Orthopaedics & Traumatology: Surgery & Research 100 (2014) 515–519

Available online at ScienceDirect www.sciencedirect.com

Original article

The suprascapular : A possible etiology for suprascapular nerve

entrapment and risk of complication during procedures around the suprascapular foramen region

a b c c d a,∗

M. Podgórski , M. Sibinski´ , A. Majos , L. Stefanczyk´ , M. Topol , M. Polguj

a

Department of Angiology, Chair of Anatomy, Medical University of Łód´z, Narutowicza 60, 90–136 Lodz, Poland

b

Clinic of Orthopaedic and Pediatric Orthopaedics, Medical University of Łód´z, Łód´z, Poland

c

Department of Radiology and Diagnostic Imaging, Medical University of Łód´z, Łód´z, Poland

d

Department of Normal and Clinical Anatomy, Chair of Anatomy, Medical University of Łód´z, Łód´z, Poland

a r t i c l e i n f o

a b s t r a c t

Article history: Introduction: Nerve can be compressed when traveling through any osteo-fibrous tunnel. Any eventual

Accepted 13 May 2014

anatomic structure limiting this passage increases the risk of neuropathy. During dissection of the shoul-

der region we recognized a vein travelling on the inferior border of the together

Keywords: with the suprascapular nerve. The aim of this work was to evaluate the morphological characteristics of

Anatomical variation

this vein in cadaveric material.

Suprascapular notch vein

Materials and methods: The suprascapular notch (SSN) region was dissected in 60 cadaveric .

Suprascapular nerve entrapment

The course, number and diameter of nerve and vessels in the suprascapluar notch region were evalu-

Superior transverse scapular ligament

ated. Length, proximal and distal width of the superior transverse scapular ligament were measured.

Suprascapular notch

Photographic documentation was taken to evaluate the suprascapular nerve passage area.

Anterior coracoscapular ligament

Results: The vein identified was named as the suprascapular notch vein. It was present in 58.3% of shoul-

ders. In 11 specimens, it was double. Its mean diameter was 1.7 mm (SD 0.7 mm) and did not correlate

with the suprascapular nerve passage area. A suprascapular notch vein co-occurred more often with

the anterior coracoscapular ligament (ACSL). In comparison with the SSN without the ACSL, it has a

significantly greater diameter (2 mm; SD 0.7 mm vs 1.5 mm; SD 0.6 mm, respectively; P = 0.021).

Conclusions: The suprascapular notch vein was a common structure that did not replace the suprascapular

vein. Its presence correlated with the occurrence of the ACSL and was independent of body side, STSL

type and SSN type.

Type of study: Observational anatomic study.

© 2014 Elsevier Masson SAS. All rights reserved.

1. Introduction suprascapular nerve (SN) and the . The supras-

capular only occasionally runs below the STSL [2,3]. The

The suprascapular notch (SSN) is the incisure at the upper border suprascapular nerve innervates the supraspinatus and infraspina-

of the scapulae. It is bridged by the superior transverse scapu- tus muscles and also provides sensory branches to joints

lar ligament (STSL) creating an osteo-fibrous tunnel whose area (acromioclavicular and glenohumeral); ligaments (the coraco-

2 2

ranges from 4.6 mm to 85.4 mm [1]. Anterior coracoscapular humeral and coracoacromial); subacromial bursa [4] and to a

ligament (ACSL) is independent fibrous band extending on the ante- variable area of the overlying skin and soft tissues [5].

rior side of the suprascapular notch, below the superior transverse Structures passing below the STSL through the osteo-fibrous

scapular ligament (Fig. 1). Such structured tunnel usually holds the tunnel may increase the risk of neuropathy by limiting the space

available for the SN. This can result in suprascapular nerve entrap-

ment syndrome which was described in 1936 by André Thomas’a

[6] and usually occurs in the SSN [7].

During dissection of the region, we found an unusual

∗ vein that passed through the SSN on its inferior border. Because this

Corresponding author. Tel.: +48 42 63 04 949.

vein may restrict the passage for the SN, we aimed to determine its

E-mail addresses: [email protected], [email protected]

(M. Polguj). morphology and the prevalence.

http://dx.doi.org/10.1016/j.otsr.2014.05.008

1877-0568/© 2014 Elsevier Masson SAS. All rights reserved.

