17 Trauma of the Distal Forearm



10.1055/b-0034-77612

17 Trauma of the Distal Forearm

Prommersberger, K.J., Fröhner, S., van Schoonhoven, J., Schmitt, R.

Basic diagnostic imaging of fractures and dislocations of the forearm near the wrist-whether acute or old, healed, malunited-healed, or not healed at all-consists of standard radiographs of the wrist in two planes, with a laterally placed cassette if necessary. CT imaging is becoming increasingly important to exclude occult fractures and to assess the congruence of the radiocarpal and distal radioulnar joints. It provides the foundation for planning surgical management of acute, complicated extra-articular and especially intra-articular fractures, for which three-dimensional (3D) reconstructions are useful. Dislocations and subluxations of the distal radioulnar joint and rotary deformities of malunited-healed radius fractures require clarification with CT of both wrists.



Acute Fractures and Dislocation Fractures of the Distal Forearm





Pathoanatomy and Clinical Symptoms

Fractures of the distal radius are among the most common injuries sustained, accounting for upwards of onesixth of all fractures seen and treated in the emergency room. The epidemiological understanding of fractures of the distal radius is based primarily on Scandinavian studies, which have revealed that distal radius fractures are more common in women than in men, with an incidence increasing rapidly after menopause and reaching a maximum between 60 and 69 years. The mechanism of injury is usually a fall from standing height rather than a highenergy mechanism. These factors all support a strong association of radius fractures with osteoporosis. Indeed, lowbone mineral density is found in most elderlywomen with a distal radius fracture, and osteoporosis is diagnosed in more than 50%. It has been suggested that the decrease in fractures of the distal radius after age 69 reflects increasing frailty resulting in an inability to extend the upper limb in protection, with the result that distal radius fractures are less common and hip fractures are more common. Thus, the isolated fracture of the distal radius typically occurs in the relatively fit osteoporotic individual, whereas fractures of the distal end of the radius associated with ipsilateral limb trauma are found with increasing frequency in young, active adults, due in part to a higher incidence of high-energy trauma or participation in sports and similar activities.
































Table 17.1 Classification of distal radius fractures by eponyms and synonyms

Colles’ fracture


Dorsal tilt of the distal fragment


Smith’s fracture


Palmar tilt of the distal fragment


Barton’s fracture


Fracture of the dorsal rim


Reversed Barton’s fracture


Fracture of the palmar rim


Chauffeur’s fracture


Fracture through the radial styloid process


Punch fracture


Impression of the lunate fossa of the radius


Greenstick fracture


Occurs during childhood. Cortical layer completely fractured on the convex side, but only cracked on the concave side


Galeazzi’s fracture


Fracture of the distal third of the radius combined with dislocation in the distal radioulnar joint



Classification

There are few areas of skeletal trauma in which eponymic descriptions are so commonly used as with fractures of the distal radius ( Table 17.1 , Fig. 17.1 ). Despite the fact that the observations of Colles, Barton, Smith, Pouteau, and Goyrand—to name just a few—were made solely from postmortem specimens, their descriptions of fracture morphology have served as guidelines for surgeons for more than 150 years and still provide a comfortable base for communication among clinicians. However, a classification system is necessary for effective description of the individual characteristics of specific fractures. Any fracture classification must consider the severity of the bone lesion and serve as a basis for treatment and evaluation of the outcome. It must have a high degree of inter-observer and intra-observer reliability. A fracture classification should help the surgeon to choose an appropriate method of treatment for any given fracture and should allow estimation of the outcome of treatment. We have found the classification system of Fernandez extremely helpful in decision making in our clinical practice and the AO/ASIF Comprehensive Classification of Fractures useful in preparing scientific papers.

Fig. 17.1a-h Classification of distal radius fractures according to eponyms and synonyms. a Colles’ fracture b Smith’ fracture c Barton’ fracture d Reverse Barton’ fracture e Chauffeur’ fracture f Punch fracture g Greenstick fracture h Galeazzi’s fracture


The Fernandez Classification

In this classification, distal radius fractures are divided into five major types (Fig. 17.2a):




  • Type I fractures are bending fractures of the metaphysis in which one cortex fails because of tension stress, and the opposite cortex shows a certain degree of comminution.



  • Type II fractures are shearing fractures of the joint surface.



  • Type III fractures are compression fractures of the joint surface with impaction of the subchondral and metaphyseal trabecular bone.



  • Type IV fractures are avulsion fractures of ligamentous attachments, including ulnar and radial styloid fractures associated with radiocarpal fracture-dislocations.



