Age / Sex : 19 / M

Age / Sex : M/19

Chief complaint :

Ulnar pain on the right wrist was developed by slip down over a period of more than 2 years

1) What is your impression?

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

* Send Application Answers to In Sook Lee, MD ([email protected])

Courtesy : Jang Gyu Cha, Soonchunhyang Univ Bucheon Hospital

Discussion

Findings:

 Ultrasongraphy on the ulnar side of right wrist shows a split tear of extensor carpi ulnaris(ECU) with subluxation overriding the styloid process of distal ulna.

Continuous sections of axial fat saturated gradient echo MR image show the disruption of ECU with distended tendon sheath at distal ulna level.

Coronal fat saturated T2 weighted MR image show bifurcation of ECU at the tip of styloid process of ulna.

Differential Diagnosis:

Diagnosis: Tear of extensor carpi ulnaris tendon with subluxation

Discussion:

ANATOMICAL REVIEW

 The ECU tendon is stabilised in the osseous groove. It lies in the sixth compartment formed

by duplication of the deep antebrachial fascia inserted on to the osseous groove, forming a

tunnel (ECU subsheath). The dorsal retinaculum,which runs over the five dorsal compartments,

passes above it, like a bridge. The retinaculum is not attached to the inferior ulna and inserts on to the triquetrum and pisiform,allowing both pronation and supination. Finally,there is an anatomical entity composed of longitudinal fibres, the ‘‘linea jugata’’, which reinforces the ulnar insertion of the ECU subsheath. These anatomical features play an important role in maintaining ECU stability in the osteofibrous groove and

ensure that the tendon is closely bound to the ulnar head. it is evident that once the osteofibrous sheath has ruptured or detached from the ulna, the ECU tendon can luxate within and slide under the intact

dorsal retinaculum.

An ultrasound scan at rest and during supination, using the method developed by JLB. From a technical point of

view, preferably two operators should be present during the ultrasound examination in order to reproduce the

tendon instability. One operator should attempt to reproduce the ECU instability using forced supination

while the other person performs the ultrasound. True instability in which the tendon leaves and re-enters its

sheath is clearly visualised on dynamic ultrasound.

An MRI with millimetre thick slices of the ulnar sheath in T1, T1 STIR, T2, T2 and FATSAT GADO modes and

comparative films obtained during pronation and supination by the method developed by JLD. Forced supination

images show tendon subluxation, clear disorganisation of the retinaculum, and finally major detachment of the ECU retinaculum from the medial surface of the ulna.

References:

 1. Montalvan B, Parier J, Brasseur JL, Le Viet D, Drape JL. Extensor carpi ulnaris injuries in tennis players: a study of 28 cases. Br J Sports Med. 2006 May;40(5):424-9