Download Variation of Nerve to Flexor Hallucis Brevis

FOOT & ANKLE INTERNATIONAL
Copyright  2008 by the American Orthopaedic Foot & Ankle Society
DOI: 10.3113/FAI.2008.1042
Variation of Nerve to Flexor Hallucis Brevis
Loretta B. Chou, MD; Lisa E. Choi, MD; Tara Ramachandra, BS; Gene Ma, BS
Stanford, CA
pollicis brevis. In comparing Hallopeau’s nerve to the aforementioned anastomoses, we draw an anatomical, rather than
functional, analogy.
The purpose of this study was to determine the presence
of this neural anastomosis in cadaveric specimens. It has
only been described once and may be of clinical significance
in the foot. In addition, we evaluated the gross anatomy
of Hallopeau’s nerve and its anastomosis with the medial
plantar nerve.
ABSTRACT
Background: Hallopeau’s nerve is a branch of the lateral
plantar nerve that supplies the flexor hallucis brevis muscle
while also forming an anastomosis with the medial plantar
nerve. In this study, the presence of this neural anastomosis was
determined through dissection of cadaveric specimens. Materials
and Methods: Twenty-six fresh-frozen adult feet (13 matched
pairs) were dissected to assess the presence or absence of Hallopeau’s nerve. Results: Dissections revealed four out of 26 specimens had this anastomosis. Conclusion: This study confirms this
anatomic variation. Clinical Relevance: The clinical significance
of these anastomoses remains unknown. These anastomoses are
analogous to some in the hand and forearm.
MATERIALS AND METHODS
Twenty-six fresh frozen adult cadaveric feet (13 matched
pairs) were dissected from the mid-tibia to investigate the
innervation of the flexor hallucis brevis muscle and the
course of the medial and lateral plantar nerves. The skin and
subcutaneous tissue were removed from the tarsal tunnel and
followed to the plantar aspect of the foot. The posterior tibial
nerve was identified at the tarsal tunnel and carefully traced
as it bifurcated into the medial and lateral plantar nerves.
The terminal branches of these nerves were identified. In
particular, the presence of a terminal branch of the lateral
plantar nerve crossing transversely into the flexor hallucis
brevis muscle was explored. If this neural anastomosis was
present, it was photographed.
Key Words: Hallopeau; Nerve of the Foot; Medial Plantar
Nerve; Lateral Plantar Nerve; Flexor Hallucis Brevis Muscle
INTRODUCTION
Hallopeau’s nerve of the foot was described in a brief
article published in 1900 that reported that the nerve is a
branch of the lateral plantar nerve that supplies the flexor
hallucis brevis muscle and communicates by anastomosis
with the medial plantar nerve (Figure 1).5 Although it has
not been discussed in any article in over a century, we
believe Hallopeau’s nerve can potentially be clinically important. The analogous anastamoses of the forearm and hand
have been studied heavily, and their clinical importance
has been established.2,3,6,7,12 – 16 The course of the Hallopeau nerve of the foot is analogous to the Riche-Cannieu
anastomosis, which provides dual innervation to the flexor
RESULTS
In four specimens, the neural anastomosis was present
(Figure 2). The nerve was a small terminal branch of the
lateral plantar nerve. When present, it clearly entered the
midportion of the midsubstance of the flexor hallucis brevis
muscle. The nerve was found on three right feet and one
left, with none present in both feet of a matched pair. The
medial plantar nerve was found to have a uniform course. It
innervated both heads of the flexor hallucis brevis muscle.
The flexor hallucis brevis muscle was the same size when
the nerve was found to be present. There were no observed
first ray structural abnormalities with or without this neural
anastomosis.
No benefits in any form have been received or will be received from a commercial
party related directly or indirectly to the subject of this article.
