Unni G. Narayanan and Fabio Ferri-De-Barros
DEFINITION
Radial neck fractures in children are typically transphyseal injuries and seldom involve the epiphysis (radial head).
The majority of these fractures are Salter-Harris type II injuries. Salter-Harris type I fractures are also common. In older children some fractures may be entirely metaphyseal (FIG 1).
Radial neck fractures represent about 14% of all elbow fractures in children.8
ANATOMY
Ossification of the proximal radial epiphysis (radial head) occurs by 4 years of age, at which time the radial head and neck have assumed their adult shape. The proximal radial physis closes at 14 years in girls and 17 years in boys.
At the level of the radiocapitellar joint, the radial nerve divides into its terminal branches, including the posterior interosseous nerve, which enters the substance of the supinator muscle at the arcade of Frohse and winds around the anterolateral aspect of the radial neck. Pronation of the forearm moves the posterior interosseous nerve more medially and away from the anterolateral side of the radial neck (FIG 2).
PATHOGENESIS
The most common mechanism of injury is due to a fall on the outstretched hand with the elbow extended and the forearm supinated.
The resultant valgus force compresses the capitellum against the radial head.
FIG 1 • Displaced radial neck fractures. A. Salter-Harris type 2. B. Salter-Harris type 1.
FIG 2 • Relationship between posterior interosseous nerve and the radial neck. A. In supination. B. In pronation.
Radial neck fractures may occur in association with a posterior dislocation of the elbow that displaces the radial head anteriorly.12
A posteriorly displaced radial neck fracture can occur during the spontaneous reduction of a posterior elbow dislocation.4
Alternatively, an unrecognized (undisplaced) radial neck fracture can be displaced posteriorly during the manipulative reduction of a posterior elbow dislocation. During the reduction maneuver, if the elbow is flexed, the distal humerus (lateral condyle) strikes the radial head, knocking it posteriorly off the metaphysis (FIG 3).
NATURAL HISTORY
Most radial neck fractures are minimally displaced or undisplaced. These heal uneventfully.
The greater the degree of angulation or translation, the greater the disruption in the relationship of the radiocapitellar joint, which may be associated with a decrease in the range of pronation and supination.2
The upper limit of acceptable angulation (0 to 60 degrees) is unclear and may be age-dependent.16 Most believe that angulation less than 30 degrees is unlikely to cause a clinically (functionally) significant loss of motion.
FIG 3 • Posteriorly displaced radial neck fracture produced during the reduction of a posterior elbow dislocation. A,B. AP and lateral views of the elbow dislocation. C. The radial head is no longer visible on the lateral view after elbow reduction. D. Displaced radial head apparent on AP view.
Other reported consequences include avascular necrosis of the radial head, heterotopic ossification, radioulnar synostosis, and premature physeal closure, which may result in pain, crepitus, and valgus deformity and stiffness.2,5,16,18,19
These outcomes may be associated with age, severity of displacement, presence of associated injuries, or delay in treatment.
Some of these might be a complication of the treatment (poor reduction, open treatment, or internal fixation) rather than the natural history.
PATIENT HISTORY AND PHYSICAL FINDINGS
History of a fall on the outstretched hand
Swelling of the elbow with limited range of motion associated with pain. Occasionally lateral ecchymosis may be evident.
Tenderness and crepitus may be localizable to the radial head, provoked by gentle pronation and supination.
The clinician should rule out an elbow dislocation and look for other areas of tenderness that might point to associated injuries.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Anteroposterior (AP) and lateral radiographs of the elbow. Oblique views can be helpful but are not routinely necessary.
Amount of displacement: angulation and translation of the radial neck are noted.
There are numerous classification systems of the severity of initial displacement. Most categorize the fractures based on amount of angulation,2 usually in 30-degree increments, while some also include translation.6,9,16,18,19
The Judet classification is a simple descriptive system (FIG 4; Table 1).6
The clinician should carefully rule out associated injuries such as fractures of the olecranon (intra-articular) (FIG 5), proximal ulna, medial epicondyle, or lateral condyle or elbow dislocation.
In posterior elbow dislocations, the clinician should carefully examine the radial neck for an occult fracture that is at risk for displacement during the reduction maneuver.
FIG 4 • Judet classification of radial neck fractures in children.
DIFFERENTIAL DIAGNOSIS
Radial neck fractures
Radial head fractures
Monteggia variant: the clinician should look for any olecranon fractures or proximal ulna fractures
Elbow dislocations
NONOPERATIVE MANAGEMENT
The Patterson reduction technique involves longitudinal traction applied to the extended arm with countertraction provided proximally.
The forearm is rotated (supinated) until the maximum tilt of the radial head is directed laterally.
A varus force is then applied to the elbow, while the radial head fragment is reduced by direct pressure.13
Kaufman and associates7 describe a closed reduction maneuver with the elbow in 90 degrees of flexion and in maximum supination (the Israeli technique).
Thumb pressure is applied to the lateral aspect of the displaced radial head while the forearm is rotated gradually into full pronation.
SURGICAL MANAGEMENT
Many displaced radial neck fractures can be satisfactorily reduced to an acceptable position with one of the above closed reduction techniques.