  • Type V fractures result from high-energy injuries and involve combinations of bending, compression, shearing, and avulsion mechanisms, often associated with bone defects.


From a biomechanical standpoint, the classification system indicates the recommended treatment for each fracture type. In addition, the classification may allow prognostic information regarding the final outcome, because the severity of the bony lesions and the probable incidence of associated soft-tissue lesions and carpal disruption increase consistently from type I through type V fractures.

Fig. 17.2a, b Classification of the distal radius fractures according to Fernandez. a I = metaphyseal bending fracture; dorsal or palmar dislocation. II = shearing fracture of the dorsal or palmar rim of the radius. III = compression fracture of the radiocarpal joint surface. IV = ligamentous avulsion fracture associated with radiocarpal fracture-dislocation. V = combination of fracture types I-IV. b Classification of associated injuries of the distal radioulnar joint: I = stable, joint surface intact (Ia, avulsion of the tip of the ulnar styloid process; Ib, stable fracture below the ulnar head). II = unstable, joint surface intact (IIa, radial or ulnar avulsion of the triangular fibrocartilage complex [TFCC]; IIb, avulsion of the ulnar styloid process near its base together with the TFCC). III = questionably stable, joint surfaces destroyed (IIIa, fracture of the ulnar notch of the radius; IIIb, fracture of the ulnar head with destruction of the distal radioulnar joint).

Depending on the residual stability of the distal radioulnar joint (DRUJ) after adequate reduction and stabilization of the fracture, three basic types of DRUJ lesions are differentiated (Fig. 17.2b).




  • Type I are stable DRUJ lesions, i.e., the joint is clinically stable and the radiographs show articular congruity.



  • Type II are unstable DRUJ lesions with clinical and radiographic evidence of subluxation or dislocation of the ulnar head.



  • Type III are potentially unstable lesions resulting from extension of a distal radius fracture in the sigmoid notch or from a fracture of the ulnar head.

























































































































Table 17.2 Classification of distal radius fractures according to the Association for the Study of Internal Fixation (ASIF)

Classification


Fracture Line(s)


Dislocation


A Extra-articular fractures


A1
ulna and radius intact


1. Styloid process

   

2. Metaphysis, nondisplaced

   

3. Metaphysis, comminuted

 

A2
radius, nondisplaced and nonimpacted


1. Not malaligned

   

2. Dorsal malalignment

   

3. Palmar malalignment

 

A3
radius, comminuted


1. Impacted with axial shortening

   

2. With a wedge

   

3. Complex


B Nondisplaced intra-articular radius fractures


B1
sagittal


1. Lateral, nondisplaced

   

2. Lateral, comminuted

   

3. Medial

 

B2
dorsal rim


1. Nondisplaced

   

2. With lateral sagittal fracture

   

3. With dorsal dislocation of carpus

 

B3
palmar rim


1. Nondisplaced with small fragment

   

2. Nondisplaced with large fragment

   

3. Comminuted


C
Complex intra-articular radius fractures


C1
nondisplaced articular, nondisplaced metaphyseal


1. With posteromedial fragment

   

2. With sagittal fracture line

   

3. With frontal fracture line

 

C2
articular nondisplaced, metaphyseal comminuted


1. With sagittal fracture line

   

2. With frontal fracture line

   

3. Extending into the diaphysis

 

C3
articular nondisplaced, comminuted


1. Metaphyseal nondisplaced

   

2. Metaphyseal comminuted

   

3. Extending into the diaphysis

Fig. 17.3 Frykman’s classification of distal radius fractures. Extra-articular fractures (I and II); fractures with involvement of the radiocarpal joint (III and IV); fractures with involvement of the distal radioulnar joint (V and VI); fractures with injury to both the radiocarpal and the distal radioulnar joints (VII and VIII). Odd numbers indicate no associated fracture of the ulna; even numbers indicate associated fracture of the ulna.
Fig. 17.4a, b Greenstick fractures of the metaphyses of the distal radius and ulna with epiphysiolysis of the radius (Aitken Ib, Salter-Harris II). Positive pronator-quadratus sign induced by a hematoma (arrows).

Computerized data analysis is possible with both classifications. The abbreviation RII D 2P – U IA indicates a radius fracture (R) type II (shearing fracture)with dorsal dislocation (D), two main fragments (2P), distal radioulnar joint (U) that is stable (I), and an avulsion fracture of the ulnar styloid (A).

