516 M. Podgórski et al. / Orthopaedics & Traumatology: Surgery & Research 100 (2014) 515–519

2. Materials and methods

The shoulder region was dissected in 60 formalin-fixed cadav-

eric shoulders, 30 left and 30 right, derived from a Polish population

(age and sex unknown). The humeral attachment of the subscapu-

laris muscle was cut and the muscle was retracted medially. The

fasciae were cleaned, revealing the anterior side of the .

When the SNV was present, its course was traced from the SNN to

the upstream . The arrangement of the ,

vein and SN was also noted. Afterwards, the posterior aspect of

the SSN was exposed. The attachment of the and del-

toid muscles were separated from the spine of the scapulae. The

was cut distally and bluntly dissected from

the supraspinatus fossa. The suprascapular notch vein was followed

to the site of its emptying.

The dissected scapulae were fixed at a standardized distance

from the camera, and their anterior aspect was photographed in

the coronal plane. The ten millimeter long scale was placed at

the level of measured structures and served for further calibration

of measuring tool. The dimensions of the STSL, the anterior cora-

coscapular ligament (ACSL) and the areas of the SSN and the SN

passage were measured using MultiScanBase 18.03 software (Com-

puter Scanning System II, Warsaw, Poland). The diameter of the SN,

Fig. 2. The representative example of the suprascapular notch vein (SNV) that passes

suprascapular vessels and SNV were also evaluated. In further anal- through the suprascapular notch together with suprascapular nerve (SN) and vein

ysis, the STSL was classified as either fan- or band-shaped [1] and (SV). Suprascapular artery (SA) travels above the superior transverse scapular liga-

ment (STSL).

the SSN to one of the 5 types [8].

For the purposes of statistical analysis, P < 0.05 was regarded

as statistically significant. Data is presented as a mean ± standard

deviation, unless stated otherwise. A comparison of the prevalence

of SNV between body sides, STSL types and SSN with or without

2

the ACSL was performed with the ␹ test. Differences in SNV diam-

eter between those variables was estimated with Student’s t test

for independent samples. This test was also employed to compare

areas of the SSN and the SN passage between specimens with and

without the SNV. The relationship between SNV diameter and the

number of its upstream veins was evaluated by means of one-way

Anova with dedicated post-hoc tests. This method was also used

to compare SNV diameter between types of the SSN. Correlations

of the SNV diameter and areas of the SSN and the SN passage were

evaluated by means of the Spearman’s rank correlation coefficient.

3. Results

The suprascapular notch vein was present in 35 shoulders

Fig. 3. Double suprascapular notch vein (SNV1 and SNV2) that passes through the

(58.3%) (Fig. 2). In 11 specimens, it was double (Fig. 3). It originated suprascapular notch together with suprascapular nerve (SN). Suprascapular artery

(SA) and vein (SV) travel above the superior transverse scapular ligament (STSL).

from 3 veins in 20 cases, 4 veins in 11, 2 veins in 3, and 5 veins

in 1 case. Veins of origin arose on the anterior side of the scapula,

inferior to the SSN, from a bone-nutrient vein of the scapula and/or

veins laying beneath the fascia of the . All SNVs

emptied into the suprascapular vein immediately after passing the

SSN. After exclusion of a single case with five upstream veins, the

diameter of the SNV differed significantly between three groups

(P = 0.0274) and tended to increase as the number of upstream veins

increased (Table 1) (Fig. 4).

In all cases, the SN (diameter = 2.1 mm; SD = 0.4 mm) travelled

below the STSL. The diameters of the suprascapular artery and vein

were 2.3 mm (SD = 0.6 mm) and 3.4 mm (SD = 0.7 mm), respectively.

In two cases, the suprascapular artery accompanied the SN beneath

Table 1

P value for post-hoc test.

Number of veins 2 3 4

2 – 0.3449 0.0493

3 0.3449 – 0.1018

Fig. 1. Schematic arrangements of the superior transverse scapular ligament (STSL)

4 0.0493 0.1018 –

and anterior coracoscapular ligament (ACSL) at suprascapular notch.

M. Podgórski et al. / Orthopaedics & Traumatology: Surgery & Research 100 (2014) 515–519 517

Fig. 6. Suprascapular notch vein (SNV) that reaches the suprascapular notch pass-

ing under anterior coracoscapular ligament (ACSL). SN: suprascapular nerve; SA:

suprascapular artery; SV: suprascapular vein; STSL: superior transverse scapular

ligament.

