MRI-based anthropometric measurements of proximal humerus in Thai population and correlation to the shoulder prostheses

Abstract

All anatomical data of the proximal humerus measured from the 3D reconstruction of the MRI of patient shoulders who performed MRI between Jan 2008 – Dec 2008. We used CATIA to measure all parameters and minimize the human error by using a computer to calculate a 3D model. The mean of total diameters of articular was 36.64±4.44 mm. The mean of male and female shoulders were 40.83±1.36 mm., 33.57±2.76 mm. respectively. Therefore, the difference between gender was significant. The mean articular thickness of total subjects was 15.48±2.38 mm. Consisting of the mean of male ; 16.83±2.05 mm., and the mean of female ; 14.50±2.13 mm. The difference of articular thickness between gender was also significant. The mean neck-shaft angle of all subjects was 137.71±6.43 mm. Separately, that the mean of male and female subjects were 138.80±4.86 mm., 136.92±7.32 mm. respectively. The mean medial offset of all subjects was 5.43±1.51 mm. It explained that the mean of male and female subjects were 5.29±1.81 mm., 5.53±1.26 mm. respectively. The mean posterior offset of all subjects was 1.15±0.94 mm. We considered about the mean of male and female subjects were 1.27±0.80 mm., 1.06±1.04 mm. respectively. The mean of all retroversion angles was 13.99±16.17 mm. The mean of male and female subjects were 10.21±16.16 mm., 16.76±15.82 mm. respectively. Subsequently, the difference of neck-shaft angle, medial offset, posterior offset and retroversion angle between gender were not significant. All data of this study when we compared to the previous in western population, we founded significant difference in diameter of articular, neck-shaft angle, medial offset and posterior offset. The diameter of articular and articular thickness were compared to the same parameters of the currently used shoulder prosthesis ( Zimmer, Johnson ). We recommended to use currently shoulder prosthesis in Thai male population that diameter more than 40 mm. and did not recommend to use in any Thai female population. In Thai male population, the Zimmer prosthesis was more suitable size to use because of the availability of the articular thickness with the same diameter. This finding showed that a implant component suitable for using in Western population may not be compatible for Thai population. The results of the project could provide fundamental data for the future design of shoulder prostheses suitable for the Thai population.