How do you interpret these radiographs and what are your clinical concerns?

Transcription

1 A 39 year-ld man presents t the ED cmplaining f severe left shulder pain fllwing a fight. He admits t having "a few beers" and cannt recall exactly hw the injury ccurred. He exhibits limited range f mtin f the shulder. His arm is carefully held against the chest wall with the shulder internally rtated. A neurvascular exam is cmpletely intact. Tw x-ray views f the shulder are rdered. The x-ray tech des his best t take internal and external rtatin views; hwever, the patient's pain limits his ability t c-perate: Hw d yu interpret these radigraphs and what are yur clinical cncerns? Case images submitted by Mark Dnnelly,MD and Tracey Demin, MD frm the Department f Emergency Medicine, University f Rchester/Strng Memrial Hspital.

2 Psterir Shulder Dislcatin The treating physician did nt immediately appreciate the subtle x-ray findings suggesting a psterir shulder dislcatin, but was cncerned abut the patient's level f discmfrt and maintained a high suspicin fr significant pathlgy. Therefre, a CT scan f the shulder was btained: On the CT scan, the humeral head is clearly seen t be rtated psterirly in relatin t the glenid. In additin, a reverse Hill-Sachs defrmity is evident (*). Rutine AP shulder films usually are sufficient t detect a variety f anterir dislcatins. Unfrtunately, this radigraph is rarely sufficient t diagnse a psterir dislcatin. It shuld be emphasized that this type f dislcatin may lk deceptively nrmal n the AP radigraph because a rutine AP film f the shulder des nt affrd a true AP view f the glenhumeral jint. As a result, the standard trauma shulder series in many institutins that cnsists f AP views in internal and external rtatin is inadequate. Nevertheless, there are specific radigraphic signs seen n the AP view that may suggest this injury: Light bulb sign: The humeral head takes n an abnrmally runded, mre symmetrical shape, like a light bulb, due t rtatin f the humerus. A side-by-side cmparisn f this patient's initial x-ray (left) and his pst-reductin film (right) reveals an bvius light bulb

3 sign. In additin, a "hllwed ut" humeral head n the initial x-ray is nted. Hllwed ut humeral head: With a psterir dislcatin, the arm is lcked in internal rtatin. The x-ray beam, therefre, passes thrugh bth the greater and lesser tubersities, creating the image f a hllw humeral head. Empty glenid sign: In psterir dislcatins, the head rests behind the glenid; as a result, the glenid fssa appears t be partially vacant and the distance between the articular surface f the humeral head and the anterir lip f the glenid may be increased. A reverse Hill - Sachs lesin may be seen. This is a defect frm cmpressin f the antermedial prtin f the humeral head prduced by the psterir crtical rim f the glenid (the mre cmmnly encuntered Hill-Sachs lesin is seen n the psterlateral humeral head in anterir dislcatins). These signs suggest psterir dislcatin and a further view shuld be btained t cnfirm the diagnsis. This may be either an axillary r transcapular-y view. Axillary view: psterir dislcatin

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5 Psterir dislcatin results frm axial lading f the adducted, internally rtated arm. Because the internal rtatr muscles are apprximately twice as pwerful as the external rtatr muscles, a sudden pwerful cntractin is required t cause the humeral head t dislcate, such as frm a seizure r electrcutin. The finding f a psterir shulder dislcatin, then, shuld always raise the pssibility that the patient experienced a seizure. In fact, the patient described in this case sustained his injury during a seizure, as relayed by witnesses wh arrived in the ED. Reducing a psterir shulder dislcatin can be mre difficult than an anterir dislcatin, and nt infrequently general anesthesia is required. Nevertheless, an attempt shuld be made in the ED. The technique is as fllws: Apply gentle, prlnged axial tractin n the humerus. Apply gentle anterir pressure while caxing the humeral head ver the glenid rim. Slw external rtatin may be needed. References: (1) Perrn AD, Jnes RL. Psterir shulder dislcatin: aviding a missed diagnsis Am J Emerg Med 2000;18: (2) Elberger ST, Brdy G. Bilateral psterir shulder dislcatins Am J Emerg Med 1995;13:331-2 (3) Ahlgren O, Lrentzn R, Larssn SE. Psterir dislcatin f the shulder assciated with general seizures Acta Orthp Scand 1981;52: