2 Fractures of the Humerus

Overview of Humeral Fractures

Anatomic Features

The humerus (▶ Fig. 2.1) is the longest and largest bone of the arm; it is divided into a body and two extremities. The proximal humerus is part of the radiographic anatomy of the shoulder. The humeral head is nearly hemispheric in shape, and articulates with the glenoid cavity of the scapula. The greater tubercle, situated lateral to the head, has three areas of muscle insertion: the supraspinatus superiorly, the infraspinatus in the middle, and the teres minor inferiorly. Situated in front of the head is the lesser tubercle, into which the tendon of the subscapularis inserts. The tubercles are separated from each other by a deep groove named the intertubercular groove, which contains the long tendon of the biceps brachii.

The articular surface of the head is called the anatomic neck, and provides attachment for the articular capsule of the shoulder joint. The surgical neck is the narrowing below the tubercles and is frequently the site of fracture of the proximal humerus. The body runs from the tubercles, is almost cylindric in its upper half, and gradually flattens and gains a prismatic shape. The radial nerve winds around the posterior aspect of the humerus, running laterally in the radial sulcus toward the forearm. The lower extremities are flattened, broad, and thin proximally, while they are thicker at the two tuberculated eminences (lateral and medial epicondyles). The trochlea and the capitulum of the humerus articulate with the semilunar notch of the ulna and the margin of the radial head, respectively, to form the humeroulnar articulation and the humeroradial articulation.

Fig. 2.1 Anterior and posterior aspects of the humerus.

AO Classification and Coding System for Humeral Fractures

The humerus is assigned the number “1” based on the AO system and is further divided into three zones: 11, proximal fracture; 12, shaft fracture; and 13, distal fracture (▶ Fig. 2.2; ▶ Fig. 2.3).

Epidemiologic Features of Humeral Fractures in the China National Fracture Study

Fig. 2.2 AO codes for humeral fractures.

Fig. 2.3 Algorithm.

Humeral Fractures by Sex in CNFS

Sex distribution of 106 patients with humeral fractures in CNFS is shown in ▶ Table 2.1 and ▶ Fig. 2.4.

Table 2.1 Sex distribution of 106 patients with humeral fractures in CNFS

Fig. 2.4 Sex distribution of 106 patients with humeral fractures in China National Fracture Study (CNFS).

Humeral Fractures by Injury Side in CNFS

Injury side distribution of 106 patients with humeral fractures in CNFS is shown in ▶ Table 2.2 and ▶ Fig. 2.5.

Table 2.2 Injury side distribution of 106 patients with humeral fractures in CNFS

Fig. 2.5 Injury side distribution of 106 patients with humeral fractures in China National Fracture Study (CNFS).

Humeral Fractures by Age Group and Sex in CNFS

Age and sex distribution of 106 patients with humeral fractures in CNFS are shown in ▶ Table 2.3 and ▶ Fig. 2.6.

Fig. 2.6 (a) Age distribution of 106 patients with humeral fractures in China National Fracture Study (CNFS). (b) Age and sex distribution of 106 patients with humeral fractures in CNFS.

Humeral Fractures by Location in CNFS

Segment distribution of 106 patients with humeral fractures in CNFS based on AO classification is shown in ▶ Table 2.4 and ▶ Fig. 2.7.

Fig. 2.7 Segment distribution of 106 patients with humeral fractures in China National Fracture Study (CNFS) based on AO classification.

Humeral Fractures by Causal Mechanisms in CNFS

Causal mechanisms distribution of 106 patients with humeral fractures in CNFS is shown in ▶ Table 2.5 and ▶ Fig. 2.8.

Fig. 2.8 Causal mechanisms distribution of 106 patients with humeral fractures in China National Fracture Study (CNFS).

Clinical Epidemiologic Features of Humeral Fractures

Humeral Fractures by Sex

Sex distribution of 35,678 patients with humeral fractures is shown in ▶ Table 2.6 and ▶ Fig. 2.9.

Table 2.6 Sex distribution of 35,678 patients with humeral fractures

Fig. 2.9 Sex distribution of 35,678 patients with humeral fractures.

