Bone density in massive rotator cuff tears and possible implications in superior capsular reconstruction

Abstract

Superior capsular reconstruction (SCR) by using either the fascia lata autograft or a dermal allograft patch are newly described solutions that could prevent superior humeral head migration and restore the anteroposterior shoulder muscle force couple. However, despite initially promising clinical and radiographic outcomes, the more recent literature shows disparity in the results. Possible predisposing factors for SCR structural failure is poor bone quality in the humeral and glenoid fixation points. The purpose of this study was to assess bone density at these points using computed tomography. We retrospectively assessed the CT-scans of 26 patients with chronic massive rotator cuff tears (MRCTs). We used the CT-scans of 10 patients without rotator cuff pathology, arthritis or fractures as a control group. Using Horos software, we performed 3D-multiplanar reconstruction of the images and we established the possible anchor placements on the glenoid and humerus. Therefore, we recognized two fixation points on the glenoid (anterior and posterior), approximately 5 mm medial to the articular surface. Respectively we established four fixation points on the humerus, two medially at the limit of the articular surface (anteriorly in the bicipital groove and posteriorly at the level of the infraspinatus) and two laterally (at the same level with medial points in the coronal plane and 1 cm lateraly in the axial plane). The Hounsfield units (HU) were measured at these points. Healthy control patients at the selected glenoid fixation points one density in HU of 235 ± 53 anteriorly and 287 ± 98 posteriorly. The respective values in patients with MRCTs were 125 ± 36 and142 ± 42, and the differences were statistically significant (p > 0.001 and p = 0.001). Medial humeral fixation points in HU were 115 ± 33 anteriorly and 178 ± 58 posteriorly in healthy patients. The respective values in MRCTs were 78 ± 40 and 77 ± 38 (p = 0.034 and p > 0.001). Finally, for the lateral humeral fixation points in the control group, the HU were 111 ± 22 anteriorly and 130 ± 45 posteriorly. In patients with MRCTs the respective values were 68 ± 40 and 69 ± 41 (p = 0.006 and p = 0.002). Assessment with computer tomography shows that bone density is severely affected in patients with MRCTs, compared to healthy controls. Additionally, the glenoid and the posterior humerus seem to be the weakest fixation points for SCR with 50 % less bone density.