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Pediatric Distal Forearm and Wrist Injury: An Imaging Review1

Injuries to the pediatric distal forearm and wrist have myriad mani-festations. Growth plate injuries can occur in the skeletally imma-ture child. An unfused growth plate is less robust than ligamentous complexes and therefore is more easily injured. The Salter-Harris fracture classification system is used to grade physeal injuries based on their imaging appearance. This grading has prognostic signifi-cance: higher grades imply an increased likelihood of eventual growth disturbance. A disrupted distal radioulnar joint charac-terizes Galeazzi-type injuries at all ages; however, before skeletal maturity is attained, a disrupted radioulnar joint can manifest as a distal ulnar physeal separation with associated epiphysiolysis of the distal ulna, termed a Galeazzi-equivalent fracture. Bone contusions can be diagnosed using fluid-sensitive fat-suppressed magnetic resonance imaging, and their detection can alter the prognosis. The unique cartilaginous cushion of the developing bony carpus imparts resilience to fracture and dislocation until carpal maturity is reached. Chronic compressive forces to the wrist in a skeletally immature gymnast can result in a distinct pattern of bone and soft-tissue injury referred to as gymnast wrist. If the distal radial physis fuses prematurely, ulnar growth will outpace radial growth, leading to positive ulnar variance and consequent chronic wrist pain from ulnar impaction.

©RSNA, 2014 • radiographics.rsna.org

Jason T. Little, MD Nina B. Klionsky, MD Abhishek Chaturvedi, MD Aditya Soral, MBBS, MS Apeksha Chaturvedi, MD

Abbreviation: TFCC = triangular fibrocarti-lage complex

RadioGraphics 2014; 34:472–490

Published online 10.1148/rg.342135073

Content Codes: 1From the Department of Imaging Sciences, University of Rochester Medical Center and Golisano Children’s Hospital, 601 Elmwood Ave, Rochester, NY 14642 (J.T.L., N.B.K., Apeksha Chaturvedi); Department of Imaging Sciences, University of Rochester Medical Cen-ter, Rochester, NY (Abhishek Chaturvedi); and Department of Orthopedics, Rungta Hospital, Jaipur, India (A.S.). Presented as an education exhibit at the 2012 RSNA Annual Meeting. Re-ceived April 23, 2013; revision requested May 31 and received July 17; accepted August 7. For this journal-based SA-CME activity, the authors, ed-itor, and reviewers have no financial relationships to disclose. Address correspondence to Apek-sha Chaturvedi (e-mail: [email protected]).

See discussion on this article by Bruno (pp 490–491).

After completing this journal-based SA-CME activity, participants will be able to: ■ Describe the primary differences

between pediatric and adult bones, es-pecially in relation to differing manifesta-tions of injury.

■ Recognize the mechanisms and imag-ing appearances of pediatric distal fore-arm and wrist injuries.

■ Identify imaging patterns of growth disturbance associated with certain bone injuries.

See www.rsna.org/education/search/RG

SA-CME LEARNING OBJECTIVES FOR TEST 6

IntroductionChildren’s bones differ from those of adults in several ways, and these differences contribute to age-specific injury manifestations. Growth plates are a uniquely pediatric phenomenon. With propor-tionately more cartilage and collagen than adult bones, the pediatric skeleton is relatively weaker but has greater elasticity, which leads to a higher likelihood of fracture but a decreased likelihood of its propa-gation (1,2). The thicker and more metabolically active periosteum in children’s bones promotes rapid and more effective osseous heal-ing and remodeling (3).

Injuries to the distal forearm and wrist are fairly common in children. If they are overlooked, some of these injuries can have de-velopmental and functional consequences. A thorough knowledge of the age-appropriate imaging appearance and relevant anatomy of the distal forearm and wrist is essential for optimal imaging interpreta-tion. This article reviews the development and anatomy of the pedi-atric distal forearm and wrist, describes various injury mechanisms, provides an imaging perspective on common acute and overuse inju-ries, and describes associated injury complications.

RG • Volume 34 Number 2 Little et al 473

Figure 1. Ulnar variance. Drawings of the wrist show neutral ulnar variance, with the radius and ulna at the same level at the site of their articulation with the lunate (a); negative ulnar variance, with the most distal aspect of the ulna projecting proximal to the radius (b); and positive ulnar variance, with the distal ulna projecting beyond the radius (c).

tion center of the distal radial epiphysis ossifies 8–18 months after birth, and that of the distal ulnar epiphysis ossifies at 5–7 years of age. Each epiphysis fuses with its metaphysis at approxi-mately 16–19 years of age (5).

