Intercostal nerve injury after rib fractures: A case series correlating electrodiagnostic testing with imaging, ultrasound, and surgical findings.

Abstract

Intercostal nerve injury can occur after rib fractures, resulting in denervation of the abdominal musculature. Loss of innervation to the rectus abdominis and intercostal muscles can cause atrophy and subsequent eventration, pain, and cosmetic issues. Intercostal electrodiagnostic testing can diagnose and localize intercostal nerve damage after rib fractures at levels T7 and below. To characterize rib fracture patterns associated with intercostal nerve injury and evaluate the diagnostic and surgical utility of preoperative nerve conduction study/electromyography (NCS/EMG) findings. Eight patients with NCS/EMG-diagnosed intercostal nerve injury following rib fractures were included in the study. A total of 17 levels with intercostal nerve damage were identified on electrodiagnostic testing. Descriptive rib fracture characteristics were obtained from preoperative chest computed tomography by a single chest wall surgeon and analyzed for displacement, degree of rib separation, fracture location, and presence of intercostal muscle, lung, and retroperitoneal hernias. Preoperative electrodiagnostic testing results were correlated with computed tomography rib fracture characteristics, ultrasound measurements of rectus abdominis cross sectional thickness, and direct intraoperative intercostal nerve evaluation using an intraoperative nerve stimulator. At the level of NCS/EMG-diagnosed intercostal nerve injury, 50% ribs were displaced and 50% were nondisplaced. Two levels demonstrated evidence of intercostal hernia, one with lung hernia and one with retroperitoneal hernia. The average degree of separation of rib fractures was 1.45 cm with two ribs demonstrating 0 cm of separation. With regard to rib fracture location, 29% were posterior, 41% posterolateral, and 23% lateral. Seven of eight patients (total of 15 nerves) underwent surgical intervention in the form of neurolysis versus intercostal nerve reconstruction with allograft nerve tissue. Direct intraoperative intercostal nerve stimulation correlated with the presence of intercostal nerve injury identified on preoperative NCS/EMG findings in 12 of 15 cases (80%). Two intercostal nerves were not explored secondary to significant intercostal trauma. A single level discrepancy was identified between preoperative NCS/EMG and intraoperative findings in one case. Ultrasound measurements demonstrated an average rectus abdominis transverse cross-sectional thickness of 0.66 cm on the affected side, compared with 1.04 cm on the nonaffected side (p = .01) and demonstrated a decrease in cross-sectional thickness as represented as a percentage of the contralateral, nonaffected side when measured against time from rib fracture (R² = 0.432). The present case series describes the rib fracture characteristics, ultrasound assessment, and interoperative intercostal nerve stimulation findings of patients with preoperative NCS/EMG-diagnosed intercostal nerve injury after rib fractures. Intercostal nerve damage resulting in rectus abdominis atrophy after rib fractures may be an underrecognized and thus undertreated complication of rib fractures. Preoperative electrodiagnostic testing demonstrates high diagnostic accuracy and can guide surgical planning. Awareness of high-risk fracture patterns may improve clinical decision-making and outcomes in rib fracture management.