Age / Sex : 64 / M

Chief complaint: Left wrist pain after falling down

palpable mass in left thigh

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Courtesy: 정지영(Jee Young Jung), 중앙대 병원(Chungang University Hospital)

Palmar lunate dislocation

Discussion

Findings: Radiograph and CT showed palmar lunate dislocation with ‘‘spilled teacup’’ sign on the lateral view or sagittal reformatted image and crowded carpus on the AP view or coronal reformatted image.

Differential Diagnosis:

Diagnosis: Palmar lunate dislocation

Discussion:  

Perilunate injuries result from high-energy wrist hyperextension, typically falls from a height, motor vehicle collisions, or sports-related injuries. Up to 25% of perilunate injuries are overlooked at initial examinations. Perilunate injuries occur in a sequence as the ligaments around the lunate fail in a radial to ulnar direction; this is called progressive perilunate instability. It starts at the scapholunate joint, then proceeds to the lunocapitate and lunotriquetral joints, and finally culminates in complete dislocation of the lunate. In 1980, Mayfield illustrated the mechanism of perilunar wrist instability as a series of four stages, resulting in perilunate dislocations or lunate dislocations. These are defined as: stage 1, progressive rupture of the scapho-lunate ligament from volar to dorsal, followed by stage 2, dorsal dislocation of the capitate with dissociation at the luno-capitate joint with tearing, then stage 3, luno-triquetral ligament disruption, with the rest of the carpus being displaced, usually dorsally, and finally, stage 4 is complete ligament disruption with the lunate forced volarwards by the proximal portion of the capitate resulting in dislocation of the lunate.

Lunate dislocation is the final stage of perilunate injuries and the most severe form of perilunate injuries and is associated with the highest degree of instability. In this injury, the lunate is dislocated volarly out of the distal radial articulation and the rest of the carpus assumes alignment with the radius. This is called the spilled teacup sign on lateral radiographs.

References:

1. Multidetector CT of Carpal Injuries: Anatomy, Fractures, and Fracture-Dislocations. RadioGraphics 2008; 28:1771–1784

2. Carpal dislocations. Current Orthopaedics (2007) 21, 288–297