Fig. 4. Plot depicting differences in SNV diameters according to the number of veins

the presence of the SNV (P = 0.3601 and P = 0.7022, respectively).

of origin.

The differences in SNV diameter between body sides, STSL types

and SSN types were also insignificant (data not presented). How-

ever, the SNV co-occurred more often with the ACSL (P = 0.0001)

the STSL. The suprascapular vein passed below the STSL in 40 cases.

(Fig. 6). In those cases, diameter of the SNV was greater than in SSNs

A double suprascapular vein was found in 15 specimens. In 11 of

without the ACSL (2 mm; SD 0.7 mm vs 1.5 mm; SD 0.6 mm, respec-

them, one vessel passed inferior to the STSL and the other superior.

tively; P = 0.021). Table 2 shows differences in the prevalence of the

In the remaining 4 shoulders, both veins ran over the STSL. Fig. 5

SNV according to the body sides and the arrangement of structures

depicts the arrangement of SN and suprascapular vessels when the

occupying the SSN.

SNV was present.

2 2

The SSN area was 87.5 mm (SD = 33 mm ) and area of SN

2 2

passage was 25.3 mm (SD = 15.9 mm ). The diameter of the SNV 4. Discussion

ranged from 0.5 mm to 3 mm (mean = 1.7 mm; SD = 0.7 mm) but

did not correlate with neither the SSN area (P = 0.645) nor with The arrangement of vascular structures in the SSN is highly vari-

the SN passage area (P = 0.8686). Furthermore, the areas of the able. The suprascapular artery incidentally travels together with

SSN and the SN passage did not differ significantly according to the SN below the STSL. We observed this pattern in 3.3% of the

Fig. 5. Relationship of SNV with other neurovascular structures in SN region. N: suprascapular nerve; A: suprascapular artery; V: suprascapular veins; V1,V2: suprascapular

notch veins.

518 M. Podgórski et al. / Orthopaedics & Traumatology: Surgery & Research 100 (2014) 515–519

Table 2

Differences in prevalence of the SNV between: body sides, types of the STSL, occurrence of the ACSL and presence of the suprascapular vein below the STSL.

Compared parameters SNV present [Number] SNV absent [Number] P

Body sides [Number] Right (30) 16 14 0.60

Left (30) 19 11

STSL type [Number] Fan-shaped (29) 17 12 0.97

Band-shaped (31) 18 13

ACSL [Number] Present (31) 27 4 0.0001

Absent (29) 8 21

Suprascapular vein below the STSL [Number] Present (40) 29 16 0.16

Absent (20) 8 12

STSL: superior transverse scapular ligament; ACSL: anterior coracoscapular ligament; SNV: suprascapular notch vein.

cases. Tubss et al. [3] found this arrangement in 3 out of 120 cadav- The anterior coracoscapular ligament may also play an ambigu-

eric shoulders (2.5%) and Reinceck et al. [2] in 3 of 100 specimens ous role in the development of SN neuropathy. On the one hand,

(3%). it may increase the risk of SN neuropathy by obstructing the nerve

Variations in suprascapular vein anatomy occur more often. passage [17]. On the other hand, the ACSL separates the SN from

Yang et al. [9] reported that the SN was accompanied either by the the bone and prevents the SNV from intruding into the SN passage

suprascapular vein or artery in 25.2% of 103 cadaveric shoulders, space. Moreover, the presence of an ACSL was not found to decrease

and by both vessels in 14.6%. Furthermore, a double suprascapular the SN passage area [18].

vein was present in 19.4% of shoulders and a triple one in 1.9%. As Considering all the above we suppose that the SNV, together

far as the suprascapular vein is concerned, our results are similar, with the ACSL, may support a cushion mechanism for the SN, pro-

however, Yang et al. [9] did not describe any vein resembling the tecting it against repeated micro-trauma.

SNV. It is possible that, in this case, the SNV could have remained The limitation of this study is that no conclusions can be derived

unrecognized as the SSN had been dissected from the posterior regarding the symmetry of SNV occurrence, as separate limbs were

aspect. dissected and the data for left and right sides was pooled. How-

The suprascapular notch vein is common, however it is not well ever, Yang et al. [9] reported that body side is not associated with

studied because more attention is generally paid to the posterior different frequencies of vascular anomalies. Our observation that

aspect of the scapulae. In this location, the SN is often compressed SNV prevalence is non-side specific supports this theory. Another

by a mass (e.g. ganglion/labral cyst, tumor) [10,11] or retracted and limitation is that veins were not injected with medium, decreasing

irritated due to a tear [12]. It can also be entrapped in accuracy of vein diameter measurements. However, in formalin-

a spinoglenoid notch by the spinoglenoid ligament [13]. fixed shoulders, that we used, veins of a small diameter were

