Jenny M. Frances and Roger Cornwall
DEFINITION
Radial neck fractures are extra-articular fractures of the radius proximal to the bicipital tuberosity.
Radial neck fractures are most common in children 9 to 12 years old and represent 14% of elbow fractures in children.9 The physis is typically involved as a Salter-Harris I or II pattern, yet Salter-Harris III and IV patterns also occur. Alternatively, the fracture often is extraphyseal, through the metaphysis.1,20
Intra-articular radial head fractures are less common elbow injuries in patients with open physes than in skeletally mature patients (7% vs. 52%).10
The Wilkins classification of radial head and neck fractures is based on the mechanism of injury and the pattern of the fracture, specifically whether there is physeal or articular involvement22:
Type I: Valgus injur.
A: Physeal injury—Salter-Harris I or II
B: Intra-articular—Salter-Harris III or IV
C: Metaphyseal fracture
Type II: Elbow dislocatio.
D: Fracture occurred during dislocation
E: Fracture occurred during reduction
The O'Brien and Judet classifications of radial neck fractures are based on degree of angulation.
O'Brien classification13.
Type I: Less than 30 degrees
Type II: 30 to 60 degrees
Type III: More than 60 degrees
Judet classification7.
Type I: Undisplaced
Type II: Less than 30 degrees
Type III: 30 to 60 degrees
Type IVa: 60 to 80 degrees
Type IVb: More than 80 degrees
ANATOMY
The radial head articulates with the capitellum and the radial notch of the ulna. The radial neck is extra-articular and has a normal 15 degrees of angulation on anteroposterior (AP) and 5 degrees on lateral radiographic views. The radial head ossific nucleus appears at about 4 years of age.
The proximal radioulnar joint is stabilized by the annular ligament and the accessory collateral ligament.
There are no muscular attachments to the radial neck. The blood supply is derived from the adjacent periosteum.
The radial nerve gives rise to the superficial radial nerve and the posterior interosseous nerve at the level of the lateral condyle. The posterior interosseous nerve travels distally anterior to the radial head and neck, enters the arcade of Frohse 2.6 cm distal to the radial head (FIG 1), and submerges between the superficial and deep fibers of the supinator 6.7 cm distal to the radial head.4 The radial recurrent artery originates from the radial artery and travels toward the lateral epicondyle in the opposite direction along the path of the radial nerve, on the anteromedial surface of the supinator.
PATHOGENESIS
The most common mechanism of radial neck fractures is a valgus and axial force to the elbow caused by a fall on an outstretched hand. This mechanism results in a lateral compression and a medial traction injury. The actual plane of maximal radial head angulation depends on the forearm position of supination or pronation at the time of impact.6
The other mechanism of injury is an elbow dislocation, where the fracture occurs either during the dislocation (radial head anterior) or during the elbow reduction (radial head posterior).6
Associated injuries, such as medial collateral ligament rupture or occult elbow dislocation, occur in 30% to 50% of radial neck fractures.17
Chronic stress fractures of the radial head and neck can occur with repetitive valgus loading, such as overhead throwing.
NATURAL HISTORY
The prognosis for radial neck fractures depends on the energy of injury, the amount of displacement, and the presence of any associated injuries.
Patients with minimal fracture displacement and a congruent joint generally have a favorable prognosis, while more severe alterations of normal joint anatomy can severely impede elbow range of motion unless reduced.
FIG 1 • The posterior interosseous nerve courses volar to the radial head and neck and enters the arcade of Frohse about 2.6 cm distal to the articular surface of the radial head.
PATIENT HISTORY AND PHYSICAL FINDINGS
Elucidating the mechanism of injury is important to truly understand the personality of the fracture, which can help in directing treatment. Higher-energy mechanisms are more likely to be associated with concomitant injuries. Elbow dislocations that have reduced before presentation are not uncommon, so it is helpful to ask the patient and family whether a marked deformity was noted at the time of injury.
Carefully palpating each anatomic area in the elbow to find the points of maximal tenderness helps diagnose the fracture as well as additional injuries. Associated injuries include medial collateral ligament tears, medial epicondyle fractures, ulna fractures, and supracondylar humerus fractures. A neurologic evaluation assesses distal radial, medial, and ulnar nerve motor and sensory function.
Assessing elbow stability and range of motion can help determine the need for treatment.
Valgus instability indicates a medial elbow injury in addition to an unstable radial neck fracture.
Blocks in forearm rotation, in particular pronation, are typically due to loss of congruity of the radioulnar joint and indicate a need for reduction.
Stability and range-of-motion assessment may necessitate either an intra-articular anesthetic injection or an examination under anesthesia.
