CASE 119

By: Dr. Nizar Al-Nakshabandi MD, FRCPC

HISTORY: 26-year-old fell on the outstretched hand

What are your findings?

What is the differential diagnosis?

What are the causes?

FINDINGS:

The AP radiograph of the left wrist [A] and lateral [B] demonstrates an increase in overlap of the lunate and capitate and disruption of the normal smooth line of the Gilula’s arc on the AP radiograph. The lateral view demonstrates that the capitate is not sitting in the distal articular cup of the lunate. However, lunate remains in articulation with the distal radius.

Coronal fat-sat T2- fat suppressed weighted images [C] and sagittal T2 fat sat weighted images demonstrate bone marrow edematous changes of the scaphoid and lunate bone suggestive microfractures but with no demonstrable cortical break.  Furthermore, scapholunate disruption is detected.

DIFFERENTIAL DIAGNOSIS:

·        Perilunate dislocation.

·        Lunate dislocation.

DIAGNOSIS:

Perilunate dislocation.

PEARLS AND DISCUSSION:

Typical mechanism of injury is fall on the outstretched dorsiflexed hand. On physical examination, there may or may not be an actual deformity. It is important to look for median nerve injury or arterial compromise. Furthermore, compartment syndrome should be thought of.

The plain radiographs, the lateral view show perilunate dislocation, lunate remains in articulation with the distal radius whereas in lunate dislocation it is lost completely in a volar position. The MRI demonstrate scapholunate ligamentous tear.

Always make sure that the scaphoid is or isn’t fractured as there is a 60% chance of a fracture in those cases it is called a trans-scaphoid perilunate dislocation.

Complications of a missed fracture is median nerve palsy, compartment syndrome, and wrist dysfunction.

It is treated with prompt open reduction ligamentous repair. Despite treatment osteoarthritis occurs in approximately of 60% of the cases.

FURTHER READING:

1.      Berquist TH. Musculoskeletal Imaging Companion. Lippincott Williams & Wilkins. (2006) ISBN:0781763746

2.      Schmitt R, Lanz U, Buchberger W. Diagnostic Imaging of the Hand. Thieme Medical Pub. (2008) ISBN:1588904539