Co-dominance of the transverse cervical artery and dorsal scapular artery in the blood supply of the trapezius muscle: Anatomical study and clinical validation

Abstract

This anatomical study aimed to demonstrate the co-dominance of the transverse cervical artery (TCA) and dorsal scapula artery (DSA) in their blood supply to the trapezius muscle. Dissection was performed on ten fresh cadavers (20 hemi-trunks), with the use of pigmented latex injections to trace the vascular course and methylene blue injections to delineate cutaneous territories. In 63% of specimens, the transverse cervical artery (TCA) and the dorsal scapular artery (DSA) originated separately, while 37% displayed a common origin from the thyrocervical trunk. The average calibre of the TCA was 2.70 mm and the DSA 2.66 mm. The DSA was found to be equal to or larger in calibre than the TCA in 56% of specimens. The cutaneous territory for the TCA measured 15 × 10 cm and was located above the spine of the scapula. The cutaneous territory of the DSA measured 20 × 15 cm and was seen below the spine of the scapula and extending 10 cm beyond the lateral border of the trapezius. There was significant overlap between these two cutaneous territories. Two clinical cases illustrate the application of simultaneous dual flaps harvested from the trapezius based on the TCA and DSA, highlighting the importance of recognising the DSA as a major vascular contributor. This study challenges the conventional notion of unilateral vascular dominance of the TCA, proposing that the trapezius muscle should be classified as a type III flap supplied by co-dominant vessels.

Introduction

Traditionally, the transverse cervical artery (TCA) is regarded as the sole dominant vessel supplying the trapezius flap. However, in literature the major complication rates of the flap have been reported to range from 0 to 75%.1, 2, 3, 4, 5 We speculate that the unpredictability of the flap could be attributed to an under-appreciation of the contribution of the dorsal scapula artery (DSA) which has been regarded as a minor blood supply of the muscle. In 2000, we reported the extended lower trapezius flap based on the DSA, showing that a sizeable fasciocutaneous extension can be raised beyond the muscle border.⁶ The purpose of this study is to demonstrate the co-dominance of the TCA and DSA in their blood supply to the trapezius muscle, based on our analysis of their calibre, course and distribution within the trapezius muscle and their relative cutaneous vascular territories. An improved understanding of the vascular pattern of the trapezius flap has impact on its reliability, versatility and execution of the surgical technique.

Materials and methods

To evaluate the vascular anatomy of the trapezius muscle and delineate the cutaneous territories of the pedicles of the trapezius flap, an anatomical study was performed on ten fresh cadavers (20 hemi-trunks) using pigmented latex injections to trace the course of the pedicles and methylene blue injections to delineate cutaneous vascular territories. In 16 hemi-trunks, the neck was first dissected to identify the TCA and DSA at their origins. The calibre of each vessel was measured and documented before being cannulated and injected with 10% buffered formalin followed by coloured latex. These specimens were stored at 4°C for five days to allow the latex to set. These specimens were later dissected under loupe magnification (2.5x) to determine the course of the vessel, its branching pattern and skin perforators. In four hemi-trunks, the TCA and DSA were isolated and sequentially injected with methylene blue to study their respective cutaneous territories. Approximately 30cc of methylene blue was injected into each territory.

Results of anatomical study

In 63% (n = 10) of dissected specimens, the TCA and DSA were found to have separate origins, with the TCA arising from the thyrocervical trunk and the DSA arising directly from the subclavian artery. In the remaining 37% (n = 6) of specimens, the TCA and DSA were found to have a common origin from the thyrocervical trunk (Figure 1).

Figure 1.

Left above: The transverse cervical artery (TCA) arises from the thyrocervical trunk, which in turn, originates from the subclavian artery (SCA). The dorsal scapula artery (DSA) arises directly from the SCA.

Left below: Both the TCA and DSA have a common origin, which is from the thyrocervical trunk.

Right above: Illustration showing the relative locations of the TCA and DSA in the posterior neck. The DSA passes through the trunks of the brachial plexus when arising directly from the subclavian artery.

Right below: When the TCA and DSA both arise from the thyrocervical trunk, they pass anterior to the brachial plexus trunks.

Calibre of the TCA and DSA at their origin

The average calibre of the TCA was 2.70 mm (range 1.7–3.6), and the average calibre of the DSA was 2.66 mm (range 1.6–3.8). In seven specimens (44%), the vessel diameter of the TCA was larger than the DSA. In six specimens (37%), the DSA was larger in calibre than the TCA. And in three specimens (19%), the TCA and DSA were equal in size (Table 1).