IMAGING AND OTHER DIAGNOSTIC STUDIES
AP, lateral, and oblique radiographs often show radial neck fractures well (FIG 2A,B). However, the true extent of fracture angulation can be underestimated on plain radiographs, as orthogonal views may fail to capture the true plane of angulation.
Radial neck fractures can occur before the ossification of the radial head, without clear evidence of fracture on plain radiographs. Ultrasound, MRI (FIG 2C), and arthrography (FIG 2D,E) are useful for diagnosing and evaluating radial neck fractures in young patients with nonossified radial heads. In the operating room, arthrography is useful in outlining the nonossified radial head when monitoring and verifying reduction.
DIFFERENTIAL DIAGNOSIS
The diagnosis of a radial neck fracture is usually easily made with appropriate imaging. However, the presence or absence of the following associated injuries should be ascertained:
Medial collateral ligament rupture
Medial epicondyle fracture
Olecranon fracture
Monteggia-equivalent type IV fracture
NONOPERATIVE MANAGEMENT
Ultimately, the objective is to obtain and maintain a congruent joint with restored elbow range of motion in all planes. Most consider 30 degrees of angulation and 3 mm of translation an acceptable reduction. Controversy exists regarding the exact numbers, however, with reported acceptable angulation ranging from 20 to 60 degrees. 1,3,8,12,16,18,19,21,22
Two things partially account for the controversy:
The accuracy of the radiographic measurement is variable and depends on whether the radiographic beam is perpendicular to the true plane of the fracture.
FIG 2 • A,B. AP and lateral radiographs demonstrate an ulna fracture and radial neck fracture in a 3-year-old with a nonossified radial head. However, it is difficult to discern the degree of angulation on plain radiographs. MRI is useful when evaluating radial neck fractures in children with nonossified radial heads. C. The MRI from the same patient clearly shows the 60-degree radial neck angulation not defined on plain films. D,E. Arthrography demonstrates a 90-degree displaced radial neck fracture not seen on plain films. It is also useful to monitor and verify reduction intraoperatively.
Twenty-five degrees of fracture angulation can have variable effects on the congruity of the radioulnar joint, depending on the direction of angulation.
It is therefore important to base the decision of treatment on the functional effects of the angulation, rather than a specific number. Any block of pronation or supination warrants a reduction of the fracture, no matter what the radiographic angulation is.
As remodeling potential decreases with advancing skeletal maturity, less residual angulation is acceptable (15 to 20 degrees).5,21
Closed reduction is recommended if there is more than 30 degrees of angulation or 3 mm of translation, or if there is any block to range of motion. Reduction can be done either with sedation in the emergency room or in the operating room. The advantage of the latter is the immediate ability to proceed to a percutaneous reduction technique should the closed techniques fail, which is more likely in cases with severe displacement.
The nature and duration of immobilization depend on the fracture pattern, the presumed stability, and the maturity of the patient. For example, a 17-year-old reliable patient with a nondisplaced stable radial neck fracture can be treated with a sling and early range of motion. Physeal fractures, fractures needing reduction, and fractures in young patients usually need immobilization in a cast for 3 weeks, however.
When clinical and radiographic signs of healing are lacking, the cast may remain for an additional 2 weeks, followed by a re-evaluation of the healing progress.
SURGICAL MANAGEMENT
If closed reduction fails, the next step is to proceed to a percutaneous reduction technique. Techniques using a Steinmann pin to push or lever are described in detail in the Techniques section.
Every attempt to achieve a closed or percutaneous reduction is made, as the rates of complications, including avascular necrosis, heterotopic ossification, and nonunion, are higher with an open approach.3,12
The markedly displaced floating fragments associated with elbow dislocations often require an open approach, while most angulated radial head fractures can be reduced by a combination of closed and percutaneous techniques.
Preoperative Planning
It is essential to obtain proper elbow and forearm radiographs and diagnose all injuries before proceeding to the operating room.
Familiarity with all of the closed and percutaneous reduction techniques described in the Techniques section is useful, as each fracture behaves and responds differently to different techniques.
It is prudent to advise both the parents and the operating room staff that a range of techniques from closed to open may be employed to obtain reduction. Doing so eliminates any element of surprise. The surgeon should ensure the availability of elastic titanium nails, Kirschner wires, and Steinmann pins if needed.
Elbow range of motion and stability are assessed under anesthesia. The elbow is then pronated and supinated under fluoroscopy to find the maximum plane of angulation before reduction (FIG 3).
Several different techniques of closed and percutaneous reduction make up the “reduction ladder” covered in the Techniques section, much like the plastic surgeon's reconstructive ladder. These tools may be used in stepwise progression or in conjunction as needed.
