An original method of CT measurement of the lateralization of the humeral intertubercular groove is described based on geometric construction following Thales theorem. A study of intra- and interobserver reproducibility was done of this measurement and humeral retroversion on 32 healthy volunteers. The results show good reproducibility of these measurements. The average value of humeral retroversion was lower than the average values found in the literature: 11.71 degrees on average on the dominant side and 7.03 degrees on average on the non-dominant side with a large spread of values. The reasons for these differences are discussed. The average values of lateralization of the intertubercular groove were 114.97 degrees on the dominant side and 121.9 degrees on the non-dominant side. These CT measurements are important to consider in the pathophysiology of chronic anterior instability of the shoulder.