The wrist is a condyloid articulation. An articu-lar cartilaginous disk sits in a concave cavity be-tween the distal end of the radius and the convex condyle formed by the scaphoid, lunate, and tri-quetrum. The joint is surrounded by a capsule that is further strengthened by several ligaments (6).

The distal radioulnar joint is a pivot joint be-tween the concave distal radial sigmoid notch and the ulnar head. The triangular fibrocartilage com-plex (TFCC) further supports the articulation of the distal ulna with the lunate and triquetrum. Support is provided by a fibrous meniscus-like structure, the articular disk, which runs from the

Development, Anatomy, and Radiologic-Anatomic Considerations

Embryologically, the carpus begins as a single car-tilaginous anlage that separates into eight distinct masses by the 10th week of gestation. The carpus is entirely cartilaginous at birth. Subsequent bone growth is appositional; the process occurs exclu-sively by endochondral ossification (3). The ossific centers of the individual carpals develop sequen-tially in a consistent order: the capitate develops first, at about 3–6 months of age, followed by the hamate, triquetrum, lunate, scaphoid, trapezium, trapezoid, and finally the pisiform at approxi-mately 6–8 years of age (4). Scaphoid ossification proceeds from distal to proximal (5).

The ossification centers of the radial and ulnar shafts appear in the 6th–8th weeks of fetal development. The cartilaginous ossifica-

474 March-April 2014 radiographics.rsna.org

Figure 4. Frontal radiograph of the left wrist in a 10-year-old boy shows a buckle fracture (ar-row) of the distal radius. An accompanying ulnar styloid fracture (*) is also seen.

Figure 3. Imaginary arcs called Gilula’s lines drawn on a frontal diagram of the wrist. Arc I (red curved line) is drawn along the radiocarpal surface, arc II (blue curved line) is formed by the distal aspect of the proximal row of carpals, and arc III (green curved line) runs along the proxi-mal aspect of the distal carpal row. Disruption of these arcs indicates carpal instability.

Figure 2. Lateral view of the wrist shows normal alignment of the radius, lu-nate, and capitate. Note that the capitate articulates with the lunate fossa. A = ante-rior (volar), P = posterior (dorsal).

sigmoid notch to the ulnar styloid, and by the surrounding soft-tissue attachments (7).

The eight carpal bones are arranged in two rows of four bones each. From the radial to the ulnar aspect, the scaphoid, lunate, triquetrum, and pisi-form bones form the proximal row, and the trape-zium, trapezoid, capitate, and hamate bones form the distal row. The pisiform is more appropriately considered a sesamoid bone in the flexor carpi ulnaris tendon instead of a true carpal bone (5).

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 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). 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 vari-ance (Fig 1) (8). Ulnar variance is an important


Figure 5. Lateral radiograph shows a greenstick fracture in a 10-year-old boy. The distal radial cortex is broken along the dorsal aspect (arrow) but is intact along the volar aspect.

concept in the imaging evaluation of skeletally im-mature gymnasts with chronically stressed wrists and children with distal radial physeal injury and consequent prematurely terminated radial growth.

Despite the presence of growth plates in adoles-cents, standard measurement techniques for ulnar variance used in adults have been found reliable in the adolescent population (9).

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). Loss of this relationship is an important indica-tor of an underlying carpal dislocation. Gilula’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). Disruption of these arcs also signi-fies a carpal dislocation. The space between the scaphoid and lunate should be less than 2 mm in the mature carpus. In the younger carpus, however, the 2-mm standard does not always apply because of incomplete ossification (12).

Radiologists should be familiar with certain developmental variants. The lunate can partially fuse with the adjacent triquetrum, a finding that mimics fracture at imaging. Accessory ossicles also may mimic fractures on radiographs. The os epilunatum is an accessory ossification center of the lunate. Similarly, the os hamulus proprium is an accessory ossification center of the hamate. The irregular appearance of the developing pi-siform can be mistaken for a chondro-osseous injury at imaging (13).

Distal Forearm FracturesDistal 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 Ar-beitsgemeinschaft für Osteosynthesefragen (AO) Pediatric Classification Group (15) has added ligamentous avulsion injuries of the wrist to this classification; however, these injuries are rare in children, and a detailed discussion is beyond the scope of this article.

