Several types of anomalous origin of the suprascapular artery are extensively studied and quantified. The deviation from the normal pattern is not unusual,[1
] as the subclavian artery and different types of common arterial trunks had been described at different locations of origin. In the present study the suprascapular artery constituted a branch of the thyrocervical trunk in all but one case (1.6%, 1/62) where it emerged from the third segment of the subclavian artery (right side of a female cadaver), very close to the first segment of the axillary artery. According to the available literature, this type of origin seems to be one of the rarest. Mishra and Ajmani[10
] reported that the suprascapular artery originated from the first part of the axillary artery with an incidence of 1.6% (1/60 sides, variation observed on the left side), whereas Adibatti and Prasanna[11
] observed the same variation in one cadaver (male, left side) out of 30 studied. Additionally, Mahato[12
] recorded a single case of anomalous bilateral origin of the suprascapular artery from the third part of the axillary artery.
] have been carried out on the subligamentous course of the suprascapular artery. According to Tubbs et al
] the suprascapular artery, accompanied by the suprascapular nerve, passes under the STSL with a median incidence of 2.5% (3/120). In one (male) cadaver, the finding was bilateral and in one other (also male) unilateral.[15
] Yang et al
] classified the arrangement of the suprascapular vessels into three types: In Type I (59.4%), all suprascapular vessels ran over the STSL; in Type II (29.7%), the vessels ran over and under the STSL simultaneously (at least one vessel passed under or over the STSL); and in Type III (10.9%), all vessels ran under the STSL. Furthermore, three cases of the suprascapular artery passing through the suprascapular notch during endoscopic suprascapular nerve release have been reported by Reineck and Krishnan.[17
Anomalous course of the suprascapular artery inside the suprascapular notch very frequently coexists with an ipsilateral variation in the origin of the artery.[1
] In particular, this variation was combined with anomalous origin from the subclavian or axillary artery.[2
] This was similar to the findings in the study of Adibatti and Prasanna.[11
] Nevertheless, Mishra and Ajmani[10
] observed three cases where the suprascapular artery coursed inside the notch, with only one of them combined with variation in the origin of the artery (1/60 = 1.6%). In the present study, the sole case of unusual origin of the suprascapular artery was indeed combined with its passage under the STSL (1.6%, 1/62).
In our case, variation of the artery's origin and course is accompanied by total absence of the suprascapular vein. This finding is not described in the available literature.
According to the available literature, the incidence of complete ossification of the STSL varied from 3.7% to 13.6%.[18
] However, complete ossification of the STSL is exceptionally rare in some populations, such as in Alaskan Eskimos or Indians.[18
] Duparc et al
] reported that STSL appeared calcified and rigid (not necessarily completely ossified) in 26.7% of the cases. The calcified STSL is considered to be a sign of entrapment. On the other hand, simultaneous ossification of the coracoid process and epiphysis, as observed mostly in Nigerian infants, might change the shape of the notch.[20
Embryologically, all main vessels develop from a primary plexus of smaller ones.[15
] The prevailing conditions lead some vessels to enlarge and form definitive channels and others to regress.[7
] During this phase of development, it is possible that different patterns in the vessels may appear, including both the origin and/or the course of either arteries or veins.
An origin of the suprascapular artery in the vicinity of the thyrocervical trunk (either from the subclavian artery itself or from a common trunk with the transverse cervical artery) is by far the most common variation and at the same time the least interesting one from an anatomical or clinical viewpoint, since in this case the course and relations of the artery are hardly influenced. On the contrary, an origin of the suprascapular artery from the third part of the subclavian artery or from the axillary artery is rarer and clinically significant. Furthermore, this variation is frequently accompanied by the passage of the artery through the suprascapular notch.
Surgeries in the anterior neck and supraclavicular region, such us radical and modified neck dissections to control the lymphogenous spread of head and neck cancer, may require ligation of the suprascapular artery. Thus, knowledge of the possible variations in the origin and the course of the artery are very important.[21
Clavicular fractures are fairly common and most often occur in the middle third of the bone.[22
] The suprascapular artery supplies with blood the proximal 4/5th
of the clavicle and constitutes the exclusive blood supply for the middle 1/3rd
of the clavicle.[25
] On doing so, it runs parallel, above and close to the clavicle, but not in touch with it. This usually avoids a disastrous damage of the artery during clavicular fractures. A direct origin of the suprascapular artery from the middle of the subclavian artery coursing below the clavicle merely enhances the probability of arterial damage during fracture of this bone. The seemingly illogical origin of the suprascapular artery from the thyrocervical trunk (since it results in its greater length) may be attributed to an effort to minimize the danger of its injury. If the suprascapular artery rises from an anomalous position it is possible that its unusual origin and course could either increase or decrease the danger of being damaged by a broken clavicle, according to the vicinity of this origin with the middle of the bone. In our case, the suprascapular artery emerged very close to the first segment of the axillary artery and almost behind the external third of the clavicle, which means that the usual middleclavicular break would not pose great danger to the artery. However, if the suprascapular artery arises from the internal thoracic, its ascending course behind the middle third of the clavicle could be extremely dangerous not only for the nutrient wigs of the bone but also for the whole suprascapular artery.
Inside the suprascapular notch, the suprascapular nerve is restrained by the transverse scapular ligament. This may lead to friction of the nerve, inflammation, and finally constriction of the nerve, leading to suprascapular neuropathy.[26
] Factors such as ossification of the STSL and anomalous course of the suprascapular artery under the ligament could lead to a faster and more severe constriction of the nerve, since they reduce the capacity of the notch.[15
] Chronically, this could lead to atrophy of the supraspinatus and infraspinatus muscles, limited decreasing abduction, and external rotation of the shoulder and chronic deep-seated pain in the shoulder that is aggravated with movement (suprascapular neuropathy symptoms).[27
] Suprascapular neuropathy may of course occur by other mechanisms as well: For example, by mikroembols in the vasa nervosum of the suprascapular nerve engendered through a damage of the suprascapular artery.[10
Thus, “unexplained” shoulder pain, namely pain not due to arthritis (inflammation of glenobrachial or acromioclavicular joints), or malfunction of the shoulder's rotator cuff must lead to investigation of an eventual neuropathy. Noticeably, in our case, in which the suprascapular vein is absent, the probability of a suprascapular neuropathy was reduced, since the suprascapular notch contained two items (artery and nerve) instead of three. However, the pulsing artery might produce minor annoyance to the nerve, especially when it contacts its sensitive fibers.