Background: Diminished vascular supply is associated with degenerative rotator cuff lesions. Orthogonal polarization spectral imaging allows noninvasive assessment of microcirculation without application of fluorescent contrast medium. The aim of our study was to visualize and quantify in vivo the microcirculation of the rotator cuff during arthroscopic surgery and to compare the results with the number of microvessels identified in vitro by immunostaining of biopsy specimens taken from the scanned areas.

Methods: Eleven patients with clinical signs of a degenerative rotator cuff lesion were studied. Prior to arthroscopic subacromial decompression, the superficial part of the supraspinatus tendon at the edge of the lesion as well as the unaffected tendon insertion was examined. Microvascular parameters established for the description of tissue perfusion with use of conventional intravital fluorescence microscopy (functional capillary density and capillary diameter) were assessed in vivo. Biopsy specimens were taken from the scanned areas, and the microvessels were localized by immunostaining for the endothelial surface marker CD31.

Results: In the region of the unaffected tendon insertion, the mean baseline functional capillary density (and standard deviation) was 106 ± 13 cm/cm ² and the mean capillary diameter was 10 ± 0.7 µm. In contrast, at the edge of the lesion, the functional capillary density was significantly reduced to 20 ± 14 cm/cm ² , whereas the diameter of the vessels that were present did not differ. The total number of vessels stained in vitro was also significantly reduced at the edge of the lesion compared with the number of vessels in the tendon insertion zone.

Conclusions: Quantitative in vivo analysis of human microcirculation during arthroscopy demonstrated that the functional capillary density at the edge of a degenerative rotator cuff lesion was significantly reduced compared with that in the control tissue. The capacity to assess microcirculatory flow in vivo may help to identify specific repair strategies based on knowledge of individual perfusion patterns.