Humeral Fractures by Injured Side

Injury side distribution of 35,678 patients with humeral fractures is shown in ▶ Table 2.7 and ▶ Fig. 2.10.

Table 2.7 Injury side distribution of 35,678 patients with humeral fractures

Fig. 2.10 Injury side distribution of 35,678 patients with humeral fractures.

Humeral Fractures by Age Group and Sex

Age and sex distribution of 35,678 patients with humeral fractures are shown in ▶ Table 2.8 and ▶ Fig. 2.11.

Fig. 2.11 (a) Age distribution of 35,678 patients with humeral fractures. (b) Age and sex distribution of 35,678 patients with humeral fractures.

Humeral Fractures by Location

Segment distribution of 21,769 humeral fractures in adults based on AO classification is shown in ▶ Table 2.9 and ▶ Fig. 2.12.

Table 2.9 Segment distribution of 21,769 humeral fractures in adults based on AO classification

Fig. 2.12 Segment distribution of 21,769 humeral fractures in adults based on AO classification.

Segment distribution of 14,041 humeral fractures in children is shown in ▶ Table 2.10 and ▶ Fig. 2.13.

Table 2.10 Segment distribution of 14,041 humeral fractures in children

Fig. 2.13 Segment distribution of 14,041 humeral fractures in children.

Proximal Humeral Fractures (Segment 11)

Anatomic Features

The proximal part of the humerus consists of the head, two eminences, the greater and lesser tubercles, and the surgical neck (▶ Fig. 2.14). The humeral head has a hemispherical shape, which has superior, medial, and posterior aspects. The narrow groove separating the head from the tubercles is the anatomic neck, where fractures rarely occur but there is a high incidence of avascular necrosis due to the disruption of blood supply to the main head fragment. The narrowing below the tubercles, called the surgical neck, is the junction of the two tubercles with the cylindric shaft. It is frequently fractured because the cortex at this part of the bone abruptly becomes quite thin. The greater tubercle is situated laterally and posteriorly to the proximal humerus, and provides insertion points for the supraspinatus, infraspinatus, and teres minor. The ridge descending down the shaft from the root of the greater tubercle is called the crest of the greater tubercle, into which the pectoralis major muscle inserts. The lesser tubercle, situated anteriorly, represents the center of the humeral head and provides an insertion point for the subscapularis. The crest descending from the lesser tubercle has attachments to the latissimus dorsi and the teretiscapularis. The intertubercular groove lodges the long tendon of the biceps brachii (▶ Fig. 2.15; ▶ Fig. 2.16).

AO Classification of Proximal Humeral Fractures

Based on AO classification, the proximal end of the humerus is delineated by a square with its lateral side equal to the maximum width of the epiphysis. The AO coding of proximal humeral fracture is “11,” and is further divided into three categories based on the severity of injury: types A, B, and C (▶ Fig. 2.17).

Fig. 2.14 The proximal part of the humerus.

Fig. 2.15 Features of the proximal part of the humerus.

Fig. 2.16 Radiographic anatomy of the shoulder.

Fig. 2.17 Algorithm.

Clinical Epidemiological Features of Proximal Humeral Fractures (Segment 11)

Sex distribution of 12,959 fractures of segment 11 is shown in ▶ Table 2.11 and ▶ Fig. 2.18.

Table 2.11 Sex distribution of 12,959 fractures of segment 11

Fig. 2.18 Sex distribution of 12,959 fractures of segment 11.

Fractures of Segment 11 by Age Group

Age and sex distribution of 12,959 fractures of segment 11 are shown in ▶ Table 2.12 and ▶ Fig. 2.19.

Fig. 2.19 (a) Age distribution of 12,959 fractures of segment 11. (b) Age and sex distribution of 12,959 fractures of segment 11.

Sex and fracture type distribution of 12,959 fractures of segment 11 are shown in ▶ Table 2.13, ▶ Table 2.14, ▶ Fig. 2.20, and ▶ Fig. 2.21.

Fig. 2.20 (a) Fracture type distribution of 12,959 fractures of segment 11. (b) Sex and fracture type distribution of 12,959 fractures of segment 11.

