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Transscaphoid Perilunate Dislocation

29M with right wrist pain and deformity after a motorcycle accident • Xray of the Week

 

Figure 1. Describe the wrist injury.

 

Figure 2. Frontal , lateral, oblique radiographs of the wrist. Red arrow points to scaphoid fracture and yellow arrow points to anteriorly dislocated lunate bone. Note the ‘spilled teacup’ sign seen on lateral radiograph indicating a stage 4 lunate dislocation.

 

Discussion:

Of the eight carpal bones that make up the wrist, the scaphoid bone is fractured
most often and accounts for 70% of all carpal fractures.(1) Less commonly,
scaphoid fractures can be associated with perilunate dislocations. The injury
mechanism in transscaphoid perilunate dislocations is typically “high energy” with
wrist hyperextension (e.g. falling from a height, sports trauma, and motor vehicle
accidents). These patients generally present with exquisite wrist pain and
swelling, exacerbated by wrist motion.(2)
Perilunate dislocations have been described to occur in 4 stages. In a stage 1
injury, the scapholunate joint is disrupted. A stage 2 injury finds the capitolunate
joint disrupted, and stage 3 injury is disruption of the lunotriquetral joint. It is
considered a stage 4 injury when there is complete lunate dislocation with volar
displacement.(2-4) 
Primary imaging required for diagnosis of transscaphoid perilunate dislocation
include PA and lateral wrist radiographs. On PA films, a transscaphoid perilunate dislocation can be recognized by the ‘Terry-Thomas sign’ which refers to a gap greater than 2 mm between the scaphoid and lunate bones, and is due to scapholunate ligament rupture. In normal lateral wrist radiographs, the capitate bone is aligned with the lunate bone and sits right above it. When perilunate dislocation occurs, the capitate can be
identified dorsally with respect to the lunate. Furthermore, the ‘spilled teacup’
sign seen on lateral radiographs indicates a stage 4 lunate dislocation. The volar
displacement of the lunate bone resembles a teacup spilling forward.(2,5)
Transscaphoid perilunate dislocations can be treated with initial closed reduction
and splint followed by surgical repair of injured ligaments after swelling has
decreased. However, in cases where progressive median nerve dysfunction is
noted, immediate open reduction with internal fixation (ORIF) is the preferred
treatment.(2,6)

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References:

1. Papp S. Carpal Bone Fractures. Hand Clinics. 2010;26(1):119-127.
doi:
10.1016/j.hcl.2009.08.014
2. Kannikeswaran N, Sethuraman U. Lunate and perilunate dislocations. Pediatr
Emerg Care. 2010;26(12):921-924. doi:
10.1097/PEC.0b013e3181fe915b
3. Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: Pathomechanics
and progressive perilunar instability. Journal of Hand Surgery. 1980;5(3):226-
241.
doi:10.1016/S0363-5023(80)80007-4
4. Kennedy A, Allan H. In Brief: Mayfield et al. Classification: Carpal Dislocations
and Progressive Perilunar Instability. Clinical Orthopaedics and Related
Research. 2012;470(4):1243-1245. doi:
10.1007/s11999-012-2275-x

5. Bashir WA, Aziz A, Jidaal I. Imaging of skeletal extremity trauma: A review.
Trauma. 2014;16(4):300-317.
doi:10.1177/1460408614542920
6. Kloss B, Patierno S, Sullivan A. Transscaphoid perilunate dislocation.
International Journal of Emergency Medicine. 2010;3(4):501-502.
doi:
10.1007/s12245-010-0212-x

 

 

 

Nirali Dave is a medical student at Medical University of Lublin in Poland, currently doing clinical rotations in New York. Before that she completed her undergraduate education at Rutgers University, and worked as a medical scribe. Nirali was first exposed to basic radiologic imaging while scribing, and was very quickly taken by the field. Her passion for radiology comes from the bridging of anatomy, health technologies, and patient care. In the future, she hopes to complete a diagnostic radiology residency and stay committed to clinical research and patient education.

 

Follow Nirali Dave on Twitter @ndave08

 

All posts by Nirali Dave

 

 

 

 

Kevin M. Rice, MD is the president of Global Radiology CME 

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

Follow Dr. Rice on Twitter @KevinRiceMD

 

All posts by Kevin M. Rice, MD

 

 

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