A Morphometric Study of the Obturator Nerve around the Obturator Foramen

OBJECTIVE: Obturator neuropathy is a rare condition. Many neurosurgeons are unfamiliar with the obturator nerve anatomy. The purpose of this study was to define obturator nerve landmarks around the obturator foramen. METHODS: Fourteen cadavers were studied bilaterally to measure the distances from the nerve root to relevant anatomical landmarks near the obturator nerve, including the anterior superior iliac spine (ASIS), the pubic tubercle, the inguinal ligament, the femoral artery, and the adductor longus. RESULTS: The obturator nerve exits the obturator foramen and travels infero-medially between the adductors longus and brevis. The median distances from the obturator nerve exit zone (ONEZ) to the ASIS and pubic tubercle were 114 mm and 30 mm, respectively. The median horizontal and vertical distances between the pubic tubercle and the ONEZ were 17 mm and 27 mm, respectively. The shortest median distance from the ONEZ to the inguinal ligament was 19 mm. The median inguinal ligament lengths from the ASIS and the median pubic tubercle to the shortest point were 103 mm and 24 mm, respectively. The median obturator nerve lengths between the ONEZ and the adductor longus and femoral artery were 41 mm and 28 mm, respectively. CONCLUSION: The obturator nerve exits the foramen 17 mm and 27 mm on the horizontal and sagittal planes, respectively, from the pubic tubercle below the pectineus muscle. The shallowest area is approximately one-fifth medially from the inguinal ligament. This study will help improve the accuracy of obturator nerve surgeries to better establish therapeutic plans and decrease complications.

Lumbosacral Plexopathy Caused by Presacral Recurrence of Colon Cancer Mimicking Degenerative Spinal Disease: A Case Report

Radiculopathy triggered by degenerative spinal disease is the most common cause of spinal surgery, and the number of affected elderly patients is increasing. Radiating pain that is extraspinal in origin may distract from the surgical decision on how to treat a neurological presentation in the lower extremities. A 54-year-old man with sciatica visited our outpatient clinic. He had undergone laminectomy and discectomy to treat spinal stenosis at another hospital, but his pain remained. Finally, he was diagnosed with a plexopathy caused by late recurrence of colorectal cancer, which compressed the lumbar plexus in the presacral area. This case report illustrates the potential for misdiagnosis of extraspinal plexopathy and the value of obtaining an accurate history. Although the symptoms are similar, spinal surgeons should consider both spinal and extraspinal origins of sciatica.