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n sports medicine update
Suprascapular Vascular Anomalies as a
Cause of Suprascapular Nerve Compression
Carlton Houtz, MD; Patrick C. McCulloch, MD
Abstract: The vascular anatomy at the spinoglenoid and suprascapular notches appears to be more variable than previously thought. In patients presenting with signs of suprascapular nerve compression, vascular causes must be considered.
Especially when considering percutaneous or arthroscopic
treatment, awareness of these entities may help to guide treatment decisions, aid in identification of the anatomy, and prevent unwanted vascular insult.
T
he first report of compression of the suprascapular
nerve was by Schilf in 1952.1
Since then, the understanding
of this neuropathy and its possible etiologies has improved
substantially. Those thought
to be at highest risk include
athletes engaging in repetitive
overhead activity, especially
tennis and volleyball players.2-6 Nerve compression has
been attributed to a stenotic
notch, an ossified transverse
scapular ligament, soft tissue
or bone tumors, cysts secondary to capsulolabral pathology, and fractures. Several
authors have described suprascapular nerve palsy in
patients with a massive rotator cuff tear associated with
fatty infiltration or muscle atrophy.7-10 At times, anatomic
variants of the neurovascular
structures may lead to compression of the suprascapular
nerve; however, this has been
sparsely described in previous
literature.8,11 The current ar-
The authors are from the Highland Clinic (CH). Shreveport, Louisiana;
and the Methodist Center for Sports Medicine (PCM), The Methodist
Hospital, Houston, Texas.
The authors have no relevant financial relationships to disclose.
Correspondence should be addressed to: Carlton Houtz, MD, Highland
Clinic, 1455 E Bert Kouns Industrial Loop, Ste 210, Shreveport, LA 71105
([email protected]).
doi: 10.3928/01477447-20121217-07
42
ticle describes one such compressive etiology and reviews
the literature on vascular
anomalies at the suprascapular and spinoglenoid notches.
Case Report
A 52-year-old man who
had undergone 2 previous
failed shoulder surgeries for
presumed rotator cuff tear presented with pain and progressive weakness of forward elevation, abduction, and external
rotation of his left shoulder.
No rotator cuff tear was seen
during the previous surgeries,
and a subacromial decompression with acromioplasty was
performed. Although he initially reported being unable to
play basketball and participate
in weight lifting, his symptoms progressed to limiting his
ability to work.
Electromyography
and
nerve conduction studies demonstrated mild denervation in
the infraspinatus and supraspinatus muscles. Physical therapy failed to improve his weakness or discomfort, which
he localized to the posterior
scapular region, and some
atrophic changes were seen on
inspection of the periscapular
muscles. Magnetic resonance
arthography
demonstrated
edema and moderate atrophy
within the supraspinatus and
infraspinatus muscles consistent with acute-on-chronic denervation, but no evidence of a
tear. No lesion was identified
within the suprascapular notch
(Figure 1).
A second electromyogram
and nerve conduction study
obtained 12 weeks after the
first studies showed dysfunction of the suprascapular
nerve at or proximal to the
suprascapular notch, with the
supraspinatus and infraspinatus demonstrating evidence
of both acute and ongoing
denervation
and
chronic
changes. The decision was
made to proceed with suprascapular nerve decompression
at the suprascapular notch.
With the patient in the
beach-chair position, a thorough diagnostic arthroscopy
was performed. Evidence
existed of a previous acromioplasty and some scarring of bursal tissues, but no
ORTHOPEDICS | Healio.com/Orthopedics
n sports medicine update
evidence existed of a rotator cuff tear. A lateral viewing portal was established in
the subacromial space. The
coracoacromial ligament was
identified and followed down
to the base of the coracoid.
A straight medial Nevasier
portal was made under direct
vision with a spinal needle,
similar to the technique described by Lafosse et al.12
Just medial to the conoid
ligament, the transverse scapular ligament was identified,
and both the suprascapular artery and nerve were identified
passing beneath the ligament.
Two smaller branches of the
suprascapular artery originating proximal to the ligament
were traveling with the main
trunk of the suprascapular
artery under the ligament.