Buckle FracturesBuckle (torus) fractures are due to compression failure of the bone without cortical disruption on the tension side of the bone (15). These fractures tend to occur at the distal radial and ulnar me-taphyses. The thicker, tougher periosteal sleeve frequently remains intact despite a break in the underlying relatively soft fibrous cortex. This gives rise to the characteristic radiographic ap-pearance of a buckle fracture (Fig 4). The appear-ance of buckle fractures can be obvious or subtle on initial radiographs. Occasionally, they only be-come evident once sclerosis and a periosteal reac-tion appear, typically 7–10 days after an injury. The stability of buckle fractures is excellent; after cast or splint immobilization, they usually heal successfully without complications (16).

Greenstick FracturesGreenstick fractures manifest with cortical dis-ruption on the tension side of the fracture but an intact cortex on the compression side (Fig 5) (15). Unlike buckle fractures, greenstick frac-tures tend to be unstable and may continue to displace after the first 2 weeks (17). When these injuries occur in the distal forearm, dorsal angu-lation as great as 20° can be tolerated because of the immense remodeling potential of young bones (18–20).

Complete or Displaced FracturesComplete fractures show disruption of both cortices in one plane (Fig 6) (15). According to classic teaching, up to 20°–30° of sagittal plane


Figure 7. Salter-Harris fracture classifications. Drawings show the normal physis with intact epiphysis and metaphysis; type I fracture, with the physis widened or displaced; type II, with the fracture extending through the physis and metaphysis; type III, with the fracture extending through the physis and epiphysis; type IV, with the fracture extending through the metaphysis, physis, and epiphysis; and type V, a compression injury to the physis.

Figure 6. Complete fractures of the radius and ulna in a 6-year-old boy. (a) Frontal radiograph reveals complete fractures that extend through the distal metaphyses of the radius and ulna (arrows), with overlying soft-tissue swelling. The distal radius and ulna continue to articulate with the carpus, even though the distal fracture fragments are radially displaced and angulated. (b) Lateral radio-graph shows dorsal displacement of the fractured distal fragments of the radius and ulna (arrow).


Figure 8. Salter-Harris type I fracture of the distal radius in a male patient aged 14 years 10 months. (a) Slightly oblique radiograph of the wrist shows a widened radial aspect of the distal radial growth plate (arrow). The radial epiphysis is displaced relative to the metaphysis. Marked overlying soft-tissue swelling (*) is seen. There is an associated minimally displaced ulnar styloid fracture (arrowhead). (b) Lateral radiograph shows dorsal displacement of the distal radial epiphysis (arrow) relative to the metaphysis. Soft-tissue swelling is seen along the volar aspect of the distal forearm (*).

angulation deformity can be accepted with com-plete or displaced fractures of pediatric extremity bones. Continued skeletal growth will ultimately lead to satisfactory alignment, especially in chil-dren younger than 12 years (21). For closed fractures of the distal shaft, Ostermann et al (22) recommend conservative management.

Physeal InjuriesGrowth plates add an element of complexity to fractures of the pediatric skeleton. Physeal in-jury becomes more common during the preado-lescent growth spurt because of the increased cortical porosity caused by enhanced bone turn-over. The Salter-Harris classification scheme describes fractures involving the physis and roughly describes the indicated treatment and prognosis for subsequent normal growth (Fig 7). The standard initial evaluation for potential physeal fractures in children consists of frontal and lateral radiographs. Oblique views can be helpful in cases of subtle injury, but stress views are not recommended because of the potential for injury aggravation (23).

Salter-Harris type I fractures are uncommon and account for only 8.5% of all Salter-Harris fractures of the wrist (24). A type I fracture consists of an isolated shear injury to the physis

with a preserved metaphyseal and epiphyseal cortex. Standard radiographs readily demon-strate this type of fracture only when the physis is widened or displaced (Fig 8); however, there may be no displacement (Fig 9). Adjacent soft-tissue swelling or a joint effusion may be the only radiographic finding and warrants further evaluation for an occult type I fracture. If the in-jury is acute, magnetic resonance (MR) imaging will show high T2 signal intensity in the physis (25). Bone scintigraphy is not an ideal modality for further imaging evaluation because of the already high radiotracer uptake of the normal physis. The prognosis is typically excellent for a type I fracture, with rapid healing and infre-quent complications after simple immobilization with casting (24). The exception is a type I in-jury due to chronic repetitive compressive force. The sequelae of this type of injury are discussed later in this article.