FIG 5 • A. Radial neck fracture with associated intra-articular fracture of the olecranon. Olecranon fracture appears minimally displaced on lateral view. B. Significant displacement is seen on AP view.
Failure to obtain or maintain an adequate closed reduction of Judet type 3 or 4 fractures (more than 30 degrees) is an indication for closed operative techniques.
Percutaneous leverage of the radial neck fracture using a Kirschner wire or Steinmann pin is one option.
Alternatively, reduction of the radial head can be accomplished by intramedullary manipulation of the radial head using a flexible or elastic nail or a Kirschner wire, with the nail or wire retained to stabilize the fracture if necessary.
Intramedullary reduction may be facilitated by the percutaneous leverage technique.
Open reduction with internal fixation is reserved for fractures that cannot be successfully managed by the above closed means.
Preoperative Planning
Careful examination of the radiographs is necessary to rule out intra-articular involvement of the radial head as well as associated injuries of the proximal ulna and distal humerus (FIG 5).
The orientation of the displaced radial head must be confirmed to ensure that the articular surface of the fragment is not flipped 180 degrees.
A set of Kirschner wires or Steinmann pins should be available if percutaneous pin-assisted reduction using the joystick or leverage technique is considered necessary.
If flexible intramedullary nail-assisted reduction is being considered, the narrowest diameter of the intramedullary canal of the radius must be measured to select the appropriate diameter of the intramedullary nail or device (Kirschner wire or elastic titanium nail).
Under general anesthesia, closed reduction of the fracture is attempted under fluoroscopic guidance before the decision is made to proceed.
Positioning
The patient is supine with the injured arm positioned over a radiolucent armboard.
The image intensifier may be positioned parallel to the operating table to allow the C-arm to be moved freely from the AP to lateral position.
Approach
For the percutaneous pin-assisted reduction technique, the pin or Kirschner wire is inserted from the posterolateral aspect of the radial neck with the forearm pronated to avoid injury to the posterior interosseous nerve.
For the centromedullary technique, the preferred entry point for the elastic nail is at the distal radius proximal to the growth plate through a 1.5-cm incision.
If the entry point is on the radial side, care is taken to avoid injury to the branches of the superficial radial nerve. The entry site is placed away from the tendons of the first extensor compartment.
An alternative entry point is the dorsal approach, just proximal to the tubercle of Lister, between the third and fourth extensor compartments.
If the elastic nail is being retained for fixation of the fracture, the radial approach is favored to prevent late rupture to the extensor pollicis longus tendon, which has been reported with the dorsal approach.
This complication can be avoided if the end of the retained nail is trimmed above the dorsal aspect of the extensor tendons so as not to abrade its volar surface.
TECHNIQUES
PERCUTANEOUS PIN (JOYSTICK) REDUCTION TECHNIQUE 1,14,18
Insertion and Manipulation of the Kirschner Wire
Using the image intensifier, the Kirschner wire is inserted from the posterolateral aspect of the radial neck (TECH FIG 1A).
During the insertion of the pin the forearm is best pronated to avoid injury to the posterior interosseous nerve. The surgeon should observe the thumb and index finger for any signs of metacarpophalangeal extension.
Once the tip of the Kirschner wire has reached the fracture site, the forearm may be rotated until the maximum displacement of the radial head is visualized (TECH FIG 1B).
The Kirschner wire is then advanced into the fracture site between the radial head (epiphysis) and the metaphysis and the fracture is disimpacted (TECH FIG 1C,D).
The Kirschner wire is then swung cephalad to lever the radial head back into position (TECH FIG 1E–G).
TECH FIG 1 • A. Position of pin for percutaneous pin-assisted reduction of a displaced radial neck fracture. B–G. When the Kirschner wire has been introduced into the fracture site, it is used to lever the radial head fragment into position by swinging it cephalad.
Use of Second Kirschner Wire
Occasionally the radial head remains translated even though the angulation has been corrected. With the first Kirschner wire in place, a second Kirschner wire may be introduced percutaneously to push the laterally translated fragment medially back into position (TECH FIG 2A–C).
The Kirschner wire is removed and the stability of the reduction assessed.
If the reduction is stable, as is usually the case, no internal fixation is required. The elbow is immobilized in 90 degrees of flexion with a posterior splint for 2 or 3 weeks.
If the reduction is unstable, the Kirschner wire may be used to repeat the leverage technique and then advanced with a power driver obliquely through the metaphysis to act as a buttress to prevent the radial head from redisplacing.
The Kirschner wire does not need to pass through the substance of the proximal fragment (TECH FIG 2D,E).
TECH FIG 2 • A–C. A second Kirschner wire is sometimes necessary to correct residual translation. D,E. The Kirschner wire can be advanced obliquely into the metaphysis to buttress the radial head fragment.
CLOSED INTRAMEDULLARY REDUCTION AND FIXATION (METAIZEAU TECHNIQUE9)
Metaizeau Technique
Metaizeau described an intramedullary reduction and fixation technique for the treatment of displaced radial neck fractures9 that has been widely adopted.3,15,17
The intramedullary manipulation of the radial head may be accomplished by an elastic titanium nail or a Kirschner wire of sufficient length, the tip of which is bent about 30 degrees.
