Pain management of the acutely injured patient with rib fractures can be difficult for even the most experienced emergency physician. Severe pain from multiple rib fractures (or even one) can impair ventilatory function, decreasing the ability to clear respiratory secretions and increasing rates of nosocomial pneumonias.^1,2 A multimodal approach to pain control via intravenous medications (eg, opioids, ketamine, acetaminophen, etc.) is reasonable but often insufficient. Epidural analgesia, recommended strongly by trauma guidelines for patients with multiple rib fractures, is often not acutely available in the emergency department. An opioid-sparing multimodal approach that integrates regional anesthesia is believed to be optimal for patients.³ Alternatives such as intercostal blocks are time-intensive, involve multiple injections, are often more difficult to perform, and necessitate patient repositioning.⁴ The ultrasound-guided serratus anterior plane block (SAPB) is a promising single-injection method to anesthetize the chest wall in patients with multiple rib fractures, providing optimal emergency department care.¹

Anatomy and Innervation

Figure 1A: View of the thoracic intercostal nerves as they exit the spine inferior to the ribs.
Figure 1B: The serratus anterior muscle sits between the pectoralis muscle (anterior) and latissimus dorsi muscle (posterior).

The chest wall is innervated from the lateral cutaneous branches of the thoracic intercostal nerves (T2–T12). The thoracic intercostal nerves run with the intercostal artery and vein, just under the rib, traveling in an anterolateral direction. As the thoracic intercostal nerve reaches the midaxillary line, the lateral cutaneous branch of the intercostal nerve pierces the internal intercostal muscle, external intercostal muscle, and serratus anterior muscle to innervate the musculature of the thorax. The serratus anterior muscle is a