Salter-Harris type II and III fractures involve the physis and adjacent cortex (the metaphy-seal cortex in type II and the epiphyseal cortex in type III) (Figs 10, 11). These injuries result from a combination of shear and angular forces. The two fracture types can be considered to-gether because they share similar mechanisms, treatments, and prognoses. Salter-Harris type II


Figure 10. Salter-Harris type II fracture in a 15-year-old boy. (a) Slightly oblique frontal radiograph of the left wrist shows an oblique fracture (arrow) through the distal radial metaphysis that reaches the physis. (b) Lateral radiograph shows distal radial physeal widening (arrow) and a tiny metaphyseal fragment (arrowhead).

Figure 9. Subtle Salter-Harris type I fracture in a nearly 18-year-old male patient who is close to attaining skeletal maturity. (a) Oblique radiograph shows slight widening of the distal radial physis along its radial aspect (arrow), with subtle cortical displacement of the epiphysis with respect to the metaphysis. Substantial overlying soft-tissue swelling (*) serves as a secondary clue to underlying bone injury. A small avulsion fracture off the ulnar styloid (arrowhead) is also seen. (b) Lateral radiograph shows a slightly widened distal radial physis (arrow) with overlying soft-tissue swelling (*). The tiny ulnar styloid avulsion fracture is not seen on this image.


Figure 11. Salter-Harris type III fracture in a 15-year-old male patient. Frontal radiograph of the wrist shows an intra-articular fracture (ar-row) that extends through the epiphysis of the distal radius and reaches the physis. An as-sociated ulnar styloid fracture is seen (arrowhead).

Figure 12. Salter-Harris type IV fracture in a 13-year-old male patient. (a) Frontal radiograph of the wrist shows a displaced fracture (arrow) that extends through the distal ulnar epiphysis and reaches the physis. An accompanying metaphyseal fragment (black arrowhead) suggests a Salter-Harris type IV fracture. An associated Salter-Harris type I fracture of the distal radius (white arrowhead) is also seen. (b) Lateral radiograph better depicts the dorsally displaced radial epiphysis (*). The dis-tal ulnar fracture seen in a is not clearly discernible on this image.

fractures are much more common than type III; 73% of Salter-Harris wrist fractures are type II, and 6.5% are type III (24). The pediatric peri-osteum is closely adherent to the bone along the primary center of ossification up to the physis. More proximally, the attachment is compara-tively loose. The Thurston-Holland metaphyseal fragment seen with Salter-Harris type II frac-tures is a result of the inability of a growth plate fracture to violate the integrity of the tightly at-tached periosteum to the growth plate. Instead, the fracture deviates to the metaphysis (3). Be-cause this finding may be radiographically subtle or occult, some apparent Salter-Harris type I

fractures are reclassified as type II at computed tomography (CT) or MR imaging. Type III fractures often occur in older children in whom the physis is partially fused (26). Radiographs are usually sufficient to diagnose type II or III wrist fractures. CT may infrequently be useful to provide fine details of severely comminuted fragments (26).

Only 12% of Salter-Harris fractures are type IV injuries that involve the physis, epiphysis, and metaphysis (Fig 12) (24). As with types II and III, radiographs may be sufficient for assessment, with CT used in cases of severe comminution. CT or MR imaging can also help identify type


Figure 13. Galeazzi-equivalent wrist fracture. Drawing shows a distal radius fracture with palmar apex angulation at the fracture site. An associated disruption at the distal radioulnar articulation manifests as distal ulnar epiphysiolysis. The detached ulnar epiphysis is dorsally displaced relative to the anteriorly angulated ulnar metaphysis.

IV fractures because it may depict subtle radio-graphically occult fractures in addition to known fractures (27).

Type V is the rarest type of Salter-Harris frac-ture and describes a crush injury of the physis that is caused by severe axial loading. Type V injuries seldom occur in the wrist, in contradis-tinction to the weight-bearing physes in the lower extremities where most Salter-Harris type V in-juries occur. An acute Salter-Harris type V injury is typically differentiated only at MR imaging (27). The prognosis for type IV and V fractures is worse and complications are more frequent than for types I–III. Complications include the development of an osseous bridge (also called a physeal bar) across the physis, which leads to growth arrest and eventual angulation or limb-length discrepancy. MR imaging is the optimal modality to detect and map the extent of physeal bridging (28). Treatment of Salter-Harris type IV and V fractures typically is surgical rather than conservative.

Galeazzi and Galeazzi-equivalent Fractures

Galeazzi fractures are distal radial fractures at any level with associated dislocation of the distal radioulnar joint that results in ulnar luxation (29). The reported prevalence of these fractures in children ranges from 0.3% to 2.8% (29,30) and is less than the reported prevalence in adults.

