Hill Sachs Lesion

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Clinically Relevant Anatomy

When we talk about 'Hill Sachs Lesion', we speak about the glenohumeral joint, which is a ball-and-socket joint. We can divide the anatomy of the glenohumeral joint into four aspects:

• bony part: the scapula with his glenoid and the humeral head;
• the fibrocartilaginous structure surrounding the glenoid, namely the labrum;
• the capsule and ligamentous structures;
• musculature.

Mechanism of Injury / Pathological Process

The glenohumeral joint is the most commonly dislocated joint in the human body and 90% of shoulder dislocations are anterior. The reason for this is that the scapula is oriented about 30 degrees anterior and this to the coronal plane of the body. Because of this the glenohumeral joint with the humerus is orienting anterior to the glenoid.

When a trauma takes place, an anterior shoulder dislocation can cause a head impression fracture what we call a Hill sachs lesion. The posterolateral aspect of the humeral head impacts on the anterior glenoid in the dislocated position, what makes the glenohumeral joint unstable (Shoulder_Instability).

90% of shoulder dislocations are anterior, so in some cases there could be a posterior dislocation what can cause a reverse Hill sachs lesion. This lesion may be present on the anterior aspect of the humeral head.

Clinical Presentation

We can order this head impression fractures according to the percent of head involvement:

• minor defect: less than 20% of the humeral head is involved;
• moderate defect: between 20% and 45% of the head is involved;
• severe defect: more than 45% of the head is involved.

Figure 1 illustrates how the percentage of the humeral head, which is involved, is calculated. Next to this percentage, a Hill sachs lesion is also characterized by the depth ('d' on figure 1) and his size ('s' on figure 1).

Figure 1: preoperative double contrast CT arthrography of a 20 year old patient.

When an anterior shoulder dislocation takes place, the arm is usually held in an externally rotated and abducted position. The acromion is prominent laterally and posteriorly, there is loss of the normal contour of the deltoid and the humeral head may well be palpable anteriorly. But, with all this, nobody can see if there is a specific damage of the bone (diagnostic procedures).

Diagnostic Procedures

When a patient whit Hill sachs lesion knocks on the door of a physiotherapist, the physiotherapist can ask some questions to his patient (history), looking to both shoulders (atrophy, asymmetry, surgical scars...), implements some passive movements (forward flexion and elevation, abduction, internal and external rotation) after which the patient is doing this movements active... Classicaly the patient with recurrent dislocation has a normal range of motion, but at some degree you will see a 'risk position'. Now, the physiotherapist know there is some instability, but there is no sign that the patient has an Hill sachs lesion.

For the identification of a Hill sachs lesion, you need specific views to demonstrate the lesion. When the use of MRI (Magnetich Resonance imaging) an CT arthrography increased, for the diagnosis of a Hill sachs lesion, a higher incidence has been reported. It's important that a physiotherapist knows that there could be some concomitants which are only visible through MRI...

Outcome Measures

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Management / Interventions

When patients have a small or moderate defect of the humeral head, it tends to be neglected. Surgical treatment is no necessity. So, there is no need of surgical treatment, but important is handle the result, the unstability.

The non-operative rehabilitation of the unstable shoulder consists about seven key factors:

• Onset of pathology (in this case: traumatic event)
• Degree of instability (in this case: dislocation)
• Frequency of dislocation (in this case acute)
• Direction of instability (in this case: anterior)
• concomitant pathologies (in this case: Hill sachs lesion)
• Neuromuscular control
• Activity level

In the non-operative rehabilitation program of the traumatic dislocation of the shoulder, it's important to consider all these seven factors and thus also with the concomitant 'Hill sachs lesion': rehabilitation program of the shoulder

Some studies say that: 'there is no relationship between the number of dislocations and Hill sachs lesion'. But several studies have shown that when the number of dislocations increases, the incidence and size of Hill sachs lesion also increase. It can be a cause of instability and in this case surgical treatment is considered. Frequently, authors consider that surgical treatment of recurrent shoulder dislocation is indicated when someone had more than five shoulder dislocations.

Differential Diagnosis

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Key Evidence

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Resources

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Case Studies

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References

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