The previously-described variations of the suprascapular vein filled with clothed blood that was not flushed during embalming

concern mainly the number of vessels and their arrangement in procedure. Clothed blood distended vein lumen enabling reliable

the SSN. Usually, the suprascapular vein starts in the infraspinatus measurements. Finally, proposed protective role of the SNV and

fossa, approaches the supraspine fossa through the spinoglenoid the ACSL against the SN irritation cannot be confirmed based on

notch and ascends to the SSN. After passing the SSN, typically under anatomic description and should be further tested in clinical set-

the STSL, it travels with the suprascapular artery and finally emp- ting.

ties into the external . It drains the same region as the Information about the relationship between the SN and ves-

corresponding artery, however the dorsal scapular vein and the cir- sels in the SSN region is of paramount importance for classical

cumflex scapular branch of the subscapular vein may also receive [19,20] and endoscopic surgical approaches [21,22]. Awareness

blood from this region [14]. In contrast to the suprascapular vein, of anatomical variations in this region has become vital due to

the SNV originates from veins emerging directly from bony foram- the increasing number of ultrasound-guided SN block procedures

ina on the anterior side of the scapula (nutrient veins) or veins [23,24], combined with the placement of a perineural catheter

running under the fascia of the subscapularis muscle. Moreover below the STSL [24,25]. Sonoanatomy of the SSN region has been

the SNV, traveling from anterior to posterior, crosses the SSN in recently described, however, the precise orientation of anatomical

the opposite direction to the suprascapular vein. Finally, the SNV landmarks is challenging and results of examination are subjec-

was always found to co-occur with the suprascapular vein, never tive [22,24]. In those procedures, the transducer is placed over the

replacing it. All the above implies that the SNV is not a variant of SSN in almost coronal plane. If the transducer is too anterior, the

the suprascapular vein but a separate structure. ACSL, together with the SNV below it, may be mistaken with the

Although the SNV was usually found to have a small diameter, in suprascapular vein passing below the STSL. Thus, the needle might

4 specimens it was wider than the suprascapular vein. Despite the be inserted too deeply, injuring the SN or suprascapular vessels.

fact that a suprascapular artery travelling together with the SN can This likelihood is even more increased by the limited visibility of

cause its neuropathy [15], it is uncertain whether a large notch vein the SN in the SNN requiring neighbouring structures to be used as

might increase this risk. Carroll et al. [16] reported the presence of landmarks in estimating the localization of the SN [26].

a venous varix in the spinoglenoid notch in six patients with symp-

toms of suprascapular nerve entrapment syndrome. Furthermore,

mechanical nerve irritation by venous dilatation has been described 5. Conclusions

in patients with tarsal tunnel syndrome [16]. These reports indicate

that the distended vessel can compress the nerve when the two The suprascapular notch vein is a common structure that was

structures travel together through the osteo-fibrous tunnel. How- found in 58.3% of the cases. It never replaces the suprascapular vein

ever, the diameter of the SNV did not correlate with the SN passage and courses against it. Its presence correlates with the occurrence

area and no varix of the SNV was found. Hence, the smooth wall of the ACSL and is independent of body side. Although its role in

of the SNV, which lines the bony floor of the SSN, might protect the development of SN neuropathy remain uncertain, knowledge

against the irritation of the SN that is kinked by the border of the about it may help to prevent unexpected bleeding while performing

SSN. procedures around the SSN region.

M. Podgórski et al. / Orthopaedics & Traumatology: Surgery & Research 100 (2014) 515–519 519

Disclosure of interest [13] Pecina MM, Krmpotic-Nemanic J, Markiewitz AD. Tunnel syndromes. Periph-

eral nerve compression syndromes. 3rd ed. Boca Raton: CRC Press; 2001. p.

49–55.

The authors declare that they have no conflicts of interest con-

[14] Pyrgakis P, Panagouli E, Venieratos D. Anomalous origin and course of the

cerning this article. suprascapular artery combined with absence of the suprascapular vein: case

study and clinical implications. N Am J Med Sci 2013;5(2):129–33.

[15] Houtz C, McCulloch PC. Suprascapular vascular anomalies as a cause of supras-

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