Table 17.3 Classification of epiphyseal and metaphyseal fractures

Type of Injury


Aitken’s Classification


Salter-Harris’ Classification


Detachment of epiphysis


Ia


I


Detachment of epiphysis and fracture of metaphysis


Ib


II


Fracture of epiphysis


II


III


Combined fracture of epiphysis and metaphysis


III


IV


Comminuted fracture of epiphysis and/or metaphysis

 

V



Frykman Classification

This classification, which is commonly used in the U.S., differentiates between extra-articular and intra-articular fractures of the distal radius and takes into consideration the presence or absence of an associated fracture of the distal ulna ( Fig. 17.3 ). However, the Frykman classification does not include the number of fragments and their dislocation. The higher the classification number, the more complex the fracture and the worse the prognosis.

Fig. 17.5a-j Intra-articular comminuted fracture of the distal radius (Fernandez V, Frykman VIII, ASIF C3.2). a-e Preoperative evaluation: extensive impaction of the radiocarpal joint surface. The extent of the impaction and involvement of the distal radioulnar joint can be seen in their entirety only in CT scans. Degenerative lesions at the styloid process of the radius, as well at the lunate and scaphoid. f-j Postoperative evaluation following reconstruction and osteosynthesis. The radiographs allow only limited assessment of the joint surfaces because of radiographic overlapping by the implants. The CT scans with no overlapping reveal good surgical reconstruction and extra-articular placement of the screws.
Fig. 17.6 Measurement of the impaction of the distal radius by means of Sennwald’s method. The fixed point is the ulna head. From here, a vertical line 3 cm long is drawn down the ulna shaft with a perpendicular line at the bottom. Using this line as a reference, vertical lines in the middle of the shaft of the radius measure the distances to the palmar and the dorsal edges of the fossa radii.


Comprehensive Classification of Fractures (AO/ASIF Classification)

In this classification system, which is adaptable for computerized documentation of all fractures of the long bones, different fractures are categorized into three major types, nine groups, and 27 subgroups. Documentation of additional ulnar lesions ultimately produces 144 different fracture patterns at the distal end of the forearm. The three basic types include extra-articular fractures (type A), partial articular fractures (type B), and complete articular fractures (type C). This classification considers the severity of the fracture according to articular and metaphyseal comminution. Observer reliability and reproducibility were considered adequate for the three major types (A, B, C) but were less reliable when analyzing the groups and subgroups ( Table 17.2 ).



Aitken’s and Salter’s Classification

Aitken’s and Salter’s classification of fractures involving the epiphysis in the growing skeleton is also used for forearm fractures in adolescence ( Table 17.3 , Fig. 17.4 ).



Anatomic Foundations

The distal radius articulates with both the proximal carpal row and the head of the ulna. The radiocarpal articular surface is divided into the scaphoid and lunate fossae. These two concave articular surfaces are separated from each other by a bony dorsal-palmar ridge, the crista radii. The articular surface of the distal radius inclines in a palmar direction an average of 10–12° in the sagittal plane and inclines in an ulnar direction an average of 22° in the frontal plane ( Table 17.4 ). The sigmoid notch is a concave structure that articulates with the ulnar head. The shape and the orientation of the sigmoid notch of the radius vary in relation to the ulnar variance.


The radiographic anatomy of the distal radius and its relationship to the distal end of the ulna can be evaluated with different measurements, especially the palmar tilt, the ulnar inclination, the radial length, and the ulnar variance. A standardized radiographic technique is essential for producing reliable data. Because the elbow and shoulder positions affect the relationship between the distal radius and the ulna, the standard dorsopalmar view of the wrist should be obtained with the elbow flexed 90°, the shoulder abducted 90°, and the forearm and wrist in a neutral position. The hand is placed with the palm flat on the cassette without any flexion, extension, or deviation. Correct positioning shows the edge or the entire groove of the extensor carpi ulnaris tendon radial to the fovea at the base of the ulnar styloid. The lateral view of the wrist is taken with the elbow flexed 90° and adducted against the trunk with the forearm and wrist in neutral position while a vertical x-ray beam enters radially and exits ulnarly at the level of the distal pole of the scaphoid. Correct positioning shows the palmar surface of the pisiform located at the midpoint between the palmar surface of the distal pole of the scaphoid and the palmar surface of the capitate. For both the dorsopalmar and the lateral views of the wrist, at least 5 cm of the distal radius must be included to allow for accurate assessment of the long axis of the radius ( Figs. 17.4 , 17.5 ).

Fig. 17.7a, b Radial and dorsal displacement of the distal fragment of the radius as measured by Abbaszadegan’s method.
Fig. 17.8a-c Combined radiocarpal trauma. Besides a distal radius fracture (chauffeur’s fracture, Fernandez type II, Frykman III, and ASIF C2.3), there is also a fracture of the scaphoid. This can be seen clearly in the oblique semipronated view.

