All the humerii from various medical colleges of the Vinayaka Missions University in Salem, namely, Vinayaka Missions Kirupananda Variyar Medical College, Annapoorna Medical College, and Vinayaka Missions Homeopathy Medical College, were included in the study. The bones which were damaged and those which had pathological abnormalities were excluded. All the adult humerii which were not necessarily paired and those of unknown age and sex were examined. The following parameters were noted; namely, the length of the humerus, the number of the nutrient foramen, the size of the nutrient foramen and the location of the nutrient foramen with respect to the surfaces and the zones and the distance of the nutrient foramen from the mid-point of the humerus were analyzed. The length of each humerus bone was measured from the superior aspect of the lesser tubercle to the inferior surface of the medial epicondyle of the humerus by using an osteometric board [2]. Further, the humerus bone was divided into three equal zones, as zone I (upper 1/3^rd), zone II (middle 1/3^rd) and zone III (lower 1/3^rd) [Table/Fig-1]. The midpoint of the humerus was calculated by dividing the length of the humerus by two and the same was identified and marked on the humerus with the help of the osteometric board. The location of the nutrient foramen was noted with respect to the three surfaces, namely, the anteromedial, the anterolateral and the posterior and the three zones, namely, zone I, zone II and zone III. The distance of the nutrient foramen from the midpoint of the humerus was measured by using a vernier caliper. The size of the nutrient foramen was determined by using hypodermic needles of various sizes, which ranged from 18 Gauge to 26 Gauge, of known diameter s (18 Gauge =1.2 mm, 20 Gauge = 0.9mm, 24Gauge = 0.55mm and 26 Gauge = 0.45mm). When more than one foramen was found, the larger nutrient foramen was considered as the dominant foramen and its size was measured. All the data were noted and the statistical analysis was done by calculating the percentage, mean, range and the standard deviation.

[Table/Fig-1]:

Measuring the length of humerus using osteometric board and dividing into zones - (I, II and III)

Totally, 258 adult dry humerii were studied, of which 51.16% were left sided bones and 48.84% were right sided bones. The mean length of the humerii was 27.96 cm, with a SD of 2.18, which ranged from 18 to 33 cm. The median length was 28cm. Though some humerii had two or more nutrient foramina, a majority of the humerii had a single nutrient foramen [Table/Fig-2].

The sizes of the foramina ranged from 0.45 to 1.2 mm, with a mean of 0.828 mm and a SD of 0.26. The distance of the dominant nutrient foramen from the mid point of the humerus ranged from 0.5- 8 cm, with a mean distance of 2.31 cm and a SD of 1.25 cm. 88.76% of the nutrient foramina were located above the mid points of the humerii and 11.24% were located below the mid points of the humerii. A majority of the nutrient foramina were located in the anteromedial surfaces of the humerii. [Table/Fig-3] Similarly, a majority of the humerii had the nutrient foramina in zone II (middle 1/3) of the bone [Table/Fig-4].

The blood supply is the main factor in the healing of fractures [3–5]. Any damage to the nutrient artery during surgical fixations or subsequent manipulations, is a significant factor which predisposes to delayed unions or nonunions [6–10]. The humerus is supplied by the nutrient artery, the metaphyseal artery and the periosteal vessels from the axillary and the brachial arteries and their branches. The periosteal and the metaphyseal arteries supply the outer cortex and the metaphysis of the bone, but the inner half of the cortex and the medulla of the shaft are predominantly dependent on the nutrient artery. The study on the blood supply of the shaft will help in knowing about the healing of fractures, delayed unions and non unions of the bone following fractures and bone transplants [11]. Laing studied the vascularity of the humerus and he opined that the main nutrient artery of the humerus must be protected from injuries during operations which are done on the humeral shaft [6]. Carroll stated that the nutrient artery enters through the restricted anteromedial surface, in the middle 1/3^rd of the humerus and that the surgeries which are done on the middle 1/3^rd of the shaft of the humerus should be handled well without causing damage to the nutrient foramen, in order to prevent delayed unions or non unions of the fractures. Our study results correlated well with those of Carroll's study [2]. Many studies which have been done on the humerus bone have revealed that a majority of the humerii had one nutrient artery and that some had additional accessory arteries. Our study results correlated well with Manjunath S Halagatti's and Pramod's study results and they differed from those of others. This could be because of the variation in the population [Table/Fig-5] [2,6,12–13]. There is no correlation between the length of the humerus and the number of the nutrient foramina according to the studies which were done by Manjunath S Halagatti and Chhatrapati DN [13,14]. Hence, we did not attempt to correlate the same. This study adds a message to the existing knowledge, that a variation in the population can result in a variation in the number of nutrient foramina.

This study concludes that the nutrient foramina of the humerii were not only located on the anteromedial surfaces but also on the anterolateral and the posterior surfaces. Similarly, the nutrient foramen of the humerus was found on both the middle and the lower third of the shaft. A majority of the humerii had a single nutrient foramen, though some humerii had more than one nutrient foramen.