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Humeral Shaft Fractures
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Humeral shaft fractures are relatively uncommon; representing only 3% of all fractures.1 Humerus fractures are responsible for 370,000 emergency visits yearly, of which humeral shaft fractures represent about 15%. The incidence of humeral shaft fractures is relatively constant regardless of age.2
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The humeral shaft extends from the insertion of the pectoralis major to the supracondylar ridges. There are four basic patterns commonly seen with humeral shaft fractures.
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Transverse
Oblique
Spiral
Comminuted
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The type of fracture is dependent on the mechanism of injury, the force of injury, the location of the fracture, and the muscular tone at the time of injury. Each of the above fracture patterns may be further classified on the basis of the presence of displacement or angulation (Figs. 15–1 and 15–2).
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The extensive musculature surrounding the humeral shaft may result in distraction and displacement of the bony fragments after a fracture. The deltoid inserts along the anterolateral humeral shaft, whereas the pectoralis major inserts on the medial intertubercular groove (Fig. 15–3). The supraspinatus inserts into the greater tuberosity of the humeral head, resulting in abduction and external rotation. The biceps and the triceps insert distally and tend to displace the distal fragment superiorly.
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A fracture proximal to the pectoralis major insertion may be accompanied by abduction and external rotation of the humeral head because of the action of the supraspinatus (Fig. 15–3A). A fracture between the insertion of the pectoralis major and the deltoid will usually result in adduction of the proximal fragment secondary to the pull of the pectoralis major (Fig. 15–3B). Fractures distal to the deltoid insertion usually result in abduction of the proximal fragment secondary to the pull of the deltoid muscle (Fig. 15–3C).
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The neurovascular bundle of the upper extremity extends along the medial border ...