2030 Below the Arcuate Line: Implications for Surgical Treatment of ACNES

INTRODUCTION: Abdominal anterior cutaneous nerve entrapment syndrome (ACNES) is characterized by chronic, undifferentiated abdominal wall pain. ACNES is caused by compression of cutaneous branches of one or more intercostal nerves (T7-T12) at the fascial foramen of the rectus sheath. Surgical techniques have only described neurectomy at the anterior and posterior rectus sheath above the arcuate line where both an anterior and posterior rectus sheath are present. METHODS: We provide a detailed anatomical description of the anterior cutaneous nerves below the arcuate line including the ACNES surgical approach for treating anterior cutaneous nerves arising from T11 and/or T12. RESULTS: The arcuate line is approximately one-half the distance from the umbilicus to the pubic symphysis. Above this line the internal oblique fascia divides into two lamina, surrounding the rectus abdominus, providing a robust anterior and posterior rectus sheath. Across this line, the posterior lamina migrates anteriorly, fusing with the anterior fascia. The anterior cutaneous nerves course between the internal oblique and transversus abdominis muscles, piercing both layers of the rectus sheath anteriorly. Above the arcuate line, this may lead to compression at the anterior or posterior rectus sheath. Below the arcuate line, there is no significant posterior rectus sheath, leaving a single site of compression. CONCLUSIONS: The course of anterior cutaneous nerves and the anatomy of the abdominal wall are anatomically unique below the arcuate line which becomes important when treating lower abdominal pain when in patients with T11 or T12 nerve ACNES. There is debate in the literature as to when an anterior or posterior decompression are needed, however, given the above anatomical constraints, decompression below the arcuate line likely only requires addressing compression at the level of the anterior rectus sheath.