Cutaneous Branch of the Obturator Nerve Extending to the Medial Ankle and Foot: A Report of Two Cadaveric Cases

Brittany Staples; Edward Ennedy; Tae Kim; Steven Nguyen; Andrew Shore; Thomas Vu; Jonathan Labovitz; Mathew Wedel

doi:10.1053/j.jfas.2019.03.007

Cutaneous Branch of the Obturator Nerve Extending to the Medial Ankle and Foot: A Report of Two Cadaveric Cases

J Foot Ankle Surg. 2019 Nov;58(6):1267-1272. doi: 10.1053/j.jfas.2019.03.007. Epub 2019 Jul 23.

Authors

Brittany Staples¹, Edward Ennedy², Tae Kim³, Steven Nguyen⁴, Andrew Shore⁵, Thomas Vu⁶, Jonathan Labovitz⁷, Mathew Wedel⁸

Affiliations

¹ Student, Western University of Health Sciences College of Podiatric Medicine, Pomona, CA; Chief Surgical Resident, SSM Health DePaul Hospital, St. Louis, MO. Electronic address: drbstaples@gmail.com.
² Student, Western University of Health Sciences College of Osteopathic Medicine of the Pacific, Pomona, CA; Resident, Medical City Forth Worth and University of North Texas Health Science Center, Fort Worth, TX.
³ Student, Western University of Health Sciences College of Osteopathic Medicine of the Pacific, Pomona, CA.
⁴ Student, Western University of Health Sciences College of Osteopathic Medicine of the Pacific, Pomona, CA; Resident, Einstein Healthcare Network, Philadelphia, PA.
⁵ Student, Western University of Health Sciences College of Osteopathic Medicine of the Pacific, Pomona, CA; Resident, University of Missouri School of Medicine, Kansas City, MO.
⁶ Student, Western University of Health Sciences College of Osteopathic Medicine of the Pacific, Pomona, CA; Resident, Mercy Health, Muskegon, MI.
⁷ Professor, Department of Podiatric Medicine, Surgery, and Biomechanics, and Associate Dean of Clinical Education and Graduate Placement, Western University of Health Sciences College of Podiatric Medicine, Pomona, CA.
⁸ Associate Professor, Department of Anatomy, Western University of Health Sciences College of Osteopathic Medicine of the Pacific and College of Podiatric Medicine, Pomona, CA.

PMID: 31350139
DOI: 10.1053/j.jfas.2019.03.007

Abstract

The area of skin supplied by the cutaneous branch of the obturator nerve (CBO) is highly variable. Although most introductory anatomy texts describe the CBO as innervating only a portion of the medial thigh, there are numerous reports in the literature of CBOs passing the knee to innervate the proximal, middle, or even distal leg. There are no previous reports of CBOs extending to the ankle and foot. Herein we describe 2 cases of CBOs extending at least to the medial foot. Both cases were discovered incidentally, during routine cadaver dissections by osteopathic and podiatric medical students in the anatomy laboratory of Western University of Health Sciences in California. In both instances, the anomalously long CBOs shared several characteristics: (1) they arose as direct branches of the anterior division of the obturator nerve, not from the subsartorial plexus; (2) they coursed immediately posterior to the great saphenous vein from the distal thigh to the distal leg, only deviating away from the saphenous vein just above the medial malleolus; and (3) they terminated in radiating fibers to the posterior half of the medial ankle and foot. In both cases, the saphenous branch of the femoral nerve was present but restricted to the area anterior to the great saphenous vein. It is likely that the variant CBOs carried fibers of the L4 spinal nerve and thus provided cutaneous innervation to the medial foot and ankle, a function most commonly reserved for the saphenous branch of the femoral nerve distal to the knee. Saphenous neuropathy is a common postoperative complication of saphenous cutdowns for coronary artery bypass grafts, so the potential involvement of a long CBO can add additional complexity to regional anesthetic blocks for foot and ankle surgery and procedures such as vein harvesting for coronary artery bypass grafts.

Keywords: anatomic variant; cutaneous nerve; dermatome; great saphenous vein; medial malleolus; obturator nerve; saphenous nerve.

MeSH terms

Aged
Ankle / anatomy & histology*
Cadaver
Foot / anatomy & histology*
Humans
Male
Obturator Nerve / anatomy & histology*