• PEDIATRIC FOREARM

   

   

   

   

  EPIDEMIOLOGY

• These injuries are very common. They make up 40% of all pediatric fractures (only 4% are diaphyseal fractures), with a 3:1 male predominance in distal radius fractures.

• Eighty percent occur in children >5 years of age.

• The peak incidence corresponds to the peak velocity of growth when the bone is weakest owing to dissociation between bone growth and mineralization.

• Fifteen percent have ipsilateral supracondylar fracture.

• One percent have neurologic injury, most commonly median nerve.

• Of pediatric forearm fractures, 60% occur in the distal metaphyses of the radius or ulna, 20% in the shaft, 14% in the distal physis, and <4% in the proximal third.

  ANATOMY

• The radial and ulnar shafts ossify during the eighth week of gestation.

• The distal radial epiphysis appears at age 1 year (often from two centers); the distal ulnar epiphysis appears at age 5 years; the radial head appears at ages 5 to 7 years; the olecranon appears at ages 9 to 10 years. These all close between the ages of 16 and 18 years.

• The distal physis accounts for 80% of forearm growth.

• With advancing skeletal age, there is a tendency for fractures to occur in an increasingly distal location owing to the distal recession of the transition between the more vulnerable wider metaphysis and the narrower and stronger diaphysis.

• Osteology

  • The radius is a curved bone, cylindric in the proximal third, triangular in the middle third, and flat distally with an apex lateral bow.

  • The ulna has a triangular shape throughout, with an apex posterior bow in the proximal third.

  • The proximal radioulnar joint is most stable in supination where the broadest part of the radial head contacts the radial notch of the ulna and the interosseous membrane is most taut. The annular ligament is its major soft tissue stabilizer.

  • The distal radioulnar joint (DRUJ) is stabilized by the ulnar collateral ligament, the anterior and posterior radioulnar ligaments, and the pronator quadratus muscle. Three percent of distal radius fractures have concomitant DRUJ disruption.

  • The triangular fibrocartilage complex (TFCC) has an articular disc joined by volar and dorsal radiocarpal ligaments and by ulnar collateral ligament fibers. It attaches to the distal radius at its ulnar margin, with its apex attached to the base of the ulna styloid, extending distally to the base of the fifth metacarpal.

  • The periosteum is very strong and thick in the child. It is generally disrupted on the convex fracture side, whereas an intact hinge remains on the concave side. This is an important consideration when attempting closed reduction.

• Biomechanics

  • The posterior distal radioulnar ligament is taut in pronation, whereas the anterior ligament is taut in supination.

  • The radius effectively shortens with pronation and lengthens with supination.

  • The interosseous space is narrowest in pronation and widest in neutral to 30 degrees of supination. Further supination or pronation relaxes the membrane.

  • The average range of pronation/supination is 90/90 degrees (50/50 degrees necessary for

    activities of daily living).

  • Middle third deformity has a greater effect on supination, with the distal third affecting pronation to a greater degree.

  • Malreduction of 10 degrees in the middle third limits rotation by 20 to 30 degrees.

  • Bayonet apposition (overlapping) of the radius and ulna does not reduce forearm rotation.

• Deforming muscle forces (Fig. 45.1)

   

   

   

• Proximal third fractures:

  • Biceps and supinator: These function to flex and supinate the proximal fragment.

  • Pronator teres and pronator quadratus: These pronate the distal fragment.

• Middle third fractures:

  • Supinator, biceps, and pronator teres: The proximal fragment is in neutral.

  • Pronator quadratus: Pronates the distal fragment.

• Distal third fractures:

  • Brachioradialis: Dorsiflexes and radially deviates the distal segment.

  • Pronator quadratus, wrist flexors and extensors, and thumb abductors: They also cause fracture deformity.

MECHANISM OF INJURY

• Indirect: The mechanism is a fall onto an outstretched hand. Forearm rotation determines the direction of angulation:

  • Pronation: Flexion injury (dorsal angulation)

  • Supination: Extension injury (volar angulation)

• Direct: Direct trauma to the radial or ulnar shaft.

  CLINICAL EVALUATION

• The patient typically presents with pain, swelling, variable gross deformity, and a refusal to use the injured upper extremity.

• A careful neurovascular examination is essential. Injuries to the wrist may be accompanied by symptoms of carpal tunnel compression and more proximal fractures may be associated with anterior interosseous nerve (AIN) or posterior interosseous nerve (PIN) injuries.