Radial length, also called radial height or length of the radial styloid, is defined as the distance between two lines perpendicular to the long axis of the radius, one passing through the distal tip of the radial styloid, and the other passing through the most distal aspect of the ulnar articular surface of the radius. The average length is 11–12 mm. This distance is less useful in assessing relative radial shortening, since it reflects the loss of ulnar inclination of the articular surface of the distal radius and not the position of the distal articular surface of the radius relative to the articular surface of the distal ulna.

Fig. 17.9a, b Intra-articular radius fracture in combination with scapholunate dissociation. a In the plain T1-weighted SE sequence, the fracture line and the widened scapholunate space indicate injury of the scapholunate ligament. b Following intravenous administration of gadolinium, the scapholunate ligament, which has been torn off the lunate, is clearly visible because of enhancement of synovial reparative tissue.











Table 17.4 The normal joint surface of the radius



  • Frontal angle of the distal radius segment:




    • Average tilt of 23° to the ulnar side



    • Normal range of tilt: 15–35°




  • Sagittal angle of the distal radius segment:




    • Average tilt of 11° to the palmar side



    • Normal range of tilt: 0–20°




  • Relationship of the length of the radius to that of the ulna:


    ±2 mm in the neutral position























Table 17.5 Step deformities in the radiocarpal joint caused by radius fractures (according to Knirk’s and Jupiter’s classification)

Grade


Size of the Step Deformity


0


Smaller than 1 mm


1


Between 1 and 2 mm


2


Between 2 and 3 mm


3


Larger than 3 mm

Fig. 17.10a, b Rotatory malalignment following distal radius fracture (Fernandez type I, Frykman II). a As a result of rotation of the radial epiphysis, the corners of the sigmoid notch of the radius are shown to be apart (arrow), leading to a step deformity on the radial side of the radius. Additionally, shortening of the radius leads to incongruence. b The diagram clearly demonstrates the effect of the malrotation on the radius (arrow and shaded areas). (Courtesy of R. Frahm, MD, Tuttlingen.)

The ulnar variance describes the relative positions of the distal articular surfaces of the radius and the ulna. All methods used to measure ulnar variance have been shown to be highly reliable with respect to intra-observer and inter-observer variation. Clinicians may therefore use whichever technique they prefer when measuring ulnar variance. The measurement can be obtained as the difference in length along the line of the longitudinal axis of the forearm, between a line perpenticular to the ulnar edge of the lunate facet of the distal radius articular surface, and another line perpendicular to the distal articular surface of the ulna head. A difference of 2 mm in length between the radius and the ulna is considered normal. A positive ulna variance occurs when the articular surface of the ulna is distal to the distal articular surface of the radius.


The palmar tilt, also known as dorsal tilt, dorsal angle, volar tilt, or volar slope, is determined by a line joining the most distal parts of the dorsal and the palmar rims of the radial articular surface. The degree of the palmar tilt is derived at the intersection of the line of palmar tilt and one perpendicular to the long axis of the radius, as determined by a line through the center of its medullary space at 2 and 5cm proximal to the radiocarpal joint.


The ulnar inclination, also called radial inclination or radial tilt, describes the angulation of the distal radial articular surface in relationship to the long axis of the radius in the frontal view. It is determined by a line perpendicular to the long axis of the radius and a line formed between the radial styloid and the distal sigmoid notch.


Shortening of the distal radius in acute fractures, but also in malunited fractures, can be assessed separately for the dorsal and palmar aspect of theradius by assessing the degree of shortening according to Sennwald ( Fig. 17.6 ).


To describe displacement of the distal fragment to the radial, the dorsal, or the palmar side in acute fractures, but also in malunited fractures, determination of the radial shift is recommended (van der Linden’s method). A dorsal shift of the radius is defined as the distance between the longitudinal axis of the radius in the lateral view and the part of the radial epiphysis that is located furthest dorsally. A radial shift of the axis of the radius is defined as the distance between the longitudinal axis of the radius in the dorsopalmar projection and the point on the radial styloid that is furthest to the radial side. Dorsal and radial displacements of the distal radius fragment in acute fractures can also be determined by Abbaszadegan’s method ( Fig. 17.7 ). Callus formation makes this method less accurate for diagnosis of malunion of distal radius fractures.

Only gold members can continue reading. Log In or Register to continue

Jul 21, 2020 | Posted by in MUSCULOSKELETAL IMAGING | Comments Off on 17 Trauma of the Distal Forearm
Premium Wordpress Themes by UFO Themes