Fractures and dislocations of the carpus By Gatobu

Fractures and dislocations of the carpus By Gatobu 6 A

$Scope • Introduction • Anatomy • Imaging of carpal bones • Lunate fractures/lunate dislocation$

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 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

$Mechanism of injury • High energy forces • Results in carpal bone fractures or$

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.

$General Principles of Treatment • Carefully evaluate x-rays for subtle fractures and/or evidence of$

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 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)

$Classification of lunate fractures • Acute fractures are classified in 5 groups: • •$

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 99 m bone scan • CT scan • Arthroscopic exam

$Lunate fractures • MRI$

Lunate fractures • MRI

$Management of lunate fractures • Undisplaced-cast immobilization for 4 wks • ORIF • Displaced$

Management of lunate fractures • Undisplaced-cast immobilization for 4 wks • 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

$Perilunate dislocation • Very commonly associated with a scaphoid waist fracture • Sometimes ulnar$

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 2 nd 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 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

$Trans-scaphoid Perilunate Injuries • Require reduction and fixation of the fractured scaphoid. • Most$

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 -Lunate-Capitate are colinear and S -L angle restored

$Perilunate Injuries Conclusion • Perilunate fracture dislocations are high-energy injuries • Must recognize different$

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

Dislocated Lunate s/s • tenderness • Swelling • ROM painful & limited • May compress median nerve

Lunate dislocation • Dislocation usually occurs in two steps – 1 st the ligaments are torn and then the bone dislocates • + Murphy’s sign Murphy’s Sign – pt makes a fist. • Indication – lunate dislocation