3 IntroductionCarpus is a complex unit of bony articulations that transfers the forces of the hand to the supporting forearm and upper extremityAllows wide range of motion in 2 planesCarpal bones are 8 in number arranged in 2 rowsMain motionsExtensionFlexionRadial and ulnar deviationThe primary axis of motion resides within the head of carpitate.
4 General, surgical and applied anatomy Bones and jointsComposed of 8 bones in 2 rowsThe 8 bones are influenced byShape of distal radiusThe distal ulnarTriangular fibrocartilage complex
5 Anatomy of the WristCarpal 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.
6 Extrinsic ligamentsExtrinsic ligaments link the carpal bones to the radius, ulna, and metacarpals.
8 LunateConnected 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.
9 Intercarpal Ligaments Injury to these ligaments leads to abnormal motion between the two rows, and non-dissociative wrist instability patterns.
10 Neurovascular anatomy Circulation of the wrist is obtained through the radial, ulnar, and anterior interosseous arteries and the deep palmar arch
11 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.
12 Mechanism of injuryMost common is an axial compression force applied with the wrist in hyperextensionMost common injury is a fall on the outstretched handOther mechanismsPalmer flexion,twisting injuries
13 Mechanism of injury High energy forces Results in carpal bone fractures or ligamentous disruption of both extrinsic and extrinsic ligaments and perilunate dislocationLow energy forces results in minor injuries such as sprains
15 ImagingGilula'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. .
16 Imaging Standard scaphoid views detect most carpal injuries PA x-ray with wrist neutral and in ulnar deviationelongates scaphoid to better visualizeMRI 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.
17 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.
18 Lunate fractures Rare <1% of all carpal fractures Isolated fractures of lunate often missed
19 Lunate anatomy Sits like a keystone in the proximal row Well protected in concavity of the lunate fossa of the radiusVascular supply-proximal carpal arcade dorsally,palmarly7-26% of lunates have single volar or dorsal blood supply
20 Mechanism of injury Hyperextension injury Others: repetitive stresses of the wristStrenuous pushAvulsion of the dorsal pole( S-L tension)
21 Classification of lunate fractures Acute fractures are classified in 5 groups:Frontal fracture of palmer poleOsteochondral fractures of the proximal articular surfaceFrontal fracture of the dorsal poleTransverse fracture of the bodyTrans articular fracture of the body
24 Management of lunate fractures Undisplaced-cast immobilization for 4wksORIFDisplaced fracturesAssociated carpal instabilityNon-union
25 Perilunate dislocation Triquetral and scaphoid malrotationResult of a fall on an outstretched, hyperextended handRelatively rareOccurs when the lunate maintains normal position with respect to the distal radius while all other carpal bones are dislocated posteriorly
26 Perilunate dislocation Very commonly associated with a scaphoid waist fractureSometimes ulnar styloid as wellLunate appears triangular in shape on PA viewLunate rotates forward slightly on lateral viewIn lateral view, all other carpal bones are dislocated posterior with respect to lunate
28 Perilunate dislocation Represents 2nd of the 4 stages of ligamentous injury around lunate bone resulting from forced hyperextensionThey are referred to as lesser arc injuriesThe 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
29 Mechanism of InjuryLoad applied to hand forcing the wrist into extension and ulnar deviationSevere ligament injury necessary to tear the distal row from the lunate to produce perilunate dislocation
30 Physical Exam Dorsal displacement of the carpus may be seen Significant swelling commonEvaluate for compartment syndromeIf lunate is dislocated, median nerve symptoms may be present
36 Initial TreatmentClosed 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.
37 Technique of Closed Reduction Longitudinal traction for minutesFor dorsal perilunate injuries: apply dorsal directed pressure to the lunate volarly while a reduction maneuver is applied to the hand and distal carpal rowPalmar flexion then reduces the capitate into the concavity of the lunate.
38 Closed Reduction and Pinning Poor results with closed reduction and pinning aloneVery difficult to reduce adequatelywrist needs to be ulnarly deviated to correct scaphoid flexionradial deviation needed to close S-L gap
39 ORIF with volar and dorsal approaches Procedure of Choice
44 Trans-scaphoid Perilunate Injuries Require reduction and fixation of the fractured scaphoid.Most of these injuries best treatedORIF with volar and dorsal approachesrepair of injured structures.Open repair supplemented by pin and screw fixation.
47 Make sure Radius-Lunate-Capitate are colinear and S-L angle restored
48 Perilunate Injuries Conclusion Perilunate fracture dislocations are high-energy injuriesMust recognize different injury patternstranscaphoidpure ligamentoustrans radial-styloidEarly open and anatomic fixation with volar and dorsal approaches provides the best chance at a reasonable functional result
49 Perilunate dislocation conclusion Median nerve dysfunction- 16% of the patients16-25% of perilunate dislocations are missed initially
50 Lunate dislocationMost severe of carpal instabilities Most frequently dislocated carpal boneMost commonly associated with a trans-scaphoid fractureInvolves all the intercarpal joints and disruption of most of the major carpal ligamentsProduces volar dislocation and forward rotation of lunate Concave distal surface of lunate comes to face anteriorly
51 Lunate dislocation Capitate drops into space vacated by lunate Results in dislocation of other carpal bonesCapitate and all other carpal bones lie posterior to lunate on lateral radiographTriangular appearance of lunate on frontal projection (piece of pie sign)Spilled tea cup sign (lateral view)