Intercostal nerve electrodiagnostic testing in rib fractures.

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 pain, atrophy, and eventual eventration, which may be an underrecognized and thus undertreated complication of rib fractures. We investigated the clinical utility of intercostal nerve electrodiagnostic testing following rib fractures to diagnose and localize nerve injury at levels T7 and below. Five patients with displaced bicortical rib fractures involving the 7th-11th ribs and clinical eventration of the ipsilateral abdominal wall underwent intercostal nerve conduction studies (NCS) and needle electromyography (EMG) on the affected side. EMG of the rectus abdominis and intercostal muscles was performed with ultrasound guidance, and ultrasound measurements of rectus abdominis thickness were obtained to assess for atrophy. Average patient age was 59.4 years and average body mass index (BMI) was 31.5 kg/m2. Intercostal NCS and EMG were able to reliably diagnose and localize intercostal nerve damage after rib fractures. Ultrasound demonstrated an average rectus abdominis transverse cross-sectional thickness of 0.534 cm on the affected side, compared with 1.024 cm on the non-affected side. Intercostal electrodiagnostic studies can diagnose and localize intercostal nerve damage after displaced rib fractures. Musculoskeletal ultrasound can be used to diagnose and quantify rectus abdominis atrophy and to accurately and safely guide needle EMG to the intercostal and rectus abdominis muscles.