Download Saphenous and Infrapatellar Nerves at the Adductor Canal

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Saphenous and Infrapatellar Nerves at the
Adductor Canal: Anatomy and Implications
in Regional Anesthesia
Sofia Anagnostopoulou, MD; George Anagnostis, MD; Theodosios Saranteas, MD;
Andreas F. Mavrogenis, MD; Tilemachos Paraskeuopoulos, MD
abstract
Conflicting data exist regarding the anatomical relationship of the saphenous
and infrapatellar nerves at the adductor canal and the location of the superior
foramen of the canal. Therefore, the authors performed a cadaveric study to
detail the relationship and course of the saphenous and infrapatellar nerves
and the level of the superior foramen of the canal. The adductor canal and
subsartorial compartment were dissected in 17 human cadavers. The distance between the superior foramen of the canal and the mid-distance (MD)
between the base of the patella and the anterior superior iliac crest were
measured; the course of the saphenous and infrapatellar nerves and the level
of origin of the infrapatellar branch were detailed. In 13 of 17 specimens,
the superior foramen of the adductor canal was distal to the MD (mean,
6.5 cm); in the remaining specimens, it was proximal to the MD. In 12 of
17 specimens, the infrapatellar branch exited the canal separately from the
saphenous nerve; in the remaining specimens, it originated caudally to the
canal. In all dissections, the infrapatellar branch had a constant course in
close proximity to the saphenous nerve within the canal and between the
sartorious muscle and femoral artery caudally to the canal. Most commonly,
the superior foramen of the adductor canal is located caudally to the MD;
the infrapatellar branch originates from the saphenous nerve within the canal
and has a constant course in close proximity to the saphenous nerve. These
observations should be considered for regional anesthesia techniques at the
adductor canal. [Orthopedics. 2016; 39(2):e259-e262.]
T
he adductor, subsartorial, or Hunter’s canal is an aponeurotic intermuscular tunnel in the middle
third of the thigh. It extends from the apex
of the femoral triangle to the adductor
hiatus. Its boundaries include the sarto-
MARCH/APRIL 2016 | Volume 39 • Number 2
rius anteriorly, the adductor longus and
adductor magnus posteromedially, and
the vastus medialis laterally. The canal
contains the femoral artery, femoral vein,
and branches of the femoral nerve, more
specifically the saphenous nerve and the
nerve to the vastus medialis. The saphenous nerve passes beneath the sartorius
and lies in front of the artery, behind the
aponeurotic covering of the adductor canal, as far as the opening in the lower part
of the adductor magnus, where it emerges
from behind the lower edge of the aponeurotic covering of the canal.1,2 The infrapatellar branch is the largest branch of the
saphenous nerve; it pierces the sartorius
and fascia lata and is distributed to the
skin in front of the patella.3
Anatomical studies have shown that
the distribution of the infrapatellar branch
demonstrates significant variability.3-9
This nerve communicates above the knee
with the anterior cutaneous branches of the
femoral nerve and/or the obturator nerve,8
below the knee with other branches of the
The authors are from the Department of
Anatomy (SA, GA, TP), the Department of Anesthesiology (TS), and the First Department of
Orthopaedics (AFM), National and Kapodistrian
University of Athens, School of Medicine, Athens,
Greece.
The authors have no relevant financial relationships to disclose.
Correspondence should be addressed to: Sofia
Anagnostopoulou, MD, Department of Anatomy,
National and Kapodistrian University of Athens,
School of Medicine, 75 Mikras Assias Str, 11527
Goudi, Athens, Greece ([email protected]).
Received: April 8, 2015; Accepted: July 6,
2015.
doi: 10.3928/01477447-20160129-03
e259
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B
A
saphenous nerve, and on the lateral side of
the joint with branches of the lateral femoral cutaneous nerve, forming the plexus
patellae.5-8 As yet, the exact anatomical
relationship between the adductor canal
and the region where the saphenous nerve
gives off the infrapatellar branch has not
been described. In addition, conflicting
data exist concerning the exact anatomic
level of the superior foramina of the adductor canal.10,11
The current authors performed this cadaveric study to describe the anatomical
relationship of the saphenous nerve and
its infrapatellar branch at the level of the
adductor canal and to precisely delineate
the anatomic area that the infrapatellar
branch separates from the main trunk of
the saphenous nerve. Possible implications for regional anesthesia techniques
are also analyzed.
