The saphenous nerve in foot and ankle surgery: Its variable anatomy and relevance

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Abstract

Background

Several studies have raised doubt regarding the role of the saphenous nerve (SN) in the foot, and some authors omit the SN from ankle blocks. Our aim was to assess the SN anatomy with reference to foot and ankle surgery.

Methods

In 29 cadaveric feet the SN was traced to its termination. At the ankle, the distances from the SN to the tibialis anterior tendon (TAT) and the long saphenous vein (LSV) were recorded.

Results

In 24 specimens, a SN was present at the ankle, and in 19 specimens extended to the foot. The mean distances from the nerve to the TAT and LSV were 15 mm and 4 mm respectively. The nerve reached the first metatarsal (MT) in 28% of specimens.

Conclusion

Although the SN anatomy is less extensive than previously described, it often reaches the first MT and therefore should routinely be included in ankle blocks for forefoot surgery.

Introduction

The saphenous nerve (SN) is classically described as innervating the skin of the medial foot and ankle, extending as far as the great toe [1], [2]. However, there is debate regarding the anatomy and relevance of this nerve in relation to the cutaneous supply of the forefoot. Some authors do not routinely include the SN when performing ankle blocks for forefoot surgery [3], [4], [5]. Several anatomical studies have shown that the SN rarely reaches the great toe and often terminates at the ankle joint [6], [7], [8]. It has also been shown that the superficial peroneal nerve consistently supplies a terminal branch to the dorsomedial forefoot which raises further doubt over the role of the SN in the foot [7], [9]. The aim of the current study was revisit the anatomy of the SN and define its course in the foot and ankle with reference to surgical incisions and ankle blocks.

Section snippets

Methods

29 fresh frozen adult cadaveric specimens (14 pairs, 1 single) were obtained from 8 females and 7 males. The mean age of the specimens was 67 years old (range 51–83). The mean distance from the anteromedial ankle joint to the first metatarsal head measured 12.9 cm (SD ± 0.8 cm) (Fig. 1).

Specimens were dissected from 10 cm proximal to the ankle joint. The SN was identified and exposed to its distal termination. At the ankle joint the distances were measured from the nerve to the tibialis anterior

Anatomy of the SN relative to the medial malleolus (Figs. 2 and 3)

In 24 of the 29 specimens (83%), the SN was identified at the level of the ankle joint. In 4 specimens the SN was completely absent, and in one specimen the SN terminated 3.2 cm proximal to the ankle joint. In a further 5 specimens the SN terminated at the level of the ankle joint. In only 19 of the 29 specimens was the SN identified extending into the foot.

In the 24 specimens with a SN present at the ankle joint, the number of branches was variable. 6 specimens had a single branch (25%), 10

Discussion

Several anatomical studies have demonstrated that the SN often terminates at the ankle joint [7], [8] and also that the superficial peroneal nerve consistently supplies a terminal branch to the dorsomedial forefoot [7], [9]. Such studies contradict the textbook description that the SN innervates the great toe [1], [2], and may explain why some authors do not routinely include the SN when performing ankle blocks for forefoot surgery [3], [4], [5]. Considering such controversy, the aim of the

Limitations

Although the sample size used in the current study is larger than other anatomical studies [6], [7], [15], [16], our findings may still be limited by sample size, especially considering the high variability in anatomy of the saphenous nerve. A variable nerve pattern was often observed between specimens from the same pair, therefore we did not consider the use of paired specimens to be an additional limitation. Visual aids such as surgical loupes or microscopes were not used, which may have

Conclusion

The saphenous nerve is at risk in various foot and ankle procedures, including anteromedial arthroscopy portal placement. Our study provides a detailed and clinically relevant description of the SN. We have demonstrated that this nerve has considerable variation in its course in the foot and ankle in relation to easily identifiable landmarks. The distal termination of the saphenous nerve is not as extensive as described in anatomy texts (in no specimen did the saphenous nerve reach the great

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