• The ipsilateral hand, wrist, forearm, and arm should be palpated, with examination of the ipsilateral elbow and shoulder to rule out associated fractures or dislocations.

• In cases of dramatic swelling of the forearm, compartment syndrome should be ruled out on the basis of serial neurovascular examinations with compartment pressure monitoring if indicated. Pain on passive extension of the digits is most sensitive for recognition of a possible developing compartment syndrome; the presence of any of the “classic” signs of compartment syndrome (pain out of proportion to injury, pallor, paresthesias, pulselessness, paralysis) should be aggressively evaluated with possible forearm fasciotomy.

• Examination of skin integrity must be performed, with removal of all bandages and splints placed in the field.

  RADIOGRAPHIC EVALUATION

• Anteroposterior and lateral views of forearm, wrist, and elbow should be obtained. The forearm should not be rotated to obtain these views; instead, the beam should be rotated to obtain a cross-table view.

• The bicipital tuberosity is the landmark for identifying the rotational position of the proximal fragment (Fig. 45.2):

  • Ninety degrees of supination: It is directed medially.

  • Neutral: It is directed posteriorly.

  • Ninety degrees of pronation: This is directed laterally.

  • In the normal, uninjured radius, the bicipital tuberosity is 180 degrees to the radial styloid.

     

     

     

    RADIUS AND ULNA SHAFT FRACTURES

    Classification

    Descriptive

    1. Location: Proximal, middle, distal third

    2. Type: Plastic deformation, incomplete (greenstick), compression (torus or buckle), or complete

    3. Displacement

    4. Angulation

    Nonoperative Treatment

• Gross deformity should be corrected on presentation to limit injury to soft tissues. The extremity should be splinted for pain relief and for prevention of further injury if closed reduction will be delayed (Fig. 45.3).

   

   

   

• The extent and type of fracture and the child’s age are factors that determine whether reduction can be carried out with sedation, local anesthesia, or general anesthesia.

• Finger traps may be applied with weights to aid in reduction.

• Closed reduction and application of a well-molded (both three-point and interosseous molds) long arm cast or splint should be performed for most fractures, unless the fracture is open, unstable, irreducible, or associated with compartment syndrome.

  • Reduction should be maintained with pressure on the side of the intact periosteum (concave side).

  • Exaggeration of the deformity to disengage the fragment and to relieve tension of the periosteum

    is only performed for distal radius fractures, not shaft fractures.

• Because of deforming muscle forces, the level of the fracture determines forearm rotation of immobilization:

  • Proximal third fractures: Supination

  • Middle third fractures: Neutral

  • Distal third fractures: Pronation

  • Placing the forearm in extremes of supination or pronation should be avoided for any location of fracture.

• The cast should be molded into an oval to increase the width of the interosseous space and

  bivalved if forearm swelling is a concern. The arm should be elevated (Fig. 45.4).

   

   

   

• The cast should be maintained for 4 to 8 weeks until radiographic evidence of union has occurred. Conversion to a short arm cast may be undertaken at 4 to 6 weeks if healing is adequate.

• Acceptable deformity:

  • Angular deformities: Correction of 1 degree per month, or 10 degrees per year, results from physeal growth. Exponential correction occurs over time; therefore, increased correction occurs for greater deformities. The amount of total correction is location and age dependent; for a patient <10 years old, up to 15 degrees of correction may occur at the wrist.

  • Rotational deformities: These do not appreciably correct.

  • Bayonet apposition: A deformity ≤1 cm is acceptable and will remodel if the patient is <8 to 10 years old.

  • In patients >10 years of age, no deformity should be accepted.

• Plastic deformation: Children <4 years or with deformities <20 degrees usually remodel and can be treated with a long arm cast for 4 to 6 weeks until the fracture site is nontender. Any plastic deformation should be corrected that (1) prevents reduction of a concomitant fracture, (2) prevents full rotation in a child >4 years, or (3) exceeds 20 degrees.

  • General anesthesia is typically necessary, because forces of 20 to 30 kg are usually required for correction.

  • The apex of the bow should be placed over a well-padded wedge, with application of a constant

    force for 2 to 3 minutes followed by application of a well-molded long arm cast.

  • The correction should have less than 10 to 20 degrees of angulation.