Materials and Methods
Seventeen lower extremities from 11
adult human formalin-embalmed cadavers (mean age, 71±11 years; male/female
ratio, 4/7) were dissected at the anatomy
department of the authors’ institution.
Approval for this study (No. 1056; 27-92010) was provided by the Committee of
the Medical School of the University of
Athens, Athens, Greece. Cadavers were
in the legal custody of the Department
of Anatomy at the Medical School of the
University of Athens, Athens, Greece. All
e260
Figure 1: Illustration showing the medial anatomy of
the thigh and the adductor canal. Abbreviations: a, artery; m, muscle; n, nerve; v, vein (A). Diagram showing the branching of the saphenous nerve. Abbreviations: I, infrapatellar branch; S, saphenous nerve (B).
cadavers were donated for teaching and
research purposes.
Each cadaver was placed in the supine
position with the legs abducted. The skin
and subcutaneous tissues of the anterior
and medial thigh from the level of the inguinal ligament to the level of the medial
tibial condyle were carefully excised to
expose the sartorious and vastus medialis
muscles. The sartorious muscle was meticulously prepared and reflected so that
the adductor canal and the subsartorial
compartment were clearly exposed and
dissected (Figure 1A). The mid-distance
(MD) between the base of the patella and
the anterior superior iliac crest was determined in each specimen. The distance
between the superior foramen of the adductor canal and the MD was also measured. The course of the saphenous nerve
from its origin from the femoral nerve
to the level of the medial epicondyle of
the femur was detailed, and the anatomical level of the origin of the infrapatellar
branch was also specified (Figure 1B).
The anatomical course, distribution, and
variations of the infrapatellar branch were
recorded.
Results
In 4 (23%) of the 17 specimens, the superior foramen of the adductor canal was
proximal to the MD. In 13 (77%) of the
17 specimens, the superior foramen of the
adductor canal was distal to the MD, with
the mean distance between the superior
foramen of the adductor canal being 6.5
cm (range, 1.8-10 cm).
In 12 (70.6%) of the 17 specimens,
the infrapatellar branch of the saphenous
nerve exited the adductor canal separately
from the saphenous nerve. In 4 (33%)
of these 12 specimens, the infrapatellar
branch of the saphenous nerve separated
the main trunk of the saphenous nerve before the superior foramen of the adductor
canal, remaining caudal to the MD (Figure 2); in 8 (67%) of these 12 specimens,
the infrapatellar branch of the saphenous
nerve separated the main trunk of the saphenous nerve within the adductor canal.
In 4 (23.5%) of the 17 specimens, the
infrapatellar branch originated from the saphenous nerve after the latter had exited the
adductor canal, where the nerve passed between the sartorious muscle and the femoral artery. In 1 (5.9%) of the 17 specimens,
the infrapatellar branch originated from the
saphenous nerve after the latter had pierced
the sartorious muscle (Figure 3).
In all anatomical dissections, the infrapatellar branch was always in close
proximity to the saphenous nerve; from
its origin to the inferior foramen of the
adductor canal, the infrapatellar branch
passed beneath the sartorius, in front of
the femoral artery, behind the aponeurotic
covering of the canal. In all specimens,
caudally to the inferior foramen of the adductor canal, the infrapatellar branch had
a constant anatomical course; the nerve
passed between the sartorious muscle and
the femoral artery and was distributed to
the skin in front of the patella.
Discussion
Previous anatomical studies have reported various origins of the infrapatellar branch from the saphenous nerve and
its distribution to the skin in front of the
patella.3-8 The exact anatomical relationship of the infrapatellar branch within the
adductor canal and the anatomical area
where the nerve originates and separates
from the saphenous nerve has not been
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documented. Some authors have reported
that the infrapatellar branch originates
most commonly from the saphenous
nerve in the middle third of the thigh.5 A
previous anatomical study5 reported that
the infrapatellar branch of the saphenous
nerve originated from the main trunk of
the saphenous nerve in the proximal third
of the thigh in 17.6% of anatomical specimens, the middle third in 58.8%, and the
distal third in 23.5%.5 Similar imaging
studies clearly identified the infrapatellar
branch using ultrasound; however, they
did not confirm the exact anatomical area
of its origin from the saphenous nerve.11-13
Moreover, there are no published studies
that examine the nerve block of the saphenous and infrapatellar branch, either
cephalad or caudal to the adductor canal.