Fig. 2.21 (a) Fracture group distribution of 12,959 fractures of segment 11. (b) Sex and fracture group distribution of 12,959 fractures of segment 11.

Injury Mechanism

The black arrows in ▶ Fig. 2.22 indicate the directions of displacement of four anatomic structures (1, greater tuberosity; 2, lesser tuberosity; 3, humeral shaft; and 4, humeral head) after fracture, under traction of the rotator cuff muscles, deltoid, and pectoralis major.

Diagnosis

Fig. 2.22 The black arrows indicate the directions of displacement of (1) greater tuberosity, (2) lesser tuberosity, (3) humeral shaft, and (4) humeral head after fracture, under traction of the rotator cuff muscles, deltoid, and pectoralis major.

Fig. 2.23 Radiographic evaluation: anteroposterior (AP) view of scapula.

When obtaining an AP view (▶ Fig. 2.23), the patient stands in a position with the shoulder to be examined in contact with the examining table. The scapula should lie parallel to the cassette and the X-ray beam must be tilted 40 degrees to the plane of the thorax. Good visualization of the subacromial space should be obtained with no overlap of the humeral head and glenoid cavity, resulting in the anterior and posterior rim of the glenoid fossa being superimposed.

To obtain an outlet view (▶ Fig. 2.24), the patient stands in an anterior oblique position, with the anterior aspect of the examined shoulder in contact with the cassette, and the X-ray beam parallel to the scapular spine with the body tilted 40 degrees.

Since the plane of the scapula is 30 to 40 degrees anterior to the coronal plane of the body, the glenohumeral joint inclines anteriorly, and the glenoid fossa directly faces the humeral head posteriorly. The common AP view and transthoracic lateral projection of the shoulder both provide a lateral view of the shoulder joint, neither of which are true reflections of the displacement, angulation, or dislocation of the proximal humeral fracture (▶ Fig. 2.25).

Fig. 2.24 Radiographic evaluation: outlet view of scapula.

To obtain an axillary view (▶ Fig. 2.26), the patient is placed in a supine position with his or her arm abducted 70–90 degrees. The cassette is placed on the superior aspect of the shoulder and the beam can be centered on the axilla.

Since abduction of the shoulder is markedly restricted due to the pain, nowadays a modified axillary view, known as a Velpeau view (▶ Fig. 2.27), is used. In this view, the patient is in a standing position and is tilted backwards ~30 degrees over the cassette on the table. The X-ray beam is then projected vertically from above the shoulder onto the cassette. This view is limited by unavoidable overlapping of structures; thus, a supine projection is the recommended choice of imaging in practice.

Fig. 2.25 Anteroposterior (AP) view and transthoracic lateral projection of the shoulder.

Fig. 2.26 Radiographic evaluation: axillary view of scapula.

Treatment

Fig. 2.27 Radiographic evaluation: Velpeau view.

Humeral Shaft Fractures (Segment 12)

Anatomic Features

The shaft of the humerus (▶ Fig. 2.28) extends from the upper border of the pectoralis major insertion site to the supracondylar ridge distally. The proximal aspect of the humeral shaft is cylindric on cross-section; distally, its anterior–posterior diameter narrows. The medial and lateral intermuscular septa divide the arm into anterior and posterior compartments. The anterior compartment contains the biceps brachii, coracobrachialis, and brachialis muscles. The brachial artery and vein, and median, musculocutaneous, and ulnar nerves course along the medial border of the biceps. The triceps brachii muscle and radial nerve are contained in the posterior compartment. The radial nerve winds around the radial sulcus in between the medial and lateral heads of the triceps brachii, perforating the lateral intermuscular septum at the junction of the middle and distal thirds of the humeral shaft and entering the anterior aspect of the arm, which makes it an easy target when fractures and dislocations occur at this location.

AO Classification for Humeral Shaft Fractures

The humeral shaft segment is coded as number “12” based on the AO classification, and is further divided into three main types depending on fracture morphology: types A, B, and C (▶ Fig. 2.29).

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