• Greenstick fractures: Nondisplaced or minimally displaced fractures may be immobilized in a well-molded long arm cast. They should be slightly overcorrected to prevent recurrence of deformity.

  • Completing the fracture decreases the risk of recurrence of the deformity; however, reduction of the displaced fracture may be more difficult. Therefore, it may be beneficial to carefully fracture the intact cortex while preventing displacement. A well-molded long arm cast should then be applied.

    Operative Indications

• Unstable/unacceptable fracture reduction after closed reduction

• Open fracture/compartment syndrome

• Floating elbow

• Refracture with displacement

• Segmental fracture

• Age (usually older than 10 years if significant angulation persists)

  Surgical stabilization of pediatric forearm fractures is required in 1.5% to 31% of cases.

  Operative Treatment

• Intramedullary fixation: Percutaneous insertion of intramedullary rods or wires may be used for fracture stabilization. Typically, flexible rods are used or rods with inherent curvature to permit restoration of the radial bow.

  • The radius is reduced first, with insertion of the rod just proximal to the radial styloid after visualization of the two branches of the superficial radial nerve.

  • The ulna is then reduced, with insertion of the rod either antegrade through the olecranon or

    retrograde through the distal metaphysis, with protection of the ulnar nerve.

  • Postoperatively, a volar splint is placed for 4 weeks. The hardware is left in place for 6 to 9 months, at which time removal may take place, provided solid callus is present across the fracture site and the fracture line is obliterated.

• Plate fixation: Severely comminuted fractures or those associated with segmental bone loss are ideal indications for plate fixation, because in these patterns, rotational stability is needed. Plate fixation is also used in cases of forearm fractures in skeletally mature individuals.

• Ipsilateral supracondylar fractures: When associated with forearm fractures, a “floating elbow” results. These may be managed by conventional pinning of the supracondylar fracture followed by cast immobilization of the forearm fracture. Stabilization of the forearm fracture may be required if there is gross instability or displacement and there is concern about a compartment syndrome.

  Complications

• Refracture: This occurs in 5% of patients and is more common after greenstick fractures and after plate removal.

• Malunion: This is a possible complication.

• Synostosis: Rare complication in children. Risk factors include high-energy trauma, surgery, repeated manipulations, proximal fractures, and head injury.

• Compartment syndrome: One should always bivalve the cast after a reduction.

• Nerve injury: Median, ulnar, and PIN injuries have all been reported. There is an 8.5% incidence of iatrogenic injury in fractures that are surgically stabilized.

  MONTEGGIA FRACTURE

• This is a proximal ulna fracture or plastic deformation with associated dislocation of the radial head.

• Comprises 0.4% of all forearm fractures in children.

• The peak incidence is between 4 and 10 years of age.

• Ulna fracture is usually located at the junction of the proximal and middle thirds.

• Bado classification of Monteggia fractures (Fig. 45.5):

  Type I: Anterior dislocation of the radial head with fracture of ulna diaphysis at any level with anterior angulation; 70% of cases; may occur from a direct blow, hyperpronation, or hyperextension

  Type II: Posterior/posterolateral dislocation of the radial head with fracture of ulna diaphysis with posterior angulation; 3% to 6% of cases; a variant of posterior elbow dislocation when the anterior cortex of the ulna is weaker than the elbow ligaments

  Type III: Lateral/anterolateral dislocation of the radial head with fracture of ulna metaphysis; 23% of cases (ulna fracture, usually greenstick); occurs with varus stress on an outstretched hand planted firmly against a fixed surface

  Type IV: Anterior dislocation of the radial head with fractures of both radius and ulna within proximal third at the same level; 1% to 11% of cases

   

   

   

  MONTEGGIA FRACTURE EQUIVALENTS (FIG. 45.6)

  Type I: Isolated radial head dislocation

  Type II: Ulna and proximal radius (neck) fracture

  Type III: Isolated radial neck fracture

  Type IV: Elbow dislocation (ulnohumeral)

   

   

   

• Treatment: Based on the type of ulna fracture rather than on the Bado type. Plastic deformation is treated with reduction of ulnar bow. Incomplete fractures are treated with closed reduction and casting (types I and III are more stable with immobilization in 100 to 110 degrees of flexion and full supination). Complete fractures are treated with Kirschner wires or intramedullary fixation if one is unable to reduce or maintain the reduction of the radial head.

