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Year : 2006  |  Volume : 16  |  Issue : 2  |  Page : 272-274
Transscaphoid lunate dislocation with ejection of proximal pole of scaphoid into forearm


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Keywords: Carpal Bone Dislocations, Greater and Lesser arcs

How to cite this article:
Chamarthi S K, Nunna S, Kumar A A, Kiranmayi A L. Transscaphoid lunate dislocation with ejection of proximal pole of scaphoid into forearm. Indian J Radiol Imaging 2006;16:272-4

How to cite this URL:
Chamarthi S K, Nunna S, Kumar A A, Kiranmayi A L. Transscaphoid lunate dislocation with ejection of proximal pole of scaphoid into forearm. Indian J Radiol Imaging [serial online] 2006 [cited 2019 Nov 17];16:272-4. Available from: http://www.ijri.org/text.asp?2006/16/2/272/29108

   Introduction Top


Dislocations of the carpal bones usually result from a fall on the outstretched hand leading to forced dorsiflexion which tears the tough ligaments that normally bind the carpal bones. We present a case of Transscaphoid Lunate Dislocation with ejection of proximal pole of Scaphoid into Volar aspect of Forearm, a very rare occurrence.


   Case report Top


A twenty two year old man presented to Emergency department following a fall from a tree. He suffered fractures involving both bones of left leg, Skull, Styloid process of both Radii and fracture dislocations of Carpal bones of left hand

The Frontal and Lateral Radiographs of left Forearm and Wrist were taken. Frontal radiograph showed fractures of Styloid process of Radius, Scaphoid and dislocations of proximal pole of Scaphoid and Lunate [Figure - 1]. The proximal pole of Scaphoid is dislocated into the distal third of forearm. The distal pole is seen positioned normally. The Capitate is driven proximally. There is disruption of Arcs I and II which are normally formed by proximal and distal articular surfaces of proximal row of Carpal bones. Arc III is seen intact

The lateral radiograph showed that proximal pole of Scaphoid and Lunate are dislocated into the Volar aspect of forearm [Figure - 2]. Lateral film in addition shows chip fracture of Triquetrum. The normal alignment of distal articular surface of Radius, Lunate, Capitate and third Metacarpal is lost.


   Discussion Top


Most injuries to the wrist are caused by a fall on the outstretched hand. This results in dorsiflexion and Ulnar deviation of the hand together with supination of the Carpus against a pronated forearm. The resultant force is focused across the waist of the Scaphoid and the Carpocarpal joint [1]. The injury depends on the age of the patient, the severity and type of force, and the point of impact. Carpal bone injuries are common in all age groups but are more common in adolescents [2].

Radiological evaluation of the acutely injured Wrist should at a minimum include PA and Lateral Radiographs to be supplemented according to the specific situation [3]. In general, when an injury to the Carpus is suspected, multiple views are necessary [3]. It is extremely important that strict positioning of the wrist be followed while taking Radiographs, otherwise false positives could become a problem. When obtaining the PA view of the wrist make certain that the wrist is flat against the cassette; making a fist with the hand is a common way to prevent elevation of the wrist. The lateral view should be taken with the wrist in a neutral position in order to evaluate the alignment of the Lunate with the rest of the wrist.

On the PA radiograph of normal Wrist three smooth arcs can be identified which are drawn by joining the articular margins of the carpal bones. The first arc is formed by the proximal articular margins of the proximal carpal row, the second by connecting the distal articular margins of the proximal carpal row, and the third by joining the proximal articular margins of the Capitate and Hamate [Figure - 4]. Any disruption of these parallel lines indicates subluxation or dislocation of the carpal bone.

On the lateral view, the normal alignment of the longitudinal axis of the Lunate, the Capitate, and the third Metacarpal over the distal Radius can be demonstrated [Figure - 5]. Any break in the imaginary line is pathognomonic of subluxation or dislocation of the Lunate.

Two major types of injury patterns at wrist are recognized [Figure - 6] the lesser arc and greater arc patterns [4].

The lesser Arc outlines the Dislocation Zone and passes through Perilunate ligaments.

Four sequential stages of lesser arc injuries are recognized.

Stage I: Scapholunate dissociation and rotary subluxation of the Scaphoid.

Stage II: dislocation of Capitate, also known as Perilunate dislocation.

Stage III: midcarpal dislocation, the result of disruption of articulation between Lunate and Triquetrum.

Stage IV: a complete Lunate dislocation.

This pattern follows the progression from the least severe injury, Scapholunate dissociation to the severest injury, Lunate dislocation.


   Greater arc pattern Top


Greater Arc outlines the Fracture dislocation zone and involves fracture of the any of the bones adjacent to Lunate associated with dislocation.

Considered as functional unit, the wrist and hand are the most commonest sites of injury in the skeletal system [4].However fractures of metacarpals and phalanges predominate in incidence over fracture and dislocations of carpal bones and joints, which constitute approximately 6% of all such injuries [4].

Simultaneous dislocation of Scaphoid and Lunate as a unit or with a large gap between the two bones are extremely rare injuries [5].Very few cases of this type of injury are reported so far making our case a very rare presentation.

 
   References Top

1.Hodgkinson D W, Kurdy N, Nicholson D A, Driscoll P A Education and debate ABC of Emergency Radiology: The wrist BMJ 1994; 308:464-468 (12 February)  Back to cited text no. 1    
2.Bryan Hoynak, MD eMedicine: Carpal Bone Injuries. emedicine.com/sports/topic16  Back to cited text no. 2    
3.Grainger & Allison Diagnostic radiology Fourth Edition Wrist: page 1797-1802.  Back to cited text no. 3    
4.Adam Greenspan Orthopedic Radiology. Dislocations of Carpal bones, Page 180- 187.  Back to cited text no. 4    
5.Baulot E, Perez A, Hallonet D, Grammont PM. Rev Chir Orthop Reparatrice Appar Mot. 1997; 83(3):265-9  Back to cited text no. 5    

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Correspondence Address:
S K Chamarthi
India

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.29108

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    Figures

[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6]

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    Introduction
    Case report
    Discussion
    Greater arc pattern
    References
    Article Figures

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