The anatomy of the scaphoid presents a unique challenge when dealing with injury . Its anatomy has been described in detail by many authors [8]. The scaphoid is the only carpal bone to cross the proximal and distal rows and acts as a strut between them. It is the largest bone in the proximal carpal row, is oriented on an oblique long axis, and is concave volarly and ulnarly. Approximately 75 % of the scaphoid is covered with articular cartilage, with only the volar surface being partially uncovered [9, 10]. Four distinct anatomic regions of the scaphoid have been described: (1) the tubercle, (2) the distal pole, (3) the proximal pole, and (4) the waist . (Fig. 1.3) In a study of 24 morphological and 11 morphometric scaphoid parameters, at least one morphometric feature was missing in 200 specimens. The scaphoid tubercle and dorsal sulcus were present consistently, with the greatest differences in waist circumference, size of the tubercle, and sulcus width [11]. A statistical model of scaphoid CT scans suggests that variations in morphology represent extremes of a normal distribution and not distinct subtypes [12]. The tubercle is directed radially and volarly and serves as an attachment point for the scaphotrapezoidal and the scaphotrapezial ligaments where it is also partially covered by the flexor carpi radialis tendon . At its distal end, the scaphoid articulates with both the trapezoid and the trapezium. However, a ridge along the scaphoid separating these articulations is not routinely identifiable [13]. At its proximal end, the scaphoid articulates with the scaphoid fossa of the distal radius. Along its ulnar border, the scaphoid articulates with the lunate proximally and the capitate distally [14].

Several studies have quantified the anthropometry of the human scaphoid. In 2007, Heinzelmann measured 30 ­cadaveric scaphoid bones with calipers. They found that male scaphoids were significantly longer than scaphoids in females (31.3 mm ± 2.1 vs. 27.3 mm ± 1.7) . The male scaphoids were significantly wider than the ­female ­specimens when measured perpendicular to the long axis 2 mm from the proximal pole (4.5 mm ± 1.4 vs. 3.7 mm ± 0.5) and at the waist (13.6 mm ± 2.6 vs. 11.1 mm ± 1.2). This has significant implications in fracture fixation as diameters of many commercially available standard headless compression screws are close to the size of the proximal pole of female scaphoids. They suggest that the usual countersunk screw length will be 27 mm for males and 23 mm for females [15]. In a study that evaluated the scaphoid using three-dimensional computed tomography scans, Pichler showed that the scaphoid had a mean length of 26.0 mm and a mean volume of 3389.5 mm³, again with a gender difference where length-adjusted female scaphoids are thinner [16]. Kivell showed that the female scaphoid body proximal-to-distal length is longer than that of males when size-adjusted; thus, as carpal size increases, female scaphoids are longer [17]. Lee characterized the osseous microstructure of the scaphoid. Articular regions showed the highest bone strength parameters (bone mineral density and trabecular density) and had thicker subchondral bone, especially at the articulations with the capitate and radius. The lowest number of trabeculae were found along the midcarpal side of the waist. Overall, the waist has thick subchondral and trabecular bone leading to a high moment of inertia against bending stresses [18].

Numerous controversies exist within the literature regarding the ligamentous attachments to the scaphoid bone . The ligaments that attach to the scaphoid play an integral role in proper wrist ­biomechanics and function. A recent anatomic study by Jupiter analyzed eight cadaveric wrists with computed tomography and an imaging cryotome. Three-dimensional reconstruction showed ligamentous attachment consists of approximately 9 % of total scaphoid surface area . The ligaments are divided into volar, dorsal, and scapholunate interosseous ligaments . The volar ligamentous complex connects the scaphoid to the distal radius and the adjacent of the carpal bones. The volar ligaments attaching to the scaphoid are made up of the radioscaphocapitate, scaphocapitate, scaphotrapezoidal, scaphotrapezial, transverse carpal, and radioscapholunate. The scaphocapitate ligament covers 40 % of the volar ligament attachment surface area and covers nearly the entire ulnar scaphoid tubercle. Only one ligament attaches to the dorsal scaphoid; the dorsal intercarpal ligament originates from the dorsoradial aspect of the triquetrum and inserts on the proximal and waist areas of the dorsoradial ridge of the scaphoid. The scapholunate interosseous ligament is a single C-shaped ligament with a volar, dorsal, and proximal bundle dominated by the proximal portion of the ligament. These bundles are difficult to differentiate and can be viewed more as thickenings rather than discrete bundles [19] (Fig. 1.4).