• Ten degrees of angulation are acceptable in children <10 years old, provided reduction of radial head is adequate.

• Complications:

  • Nerve injury: There is a 10% to 20% incidence of PIN (most common in types I and III).

  • Myositis ossificans occurs in 7% of cases.

     

    GALEAZZI FRACTURE

• A middle to distal third radius fracture, with intact ulna, and disruption of the DRUJ. A Galeazzi equivalent is a distal radial fracture with a distal ulnar physeal fracture (more common).

• This injury is rare in children; 3% of distal radius fractures have concurrent DRUJ disruption.

• Peak incidence is between ages 9 and 12 years.

• Classified by position of radius (Fig. 45.7)

  Type I: Dorsal displacement of distal radius, caused by supination force. Reduce with forced pronation and dorsal to volar force on the distal radius.

  Type II: Volar displacement, caused by pronation. Reduce with supination and volar to dorsal force on the distal radius.

   

   

   

• The operative indication is a failure to maintain reduction. This is treated with cross pinning, intramedullary pins, or plating.

• Complications:

  • Malunion: This results most frequently from persistent ulnar subluxation.

  • Ulnar physeal arrest: Occurs in 55% of Galeazzi equivalent fractures.

     

    DISTAL RADIUS FRACTURES

    Physeal Injuries

• Salter-Harris types I and II: Gentle closed reduction is followed by application of a long arm cast or sugar-tong splint with the forearm pronated (Fig. 45.8); 50% apposition with no angular or rotational deformity is acceptable. Growth arrest can occur in 25% of patients if two or more manipulations are attempted. Open reduction is indicated if the fracture is irreducible (periosteum or pronator quadratus may be interposed).

   

   

   

• Salter-Harris type III: Anatomic reduction is necessary. Open reduction and internal fixation with smooth pins or screws parallel to the physis is recommended if the fracture is inadequately reduced.

• Salter-Harris types IV and V: Rare injuries. Open reduction and internal fixation is indicated if the fracture is displaced; growth disturbance is likely.

• Complications

  • Physeal arrest may occur from original injury, late reduction (>7 days after injury), or multiple reduction attempts. It may lead to radial deformity or ulnar positive variance.

  • Ulnar styloid nonunion is often indicative of a TFCC tear. The styloid may be excised and the

    TFCC repaired.

  • Carpal tunnel syndrome: Decompression may be indicated.

     

    Metaphyseal Injuries

• Classified by the direction of displacement, involvement of the ulna, and the biomechanical pattern (torus, incomplete, complete).

• Treatment

  • Torus fractures: If only one cortex is involved, then the injury is stable and may be treated with protected immobilization for pain relief. Bicortical injuries should be treated in a long arm cast.

  • Incomplete (greenstick) fractures (Table 45.1): These have a greater ability to remodel in the

    sagittal plane than in the frontal plane. Closed reduction with completion of the fracture is indicated to reduce the risk of subsequent loss of reduction. The patient should be placed in supination to reduce the pull of the brachioradialis in a long arm cast.

     

     

     

  • Complete fractures: Finger traps may hinder reduction because the periosteum may tighten with traction. Exaggeration of the deformity (often >90 degrees) should be performed to disengage the fragments. The angulated distal fragment may then be apposed onto the end of the proximal fragment, with simultaneous correction of rotation. The patient should be placed in a well-molded long arm cast for 3 to 4 weeks (Fig. 45.9). Indications for percutaneous pinning include loss of reduction, excessive local swelling preventing placement of a well-molded cast, floating elbow, and multiple manipulations. Open reduction is indicated if the fracture is irreducible (<1% of all distal radius fractures), if the fracture is open, or if the patient has compartment syndrome.

     

     

     

• Complications

  • Malunion: Loss of reduction may occur in up to 30% of metaphyseal fractures with bayonet opposition. Residual malangulation of more than 20% may result in loss of forearm rotation.

  • Nonunion: This rare complication is usually indicative of an alternate pathologic state.

  • Refracture: Usually results from an early return to activity (before 6 weeks).

  • Growth disturbance: The average disturbance of growth is 3 mm (either overgrowth or undergrowth) with maximal overgrowth in 9- to 12-year-olds.

  • Neurovascular injuries: One needs to avoid extreme positions of immobilization.