Distribution of haematopoietic and fatty bone marrow of the shoulder: MR imaging and macroscopic anatomy

Purpose: To establish the distribution pattern of haematopoietic and fatty bone marrow on MRI of the proximal humerus and the scapula in correlation with age, gender and nutritive factors. Material and methods: 32 shoulder MK examinations (T-1-weighted spin-echo and opposed-phase gradient-echo sequences) from 23 patients and 8 volunteers were analysed retrospectively The amount of haematopoietic bone marrow within the proximal humerus and scapula was classified into four groups and was correlated with age (H-test), gender (chi(2)-Test), and thickness of subcutaneous fat (H-test). The marrow distribution within 10 scapulae of cadavers over 60 years of age at death was studied. Results: With increasing age, the amount of haematopoietic bone marrow in the proximal humeral metaphysis tends to decrease from lateral towards medial (H-test, p=0.3). Diaphysis and epiphysis did not show haematopoietic marrow. The amount of haematopoietic bone marrow within the paraglenoid region of the scapula also revealed a decrease with increasing age (H-test, p=0.003). Females had higher amounts of haema topoietic marrow than males (chi(2)-test, p=0.03). The thickness of subcutaneous fat was independent of the marrow distribution. Concluson: The amount of haematopoietic bone-marrow of the shoulder girdle decreases with increasing age. The knowledge of marrow distribution patterns based upon these changes is important for shoulder MRI interpretation to prevent confusion with infiltrative disease.