The Gross Anatomical and Histological Features of the Humerus in African Green Monkeys (Chlorocebus sabaeus) from Saint Kitts and Nevis, West Indies

Abstract

This paper presents a detailed gross description of all anatomical elements of the humerus in the African green monkey and provides comparative and differential elements on monkey osteology. The osteometric investigation adds value to the gross morphological investigation, adjoining metric data to the gross descriptive data set. An in-depth investigation of the microstructural aspects of the humeral bone tissue is provided, with qualitative and quantitative details and potential for diagnostic applications. Of the gross morphological elements described, several unique features specific to this species include the humeral head shape that presents with distinctive low convexity and caudal placement, the shape of the intertubercular groove, the less developed greater tubercle, and the disposition of the rotator cuff muscle insertion. Furthermore, the overall cranio-lateral curvature of the bone shaft was found to have a distinctive 154-155 degree of angulation of the diaphysis, and the well-developed medial epicondyle was observed with its distinctive medio-caudal retroflexion. The histological investigation was more indicative of a typical non-primate organization of the bone tissue, with laminar vascular and avascular structures combined with the presence of the secondary Haversian system involving a mixture of scattered and dense unorganized secondary osteonal structures. The histomorphometric investigation yielded metrical data for the secondary osteonal structures in terms of area (20,331 ± 5105 µm²), perimeter, and vascular canal area (64,769 ± 257 µm²).

Keywords: African green monkey; Haversian systems; drifting osteon; giant osteon; histology; histomorphometry; humerus; osteology; osteometry; osteon.

Figure 1

Measurements of humerus (A,B). Whole-bone measurements (C,E), proximal extremity measurements (D,F), and distal extremity measurements. 1. ML/MLH, maximum humeral length; 2. lesser tuberosity diameter; 3. greater tuberosity diameter; 4. WDASL, width of surface of lower end; 5. BED, biepicondylar distance; 6. TDH, transverse diameter of humeral head; 7. VDH, vertical diameter of humeral head; 8. WDU, width of upper end; 9. VDG, width of bicipital groove; 10. TDMS, transverse midshaft diameter; 11. TWD, width of trochlea; 12. CWD, width of capitulum.

Figure 2

The divisions of the humeral shaft. SN—surgical neck area, H50—50% of the biomechanical length, and H40—40% of the biomechanical length.

Figure 3

The angulations of the humerus in the standard presentation. The points of reference for the angle tools are marked by the blue dots (surgical neck area).

Figure 4

(A) Proximal extremity, (B) lateral perspective of bone shaft, and (C) detailed perspective of proximal–lateral part of bone. 1. Greater tubercle, caudo-lateral segment, 1′. greater tubercle, cranial segment, 2. lesser tubercle, 3. intertubercular groove, 4. humeral head, 5. anatomical neck of humerus, 6. teres major tuberosity, 7. crest of greater tubercle, 8. humeral diaphysis, caudal aspect, 9. humeral condyle, 10. fossa of bursa subtendinea m. infraspinati 11. insertion point for teres minor muscle, 12. tricipital line, and 13. deltoid tuberosity.

Figure 5

Morphological features of humerus bone shaft (B) and distal end (A,C–E). 1. Medial epicondyle, 2. medial trochlear keel, 3. lateral trochlear keel, 4. humeral capitulum, 5. lateral epicondyle, 6. zona conoidea, 7. humeral head, 8. lesser tubercle, 9. deltoid tuberosity, 10. teres major tuberosity, 11. olecranon fossa, 12. tail of lateral epicondyle, 13. radial fossa, 14. coronoid fossa, 15. supratrochlear foramen 16. Medial epicondyle, and 17. Lateral epicondyle Dotted line—humeral surgical neck area.

Figure 6

The osteonal units with no clear arrangement (surgical neck area), SN/33.

Figure 7

The drifting osteon: a rarely seen drifting osteonic unit situated close to the endosteal area of the A40 section.

Figure 8

Area of H50/62 with dense secondary osteonal units.

Figure 9

Osteon banding in H40/97 area.

Figure 10

A plot of the osteonal area vs. the vascular canal area based on their region of origin (H40, H50, SN).