These 3 arterial vessels were
compressing the nerve within
the notch (Figure 2).
A narrow arthroscopic biter was then used to divide and
resect the transverse scapular
ligament. However, the artery
was still tethered medially by
the smallest of the branches (Figure 3). This branch
was cauterized using an ar-
1A
1B
Figure 1: Sagittal magnetic resonance imaging anatomy sequence showing mild decreased muscle bulk and early fatty
change of the supra- and infraspinatus consistent with acute-on-chronic changes (A). Fat-suppressed, fluid-sensitive
sequence showing significant interstitial edema of muscles consistent with acute denervation changes (B).
throscopic cautery device and
then divided. The artery then
lifted superiorly off the nerve,
leaving the nerve freely mobile in the notch (Figure 4).
Six months postoperatively, the patient had no
pain, full range of motion,
and 5/5 rotator cuff strength.
Electromyography
demonstrated significant interval
improvement with no signs
of active denervation, normal
recruitment, and a full 100%
interference pattern. At 1-year
follow-up, the patient remained symptom free and had
returned to manual labor.
2
Figure 2: Arthroscopic image of the suprascapular
artery passing under the transverse scapular ligament.
Discussion
The suprascapular nerve
has contributions from C4C6 via the upper trunk of the
brachial plexus. It is a mixed
nerve with sensory branches
to the acromioclavicular joint,
coracoacromial ligament, and
glenohumeral joint capsule
and has 2 motor branches that
innervate the supraspinatus
muscle. The nerve descends
through the posterior triangle
of the neck before passing
beneath the superior transverse scapular ligament in
the suprascapular notch. The
superior transverse scapular
3
Figure 3: Arthroscopic image after release of the
ligament showing the pulsatile artery in the notch,
tethered by a small medial branch.
ligament is approximately
1.3 cm posterior to the posterior aspect of the clavicle, 2.9
cm medial to the acromioclavicular joint, and 4 cm deep to
the skin surface.13 The nerve
then courses approximately
3 cm medial to the supraglenoid tubercle and 1.8 cm medial from the posterior glenoid
rim at the base of the scapular
spine.14 The distance from the
palpable posterolateral corner
of the acromion to the base of
the scapular spine is approximately 4.5 cm.15 It then travels beneath the inferior transverse scapular ligament in
4
Figure 4: Arthroscopic image of ligation of the
smallest branch allowing the artery to lift superiorly out of the notch, exposing the nerve.
JANUARY 2013 | Volume 36 • Number 143
n sports medicine update
the spinoglenoid notch before
innervating the infraspinatus
muscle via 2 or more motor
branches.14,15
Suprascapular nerve injuries are common in repetitive
overhead athletes, such as tennis, volleyball, and throwing
athletes, for 2 main reasons.
First, this nerve is vulnerable
to stretch injuries because it
takes a circuitous course and
can become tethered in several
places, such as the suprascapular and spinoglenoid notches.
Second, those sports are often
associated with labral pathology, which can lead to nerve
compression from paralabral
cysts. The resultant loss of rotator cuff strength can cause decreased performance, and the
pain can lead to the inability to
participate.
Suprascapular nerve compression causing posterior
shoulder pain can be attributed
to previous cadaveric findings
of sensory branches to the glenohumeral joint, acromioclavicular joint, coracoacromial
ligament, and skin.14,15 Some
evidence indicates that the
nerve may supply up to 70% of
the sensation of the shoulder.16
Vorster et al17 demonstrated a
glenohumeral sensory branch
in 87% of 31 cadavers and an
acromial sensory branch in
74%.
The suprascapular artery is
a branch of the thyrocervical
trunk of the subclavian artery.
