The arterial integrity of the “critical zone” of the rotator cuff has led to much uncertainty regarding rotator cuff tendinopathy. As the region of the supraspinatus tendon is the most common area affected by impingement, its central aspect is situated approximately 10 mm from the insertion at the greater humeral tubercle. Although many studies have investigated the vascularity of the “critical zone”, there still appears to be lack of consensus regarding its extent. Through the employment of gross dissection and standard histology analysis of twenty-five adult bilateral cadaveric scapulo-humeral regions (n = 50), this study aimed to quantify the degree of vascularity, or lack thereof, within the “critical zone” by evaluating its relative morphometric features. The demographic representation of the sample was also considered. Results: i) Mean diameter of arteriole lumen: 91.6±75.2 μm; ii) Mean diameter of entire arteriole: 119.8±87.1 μm; iii) Mean arteriole wall thickness: 15.1±9.5 μm; iv) Mean area occupied by an arteriole: 20644.4±3358.0 μm2; v) Mean number of arterioles within “critical zone”: 14.6±8.7. All tissue samples displayed a scarce distribution of arterioles along the musculo- tendinous junction relative to the “critical zone”. A directly proportional relationship between the morphometric parameters was indicated by positive strong correlations and accompanying statistically significant P values. As 66 % of the number of arterioles within the “critical zone” were distributed between the minimum value and the upper quartile, it was postulated to be hypovascular, therefore confirming the findings of previous studies.
KEY WORDS: “Critical zone”; Arterioles; Vascularity; Morphometric parameters.