INTRODUCTION

Proximal ulnar fractures in children and adolescents are uncommon, accounting for between 4% and 7% of pediatric and adolescent elbow fractures.^1,2,6,8 As a result, (1) they are often completely missed, (2) the variation in growth centers makes the radiographic interpretation confusing, (3) the precise fracture line is often not appreciated, and (4) the potential for a poor outcome occurs if the displacement is not appreciated. In this chapter, we review fractures of the physis, metaphysis, and coronoid (Table 18-1).

TABLE 18-1 Types of Proximal Ulnar Fracture in the Pediatric Age Group

GROWTH AND DEVELOPMENT

As noted in Chapter 1, at birth none of the articular elements of the ulna, including the coronoid and olecranon, are ossified. At age 9, the secondary center of ossification appears at the olecranon (Fig. 18-1). The ossification center may be bipartite and eccentric, and as the proximal ulna grows, the growth plate orientation alters from transverse to oblique. Closure of the physis begins at the articular surface and progresses toward the extensor surface of the bone. Just before fusion of the growth plate, the metaphyseal bone develops a sclerotic margin and may be widely separated from the apophysis, resembling a fracture. These vagaries can make it difficult to recognize a fracture of the olecranon in a child, and comparative views of the opposite side are often valuable.² Although a secondary center may appear in the olecranon tip, there is no secondary ossification center of the coronoid. This helps explain the fracture pattern observed in the proximal ulna of the various age groups (Fig. 18-2).

FIGURE 18-1 Schematic of ossification of the proximal ulna observed at birth (A) and at adolescence (B). This explains the fracture patterns seen in the young and the adolescent age groups.

FIGURE 18-2 Fracture of the apophysis may (open arrow) or may not (closed arrow) include the coronoid process.

APOPHYSEAL FRACTURE

Apophyseal fractures are extremely rare. Reviewing his experience and that of the literature up to 1991, Wilkins¹⁷ identified only 16 such cases. As a matter of fact, a review of the literature of the less rare olecranon or proximal ulnar fracture resulted in the identification of 192 cases but no mention of a fracture of the apophysis.¹⁷

The fracture may or may not include the coronoid as the fracture line passes between the growth center and the proximal ulna (see Fig. 18-2). This is because the coronoid does not develop from a separate growth center; thus, the fracture line in this rarest of fractures may be rather variable (Fig. 18-3).

FIGURE 18-3 A 13-year-old boy slipped and fell onto his left arm and presents with point tenderness over his olecranon. (A) Lateral radiograph suggests an olecranon apophysis fracture, which is confirmed by comparison with the contralateral uninjured elbow (B). At the time of his olecranon fracture, the patient was using crutches because he had sustained a left femur fracture 1 month earlier in a motor vehicle accident. The decision was made to perform open reduction with tension band internal fixation (C).

METAPHYSEAL FRACTURE

Metaphyseal fractures, although more common than fracture of the apophysis, still account for only approximately 5% of elbow injuries.^3,11,15 Wilkins¹⁷ identified only 230 cases among 4,684 proximal ulnar fractures reported in the child before 1991. It appears that there is a biphasic frequency by age, with the greatest early frequency occurring between 5 and 6 years¹²