation
Perilunate dislocation
• Represents 2nd of the 4 stages of ligamentous injury around lunate
bone resulting from forced hyperextension
• They are referred to as lesser arc injuries
• The 4 stages of injury are:
•
•
•
•
Scapholunate dissociation(stage I)
Perilunate dislocation(II)
Midcarpal dislocation(III)
Lunate dislocation(IV)
• With increasing hyperextension perilunate dislocation may become a
lunate dislocation
Mechanism of Injury
• Load applied to hand forcing the wrist into extension and
ulnar deviation
• Severe ligament injury necessary to tear the distal row
from the lunate to produce perilunate dislocation
Physical Exam
• Dorsal displacement of the carpus may be seen
• Significant swelling common
• Evaluate for compartment syndrome
• If lunate is dislocated, median nerve symptoms may be present
Imaging
Imaging
• Note lack of “colinearity”
among the radius, lunate,
and capitate on the lateral
x-ray.
Imaging
• Note loss of normal carpal
“arcs” and abnormal widening
of the scapholunate interval.
• Look for associated fractures
“trans-scaphoid” injuries
X-ray usually
Obvious
X-ray may be subtle
Initial Treatment
• Closed reduction is performed with adequate
sedation.
• Early surgical reconstruction if swelling allows.
• Immediate surgery needed if there are signs of
median nerve compromise.
• Delayed reconstruction if early intervention is
not necessary.
Technique of Closed Reduction
• Longitudinal traction for 5 -10 minutes
• For dorsal perilunate injuries: apply dorsal directed pressure to the
lunate volarly while a reduction maneuver is applied to the hand and
distal carpal row
• Palmar flexion then reduces the capitate into the concavity of the
lunate.
Closed Reduction and Pinning
• Poor results with closed reduction and pinning
alone
• Very difficult to reduce adequately
• wrist needs to be ulnarly deviated to correct
scaphoid flexion
• radial deviation needed to close S-L gap
ORIF with volar and dorsal approaches
Procedure of Choice
Dorsal Approach
Repair S-L ligament
Volar Approach
Reduce lunate
first- may need
to temporary
pin to radius
Pin Carpus: S-L,
L-T and midcarpal joints
Trans-scaphoid
Perilunate Injuries
• Require reduction and fixation of the fractured
scaphoid.
• Most of these injuries best treated
• ORIF with volar and dorsal approaches
• repair of injured structures.
• Open repair supplemented by pin and screw
fixation.
Fix scaphoid first: dorsal
approach
Pin L-T and Mid-carpal
joints
Make sure
Radius-LunateCapitate are
colinear and S-L
angle restored
Perilunate Injuries Conclusion
• Perilunate fracture dislocations are high-energy
injuries
• Must recognize different injury patterns
• transcaphoid
• pure ligamentous
• trans radial-styloid
• Early open and anatomic fixation with volar and
dorsal approaches provides the best chance at a
reasonable functional result
Perilunate dislocation conclusion
• Median nerve dysfunction- 16% of the patients
• 16-25% of perilunate dislocations are missed initially
Lunate dislocation
• Most severe of carpal instabilities
Most frequently dislocated carpal bone
• Most commonly associated with a trans-scaphoid fracture
• Involves all the intercarpal joints and disruption of most of the major carpal
ligaments
• Produces volar dislocation and forward rotation of lunate
Concave distal surface of lunate comes to face anteriorly
Lunate dislocation
• Capitate drops into space vacated by lunate
• Results in dislocation of other carpal bones
• Capitate and all other carpal bones lie posterior to lunate on lateral
radiograph
• Triangular appearance of lunate on frontal projection (piece of pie sign)
• Spilled tea cup sign (lateral view)
Lunate dislocation
Lunate dislocation
Dislocated Lunate
s/s
• tenderness
• Swelling
• ROM painful & limited
• May compress median nerve
Lunate dislocation
• Dislocation usually occurs in two
steps – 1st the ligaments are torn
and then the bone dislocates
• + Murphy’s sign
Murphy’s Sign – pt makes a fist.
• Indication – lunate dislocation
Lunate dislocation-imaging
comparison
Other imaging modalities
• CT scan
• MRI
Treatment
• Closed reduction at A/E
• ORIF
Complications
• Wrist arthritis
• Persistent pain
• Joint instability
• Recovery takes at least 6months
Thank you