Positioning
The patient is positioned supine on the operating room table, with the elbow on the fluoroscopy C-arm and the arm positioned on the collimator of the C-arm (FIG 4).
The imaging monitor is placed at the opposite side of the bed for easy visualization.
Approach
The posterolateral Kocher approach is used for open reduction of severely displaced floating fragments. The approach is further described in the Techniques section.
FIG 3 • The maximal angle of displacement is found with fluoroscopy imaging through the ranges of full supination (A) to pronation (B). In this case, maximal angulation is noted with 50 degrees of pronation.
FIG 4 • After sterile preparation the arm is draped out using the C-arm as an operating table. The imaging monitor is placed for easy visualization on the other side of the bed.
TECHNIQUES
CLOSED REDUCTION
Israeli or Kaufman Technique
Kaufman described a closed reduction technique with the elbow flexed 90 degrees.8
Fluoroscopy is used to establish the forearm position demonstrating maximal angulation (see FIG 3).
One hand is used to control forearm rotation, and the other hand is used to provide lateral pressure to the displaced radial head with the thumb (TECH FIG 1A–C).
After reduction, fracture stability and range of motion are assessed (TECH FIG 1D–G).
TECH FIG 1 • A–C. Kaufman (Israeli) technique. One hand grips the forearm distally to control supination and pronation (A), while the thumb of the other hand reduces the fragment in the plane of maximal reduction (B), milking the head from distal to proximal (C). D–G. After reduction has been obtained, the stability and range of motion (pronation–supination) are assessed in extension and 90 degrees of flexion.
Patterson Technique
With the elbow extended and forearm supinated, varus stress is applied to the elbow by an assistant. The surgeon reduces the fragment with lateral digital pressure (TECH FIG 2).
Drawbacks of this technique include the need for an understanding assistant providing countertraction and varus stress, and the potential difficulty in palpating the radial head in this position.
TECH FIG 2 • Patterson technique. A. The assistant helps with positioning the elbow in extension, applying a varus force, while holding the forearm in supination. B,C. Digital pressure from the thumb is applied to the radial head to achieve reduction.
PERCUTANEOUS REDUCTION WITH A KIRSCHNER WIRE OR STEINMANN PIN
If closed reduction fails, a Kirschner wire or a Steinmann pin can be used to directly push or lever the radial head into anatomic position.
The surgeon must beware of the posterior interosseous nerve coursing volar and distally over the radial head. The radial head can be protected by pronating the forearm and by using a posterolateral pin approach (TECH FIG 3).
The forearm is rotated during fluoroscopic guidance so that the plane of maximal angulation is visualized.
Push Technique
The blunt end of a larger Kirschner wire, 0.062 inch or larger, is percutaneously inserted through the skin distal to the fracture and just off the lateral border of the ulna (TECH FIG 4A,B) through a 2-mm incision.
With fluoroscopic guidance, the pin is placed against the posterolateral aspect of the proximal fragment and the radial head is pushed into place (TECH FIG 4C,D).
Axial traction and rotation of the forearm can dislodge an impacted fracture and assist in the reduction.
Lever Technique
Alternatively, the pin (or a Freer elevator) can be used as a lever. When doing so, the skin entry site of the pin must be placed more proximally, however, at the level of the fracture site (TECH FIG 5A).
With the pin just through the skin, the pin is pulled distally (applying tension to the skin) to allow a retrograde approach to the fracture.
TECH FIG 3 • The posterior interosseous nerve moves volar and medial with pronation, moving it away from the working area during percutaneous or open treatment of radial head and neck fractures.
TECH FIG 4 • Push technique for percutaneous reduction of radial neck fracture. A,B. Imaging is used to plan the trajectory of the push pin. The pin is inserted posterolaterally, avoiding the volar posterior interosseous nerve. C,D. Using imaging as guidance, the radial head fragment is pushed into reduction.
The deeper soft tissues are then pierced, the fracture site is entered (TECH FIG 5B), and the proximal fragment is levered proximally to correct the angulation while translation is corrected with simultaneous lateral digital pressure. During the levering maneuver, the tensioned skin relaxes, thus making the reduction easier (TECH FIG 5C).
If the skin instead were entered distally for the lever maneuver, however, the skin tension during the reduction maneuver would make the reduction substantially more difficult.
After percutaneous reduction, fracture stability in all planes is assessed. If unstable, pin fixation of the fragment is recommended.
TECH FIG 5 • Lever technique. A. The lever pin is inserted at the level of the fracture through the skin. B. The pin is then pushed distally, applying tension to the skin before approaching the physeal side of the fracture and (C) levering the fragment into place, allowing the built-up tension of the skin to aid in the reduction.
