Distal radius fractures are the most common fractures in childhood (14) and can be broadly grouped into four categories: buckle, greenstick, complete, and physeal fractures (15). The irregular appearance of the developing pisiform can be mistaken for a chondro-osseous injury at imaging (13). Similarly, the os hamulus proprium is an accessory ossification center of the hamate. The os epilunatum is an accessory ossification center of the lunate. Accessory ossicles also may mimic fractures on radiographs. The lunate can partially fuse with the adjacent triquetrum, a finding that mimics fracture at imaging. Radiologists should be familiar with certain developmental variants. In the younger carpus, however, the 2-mm standard does not always apply because of incomplete ossification (12). The space between the scaphoid and lunate should be less than 2 mm in the mature carpus. Disruption of these arcs also signi- fies a carpal dislocation. GilulaвЂ™s lines, which have been described on a neutral dorsovolar projection of the wrist (Fig 3), are three smooth arcs that can be drawn to out- line the proximal and distal rows of the carpus (8,10,11). Loss of this relationship is an important indica- tor of an underlying carpal dislocation. When the wrist is viewed laterally in a neutral position (Fig 2), the radius, lunate, and capitate are aligned longitudinally in a straight line (8). Despite the presence of growth plates in adolescents, standard measurement techniques for ulnar variance used in adults have been found reliable in the adolescent population (9). Ulnar variance is an important concept in the imaging evaluation of skeletally immature gymnasts with chronically stressed wrists and children with distal radial physeal injury and consequent prematurely terminated radial growth. When the articular surfaces of the radius and ulna are at the same level, ulnar variance is neutral a proximally projecting ulna relative to the radius is considered negative ulnar variance, and a distally projecting ulna is considered positive ulnar variance (Fig 1) (8). The term ulnar variance refers to anatomic variation in the length of the distal radius and ulna as measured at the site of their articulation with the lunate (Fig 1) (8). Thorough imaging evaluation of injuries to the distal forearm and wrist requires radiologists to be familiar with the normal relationships of the distal radius and ulna and the carpus. The pisiform is more appropriately considered a sesamoid bone in the flexor carpi ulnaris tendon instead of a true carpal bone (5). From the radial to the ulnar aspect, the scaphoid, lunate, triquetrum, and pisiform bones form the proximal row, and the trapezium, trapezoid, capitate, and hamate bones form the distal row. The eight carpal bones are arranged in two rows of four bones each. Support is provided by a fibrous meniscus-like structure, the articular disk, which runs from the sigmoid notch to the ulnar styloid, and by the surrounding soft-tissue attachments (7). The triangular fibrocartilage complex (TFCC) further supports the articulation of the distal ulna with the lunate and triquetrum. The distal radioulnar joint is a pivot joint between the concave distal radial sigmoid notch and the ulnar head. The joint is surrounded by a capsule that is further strengthened by several ligaments (6).

An articular cartilaginous disk sits in a concave cavity between the distal end of the radius and the convex condyle formed by the scaphoid, lunate, and triquetrum. Each epiphysis fuses with its metaphysis at approximately 16вЂ“19 years of age (5). The cartilaginous ossifica- tion center of the distal radial epiphysis ossifies 8вЂ“18 months after birth, and that of the distal ulnar epiphysis ossifies at 5вЂ“7 years of age. The ossification centers of the radial and ulnar shafts appear in the 6thвЂ“8th weeks of fetal development. Scaphoid ossification proceeds from distal to proximal (5). The ossific centers of the individual carpals develop sequen- tially in a consistent order: the capitate develops first, at about 3вЂ“6 months of age, followed by the hamate, triquetrum, lunate, scaphoid, trapezium, trapezoid, and finally the pisiform at approximately 6вЂ“8 years of age (4).

Subsequent bone growth is appositional the process occurs exclusively by endochondral ossification (3). The carpus is entirely cartilaginous at birth. the carpus begins as a single cartilaginous anlage that separates into eight distinct masses by the 10th week of gestation.

Wrist xray normal