Injury mechanisms such as hyperprona-tion and hypersupination, which tend to cause ligamentous disruption in adults, can cause epiphyseal avulsion in children because of the relative structural weakness of the pediatric phy-

sis (31,32). These fractures are called Galeazzi-equivalent injuries and are seen exclusively in skeletally immature children (Fig 13). Varia-tions of Galeazzi-equivalent fractures have been described in a classification scheme developed by Letts and Rowhani (33) that specifies four primary types and two modifying subtypes. The four primary types describe the site, pattern, and angulation of the radial fracture. The modifying subtypes refer to the associated ulnar dislocation or epiphysiolysis (33). According to the literature, the prognosis for these pediatric injury patterns is better than for adult patterns (34,35).

Additional fractures may be superimposed on one of the Galeazzi-equivalent fractures de-scribed by Letts and Rowhani (33). Recognition of complicating coexisting injuries is important for proper management and overall prognosis.

Bone ContusionA newly recognized distinct category of acute bone injury in children is bone contusion or bone bruise. This injury consists of subcortical trabecular microfractures that result in intraos-seous hemorrhage and edema without a defined cortical fracture line. The time required for heal-ing, often 12–16 weeks, is much longer than for a typical cortical fracture. Chronic pain may result from persistently elevated intraosseous pressure from a hematoma or from insufficiency fractures caused by a return to normal physical activity before complete healing. Diagnosis of an acute bone contusion will prevent ongoing pain and worsening of the injury (27).

Bone contusions are not visible on conven-tional radiographs or CT images. MR imaging is the only modality that will depict a bone contusion.


Figure 14. Bone bruising in a 16-year-old female patient who presented with a history of trauma to the distal forearm and wrist and persistent pain despite negative initial radiographic findings. Continued clinical concern led to MR imaging evaluation. (a) Frontal radiograph of the distal forearm and wrist shows normal findings. (b) Lateral radiograph reveals slight dis-placement of the pronator fat pad (*), a finding suggestive of underlying bone injury. (c) Coronal fluid-sensitive fat-suppressed MR image of the distal forearm and wrist shows marrow edema through the distal radius (arrows) extending onto both sides of the growth plate, a finding that is the imaging hallmark of a bone contusion. (d) Axial fluid-sensitive fat-suppressed MR image shows high signal intensity in the pronator quadratus muscle (*), a find-ing suggestive of an associated soft-tissue injury. Distal radial bruising (arrow) is again seen.

On fluid-sensitive fat-suppressed MR images, the injured portion of the bone shows high T2 signal intensity, a finding that represents mar-row edema and hemorrhage (Fig 14). The distal radius and carpal bones are common locations

for a bone contusion in the pediatric wrist. Bone contusions can occur in isolation or in combina-tion with other fractures. Regardless of whether a coexisting injury has been identified, persistent pain after the expected healing time for a fracture


Figure 16. Ulnar deviation radiograph in a 17- year-old female patient shows a fracture through the proximal pole of the scaphoid (arrow).

Figure 15. Slightly oblique radiograph of the right wrist in an 18-year-old male patient shows a slightly displaced fracture (arrow) through the distal pole of the scaphoid.

should prompt evaluation for a bone contusion with fat-suppressed MR imaging (27).

Carpal FracturesA spherical growth plate circumferentially sur-rounds the entire ossific center of each individual carpal bone during development (3). This growth plate is protective and offers resistance to fracture until sometime in adolescence, when a critical bone-to-cartilage ratio is reached. From this point on, carpal bone fractures become more common.

The carpals lack a periosteal covering. There-fore, a periosteal reaction is not seen at imaging of healing carpal fractures (3). Sclerosis and bone resorption are more common radiographic find-ings in the late subacute stage. This is another important consideration in the search for healing carpal bone fractures on follow-up radiographs, especially because carpal fractures may not have been readily apparent at initial imaging.

Scaphoid FracturesThe scaphoid is the most frequently fractured carpal bone in children. Most pediatric scaphoid injuries result from falls onto an outstretched pronated hand, but any compressive force, such as a direct blow that causes a crush injury, can result in a scaphoid fracture (36). Histori-cally, the distal pole was considered the most frequently fractured portion of the scaphoid in children (Fig 15). Gholson et al (37) have docu-mented a changing pattern of scaphoid fracture location in children that has become more similar to the adult pattern, with more scaphoid waist injuries. This is likely attributable to the increas-ing average body mass index of children and their increased participation in high-impact athletic activities. Proximal pole scaphoid fractures can also occur (Fig 16).

