Hill-Sacks Lesion

This is a defect in the posterolateral aspect of the humeral

head resulting from anterior dislocation (often associated

with recurrent injuries). The lesion occurs when the dislocated humeral head strikes the inferior margin of the glenoid, producing a “hatchet” compression fracture defect of

the humeral head. It usually is demonstrated on the antero1 Skeletal Anatomy 25

posterior view radiograph of the shoulder with the humerus

internally rotated. The presence of this lesion is virtually

diagnostic of previous anterior dislocation (17).

Bankart Lesion

Injury to the anterior-inferior cartilaginous labrum, which

is usually associated with an avulsion of the inferior glenohumeral ligament from the anterior-inferior glenoid rim.

Associated from anterior dislocation of the glenohumeral

joint. It may affect only fibrocartilaginous portion of the

glenoid, but is commonly noted in association with a fracture of the anterior aspect of the inferior osseous rim of the

glenoid. The Bankart lesion is less commonly seen than the

Hill-Sacks lesion. The presence of this lesion is virtually

diagnostic of previous anterior dislocation (17).

Posterior Dislocation of the Shoulder

This accounts for 2% to 3% of shoulder dislocations. It can

occur from direct force or a blow to the anterior shoulder,

from indirect force applied to the arm combining adduction,

flexion, and internal rotation, or it can be associated with

severe muscle contraction from electric shock or convulsive

seizures. The humeral head is located posterior to the glenoid

fossa, and usually impacts on the posterior rim of the glenoid.

The shoulder usually is positioned or locked in adduction

and internal rotation. Standard radiographs may not demonstrate the lesion (because the humeral head lies directly posteriorly, and radiographs may appear unremarkable on standard anteroposterior views). Injury can be demonstrated by

either an axillary view (often difficult to obtain because of the

arm locked in adduction) or by a special anteroposterior view

with the patient rotated 40 degrees toward the affected side.

With this view, the normal clear space of the glenohumeral

joint is obliterated by the overlap of the humeral head located

posterior and slightly medial to the surface of the glenoid.

Fractures of the Shaft Proximal to the

Insertion of the Deltoid Muscle

If a fracture of the humeral shaft occurs just proximal to the

insertion of the deltoid, the proximal fragment of the

humerus usually is adducted or pulled medially by the pectoralis major, latissimus dorsi, and teres major. The distal

fragment usually is displaced or angulated laterally (apex

medially, or fracture in valgus) because of the deltoid.

Fractures of the Humeral Shaft Distal to the

Insertion of the Deltoid Muscle

If a fracture of the humeral shaft occurs just distal to the

insertion of the deltoid, the proximal fragment usually is

displaced laterally by the deltoid and supraspinatus muscle.

The distal fragment usually is pulled medially and upward

by the triceps, biceps, and the coracobrachialis muscles.

Fractures of the Humeral Shaft Associated

with Radial Nerve Palsy

Up to 18% of humeral shaft fractures have an associated

radial nerve injury (33–36). Most nerve injuries represent a

neurapraxia or axonotmesis, and 90% resolve in 3 to 4

months (37–39). This injury often is referred to as the Holstein-Lewis fracture, which describes an oblique fracture of

the distal third of the humerus. However, radial nerve palsy

is associated most commonly with fractures of the middle

third of the humerus (34,38).

Supracondylar Fractures

The area of bone at the supracondylar level is relatively thin,

and fractures through this area are common, especially in

children. Structures at risk for injury in supracondylar fractures include the brachial artery and median nerve anteriorly and the radial nerve laterally. Brachial artery injury

subsequently is associated with compartment syndrome of

the forearm.