The humeral shaft extends from the insertion of the pectoralis major to the supracondylar ridges. Humeral shaft fractures are most frequently seen in patients older than 50 years of age and usually involve the middle third of the shaft. There are four basic patterns commonly seen with humeral shaft fractures.
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 based on the presence of displacement or angulation (Figs. 15–1 and 15–2).
Humeral shaft fractures—nondisplaced.
Humeral shaft fractures—displaced or angulated.
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.
In humeral shaft fractures, the muscles of the proximal humerus cause displacement of the fracture fragments. Five muscles play a major role in displacing fractures in this region: the deltoid, supraspinatus, pectoralis major, biceps, and triceps. A. In fractures between the rotator cuff and the pectoralis major, abduction and rotation of the proximal fragment occur. B. Fractures occurring between the pectoralis major insertion and the insertion of the deltoid are associated with adduction deformity of the proximal fragment. C. Fractures occurring below the deltoid insertion are associated with abduction of the proximal fragment.
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).
The neurovascular bundle of the upper extremity extends along the medial border of the humeral shaft. Although it is true that any of these structures may be injured with a fracture, the most commonly injured structure is the radial nerve. The radial nerve lies in close proximity to the humeral shaft at the junction of its middle and distal thirds (Fig. 15–4). Fractures in this area are often accompanied by radial nerve impairment.
The radial nerve courses in the lateral intermuscular septum along the lateral aspect of the humerus and can be involved in fractures of the shaft.
Several mechanisms cause humeral shaft fractures. The most common mechanism of injury is direct force usually resulting from a fall or direct blow.1 Typically, a direct force results in a transverse fracture.
An indirect mechanism involves a fall on the elbow or outstretched arm. In addition, a violent contraction in an area of pathologically weakened bone may result in a fracture. The indirect mechanism usually results in a spiral fracture.
A relatively minor injury may result in a fracture of the humeral shaft in patients who have had a humeral head prosthesis. This fracture occurs after overzealous reaming or impaction during the secure fitting of the prosthesis.2
The patient will present with pain and swelling over the area of the humeral shaft. On examination, shortening, obvious deformity, or abnormal mobility with crepitation may be detected (Fig. 15–5). It is imperative that a thorough neurovascular examination accompanies the initial assessment of all humeral shaft fractures.
A patient with the humeral shaft fracture.
The examiner should give particular emphasis to the radial nerve function and document the time at which radial nerve injury is first detected. This information is important because:
Damage at the time of injury is most often a neurapraxia.
Damage detected after manipulation or immobilization may lead to axonotmesis if the pressure is not relieved.
Damage detected during healing is typically due to a slowly progressive axonotmesis.
Anteroposterior and lateral views of the entire humerus are essential (Fig. 15–6).
Comminuted fracture of the distal one-third humeral shaft.
Humeral shaft fractures may be associated with several significant injuries including brachial artery injury, nerve injury, or additional fractures to the shoulder or distal humerus.1 Radial nerve injury is more common than ulnar or median injury. Radial nerve injury is present in 6% to 15% of humeral shaft fractures.3–5 These injuries are commonly associated with spiral fractures of the distal third, but may also be ...