Scaphoid fractures may accompany other wrist injuries. One study reports that 1%–4% of pa-tients with distal radius fractures have concomi-tant scaphoid fractures; the risk of multiple frac-tures increases with male gender, younger age, and high-energy impact (38). Coexisting soft-tis-sue injuries are being discovered more frequently with the increasing utilization of MR imaging to evaluate suspected scaphoid fractures (39).

Initial evaluation of scaphoid fractures in-cludes radiography with posteroanterior, lateral, pronated oblique, and “scaphoid” views. On a scaphoid view, the wrist pronates and dorsiflexes with ulnar deviation. Indirect signs such as soft-tissue edema may suggest a subtle or occult frac-ture. The sensitivity of radiography for detection of scaphoid fractures is low; therefore, normal radiographic findings do not exclude fractures. Overall, the reported radiographic sensitivity for

scaphoid fracture varies widely in the pediatric radiology literature, with some reports of sensi-tivity as low as 21% (36).

Potentially serious complications of missed scaphoid fractures include progression to non-union and avascular necrosis. Missed scaphoid fractures have a higher incidence of nonunion for several reasons. The vascular anatomy of the scaphoid is inherently vulnerable because it is sup-plied by only a single dorsal branch and a single volar branch of the radial artery (36,40). When a scaphoid fracture is missed, premature resumption


Figure 17. Scaph-oid bruise in a 16- year-old female pa-tient. (a) Frontal radiograph shows a normal-appearing scaphoid (arrow). (b) Sagittal oblique fat-suppressed MR image shows bruis-ing (arrow) in the distal scaphoid, a finding that was ra-diographically occult in a. The clinical suspicion for scaph-oid fracture was high because of persistent pain in the anatomic snuffbox.

of normal physical activity subjects the fractured bone to increased stress and increases the risk of avascular necrosis with possible eventual nonunion and carpal architectural disruption.

MR imaging is the modality formally endorsed by the American College of Radiology for diagno-sis of radiographically occult scaphoid fractures in children. MR imaging has been shown to have an extremely high negative predictive value for scaphoid fracture (100% when used as early as 2 days after injury in one study) (36). If MR imag-ing findings are negative, the provider can safely allow the patient to mobilize and return to normal activities soon after injury. Additionally, MR imag-ing can detect significant soft-tissue injuries. In one study of MR imaging evaluation of suspected scaphoid fractures, up to one-third of patients had a TFCC tear, approximately 13% had an intercar-pal ligament injury, and 40% had a bone contu-sion with no distinct fracture (Fig 17) (39).

Other Carpal Bone FracturesPediatric lunate injuries are extremely uncom-mon and usually are secondary to severe direct trauma such as crush injury. CT, technetium 99m bone scintigraphy, and MR imaging demonstrate fractures better than does standard radiography. In children younger than 10 years, osteonecrosis

or lunatomalacia is a recognized complication of lunate injuries and manifests with slightly in-creased density on radiographs (5).

Triquetrum injuries are rare, although their prevalence may be underestimated because of late ossification. Direct trauma or avulsion of the dorsal ligamentous structures of the wrist can result in triquetrum injury (7). Standard radio-graphic views can aid diagnosis of most of these fractures (5).

Because the pisiform is the last carpal to ossify, no specific discussions about pisiform injury exist in the pediatric literature. Marked developmental irregularity of the pisiform can be seen at imaging and should not be mistaken for injury (13).

Trapezium fractures, which also are rare, occur secondary to axial loading of the adducted thumb and consequent dorsal impaction injury of the articular aspect of the trapezium with the base of the first metacarpal (Fig 18) (7). Avulsion inju-ries can also occur at this site. After ossification, standard radiographic views will usually suffice for detection and may occasionally be supple-mented with a Robert or true axial view of the first carpometacarpal joint (5).

Trapezoid fractures are rare and usually occur secondary to direct trauma (Fig 19). A radio-graphic finding of loss of the normal relationship


Figure 19. Slightly oblique radiograph of the right wrist in a 17-year-old patient demonstrates a slightly displaced fracture along the proximal radial aspect of the trapezoid (arrow).

Figure 18. Frontal radiograph of the left wrist in a 17-year-old patient shows a fracture along the radial aspect of the trapezium (arrow).

between the second metacarpal base and the trap-ezoid can be helpful in identification. Late ossifica-tion of the trapezoid contributes to the difficulty of identifying trapezoid fractures at imaging (5).

