Hill-Sachs lesion
| Hill–Sachs lesion | |
|---|---|
 |
|
| Anterior shoulder dislocation on X-ray with a large Hill–Sachs lesion | |
| Classification and external resources | |
| ICD-10 | Xxx.x |
| ICD-9-CM | xxx |
A Hill–Sachs lesion, or Hill–Sachs fracture, is a cortical depression in the posterolateral head of the humerus. It results from forceful impaction of the humeral head against the anteroinferior glenoid rim when the shoulder is dislocated anteriorly.
The lesion is associated with anterior or posterior shoulder dislocation. When the humerus is driven from the glenohumeral cavity, its relatively soft head impacts against the anterior edge of the glenoid. The result is a divot or flattening in the posterolateral aspect of the humeral head, usually opposite the coracoid process. The mechanism which leads to shoulder dislocation is usually traumatic but can vary, especially if there is history of previous dislocations. Sports, falls, seizures, assaults, throwing, reaching, pulling on the arm, or turning over in bed can all be causes of anterior dislocation.
The incidence of Hill–Sachs lesion is not known with certainty. It has been reported to be present in 40% to 90% of patients presenting with anterior shoulder instability, that is subluxation or dislocation. In those who have recurrent events, it may be as high as 100%. Its presence is a specific sign of dislocation and can thus be used as an indicator that dislocation has occurred even if the joint has since regained its normal alignment. The average depth of Hill–Sachs lesion has been reported as 4.1 mm. Large, engaging Hill-Sachs fractures can contribute to shoulder instability and will often cause painful clicking, catching, or popping.
Imaging diagnosis conventionally begins with plain film radiography. Generally, AP radiographs of the shoulder with the arm in internal rotation offer the best yield while axillary views and AP radiographs with external rotation tend to obscure the defect. However, pain and tenderness in the injured joint make appropriate positioning difficult and in a recent study of plain film x-ray for Hill–Sachs lesions, the sensitivity was only about 20%. i.e. the finding was not visible on plain film x-ray about 80% of the time.
By contrast, studies have shown the value of ultrasonography in diagnosing Hill–Sachs lesions. In a population with recurrent dislocation using findings at surgery as the gold standard, a sensitivity of 96% was demonstrated. In a second study of patients with continuing shoulder instability after trauma, and using double contrast CT as a gold standard, a sensitivity of over 95% was demonstrated for ultrasound. It should be borne in mind that in both those studies, patients were having continuing problems after initial injury, and therefore the presence of a Hill–Sachs lesion was more likely. Nevertheless, ultrasonography, which is noninvasive and free from radiation, offers important advantages.
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