Table 1.

Table showing calibre of the transverse cervical artery (TCA) and dorsal scapula artery (DSA) at their origins.

Specimen No.	TCA (mm)	DSA (mm)
1.	3.0	1.6
2.	2.8	1.8
3.	3.6	2.0
4.	2.7	2.4
5.	3.3	3.2
6.	3.1	2.5
7.	3.0	2.6
8.	2.0	2.0
9.	2.8	2.8
10.	3.0	3.0
11.	1.8	2.3
12.	2.4	2.6
13.	2.7	3.2
14.	1.7	3.3
15.	3.3	3.5
16.	2.0	3.8
Mean	2.70	2.66

Course of the TCA

The TCA arose from the thyrocervical trunk and ran laterally and posteriorly across the base of the neck, passing anterior to the scalene muscles and the brachial plexus. It then coursed superficial to the levator scapulae and entered the deep surface of the trapezius muscle at its anterior border. It arborised on the deep surface of the middle trapezius, sending branches superiorly, laterally and inferiorly (Figure 2). The inferior branches anastomosed with the DSA network. The cutaneous perforators that arose from the TCA were located over the superior and posterior shoulder. The veins that accompanied the TCA were usually superficial. They ran deep or superficial to the omohyoid muscle and accompanied or diverged from the TCA as they travelled across the base of the neck from lateral to medial. They terminated in the external jugular vein or subclavian vein.

Figure 2.

Left: Right trapezius muscle specimen, deep surface.

Right: Left trapezius muscle specimen, deep surface.

The transverse cervical artery (TCA) supplies the middle and upper trapezius (dark blue vascular system). The dorsal scapula artery (DSA, light blue vascular system) supplies the middle and lower trapezius, as well as the medial edge of the scapula (big white arrow). Vascular connections between both systems occur in the middle trapezius. The DSA arises directly from the subclavian artery (SCA), while the TCA arises from the thyrocervical trunk of the SCA. The DSA anastomoses with the posterior intercostal arterial system along the midline. The vessel calibre at their origins are comparable.

A: Internal mammary artery.

B: Vertebral artery.

C: Costocervical trunk.

D: Inferior thyroid artery.

E: Supraclavicular artery.

Course of the DSA

The DSA arose directly from the subclavian artery in 63% specimens and from the thyrocervical trunk in 37% specimens. It passed posterolaterally in the lower neck and ran between the brachial plexus trunks, descending deep to the levator scapulae and rhomboid minor, sending contributory branches to these muscles as well as a branch to the medial border of the scapula bone. It emerged between the rhomboid minor and major muscles along the medial border of the scapula bone to enter the lower part of the middle trapezius (Figure 3). On the deep surface of the muscle, it arborised, sending branches superiorly to anastomose with the TCA muscular network (Figure 2). The perforators to the skin were both musculocutaneous and fasciocutaneous - the musculocutaneous perforators penetrated the muscle to supply the overlying skin directly, and the fasciocutaneous perforators travelled laterally beyond the lateral border of the trapezius muscle, contributing to the thoracodorsal fascial network before supplying the skin. These fasciocutaneous perforators form the basis for the extended trapezius flap⁶ (Figure 4). Two or three venae comitantes consistently accompanied the DSA. They ran deep to the omohyoid and levator scapulae muscles and drained into the subclavian vein.

Figure 3.

Course of the DSA along the right posterior shoulder. The levator scapulae (LS), rhomboid minor (Rm), and trapezius muscles are reflected laterally showing their deep surfaces.

The DSA originates from the subclavian artery (SCA), and travels deep to the LS and Rm muscles. It emerges from between the rhomboid minor and major to supply the middle and lower trapezius. It contributes arterial branches to the LS, Rm and rhomboid major.

Figure 4.

Perforators of the DSA after colored latex injection. Vessels are seen extending beyond the lateral edge of the right trapezius muscle, into the fascia overlying the latissimus dorsi muscle. The corresponding cutaneous branches are seen on the reflected subcutaneous layer of the skin. Anastomoses medially to the posterior intercostal arterial system are also noted.