Conflicting data also exist regarding the anatomic level whereby proper
needle insertion can result in successful
adductor canal block. Jæger et al11 advocated placing the needle for adductor canal
saphenous/infrapatellar nerve block in the
MD between the anterior superior iliac
spine and the base of the patella, whereas
others supported a more distal placement
of the needle.10 Recently, a clinical study
reported successful nerve block of both
the saphenous nerve and the infrapatellar branch using subsartorial ultrasoundguided local anesthetic injection within the
adductor canal.14 These observations and
conflicting reports have important implications for regional anesthesia nerve block
techniques at the anatomic region of the
adductor canal.
In the current anatomical study of human cadavers, the infrapatellar branch
of the saphenous nerve most commonly
separated the main trunk of the saphenous
nerve within the adductor canal. In addition, once the main trunk of the saphenous
nerve divided prior to the superior foramen
of the adductor canal, the 2 nerves entered
together within the adductor canal. During
dissection, the infrapatellar branch, either
as a part of the main trunk of the saphenous nerve or as a separate branch, always
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Figure 2: The adductor canal has been dissected
to reveal the anatomical relationship of the saphenous nerve (S) and infrapatellar branch (I). The
infrapatellar branch separates from the main trunk
of the saphenous nerve cephalad to the superior
foramen of the adductor canal. Both nerves exit independently from the inferior foramen of the canal.
Abbreviations: F, femoral artery; T, tendon of the
adductor magnus; V, vastoadductors membrane.
coursed beneath the sartorious muscle in
close proximity to the saphenous nerve
within the adductor canal. Therefore, in
the clinical setting of adductor canal nerve
block, irrespective of the level of origin of
the infrapatellar branch from the saphenous nerve, subsartorial injection of local
anesthetic will likely lead to successful
nerve block of both the saphenous nerve
and the infrapatellar branch.
The adductor canal nerve block occurs more distally with respect to femoral nerve block and therefore covers a
smaller area of the leg. Previous research
demonstrated that adductor canal blocks
are effective in providing analgesia after
knee surgery and can spare function of
the quadriceps.11 Doses as high as 8 mL
of local anesthetic can lead to sufficient
blockade of the saphenous nerve in the
adductor canal, whereas lower volumes
of local anesthetic (5 mL)15 have been
proven less effective.16 Although the literature confirms the significance of this
block in clinical practice, questions remain regarding the exact anatomic region
where this block must be implemented.11,15,16 Therefore, the insertion point of
the needle for adductor canal nerve block
is also clinically important for the accurate implementation of adductor canal
nerve block. According to the authors’
observations, the infrapatellar branch
always originated from the saphenous
Figure 3: The sartorious muscle has been dissected to show the exit of the saphenous nerve (S)
and the femoral artery (F) from the inferior foramen of the adductor canal (AC). The saphenous
nerve pierces the sartorious muscle, and then the
infrapatellar branch (I) originates.
nerve caudal to the MD, whereas in most
cases the MD was always cephalad to the
superior foramen of the adductor canal.
Based on these observations, the adductor canal block by Jæger et al11 is mainly
a subsartorial saphenous nerve block out
of the canal, whereas an accurate adductor canal block is that described by Manickam et al.14 Importantly, comparison of
the 2 techniques, either on infrapatellar
or saphenous nerve blocks, has not yet
been performed.
Fresh-frozen cadavers were not used in
the current study; this may be considered a
limitation. The authors acknowledge that
the type of preservation directly affects
the biomechanical properties of tissues.
Frozen cadavers are frozen and stored
at subzero temperatures, approximately
-20°C. Embalmed cadavers are preserved
with embalming chemical compounds,
including preservatives, sanitizers, disinfectant agents, and additives, used to
temporarily delay the decomposition process from anaerobic bacteria. Embalming
agents are administered to the cadaveric
body mainly through the femoral or carotid artery. Frozen cadavers provide betterquality tissues for teaching in surgical
specialties. Formalin-embalmed cadavers
are considered the method of choice in
dissection anatomy.