OPEN REDUCTION
Kocher's posterolateral approach to the radial head is used. Pronating the forearm brings the posterior interosseous nerve further anteromedially, away from the surgical field.
A skin incision about 5 cm long is made, centered over the posterolateral aspect of the radial head (TECH FIG 6A). The interval between the anconeus (radial nerve) and the extensor carpi ulnaris (posterior interosseous nerve) is developed (TECH FIG 6B).
A longitudinal incision is made along the capsule, unless the capsule has not already been torn open by the injury causing trauma (TECH FIG 6C).
The proximal fragment is identified and reduced under direct visualization and fluoroscopic guidance. If the annular ligament has been injured it should be repaired.
Occasionally, the fracture is widely displaced anteromedially, necessitating further exposure before identification. In such a case, a more extensile approach is recommended, as well as a formal proximal identification of the radial nerve and posterior interosseous nerve.
If the fracture requires open reduction, internal fixation is recommended.
A recent retrospective review of radial neck nonunions noted that they were commonly associated with an early loss of fixation, related to either displacement or premature removal of pins.20
Options for internal fixation include pins placed obliquely though the radial head in an “ice-cream cone” pattern throughout the safe zone. Absorbable pins can also be used. Radial head fixation can be achieved with epiphyseal–metaphyseal interrupted, circumferentially placed absorbable sutures.2 For skeletally mature children, headless screws or a Tplate in the safe zone can be used.
TECH FIG 6 • A. The Kocher posterolateral approach to the elbow uses the interval between the anconeus and the extensor carpi ulnaris. B. The capsule is incised longitudinally. C. The radial head fragment may be readily visualized after exposure, unless medially or posteriorly displaced.
Although seldom indicated, Leung and Tse described a lateral mini-plate buttress technique for the open physis. The plate is anchored distally in the radial neck with 2-mm screws and left unattached proximally, providing a buttress preventing lateral dislocation of the radial head.11
Transcapitellar pin fixation has been described, but it provides poor distal fixation and is associated with pin breakage at the radiocapitellar joint.3
POSTOPERATIVE CARE
After reduction, the elbow is immobilized in 90 degrees of flexion in the position of supination–pronation that is most stable for 3 weeks.
If a splint is used postoperatively because of swelling, it is changed to a cast at 1 week.
At follow-up, the cast is removed for radiographic and clinical examination. If healing is inadequate (which is more likely in higher-energy injuries in older children), the cast (and the pins if used) is continued for 2 more weeks, after which patient is re-evaluated for healing.
If pin fixation is used, no elbow motion is allowed until pins are removed.
Graduated range-of-motion exercises begin when the cast is removed.
OUTCOMES
Many series have shown a good to excellent outcome in 76% to 94% of children with radial neck fractures.1,3,16–18
Indicators for a favorable prognosis include younger age (less than 10 years), isolated low-energy injury, closed reduction, early treatment, less than 30 degrees of initial angulation, less than 3 mm of initial translation, and reduction within parameters discussed above.3,12,17
Poor outcomes, such as limitations in range of motion, have been reported in 6% to 30% of patients, usually after a severely displaced radial neck fracture.
Risk factors for a poor outcome include severe displacement, associated injuries, delayed treatment, poor reductions, old age, fractures needing open treatment and internal fixation, and intra-articular fractures in patients with an open physis.10,12,16,17,20
Poor outcomes that have been noted with open procedures are partially due to a selection bias, where patients needing open procedures are more likely to have had high-energy injuries with additional vascular and soft tissue trauma.
COMPLICATIONS
Loss of joint congruity, fibrous adhesions, and radial head overgrowth result in a loss of elbow motion. In order of decreasing frequency, pronation, supination, extension, and flexion are affected.17
Radial head overgrowth is observed in 20% to 40% of cases due to presumed increased vascularity stimulating the physis. Premature physeal closure can occur and is seldom symptomatic, but it can accentuate a valgus deformity. Delayed appearance of the ossific nucleus is possible after a fracture occurring before ossification.
Avascular necrosis of the radial head occurs in 10% to 20% of patients.3,12 Seventy percent of cases occur in cases of open reduction.3
Radial neck nonunions are rare but have been reported and are often associated with premature loss of fixation.20
Posttraumatic radioulnar synostosis occurs in 0% to 10% of cases,3,12,16 typically in association with open reductions, extensive dissection, residual displacement, and concurrent ulna fracture. Exostectomy of synostosis is a technically demanding procedure with a variable success rate.
Heterotopic ossification (6% to 25% of cases)3,12 can occur as myositis ossificans in the supinator or as ossification within the capsule. Surgical treatment is rarely indicated.
REFERENCES
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