It passes downward and laterally across the scalenus anterior muscle and phrenic nerve
before running behind and parallel to the clavicle and subclavius muscle. It then crosses the
suprascapular notch above the
44
superior transverse scapular
ligament, after which it typically gives off branches that
supply the supraspinatus muscle. The artery then continues
distally, traveling beneath the
inferior transverse scapular
ligament before forming an
anastamosis with the scapular
circumflex artery and descending branch of the transverse
cervical artery.18
The most common anatomic arrangement at the suprascapular notch is that the
artery travels superior to the
transverse scapular ligament
while the nerve travels under
it. This spawned the classic
teaching pneumonic that when
faced with an obstacle, “the
Army [artery] goes over and
the Navy [nerve] goes under
the bridge.” However, previous
cadaveric work showed that
the suprascapular artery has a
subligamentous course in up
to 2.5% of dissections.19-21
In the first clinical report on the subject, Reineck
and
Krishnan11
reported
finding a subligamentous
artery with evidence of suprascapular nerve compression in 3 of 100 patients
undergoing arthroscopic suprascapular nerve release.
They reported that the ligament was released but offered
no follow-up results. They did
not trace the artery back to its
origin and therefore may have
been visualizing a branch of
the suprascapular artery proper as opposed to the main artery itself; they suggested that
an anterior approach, rather
than a lateral approach, may
be preferable for better visualization of the suprascapular
notch to avoid placing the artery at risk.11
Recently, Yang et al22 dissected 103 cadaveric shoulders
and found a single suprascapular artery that passed under
the superior transverse suprascapular ligament in 26.2% of
the shoulder specimens. They
noted that the venous anatomy
was more variable, with 21.3%
having multiple veins, and all
of the vessels passing superior
to the ligament only 59.4% of
the time. The same vascular
arrangement described in the
current case (with the suprascapular vein crossing over the
transverse scapular ligament
and the artery running under)
occurred in 10.9% of their cadaveric specimens.22
Although venous compression at the suprascapular notch
has not been reported, venous
compression at the spinoglenoid notch has been reported.
Carroll et al8 were the first
to report enlarged spinoglenoid notch veins as a cause of
compression leading to pain
and infraspinatus weakness.
They identified 6 patients, 3 of
whom underwent surgery, and
all showed clinical improvement. The inferior transverse
scapular ligament was divided
in all patients, and 1 also had a
varicosity ligated. Not all fluid
signal seen in the notch on
magnetic resonance imaging
is a ganglion, and they stressed
the importance of recognizing
this entity when considering
percutaneous aspiration.8 This
has also been described in a
patient with varicose veins in
the lower extremity who developed a large varix in the
spinoglenoid notch resulting
in nerve compression.23 The
patient underwent an open
vessel ligation and resection
with good clinical improvement. They noted that the addition of intravenous contrast
when performing magnetic
resonance imaging may help
to differentiate this from the
more common ganglion cyst.23
The vascular anatomy at
the spinoglenoid and suprascapular notches appears to be
more variable than previously
thought. In patients presenting
with signs of suprascapular
nerve compression, vascular
causes must be considered.
Especially when considering
percutaneous or arthroscopic
treatment, awareness of these
entities may help to guide
treatment decisions, aid in
identification of the anatomy,
and prevent unwanted vascular
insult.
References
1. Schilf E. Unilateral paralysis
of the suprascapular nerve [in
German]. Nervenarzt. 1952;
23(8):306-307.
2. Ferretti A, Cerullo G, Russo G.
Suprascapular neuropathy in
volleyball players. J Bone Joint
Surg Am. 1987; 69(2):260-263.
3.Holzgraefe M, Kukowski B,
Eggert S. Prevalence of latent
and manifest suprascapular neuropathy in high-performance
volleyball players. Br J Sports
Med. 1994; 28(3):177-179.
4.
Lajtai G, Pfirrmann CW,
Aitzetmüller G, Pirkl C, Gerber
C, Jost B. The shoulders of professional beach volleyball players: high prevalence of infraspinatus muscle atrophy. Am J Sports
Med. 2009; 37(7):1375-1383.
5. Safran MR. Nerve injury about
the shoulder in athletes, part 1:
suprascapular nerve and axillary nerve. Am J Sports Med.
2004; 32(3):803-819.
