Lumbar foot innervation of the medial foot and ankle region.
BACKGROUND
Differences in the dermatomal maps appearing in standard anatomic texts which are in common use may lead to diagnostic confusion in the assessment of patients who suffer from nerve root deficiency. This is particularly evident in the variable depiction of the L4 nerve root dermatome which is carried distally in the saphenous nerve. The purpose of this study is to establish the distal limit of L4 nerve root innervation in the foot by performing cadaveric dissection of the saphenous nerve.


METHODS
Dissection of the dorsum of the medial foot and ankle was performed on 20 cadaveric specimens.


RESULTS
The saphenous nerve was found to enter the dermis of the medial ankle region (mean = 14.75 mm) distal to the tip of the medial malleolus in the direction of the hallux. In three cases the nerve terminated proximal to the medical malleolus. In all cases the medial forefoot and hallux were supplied by the most medial branch of the superficial peroneal nerve.


CONCLUSIONS
These findings suggest that the sensory component of the L4 nerve root terminates in most cases near the medical malleolus, well proximal to the bunion area of the forefoot.
Department of Orthopaedics, Prince Charles Hospital, Brisbane, Queensland, Australia.
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RP
Williams
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Sugars
D000842:Ankle / Q000294:innervation*; D002102:Cadaver; D005528:Foot / Q000294:innervation*; D006801:Humans; D008160:Lumbosacral Plexus / Q000033:anatomy & histology*; D010525:Peripheral Nerves / Q000502:physiology; D012677:Sensation; D013126:Spinal Nerve Roots / Q000033:anatomy & histology / Q000502:physiology