The conventional measuring method for glenoid version is greatly influenced by the scapular body shape that varies widely between patients. We postulated that the glenoid vault version could be more useful than the conventional glenoid version in clinical cases. The purposes of this study were to compare the values of glenoid version measured with the conventional method to those with the vault method and to investigate the feasibility of the glenoid vault version. Computed tomography scans of 150 normal shoulders and 150 arthritic shoulders were analyzed. Three-dimensionally corrected slices were reconstructed from the Digital Imaging and Communications in Medicine (DICOM) data, and glenoid version was measured with both the conventional and vault methods. After determining intra- and interrater reliabilities, differences in glenoid version values between the conventional and vault methods were assessed. In the normal shoulder group, side-to-side differences of glenoid version values were also evaluated in both methods. Both measuring methods demonstrated high intra- and interrater reliabilities. The normal glenoid had 1.1° ± 3.2° retroversion with the conventional method and 8.9° ± 2.7° retroversion with the vault method. The average glenoid retroversion of arthritic shoulders was 10.8° ± 9.3° measured with the conventional method and 18.2° ± 9.1° with the vault method. The vault method showed significantly larger glenoid retroversion than the conventional method in both normal and arthritic shoulder groups. Both conventional glenoid retroversion and glenoid vault retroversion were significantly larger on dominant sides than on nondominant sides in the normal shoulders. The glenoid vault version could be used as an alternative measuring method for glenoid version with high reliability. In clinical use, the glenoid vault version appears to be more useful than the conventional glenoid version to assess the severity of arthritis and difficulty of glenoid replacement. The glenoid vault is not symmetric, but usually retroverted in both normal and arthritic shoulders.

Fatty infiltration in muscle is often observed in patients with sizable rotator cuff tear (RCT) and is thought to be an irreversible event that significantly compromises muscle plasticity and contraction strength. These changes in the mechanical properties of the affected muscle render surgical repair of RCT highly formidable. Therefore, it is important to learn more about the pathology of fatty infiltration to prevent this undesired condition. In the present study, we aimed to generate a mouse model that can reliably recapitulate some of the important characteristics of muscular fatty infiltration after RCT in humans. We found that fatty infiltration can be efficiently induced by a combination of the following procedures: denervation of the suprascapular nerve, transection of the rotator cuff tendon, and resection of the humeral head. Using this model, we found that platelet-derived growth factor receptor-α (PDGFRα)-positive mesenchymal stem cells are induced after this intervention and that inhibition of PDGFR signaling by imatinib treatment can significantly suppress fatty infiltration. Taken together, the present study presents a reliable fatty infiltration mouse model and suggests a key role for PDGFRα-positive mesenchymal stem cells in the process of fatty infiltration after RCT in humans.

Background: Although humans spend most of their day in a standing or sitting position, it is difficult to accurately evaluate the alignment of the shoulder girdle during daily activity, and its alignment changes between positions. The purpose of this study was to evaluate the 3-dimensional alignment of the shoulder girdle in the supine and standing positions by computed tomography (CT) and to assess the alignment changes of the shoulder girdle between these two positions. Methods: CT scans of both shoulders of 100 healthy volunteers were prospectively taken in both supine and standing positions on the same day. The local 3-dimensional coordinate systems of the thorax, clavicle, and scapula were defined from the specific bony landmarks, and 3-dimensional angular rotations and positions of the clavicle and scapula were calculated. Differences in rotations and positions of the clavicle and scapula were evaluated between the supine and standing positions. Results: Compared with the supine position, the clavicle showed significantly less elevation and greater retraction, and the scapula showed significantly less upward rotation, anterior tilting, and internal rotation in the standing position. Compared with the supine position, the clavicle center was located more inferiorly, posteriorly, and laterally, and the scapula center was located more inferiorly, posteriorly, and medially in the standing position. Conclusions: The present study showed that angular rotations and positions of the clavicle and scapula change significantly with position due to the effect of gravity.