6. Witvrouw E, Cools A, Lysens
R, et al. Suprascapular neurop-
ORTHOPEDICS | Healio.com/Orthopedics
n sports medicine update
athy in volleyball players. Br J
Sports Med. 2000; 34(3):174180.
7.Albritton MJ, Graham RD,
Richards RS II, Basamania CJ.
An anatomic study of the effects on the suprascapular nerve
due to retraction of the supraspinatus muscle after a rotator
cuff tear. J Shoulder Elbow
Surg. 2003; 12(5):497-500.
8. Carroll KW, Helms CA, Otte
MT, Moellken SM, Fritz R.
Enlarged spinoglenoid notch
veins causing suprascapular
nerve compression. Skeletal
Radiol. 2003; 32(2):72-77.
9.
Mallon WJ, Wilson RJ,
Basamania CJ. The association
of suprascapular neuropathy
with massive rotator cuff tears:
a preliminary report. J Shoulder
Elbow Surg. 2006; 15(4):395398.
10.Vad VB, Southern D, Warren
RF, Altchek DW, Dines D.
Prevalence of peripheral neurologic injuries in rotator cuff tears
with atrophy. J Shoulder Elbow
Surg. 2003; 12(4):333-336.
11.Reineck JR, Krishnan SG.
Subligamentous suprascapular
artery encountered during arthroscopic suprascapular nerve
release: a report of three cases.
J Shoulder Elbow Surg. 2009;
18(3):e1-e3.
16. Brown DE, James DC, Roy S.
Pain relief by suprascapular
nerve block in gleno-humeral
arthritis. Scand J Rheumatol.
1988; 17(5):411-415.
12. Lafosse L, Tomasi A, Corbett S,
Baier G, Willems K, Gobezie R.
Arthroscopic release of suprascapular nerve entrapment at
the suprascapular notch: technique and preliminary results.
Arthroscopy. 2007; 23(1):34-42.
17.Vorster W, Lange CP, Briët
RJ, et al. The sensory branch
distribution of the suprascapular nerve: an anatomic study.
J Shoulder Elbow Surg. 2008;
17(3):500-502.
13.Plancher KD, Peterson RK,
Johnston JC, Luke TA. The
spinoglenoid ligament. Anatomy,
morphology, and histological
findings. J Bone Joint Surg Am.
2005; 87(2):361-365.
14.Bigliani LU, Dalsey RM,
McCann PD, April EW. An
anatomical study of the suprascapular nerve. Arthroscopy.
1990; 6(4):301-305.
15. Warner JP, Krushell RJ, Masquelet
A, Gerber C. Anatomy and relationships of the suprascapular
nerve: anatomical constraints to
mobilization of the supraspinatus
and infraspinatus muscles in the
management of massive rotatorcuff tears. J Bone Joint Surg Am.
1992; 74(1):36-45.
20.Pye-Smith PH, Howse HG,
Davies-Colley JNC. Notes of
abnormalities observed in the
dissecting room during winter
sessions of 1868-9 and 186970. Guys Hosp Rep. 1871;
16:147-164.
21. Saadeh FA. The suprascapular
artery: case report of an unusual origin. Anat Anz. 1979;
145(1):83-86.
18.Wijdicks CA, Armitage BM,
Anavian J, Schroder LK, Cole
PA. Vulnerable neurovasculature with a posterior approach to
the scapula. Clin Orthop Relat
Res. 2009; 467(8):2011-2017.
22. Yang HJ, Gil YC, Jin JD, Ahn
SV, Lee HY. Topographical
anatomy of the suprascapular
nerve and vessels at the suprascapular notch. Clin Anat.
2012; 25(3):359-365.
19.Cummins CA, Anderson K,
Bowen M, Nuber G, Roth SI.
Anatomy and histological characteristics of the spinoglenoid
ligament. J Bone Joint Surg Am.
1998; 80(11):1622-1625.
23.Van Meir N, Fourneau I,
Debeer P. Varicose veins at the
spinoglenoidal notch: an unusual cause of suprascapular nerve
compression. J Shoulder Elbow
Surg. 2011; 20(7):e21-e24.
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