Humerus Fracture Secondary to Shoulder Dystocia

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A male infant born to a 35-year-old woman (gravida 4, para 2-0-1-2) at 39 weeks’ gestation was noted to have no right arm movement after birth. The mother was in labor for 18 hours and was given an epidural block. The fetus presented in the occipitoanterior position with right shoulder dystocia, which was reduced for vaginal delivery. Apgar scores were 5 and 8 at 1 and 5 minutes, respectively. The infant required blow-by oxygen therapy for only few minutes. During examination, the newborn did not use his right arm but moved his fingers with good hand grasp. His clavicles were intact. All other findings were normal.

A radiograph of the right upper extremity showed a complete transverse fracture through the midshaft of the right humerus, with mild valgus angulation at the fracture site.

When a newborn has no upper limb movement at birth, the most commonly considered causes are clavicle fracture and brachial plexus injury. However, the differential diagnosis also includes humeral fracture.¹ The incidence of long bone fractures in newborns is 0.05 per 1000 vaginal births and 0.2 per 1000 cesarean section births.^2,3 Long bone fractures coexist with brachial plexus injuries in 10% of newborns with these injuries.^4,5 In neonates born with shoulder dystocia, the association with humeral fractures is 0.4% to 4.2%.⁶ In humeral fractures, often the proximal third of the humerus is involved with a complete transverse fracture. The risks for long bone fractures are breech position, cesarean section, low birth weight, macrosomia, and shoulder dystocia.

Frequent findings on clinical examination are preserved bicep reflex with decreased motion, swelling at the fracture site, and pain with palpation or passive range of motion of the limb.⁷ Diagnosis of long bone fracture is usually confirmed by 2 radiographic views. When physis involvement is a concern, clinicians should obtain an ultrasonogram at birth or plain radiographs within 7 to 10 days to evaluate for a callous site.⁸ If multiple fractures are present at birth, one must consider osteogenesis imperfecta in the differential.

Treatment of long bone fractures consists of immobilization and splinting for about 2 weeks’ duration. Pinning the sleeve of the affected limb to the chest helps with immobilization. Because of the high incidence of brachial plexus injuries in long bone fractures, follow-up must include a thorough neurological examination.

This newborn’s right arm was immobilized for 2 weeks; he was then allowed to have normal activity. The fracture had healed completely by 4 months of age. ■