The glenohumeral joint – a mismatching system? A morphological analysis of the cartilaginous and osseous curvature of the humeral head and the glenoid cavity

V. Zumstein, M. Kraljević, S. Hoechel, A. M. Nowakowski, M. Müller-Gerbl

Please note: Valentin Zumstein and Marko Kraljević contributed equally to this work

Background

Radial mismatch, glenohumeral conformity ratios and differences between cartilaginous and osseus radii highly depend on the measured plane. The comparison of cartilaginous radii between humeral head and glenoid in different planes provides new information to understand the degree of conformity during abduction of the upper limb.

Methods

To investigate the radii, CT-images in soft-tissue kernel of 9 specimen were analysed using an image visualization software. Statistical analysis of the obtained data was performed using the t-test.

Results

Measurements of the radii in the glenoid revealed a significantly larger radius for bone than cartilage, whereas for the humeral head the opposite was the case. Highest ratios for cartilage in the transverse plane were found in the inferior and central areas of the joint surface, whereas the smallest ratios were found in the superior area. The radial mismatch varied between 0.1 mm and 13.6 mm, depending on the measured plane.

Conclusion

The results suggest that in abduction, the cartilaginous guidance of the humeral head decreases. This might permit the humeral head an anterior-posterior shifting as well as superior-inferior translation. Surgical reconstruction of the normal glenohumeral relationships necessitates precise information about the glenohumeral morphology to ensure proper sizing and correct placement of prosthetic components and osteochondral allografts.

Figure 1: (a) Five points determined by equidistance were marked along the length axis (AG) and 3 along the transverse axis (E’E’’) to determine the planes to measure the horizontal and vertical radii (B’B’’ - F’F’’ and H’H’’ - I’I’’). (b) For the humeral head 5 points determined by equidistance were calculated for both the length (KQ) and transverse axis (RX) to determine the individual planes where radii were measured (L’L’’ - P’P’’ and S’S’’ - W’W’’).
Figure 2: Radius measurement in the transverse plane of the (a) glenoid cavity and (c) humeral head. (b) 3D view of cartilaginous (green circle) and osseus (red circle) radii in the transverse plane of the glenoid cavity. (d) Radius of curvature in the coronal and transverse plane of the humeral head.
Figure 3: Visualisation of the cartilaginous (yellow mesh) and osseous structure (blue) in (a) infero-superior view of the glenoid, (b) antero-posterior view of the glenoid and (c) frontal view of the humeral head.
Table 1: Mismatch and ratios of selected cartilaginous radii of the glenoid and the humeral head.