Conclusion
The infrapatellar branch of the saphenous nerve most commonly originates
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from the saphenous nerve within the adductor canal; the superior foramen of the
adductor canal is mainly caudal to the
MD between the base of the patella and
the superior iliac crest, and the infrapatellar branch has a constant course in close
proximity to the saphenous nerve within
the adductor canal. These observations
should be kept in mind for accurate and
successful saphenous/infrapatellar nerve
block at the level of the adductor canal.
References
1. Saranteas T, Anagnostis G, Paraskeuopoulos
T, et al. Anatomy and clinical implications of
the ultrasound-guided subsartorial saphenous
nerve block. Reg Anesth Pain Med. 2011;
36(4):399-402.
2. Gosling JA, Harris PF, Whitmore I, Willan P.
Medial compartment of the thigh. In: Gosling
JA, Harris PF, Whitmore I, Willan P, eds. Human Anatomy Color Atlas and Text. 4th ed.
Philadelphia, PA: Mosby Elsevier; 2002:234236.
3. Ebraheim NA, Mekhail AO. The infrapatellar
branch of the saphenous nerve: an anatomic
e262
study. J Orthop Trauma. 1997; 11(3):195-199.
4. Arthornthurasook A, Gaew-Im K. Study of
the infrapatellar nerve. Am J Sports Med.
1988; 16(1):57-59.
5. Horner G, Dellon AL. Innervation of the human knee joint and implications for surgery.
Clin Orthop Relat Res. 1994; 301:221-226.
6. Arthornthurasook, A, Gaew-Im K. The sartorial nerve: its relationship to the medial
aspect of the knee. Am J Sports Med. 1990;
18(1):41-42.
7. Tubbs RS, Loukas M, Shoja MM, Apaydin
N, Oakes WJ, Salter EG. Anatomy and potential clinical significance of the vastoadductors membrane. Surg Radiol Anat. 2007;
29(7):569-573.
8.Purner J. Peripheral course of saphenous nerve [in German]. Anat Anz. 1971;
129(2):114-132.
9. Marhofer P, Harrop-Griffiths W, Kettner SC,
Kirchmair L. Fifteen years of ultrasound
guidance in regional anaesthesia: part 1. Br J
Anaesth. 2010; 104(5):538-546.
10.Bendtsen TF, Moriggl B, Chan V, Peder
sen EM, Børglum J. Defining adductor
canal block. Reg Anesth Pain Med. 2014;
39(3):253-254.
11. Jæger P, Zaric D, Fomsgaard JS, et al. Adductor canal block versus femoral nerve block
for analgesia after total knee arthroplasty: a
randomized, double-blind study. Reg Anesth
Pain Med. 2013; 38(6):526-532.
12. Le Corroller T, Lagier A, Pirro N, Champsaur P. Anatomical study of the infrapatellar
branch of the saphenous nerve using ultrasonography. Muscle Nerve. 2011; 44(1):50-54.
13. Lundblad M, Kapral S, Marhofer P, Lön
nqvist PA. Ultrasound-guided infrapatellar
nerve block in human volunteers: description
of a novel technique. Br J Anaesth. 2006;
97(5):710-714.
14. Manickam B, Perlas A, Duggan E, Brull R,
Chan VW, Ramlogan R. Feasibility and efficacy of ultrasound-guided block of the
saphenous nerve in the adductor canal. Reg
Anesth Pain Med. 2009; 34(6):578-580.
15. Head SJ, Leung RC, Hackman GP, Seib R,
Rondi K, Schwarz SK. Ultrasound-guided
saphenous nerve block—within versus
distal to the adductor canal: a proof-ofprinciple randomized trial. Can J Anaesth.
2015; 62(1):37-44.
16. Adoni A, Paraskeuopoulos T, Saranteas T,
Sidiropoulou T, Mastrokalos D, Kostopanagiotou G. Prospective randomized comparison
between ultrasound-guided saphenous nerve
block within and distal to the adductor canal
with low volume of local anesthetic. J Anaesthesiol Clin Pharmacol. 2014; 30(3):378-382.
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