Cutaneous territories of the TCA and DSA

The cutaneous territory of the TCA measured 15 × 10 cm, centred over the superior and posterior shoulder, extending medially to the nape of the neck and laterally to the deltoid region. The inferior limit of the cutaneous flare was at the level of the spine of the scapula.

The cutaneous territory of the DSA measured 20 × 15 cm and was centred over the medial border of the scapula, and extending significantly beyond the lateral border of the muscle. It extended medially to the midline, laterally to the posterior axillary line and inferiorly 15 cm past the lateral border of the trapezius muscle, indicating an extended fascial network (Figure 5).

Figure 5.

Cutaneous territories of the TCA, DSA and thoracodorsal artery (TDA).

Left: Above, 15 × 10 cm cutaneous flare created by injecting the TCA with methylene blue. Below, 20 × 15 cm methylene blue cutaneous flare created by injecting the DSA. Notice the dispersal of dye 10 cm beyond the lateral border of the inferior trapezius muscle (white arrow). This gives the basis for the extended trapezius flap.

Right: Illustration demonstrating the respective cutaneous territories of the TCA (blue), DSA (purple) and TDA (pink). Notice that there is considerable overlap between adjacent territories.

Clinical cases illustrating the trapezius muscle’s dual blood supply

Case 1

This 26 year-old female sustained 70% total body surface area burns. Following recovery from acute burns, she presented with severe scar contractures over her chin and neck with loss of the cervicomental angle. Conventional free flap donor sites (anterolateral thigh, radial forearm, scapula, groin) were unsuitable due to extensive scarring. The anterior chest skin was also severely scarred, obviating the possibility of utilizing locoregional flaps from that area. The only unaffected area was skin over her right shoulder and deltoid. A middle trapezius flap measuring 16 × 4 cm centred over the axis of the right shoulder was raised in a fasciocutaneous fashion to resurface the chin. It was based on sizeable TCA perforators located along the middle trapezius. The perforator was identified using a hand held doppler. Next, an extended lower trapezius flap based on the DSA was used to cover the secondary defect and restore shoulder contour. The extended lower trapezius flap was centred on the inferolateral edge of the trapezius, at the level of T10 just distal to the tip of the scapula. The skin paddle had a 10 cm proximal overlap with the trapezius muscle to capture perforators and a 15 cm distal fasciocutaneous extension. It was planned with a width of 6 cm to allow primary closure. The medial border of the trapezius was identified first and traced inferiorly to confirm the position of its tip. The flap was then elevated from distal to proximal, ensuring inclusion of the deep fascia over the latissimus dorsi as the vascular plexus here supplies the overlying skin. Delay procedures were employed for these flaps to ensure complete survival. The middle trapezius flap pedicle was divided after three weeks, and flap debulking was performed subsequently. At two years, and after minor scar revisions, the patient achieved satisfactory restoration of chin contour, cervicomental angle and improvement of perioral contractures (Figure 6).

Figure 6.

Clinical case 1.

A: Pre-operative photo showing hypertrophic scarring of the chin and submental region, causing peri‑oral contractures and loss of cervicomental angle.

B: Above – Intra-operative photo of the extended fasciocutaneous middle trapezius flap based on perforators from the TCA, and extended lower trapezius flap based on the DSA. Below – Intra-operative photo of the inset of the extended fasciocutaneous middle trapezius flap.

C: Post-operative photos showing restoration of cervicomental angle, improvement of peri‑oral contractures and preservation of right shoulder contour.

D: Illustration of dual flap harvest and transposition.

Case 2

This 78-year-old female presented with a squamous cell carcinoma over her left cheek. Her medical history was significant for ischaemic heart disease with decreased ejection fraction of 40%. Given her age and co-morbidities, she was not fit to undergo free flap surgery. An upper trapezius fasciocutaneous flap measuring 16 × 6 cm based on perforators from the TCA was designed over the posterior neck and nape of neck. The perforators were identified using a hand held doppler. The flap was raised in a sub-fascial plane until adequate reach was obtained. Thereafter, it was lightly tubed and transposed anteriorly to cover the cheek defect. The secondary defect over the neck was covered using an extended lower trapezius flap based on the DSA as described in case 1. The upper trapezius flap was divided three weeks later under local anesthesia. She achieved good cheek contour and coverage (Figure 7).

Figure 7.

Clinical case 2.

A: Surgical defect over the left cheek and inset of the upper trapezius fasciocutaneous flap, which was based on perforators from the TCA.