Capitate fractures are rare and are caused by high-energy trauma (41). If the bone is commi-nuted, malunion can occur. Radiographic evalu-ation usually involves standard anteroposterior and lateral views; lateral views are helpful in determining capitate rotation or displacement (5). Angled-beam radiographs may occasionally be required (7).

Hamate fractures are rarely described in the pediatric literature and usually require a carpal tunnel or 20°-supination oblique radiographic view for detection, in addition to standard ra-diographic views. The potential complications of hamate fractures are symptomatic malunion and ulnar or median neuropathy (5).

As a general guideline, most nondisplaced carpal fractures heal in a short-arm cast or splint. Displaced or comminuted fractures typically re-quire surgical management.

Carpal DislocationsThe wrist is stabilized by a complex array of ligaments that link individual carpal bones to each other and to the distal radius and ulna. High-energy injury mechanisms, including mo-tor vehicle collisions, sports accidents, and falls from a height onto an outstretched hand, can induce ligamentous disruption and consequent carpal dislocation (10). Dislocations of the carpus can occur alone or in combination with fractures. In children, the viscoelastic properties of the developing carpus offer some protection against carpal dislocations (10). The two major types of injury patterns are greater and lesser arc injuries. Coexistent perilunate fractures and dis-locations are referred to as greater arc injuries. Lesser arc injuries are purely capsuloligamen-tous (Fig 20) (8).

Mayfield et al (42) have described four distinct stages of lesser arc injury secondary to the sequen-tial disruption of ligaments from a radial to ulnar direction (Fig 20): (a) rotary subluxation of the scaphoid secondary to scapholunate disruption (stage 1), (b) capitolunate failure and consequent perilunate dislocation (stage 2), (c) triquetrolunate failure and midcarpal disruption (stage 3), and (d) the most severe injury of the spectrum, lunate dislocation (stage 4) caused by dorsal radiocarpal ligament failure (Fig 21) (8).

Greater arc injuries proceed in a similar direction but additionally involve fractures through the radial styloid, scaphoid, capitate, triquetrum, or ulna. A multicenter study of 166 patients with perilunate injuries found that greater arc injuries occurred twice as frequently

as lesser arc injuries (43). However, this pat-tern of occurrence is more typical in adults and older adolescents because of the requisite force to cause carpal dislocation and concomitant fractures. Carpal architectural collapse follows untreated lunate dislocation or destruction and underscores the role of the lunate as the “key-stone” of the proximal carpal row.

Posteroanterior and lateral radiographs of the wrist usually suffice for diagnosis, but stress views may occasionally be needed to diagnose carpal dislocations or instability. The key finding on lat-eral images is a disrupted radius-lunate-capitate axis. On posteroanterior radiographs, any one of the three Gilula’s lines can be disrupted (8).


Figure 20. Carpal dislocation. (a) Diagram shows the stages (from left to right) of carpal dislocation that occur as a result of sequential ligamentous disruption from the radial to the ulnar aspect. These injuries manifest with a progressive dorsal tilt of the capitate and a volar tilt of the lunate. In the severest form (right), the capitate directly articulates with the radius, and the lunate falls forward. A = anterior (volar), P = posterior (dorsal). (b) Diagram shows the fracture-dislocation zones of the carpal lesser arc (curved blue line) and greater arc (curved burgundy line). Purple shading indicates the vulnerable zone of the carpus. (For normal alignment of the radius, lunate, and capitate on a lateral view, see Figure 2.)

comprise the primary demographic for chronic pediatric wrist injuries (2).

One of the earliest injuries caused by repeti-tive compressive force is a chronic Salter-Harris I fracture of the distal radius. Changes seen radio-graphically at this stage include physeal widen-ing, metaphyseal irregularity, and sclerosis (Fig 23). The prolonged healing response can lead to physeal bridging and, if uncorrected, to radius growth disturbance or arrest.

A prematurely fused radius results in ulnar overgrowth and positive ulnar variance, itself a risk factor for ulnar impaction and its sequelae of ligamentous and carpal disturbances. Most children aged 12–16 years have negative ulnar variance (44); however, gymnasts show a predi-lection for positive ulnar variance (45). Patterns of subsequent injury described in the literature (45) include TFCC tears and focal chondral injury to the lunate (45). The spectrum of im-paction injuries to the wrist and hand depends on the patient’s skeletal maturity and the type of exercise performed. Before pubertal growth, the physis is most vulnerable to injury. After puber-tal growth, the area of failure shifts to the liga-mentous tissues, in particular the TFCC (45).

