Anatomic validation of an "anatomic" shoulder system.

An anatomic study was conducted on 49 dried cadaveric humeri and 24 dried cadaveric scapula to ascertain the variability of the following parameters: humeral neck angle, humeral head retroversion, humeral head medial offset, humeral head posterior offset, humeral head diameter glenoid height, glenoid width, and the glenoid height to width ratio. For verification purposes, the results of this study were found to be within 1.5% to 14.3% of other anatomic studies published in the literature. This observed variability was then compared to that provided by an "anatomic" shoulder prosthesis (Equinoxe, Exactech, Inc.); viewed independently, this prosthesis can restore humeral neck angle in 94% of humeri, "secondary" retroversion in 92% of humeri, medial offset in 100% of humeri, posterior offset in 100% of humeri, and humeral head diameter in 96% of humeri. Additionally, the glenoid prosthesis height to width ratio was found to be within 5% and 10% of 71% and 96% of cadaveric glenoids, respectively. The results of this analysis indicate that a dual-offset "anatomic " shoulder prosthesis has the capability to successfully restore glenohumeral anatomy in this representative population.