1. Stage 2, Perilunate dislocation Test Cases Introduction
Role of Plain Films in Diagnosing Wrist Dislocations/Ligamentous Injuries: Often an Underutilized Modality That Can Diagnose Complex/Rare Cases Utilizing Simple Rules Rami E Eldaya, Jorge Lee-Diaz, Glen M. Garcia University of Texas Medical Branch
Stage 2, Perilunate dislocation
Test Cases
Introduction
Value of frontal image for detection of carpal ligamentous injuries
Gilula’s lines
Wrist Dislocation Summary
Stage
Pathophysiology
Radiographic appearance
Miscellaneous
Stage 1, sacpholunate dissociation
rupture of the scapholunate ligament
Frontal:
widening of the scapolunate interval > 3mm
can see ring sign on AP secondary to rotatory subluxation of the scaphoid
Lateral:
typically normal
Normal scapholunate interval is less than 3 mm
Stage 2, Perilunate dislocation
Capitate dorsal
Lunate can appear triangular in appearance (not specific)
Disruption of Gilula’s lines
capitate dislocates dorsally and the lunate maintains a normal articulation with the radius
Much more common than lunate dislocation
High association with transcaphoid fractures
Triquetrum, capitate and ulnar styloid fractures can also be seen
Stage 3, midcarpel dislocation
Triquetral ligaments disruption
lunate dislocates volarly and the capitate and carpus dislocate dorsally.
Stage 4, lunate dislocation
Lunate dislocation
lunate overlaps the capitate and has a triangular or piece of pie appearance
lunate seen displaced and angulated volarly
the capitate remains aligned with the radius
Can lead to median nerve entrapment
Most of carpal ligamentous / dislocation injuries present acutely to the emergency department with pain or deformity after recent traumas. Plain films are the initial modality of evaluation. Also, carpal and carporadial  dislocations/ligamentous injuries have been described in literature since 1970s yet they remain puzzling  plain film diagnosis for a lot of junior residents. This is likely due to relative rarity of the injury, complex nature of the injury, and lack of familiarity of radiographic findings of such injuries secondary to growing dependence on MR for evaluation of these injuries
Frontal radiographs depicting Gilula’s Lines:
Black arc: outlining the proximal convexities of the scaphoid, lunate, and triquetrum
Orange arc: outlines the distal surfaces of the scaphoid, lunate, and triquetrum
Green line: outlines the proximal capitate and hamate
Disruption of any of these lines is suggestive of carpus injury with two exceptions:
A triquetrum that is shorter than the lunate leads to a step-off in the first arc (the second arc remains normal)
Bi-lobed appreance of the second arc secondary to lunate type II morphology
Note on frontal images disruption of the second (blue) and third (green) Gilula lines suggestive of carpus dislocation/ligamentous injury. The red arrow highlights a scaphoid fracture, a typical associated injury.
Lateral image demonstrate disruption of the radius, capitate, and lunate line (blue arrow). The lateral image is imperative in differentiating stage 2 from 4 based on displacement of bones. In this case dorsal capitate displacement is present.
Purpose of Abstract
We will review the complex-ligamentous anatomy of the wrist on plain film
We will introduce a systemic method to help detect these injuries on radiographs
We will review the pathophysiology of such injuries with emphasis on the perilunate-lunate injury complex 4 stages
We will test the attendant knowledge with complex rare case
Value of the lateral image for evaluating of carpal ligamentous injuries
Stage 4, Lunate dislocation
Lateral view is the optimal view to diagnose carpal dislocations.
Normal wrist should exhibit alignment between the radius, capitate, and lunate as suggested by a line drawn through the radius (red line).
If the line fails to intersect any of the three bones, a carpal dislocation injury is suggested.
Stage 1, Scapholunate dissociation
References
Note widened scapholunate interval (arrow). The Stage 1 SLD is best appreciated on frontal radiographs
1) Mayfield JK. Mechanism of carpal injuries. Clin Orthop Rel Res. 1980;149:45–54 2) NA Siddiqui, SP Sarkar Isolated Dorsal Dislocation of the Lunate Open Orthop J. 2012; 6: 531–534. Published online 2012 November 30 3)Gilula LA. Carpal Injuries: Analytic approach and case exercises. Am J Roentgen. 1979;133:503–17 4). Bilos ZJ, Hui PW. Dorsal dislocation of the lunate with carpal collapse. Report of two cases. J Bone Joint Surg. 1981;63-A(9):1484–6. [PubMed] 5). Seidenstein H. Two Unusual dislocations at the wrist. J Bone Joint Surg. 1956;38-A:1137–41.
Frontal Image demonstrate disruption of the second Gilula’s line (blue arrow)
Lateral Image demonstrate volar displacement of the lunate (blue arrow)