Hong Kong Journal of Emergency Medicine

Ultrasound diagnosis of anterior shoulder dislocation

CK Yuen , KL Mok , PG Kan , YT Wong

Correspondence to:Yuen Chi Kit, FHKCEM

Ruttonjee Hospital, Accident & Emergency Deparment,266 Queen's Road East, Wanchai, Hong Kong.Email: yuenchikit@gmail.com

Mok Ka Leung, FHKCEM

Kan Pui Gay, FHKCEM

Wong Yau Tak, FHKCEM

We describe the ultrasound evaluation technique and sonographic findings of a case of anterior shoulderdislocation. The sonographic features of anterior shoulder dislocation include: "sign of widening ofsubacromial space", "sign of disappearance of humeral head", "artery/vessel sign", "humeral head belowcoracoid process sign" and "empty glenoid fossa sign". It is a safe, real time, readily available, convenient,and well tolerated diagnostic technique. The time to confirming the diagnosis of anterior shoulder dislocationmay be shortened and hence close reduction in a timely manner may be achieved. We suggest the use of highresolution ultrasound for confirmation of the diagnosis of anterior shoulder dislocation and relocation ofthe humeral head after close reduction. The potential of using ultrasonography to replace pre-reductionradiograph should be explored. (Hong Kong j.emerg.med. 2009;16:29-34)

Keywords: Dislocations, radiography, shoulder joint, ultrasonography

Case summary

Our patient was a 73 years old Chinese lady who hadhistory of recurrent left shoulder dislocation. Shepresented to the emergency department in August 2007with acute right shoulder pain and deformity after she

fell and landed on her out-stretched right hand. Thephysical examination revealed fullness and tendernessover the anterior shoulder. The right arm was lockedat 20 degree abduction. There was no neurovasculardeficit.

The patient was routinely sent to the X-ray departmentfor taking pre-reduction shoulder radiographs.However, ultrasound examination was also performedduring the time while the patient was waiting for theprocessing of the X-ray films. Verbal consent for theexamination was obtained from the patient. It wasperformed by an emergency physician on an EsaoteMyLab 30 ultrasound machine with a 7.5-13 MHzlinear transducer. The examination was done in acubicle in the emergency department. The patient wassitting on a stretcher with the injured arm held in the

Hong Kong j. emerg. med. Vol. 16(1) Jan 200930

position of comfort by the patient. The ultrasonographicexamination protocol is described below.

Ultrasound technique for the detection ofanterior shoulder dislocation and thespecific findings

RemarkThe photographs at the right lower corner of theFigures just serve to illustrate the position of theultrasound probe. They are not the photographs of theoriginal patient.

1. Coronal subacromial viewThe lateral end of the acromion was located bypalpation and the ultrasound probe was positionedlongitudinally just below the acromion. Normally, thehumeral head is seated just below the acromion (Figure 1).When the humeral head is dislocated anteriorly, thealignment of the humeral head with the acromion islost and the distance between the acromion andhumeral head is widened. This can be named as the"sign of widening of subacromial space" (Figure 2).

2. Trasnsverse coracoid viewThe coracoid process which is situated below the lateralend of the clavicle, was located by the operator bypalpation. The ultrasound probe was then placedtransversely directly over the coracoid process.Normally, the humeral head is in the lateral aspect ofthe coracoid process (Figure 3). When the humeralhead is dislocated anteriorly, it seats below the coracoidprocess. Therefore, the humeral head was not shownin the lateral aspect of the coracoid process (Figure 4).This may be called the "sign of disappearance ofhumeral head".

3. Transverse subcoracoid viewThen the ultrasound probe was moved caudally, thehumeral head was encountered and the axillary arterywas seen adjacent to the humeral head (Figure 5).Under normal circumstances, the humeral head is notin close contact with the axillary vessel unless there isshoulder joint dislocation. This phenomenon may becalled the "artery/vessel sign".

Figure 1. Coronal subacromial view: post-reduction.

Figure 3. Transverse view of coracoid process: post-reduction.

(a)

Figure 2. Coronal subacromial view: pre-reduction (sign of

widening of subacromial space).

Yuen et al./Ultrasound diagnosis of shoulder dislocation 31

4. Longitudinal subcoracoid viewThe coracoid process was located by the operator bypalpation and the ultrasound probe was placedlongitudinally directly over the coracoid process. Theprobe was then moved downward slowly to obtainimage of this area. Because the humeral head is inthe lateral aspect of the coracoid process, it shouldnot be encountered in this longitudinal view undernormal circumstances (Figure 6). In our patient,because the humeral head was dislocated anteriorly,the image of the humeral head was found below thecoracoid process in this longitudinal scan (Figure 7).The humeral head appeared as a curvilinear echoicline with distal acoustic shadow seating below thecoracoid process. It may be called the "humeral headbelow coracoid process sign".

5. Transverse posterior glenoid viewThen the ultrasound probe was moved to the back ofthe patient. The lateral end of the spine of the scapulawas located by palpation and the ultrasound probe wasplaced transversely below the scapular spine to obtainthe image of the glenohumeral joint. The position ofthe ultrasound probe is the same as when we try toimage the infraspinatus in longitudinal section (i.e. inthe transverse plane of the body). Normally, thehumeral head is seating on the glenoid fossa and iscovering the glenoid fossa (Figure 8). In our patientthe humeral head was dislocated leaving the glenoid

Figure 4. Transverse view of coracoid process: pre-reduction

(sign of disappearance of humeral head).

Figure 5. Transverse view of subcoracoid region: pre-reduction

(artery/vessel sign).