Ulnar impaction, whether caused by radial growth arrest from a chronic physeal fracture or another injury, can provoke a cascade of injuries

The majority of carpal dislocations are man-aged surgically. Long-term functional disability, chronic wrist pain, and carpal collapse can occur despite appropriate management.

Chronic Overuse InjuriesA variety of chronic wrist injuries in the pediatric population have been characterized as gymnast wrist because of their frequent association with children who participate in gymnastics. These often-interrelated osseous and ligamentous inju-ries are typically caused by repetitive compressive force sustained over long periods, such as dur-ing participation in a high-impact sport such as gymnastics or weight lifting (Fig 22). Adolescents


that begins with degeneration of the articular cartilage (Figs 24, 25). Chondral fibrillation and chondromalacia are radiographically occult but are readily seen at MR imaging during this early stage. Because early detection is crucial to prevent fur-ther and more permanent damage, MR imaging is an invaluable tool in the analysis of chronic wrist pain in high-risk individuals. If the injury pattern continues, carpal marrow edema and hyperemia, subsequent subchondral cysts, and eventual scle-rosis will develop and will be evident on radio-graphs. The end-stage result of ulnar impaction is advanced arthritis of the wrist (46).

ConclusionDistal forearm and wrist injuries in children are common but complex entities. Confident imag-ing interpretation requires a firm knowledge of the developmental anatomy, injury mechanisms, and age-specific manifestations of injury.

Acknowledgments.—The authors thank Gwendolyn Mack, MFA, and Nadezhda D. Kiriyak, BFA, from the Department of Imaging Sciences, University of Roch-ester Medical Center, for contributing original artwork to the article. We also thank Margaret A. Kowaluk, BS, from the Department of Imaging Sciences, University of Rochester Medical Center, for providing expert help with photographic images.

Figure 21. Carpal fracture-disloca-tion in a 17-year-old boy after a motor vehicle collision. (a) Frontal radiograph of the right wrist shows a transverse scaphoid waist fracture (white arrow) and a displaced detached ulnar styloid (arrowhead). Disruption of Gilula’s lines (black arrows) indicates carpal dislocation. Marked swelling in the surrounding soft tissue is also seen. (b) Lateral radiograph shows volar rota tion and displacement of the lu-nate (*), a finding referred to as the “spilled-teacup” sign, with loss of the radius-lunate-capitate axis. The capitate (arrow) is proximally displaced and di-rectly articulates with the distal radius. (c) Lateral radiograph after surgical fixation shows correction of the radius-lunate-capitate axis (arrows).


Figure 23. Gymnast wrist in a 13-year-old female competitive gymnast. (a) Frontal ra-diograph of the right wrist shows distal radial physeal widening and underlying sclerosis (arrow). (b) Coronal proton-density–weighted MR image demonstrates marked widening and irregularity of the distal radial physis. Associated low-signal-intensity intrusions into the metaphysis (arrows) suggest focal failure of ossification of the physeal cartilage.

Figure 22. Development of gymnast wrist. Drawings show how abnormal compressive forces to the wrist in a skeletally immature gymnast lead to progressive growth plate injury that is most marked along the radial aspect of the distal radius (inset).

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This journal-based SA-CME activity has been approved for AMA PRA Category 1 CreditTM. See www.rsna.org/education/search/RG

Teaching Points March-April Issue 2014

Pediatric Distal Forearm and Wrist Injury: An Imaging ReviewJason T. Little, MD • Nina B. Klionsky, MD • Abhishek Chaturvedi, MD • Aditya Soral, MBBS, MS • Apeksha Chaturvedi, MD

RadioGraphics 2014; 34:472–490 • Published online 10.1148/rg.342135073 • Content Codes:

Page 480Complications include the development of an osseous bridge (also called a physeal bar) across the physis, which leads to growth arrest and eventual angulation or limb-length discrepancy.

Page 480Injury mechanisms such as hyperpronation and hypersupination, which tend to cause ligamentous dis-ruption in adults, can cause epiphyseal avulsion in children because of the relative structural weakness of the pediatric physis.

Page 482Therefore, a periosteal reaction is not seen at imaging of healing carpal fractures.

Page 484Coexistent perilunate fractures and dislocations are referred to as greater arc injuries. Lesser arc inju-ries are purely capsuloligamentous.

Page 485 A prematurely fused radius results in ulnar overgrowth and positive ulnar variance, itself a risk factor for ulnar impaction and its sequelae of ligamentous and carpal disturbances.

pediatric distal forearm and wrist injury: an imaging review

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