The diameter of the elastic nail or Kirschner wire is usually 2 mm. A 2.5-mm nail may be suitable in some children older than 10 years. The curved nail tip can be bent additionally.
The preferred entry point for the nail is on the lateral cortex of the distal radius 1.5 to 2 cm proximal to the physis. It is created with a sharp awl or drill through a 1.5-cm incision, taking care to avoid injury to the sensory branch of the radial nerve (TECH FIG 3).
TECH FIG 3 • A–F. Radial-side entry point for elastic nail for centromedullary reduction technique. A. Incision centered over the distal radial physis. B. The surgeon should avoid injury to the superficial branch of the radial nerve. C. Entry point is 1.5 cm proximal to the distal radial physis. D. Awl is initially directed perpendicular to the bone. E,F. Under fluoroscopic guidance the awl is directed obliquely and proximally into the middle of the medullary canal. G. Alternate entry site: dorsal entry point for elastic nail for centromedullary reduction technique proximal to the tubercle of Lister.
Engaging the Fragment
The elastic nail is attached to a T-handle and advanced proximally through the medullary canal under fluoroscopic guidance (TECH FIG 4A–C).
The forearm is rotated until the plane of maximum deformity is visualized.
The curved tip of the nail or the Kirschner wire is directed toward the displaced proximal fragment and gently advanced across the fracture until the tip engages the epiphyseal fragment without penetrating the articular surface (TECH FIG 4D–F).
AP and lateral radiographs are obtained to confirm the position of the nail tip in the epiphyseal fragment.
Rotating the Fragment into Place
The nail tip is used to elevate the fragment to reduce the tilt anchoring the proximal fragment against the lateral condyle.
The T-handle is then used to rotate the nail or Kirschner wire typically anteriorly and medially, thereby reducing the lateral or posterolaterally displaced radial head back to its normal location (TECH FIG 5).
If the epiphysis is displaced anterolaterally, the nail is rotated posteriorly and medially.
The intact periosteum prevents overcorrection of the fragment medially.
Completing the Procedure
The reduction maneuver may be facilitated with a prior or concurrent closed reduction. In severely displaced radial neck fractures, the percutaneous technique described above may be performed concurrently to facilitate the intramedullary reduction (TECH FIG 6A).
With the nail tip engaged in the epiphysis and the reduction complete, the stability of the fracture is assessed and the nail is left in situ.
The nail is trimmed 1 cm proud of the bone at the entry site (TECH FIG 6B).
If the dorsal approach is used, the nail can be bent 90 degrees dorsally and trimmed just above the plane of the extensor pollicis longus tendon to ensure that the end of the nail does not abrade the tendon (TECH FIG 6C).
TECH FIG 4 • Closed intramedullary reduction and fixation technique of Metaizeau with an elastic nail. A–C. Proximal advancement of elastic nail through the medullary canal. D–F. The curved tip is directed toward and advanced into the displaced epiphyseal fragment.
TECH FIG 5 • The elastic nail is rotated anteriorly and medially to reduce the radial head.
TECH FIG 6 • A. Intramedullary reduction can be facilitated by concurrent percutaneous pin reduction technique. B. The end of the nail is left proud off the entry site to facilitate removal. C. If a dorsal entry point is used, the end of the nail is trimmed above the level of the tendons to prevent rupture.
POSTOPERATIVE CARE
A short period of immobilization may be necessary, but usually active range of motion can be started after 2 to 3 weeks. If the fracture is stable or stabilized by the elastic nail, the arm can be placed in a sling and gentle active range of motion encouraged as soon as tolerated.
Early passive range of motion is not recommended because of the risk of heterotopic ossification.
The elastic nail or Kirschner wire is removed after 6 to 8 weeks, when the fracture has healed clinically and radiographically.
OUTCOMES
A good outcome, defined as a functional painless range of motion without complications, can be expected in 78% to 93% of Judet grade 3 or 4 fractures treated by elastic stable intramedullary nailing.9,15,17
COMPLICATIONS
Posterior interosseous nerve injury15
Injury to sensory branch of radial nerve
Late extensor pollicis longus rupture
Penetration of the articular surface of the epiphysis, requiring early removal (FIG 6A)
Malreduction of the radial head flipped 180 degrees11 (FIG 6B–E)
Loss of reduction can be avoided by checking stability intraoperatively or retaining the Kirschner wire or elastic nail for fixation.
Minor limitation of motion
Avascular necrosis
Radial head overgrowth
Premature physeal closure is common as a consequence of the injury, treatment, or both. The clinical significance of this is unknown but it is unlikely to be problematic.
Nonunion21
Radioulnar synostosis
Periarticular heterotopic ossification
FIG 6 • A. Penetration of the articular surface of the epiphysis may irritate the joint. B–E. Malreduction of radial head flipped 180 degrees. B. Salter-Harris type II Judet 4 fracture. C. Pin-assisted reduction. D. Apparent anatomic reduction. E. AP view reveals radial head fragment is flipped over 180 degrees.
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