Figure 6. Longitudinal view of subcoracoid region: post-reduction.

Figure 7. Longitudinal view of subcoracoid region: pre-

reduction (humeral head below coracoid process sign).

Hong Kong j. emerg. med. Vol. 16(1) Jan 200932

fossa unobscured. It may be called the "empty glenoidfossa sign" (Figure 9).

6. Longitudinal views of the humeral head,neck and shaftThese were performed to exclude any obvious bonefracture.

For our patient, the anteroposterior shoulderradiograph confirmed anterior shoulder dislocation(Figure 10). It was reduced by a traction-countertraction method. Successful reduction was confirmed

Figure 8. Transverse (posterior glenoid) view of infraspinatus:

post-reduction.

Figure 9. Transverse (posterior glenoid) view of infraspinatus:

pre-reduction (empty glenoid fossa sign).

Figure 10. Pre-reduction radiography of the right shoulder.

Figure 11. Post-reduction radiograph of the right shoulder.

by ultrasound scan and post-reduction radiograph(Figure 11) . The pat ient was g iven shoulderimmobilisation for one week, followed by mobilisationexercise. The outcome of the rehabilitation wassatisfactory.

Discussion

The glenohumeral joint is one of the most commonlydislocated joints. Shoulder dislocation is classifiedaccording to the direction of dislocation into anterior,posterior, inferior and superior dislocations. Themajority, about 95-97%, are anterior dislocation.1

Yuen et al./Ultrasound diagnosis of shoulder dislocation 33

The patients usually present with shoulder pain aftersustaining an injury to the shoulder. They often holdtheir affected extremity in slight external rotation andabduction by the unaffected hand.2 Other physicalsigns of anterior shoulder dislocation include squaringoff of the shoulder contour, and fullness and tendernessin the anterior aspect of the shoulder. Any movementis usually limited by severe pain. Other specific physicaltests such as Dugas' test, Bryant's sign, Colloway'ssign and Hamilton's sign are suggestive but notconfirmatory of the diagnosis of shoulder dislocation.

Traditionally, shoulder radiographs including antero-posterior view and scapular Y view or axillary viewshould be obtained to confirm the diagnosis andexclude associated osseous fractures before attemptingclose reduction.1-3 Recently, the necessity of pre-reduction shoulder radiographs in all patients withsuspected shoulder dislocation was challenged byseveral authors.4-7 They concluded that pre-reductionshoulder radiographs in a selected group of patientsrarely affect the management of the patients. Routinepre-reduction radiographs delay close reduction, over-utilise radiology resources and cause unnecessaryradiation hazard and discomfort to the patients.However, the practice of abandoning pre-reductionradiograph is not widely accepted because the selectioncriteria were not completely accurate, and moreimportantly, close reduction of a non-dislocatedshoulder, e.g. misdiagnosing fracture neck of humerusas anterior shoulder dislocation, is certainly harmful tothe patient and may have medico-legal consequence.

We consider that bedside ultrasound may confirm thediagnosis of anterior shoulder dislocation and shortenthe time to close reduction. The value of diagnosticultrasonography performed by emergency physiciansfor evaluation of emergency department patients isundisputed. The use of ultrasound for the diagnosisof both bony (e.g. fracture of greater tuberosity8) andsoft tissue pathologies of the shoulder (e.g. rotator cufftear9) is well established. The application of ultrasoundin the diagnosis of congenital hip dislocation is astandard technique.10 The diagnosis of posteriorshoulder dislocation by ultrasound has also been

reported.11,12 However, to the best knowledge of theauthors, the ultrasonographic findings in anteriorshoulder dislocation have not been described in theliterature. Ultrasound is non-ionising and without theradiation hazard of X-ray. Ultrasound examination canbe performed in settings without radiation protectionand the need to transfer patients to the X-raydepartment is obviated. The modern ultrasoundmachines are usually portable and examination can beperformed at the bedside, in the clinic, in the sportsfield, battlefield or even in a spacestation.13,14 It is asafe, real time, repeatable, convenient and readilyavailable diagnostic technique.

This case report describes the sonographic features ofanterior shoulder dislocation and explores the potentialof using ultrasound to confirm dislocation of theglenohumeral joint. The authors designed a protocolfor evaluating the relationship between the humeralhead and anatomical structures in the neighbourhoodof the glenohumeral joint based on bony landmarkssuch as the coracoid process, humeral head, acromionand glenoid fossa. These osseous landmarks havedistinct sonographic appearances because of the strongreflection of echo from the soft tissue-bone interfacewith distal acoustic shadow as well as the characteristicshapes of the bony structures. Using bony landmarksmakes it a technique easier for the operator to masterand the examination can be performed by mostultrasound equipments with adequate penetration.

Although ultrasound may obviate the need of a pre-reduction radiograph, a post-reduction shoulderradiograph is still needed to exclude associated fracturesand to evaluate the result and any complication of thereduction procedure.

Limitations of ultrasound techniques in generalsuch as operator dependency also apply in thiscondition. Although ultrasound machines are nowavailable in all emergency departments in HongKong, the appl ica t ion of u l t ra sound for thediagnosis of anterior shoulder dislocation is a newtechnique. It takes time and some training foremergency physicians to learn the skill. In our

Hong Kong j. emerg. med. Vol. 16(1) Jan 200934

experience, it is a simple technique for sonographerswith experience in musculoskeletal ultrasound andthe expertise can be acquired with simple hands-ontraining and practice with real cases. Moreover, thesens i t iv i ty and speci f ic i ty of thi s u l t rasoundtechnique have not been established and furtherresearch to validate this technique is needed.

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