B: Extended lower trapezius flap based on the DSA transposed to the posterior neck to cover the secondary defect, with the donor site closed primarily.

C: Post-operative result showing good coverage and cheek contour.

D: Illustration demonstrating dual flap harvest and transposition.

In both cases, there were no flap complications or donor site issues.

Discussion

Under the Mathes and Nahai system,⁷ the trapezius muscle is classically described as a type II muscle consisting of one dominant pedicle (TCA) with additional minor pedicles. Many authors adhere to this concept regarding the sole dominance of the TCA, thereby discounting the contribution of the DSA. In our study, the calibre of the DSA was equal to or larger than the TCA in 56% of specimens (Table 1). This corroborates Netterville’s⁸ anatomical study which also measured the calibre of the TCA and DSA at their origin and found that 50% had a dominant DSA, 30% had a dominant TCA, and 20% had a co-dominant TCA and DSA. These findings contradict conventional beliefs that regard the TCA as the sole dominant pedicle to the trapezius. From our findings, we conclude that the DSA is a major vascular contributor to the middle and lower trapezius and caution against simply ligating it when raising the lower trapezius flap. Additionally, we believe that the trapezius muscle is in fact a type III flap supplied by two co-dominant vessels. Our two clinical cases illustrate this new concept, showing it is possible to harvest dual flaps simultaneously based on this co-dominant system. In case 1, we raised an extended fasciocutaneous middle trapezius flap following the TCA’s cutaneous territory (Figure 5). As we required a longer reach, we employed delay procedures to prevent tip necrosis. Usually, this flap can be safely raised in a single stage.^6,9 The extended lower trapezius flap which we used in both cases is a robust and reliable flap based on the DSA.⁶ Angrigiani¹⁰ has reported an island flap based on the DSA, corroborating our concept. As demonstrated in our cases, it can reach as far as the shoulder trip and nape of neck. If further reach is required, the length of the pedicle can be extended by dividing the overlying rhomboid minor safely. Winging of the scapula is prevented by leaving the rhomboid major intact.

In cases with unscarred anterior chest skin, other options for similar defects would include the supraclavicular artery flap and its variants including the pre-expanded transverse cervical artery perforator flap,¹¹ anterior supraclavicular artery perforator flap¹² and the supraclavicular transverse cervical artery perforator flap¹³; although flap delay through tissue expansion is required to capture anterior chest skin territory.

A common concern is whether the trapezius flap can be raised safely in patients after radical neck clearance. The transverse cervical vein is usually divided early during a posterior triangle (level V) neck dissection, once it is identified crossing the field, to allow safe exposure of deeper structures. However, the transverse cervical artery is usually preserved. The high failure rate of up to 75%² of trapezius flaps historically reported is likely due to sole reliance on the TCA without its corresponding venous system. Based on our dissection findings, we believe that the lower trapezius flap is safe even after neck dissections, since the DSA is almost never ligated. The DSA had a separate origin in 63% of our dissections and also travelled in a distinct and deeper course at the level of the brachial plexus, in contrast to the TCA. This makes its exposure unlikely during neck dissection. The DSA is also consistently accompanied by venae comitantes, making venous drainage separate from the transverse cervical venous system.

The DSA is not to be confused with the “deep branch” of the TCA as its course is well-defined and different from that of the TCA. Based on our dissections, the DSA consistently ran between the brachial plexus trunks, descending deep to the levator scapulae and rhomboid minor, and emerged between the rhomboid major and minor muscles along the medial border of the scapula bone to enter the lower part of the middle trapezius (Figure 3). It contributed blood supply to the above-mentioned muscles as well as the medial scapula. This is in contrast to the TCA which ran superficial to the brachial plexus and the levator scapulae. These anatomical findings were consistent with the cadaveric studies performed by Huelke¹⁴ and Haas.¹⁵

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Ethical approval statement

This study was conducted in accordance with the principles outlined in the Declaration of Helsinki. It did not require approval from the Singhealth Centralized Institutional Review Board. Written informed consent was obtained from all patients for treatment and the use of their clinical data for research and publication purposes. Patient confidentiality and anonymity have been strictly maintained throughout the study.

Patient consent

Informed written consent was obtained from the patients included in this study for photography, surgical procedures and publication.

Declaration of competing interest

The authors declare no conflicts of interest related to this study.