Corresponding Author:
Loretta B. Chou, MD
Stanford University Medical Center
Department of Orthopaedic Surgery
300 Pasteur Drive
Room R111, MC 5343
Stanford, CA 94305-5343
E-mail: [email protected]
For information on prices and availability of reprints, call 410-494-4994 x226
1042
Downloaded from fai.sagepub.com at PENNSYLVANIA STATE UNIV on September 18, 2016
Foot & Ankle International/Vol. 29, No. 10/October 2008
FLEXOR NERVE VARIATION
1043
Fig. 2: Dissection of the fresh frozen matched pairs revealed four specimens
with Hallopeau’s nerve. The nerve (small black arrow) is traced from the
lateral plantar nerve (large white arrow) as it crosses medially to insert into
the flexor hallucis brevis muscle (large black arrow). The medial plantar
nerve is also present over the flexor hallucis brevis (small white arrow).
Fig. 1: This is the original illustration by Hallopeau, published in 1900
(Reproduced by kind permission of Bulletin and Memories of the Anatomical Company of Paris, 1900, p 1079).
DISCUSSION
Henri Hallopeau was a French dermatologist who lived
from 1842 to 1919. In his article, he described the nerve as
the “lateral adductor nerve” that crossed transversely into the
flexor hallucis brevis muscle. Furthermore, he described the
main nerve ending bending upward and passing superficial to
the muscle. He also noted it to delve into the inner fascicule
of the fibers of the muscle. The anastomosis was spindly and
ended in the thickness of the muscle superficial or deep to
the tendon of the flexor hallucis longus. He also stated that
he had not yet done the necessary research to determine the
significance of the anastomosis.
In Sarrafian’s16 description of the nerves of the plantar
aspect of the foot, the medial plantar nerve divides into
a medial and lateral branch. The medial branch courses
anteromedially over the medial head of the flexor hallucis
brevis and provides innervation to both heads of the flexor
hallucis brevis muscle. Additionally, the lateral branch of
the medial plantar nerve can innervate the lateral head of the
flexor hallucis brevis. There is no mention of an anastomotic
branch from the lateral plantar nerve.
In our investigation of Hallopeau’s nerve, four nerves were
found in 26 specimens. This demonstrates that anatomic
variation exists among individuals with respect to this
nerve. The analogy to Hallopeau’s nerve may well be the
communicating branch between the medial and lateral plantar
nerves, often responsible for Morton’s neuroma.11,16 In the
Jones and Klenerman study, 20 cadaveric feet were dissected
and this communicating branch was found to be present in
all feet.8 The Jones and Klenerman study stated regarding
this type of communication: “similar variations in the sole
of the foot have not been documented before, as far as we are
aware.” Hallopeau’s nerve is an exception to their finding.
In contrast to the limited information available regarding
the anastomosis of Hallopeau’s nerve and medial plantar
nerve, the analogous anastomosis of the hand and forearm
have been well studied. These anastomoses of the hand
and forearm have proven to be of importance for surgical
procedures as well as for their involvement in carpal tunnel
syndrome.2,3,6,7,12,13,15,17
The Martin-Gruber anastomosis, a median to ulnar communication of the forearm, is present in 15% to 25% of
specimens.2,13 In the anastomosis described by Riche12 and
Cannieu,1 the deep branch of the ulnar nerve and the recurrent branch of the median nerve innervate the deep and superficial heads of the flexor pollicis brevis, respectively. Harness
and Sekeles detected the anastomosis in 27 of 35 (77%)
hands and elaborated upon the paths taken by the nerve’s
tunnel.6 The authors concluded that the thenar muscles have
a double motor innervation. The clinical significance of this
Downloaded from fai.sagepub.com at PENNSYLVANIA STATE UNIV on September 18, 2016
1044
CHOU ET AL.
Foot & Ankle International/Vol. 29, No. 10/October 2008
anatomical relationship has been demonstrated by Highet,7
who detected that flexor pollicis brevis function was spared
in 40 of 45 patients with complete division of the median or
ulnar nerves. Falconer and Spinner2 performed high magnification dissections of ten specimens and found the RicheCannieu anastomosis in three.
