Morphometry of the proximal humerus and the relationship to global offset

Background

Previous research has consistently identified the medial and posterior offset of the native humeral head in relation to the intramedullary canal. These anatomic parameters and others such as humeral head and intramedullary diameter provide valuable insight for prosthesis development. However, it is critical to understand the relationship of morphometry to the native center of rotation. Our objective was to use 3-dimensional analysis to demonstrate the native morphometry of the proximal humerus and those relationships to global offset.

Methods

Fourteen cadaveric humeri were manually measured then digitally analyzed following 3-dimensional scanning. Pearson’s r was used to determine the relationship between variables.

Results

The mean digital humeral head diameter (Hd^d) was 46.5 (± 4.67) mm and the mean manual humeral head diameter was 46.8 (± 4.42) mm. The mean global offset (GO) was 6.36 (± 2.21) mm, and the mean best fit sphere diameter was 46.5 (± 4.63) mm. Pearson’s r = 0.58 (95% confidence interval 0.07-0.84, P = .021) for GO and Hd^d which indicates a moderate correlation. Pearson’s r = 0.96 (95% confidence interval 0.89-0.99, P < .001) for Hd^d and manual humeral head diameter which indicates a strong correlation.

Discussion

Native GO demonstrated a moderately positive correlation to humeral head diameter. The manual measurement of head diameter was strongly correlated to the 3-dimensional software value which reinforces the importance of intraoperative measurement. These data contribute to further understanding of shoulder morphometry which is integral to prosthesis design which impacts postoperative function and complications.