Hill-Sachs lesion
Encyclopedia
A Hill-Sachs lesion, also Hill-Sachs fracture, is a cortical depression in the posterior superior head of the humerus bone
. It results from forceful impaction of the humeral head against the anteroinferior glenoid rim when the shoulder is dislocated
anteriorly.
. When it is driven from the glenohumeral cavity, the relatively soft head of the humerus impacts against the anterior edge of the glenoid. The result is a divot or flattening in the posteromedial
aspect of the humeral head (typically referred to as a 3 to 6 o'clock lesion for the right humeral head if seen from the bottom). 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 even just turning over in bed can all be causes of anterior dislocations.
The majority of these fractures are found on 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. A special view, the Stryker-Notch view, is often used specifically to look for a Hill-Sachs lesion. The sensitivity and specificity
of radiography have been found to be 65% and 67%, respectively. Ultrasonography has also proven itself as a useful method of idenitifying Hill-Sachs lesions with a sensitivity of 96% and specificity of 100%. Finally, MRI has been shown to be 97% sensitive and 91% specific at detecting the fractures.
, and use of allografts for patients with greater than 40% involvement of the articular surface.
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
. It results from forceful impaction of the humeral head against the anteroinferior glenoid rim when the shoulder is dislocated
Dislocated shoulder
A dislocated shoulder occurs when the humerus separates from the scapula at the glenohumeral joint. The shoulder joint has the greatest range of motion of any joint in the body and as a result is particularly susceptible to dislocation and subluxation. Approximately half of major joint...
anteriorly.
Eponym
It is named after Harold Arthur Hill (1901-1973) and Maurice David Sachs (1909-1987), two prominent radiologists from San Francisco, USA. In 1940, the pair published a report of 119 cases of shoulder dislocations and showed that the defect resulted from direct compression of the humeral head. Before their paper, the fracture was already known to be a sign of shoulder dislocation, but the precise mechanism of the lesion was uncertain.Causes
The lesion is associated exclusively with anterior shoulder dislocationsDislocated shoulder
A dislocated shoulder occurs when the humerus separates from the scapula at the glenohumeral joint. The shoulder joint has the greatest range of motion of any joint in the body and as a result is particularly susceptible to dislocation and subluxation. Approximately half of major joint...
. When it is driven from the glenohumeral cavity, the relatively soft head of the humerus impacts against the anterior edge of the glenoid. The result is a divot or flattening in the posteromedial
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
aspect of the humeral head (typically referred to as a 3 to 6 o'clock lesion for the right humeral head if seen from the bottom). 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 even just turning over in bed can all be causes of anterior dislocations.
Clinical relevance
Hill-Sachs lesions have been reported in as many as 92% of recurrent anterior dislocations. In all shoulder dislocation patients, the prevalence has been found to be between 35-76%. The presence of a Hill-Sachs lesion is an extremely 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 arrangement. 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, popping.The majority of these fractures are found on plain film radiography
Radiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
. 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. A special view, the Stryker-Notch view, is often used specifically to look for a Hill-Sachs lesion. The sensitivity and specificity
Sensitivity and specificity
Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
of radiography have been found to be 65% and 67%, respectively. Ultrasonography has also proven itself as a useful method of idenitifying Hill-Sachs lesions with a sensitivity of 96% and specificity of 100%. Finally, MRI has been shown to be 97% sensitive and 91% specific at detecting the fractures.
Treatment
Repair of a Hill-Sachs lesions is only indicated when it is associated with significant shoulder instability. The most effective and simplest approach is to prevent the lesion from straddling the anterior glenoid by slightly imbricating the capsule and thus limiting external rotation. The Connolly procedure is an alternative treatment approach and involves transferring the infraspinatus with a portion of the greater tuberosity into the defect. This leaves the lesion extraarticular and again prevents it from coming into contact with the glenoid rim. Finally, some surgeons using humeral osteotomy with subscapularis shortening, hemiarthroplasty, total shoulder arthroplastyArthroplasty
Arthroplasty is an operative procedure of orthopedic surgery performed, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodeling or realigning the joint by osteotomy or some other procedure.-Background:Previously, a popular form of arthroplasty was...
, and use of allografts for patients with greater than 40% involvement of the articular surface.
External links
- Hill-Sachs lesions (frontal X-ray) - szote.u-szedeg.hu.