While the purpose of this study was to determine the
presence of Hallopeau’s nerve, we can not comment on
the incidence in the general population or its definitive
clinical importance. We may infer that because the course of
Hallopeau’s nerve of the foot is anatomically analogous to
the Riche-Cannieu anastomosis, Hallopeau’s nerve may have
some clinical meaning or purpose. One instance may be an
isolated injury to the medial plantar nerve, with sparing of the
motor function of the flexor hallucis brevis muscle. Another
instance may be an ulcerative lesion on the plantar aspect
of the medial forefoot in a diabetic patient. This common
site of injury in diabetic patients bears a significant amount
of weight, making wound healing even more difficult.3,10 A
flexor hallucis brevis muscle that can be mobilized distally
and proximally could be transposed to facilitate this healing
process when conservative measures are unsuccessful. In
cases where this muscle has dual innervation, it may be more
suitable for transfer and transplant procedures to cover an
ulcer of the plantar medial forefoot.4,10 Thus, further study
to reveal the clinical implications of Hallopeau’s nerve could
prove a muscle with redundant nervous supply may be more
useful in transfer and transplant procedures to cover an ulcer
of the plantar medial forefoot. Thus, further study to reveal
the clinical implications of Hallopeau’s nerve could prove to
be valuable.
REFERENCES
1. Cannieu, JMA: Recherche sur l’innervation de l’eminence thenar par
le cubital. J Med Bordeaux. 377, 1896.
2. Falconer, D; Spinner, M: Anatomic variations in the motor and sensory
supply of the thumb. Clin Orthop Rel Res. 195: 83 – 96, 1985.
3. Ferrari, GP; Gilbert, A: The superficial anastomosis on the palm
of the hand between the ulnar and median nerves. J Hand Surg.
16B:511 – 514, 1991.
4. Ger, R: Clinical anatomy of the flexor hallucis brevis muscle. Clin
Anat. 1:117 – 124, 1988. http://dx.doi.org/10.1002/ca.980010205
5. Hallopeau, MP: Note sur le nerf de l’adducteur oblique du gros orteil.
Société Anatomique 2:1078, 1900.
6. Harness, D; Sekeles, E: The double anastomotic innervation of thenar
muscles. J Anat. 109:461 – 466, 1971.
7. Highet, WB: Innervation and function of the thenar muscles. Lancet.
I:227 – 230, 1943.
8. Jones, JR; Klenerman, L: A study of the communicating
branch between the medial and lateral plantar nerves. Foot Ankle.
4:313 – 315, 1984.
9. Komar, J; Szalay, M; Mate, A: A disease pattern simulating a
cubitocarpal “double-tunnel” syndrome due to anastomosis after MartinGruber. Fortschr Neurol Psychiatr Grenzgeb. 48:612 – 615, 1980.
10. Macchi, V; Tiengo, C; Porzionato, A; et al.: Correlation between
the course of the medial plantar artery and the morphology
of the abductor hallucis muscle. Clin Anat. 18:580 – 588, 2005.
http://dx.doi.org/10.1002/ca.20147
11. Morton, TG: A peculiar and painful affection of the fourth metatarsophalangeal articulation. J. Med. Sci. 71:37 – 45, 1876.
12. Riche, P: Le nerf cubital et les muscles de l’minance thenar. Bull Mem
Soc Anat Paris. 72:251, 1897.
13. Rowntree, T: Anomalous innervation of the hand muscles. J Bone Joint
Surg. 31B:505 – 510, 1949.
14. Rotman, MD; Donovan, JP: Practical anatomy of the carpal
tunnel. Hand Clin. 18:219 – 230, 2002. http://dx.doi.org/10.1016/S07490712(01)00003 – 8
15. Sachs, GM; Raynor, EM; Shefner, JM: The all ulnar motor
hand without forearm anastomosis. Muscle Nerve. 18:309 – 313, 1995.
http://dx.doi.org/10.1002/mus.880180307
16. Sarrafian, SH: Nerves. In Sarrafian, SH: Anatomy of the foot and ankle,
2nd ed., Philadelphia, JB Lippincott Company, pp. 376 – 377, 1993.
17. Tomagawa, C; Shiga, K; Ohshima, Y; Tokunaga, D; Nakagawa,
M: Riche-Cannieu anastomosis and a paradoxical preservation of the
thenar muscles in carpal tunnel syndrome: a case report. No To Shinkei.
56:53 – 58, 2004.
Downloaded from fai.sagepub.com at PENNSYLVANIA STATE UNIV on September 18, 2016