Charles T. Mehlman
DEFINITION
Forearm shaft fractures represent the third most common fracture encountered in the pediatric population.1
Closed fracture care is successful in the large majority of children who sustain forearm shaft fractures (especially the common greenstick fracture pattern).
For children who are 8 to 10 years of age and older with complete fracture patterns, the limits of acceptable displacement (angulation, rotation, and translation) become more strict and the likelihood of surgical intervention increases.5
ANATOMY
The forearm represents a largely nonsynovial two-bone joint with a high-amplitude range of motion (roughly 180 degrees). In the fully supinated anteroposterior (AP) plane the radius bows naturally out and away from the relatively straight ulna, while both bones are predominantly straight in the lateral plane.
Anatomically the shaft of the radius extends from the most proximal aspect of the tubercle of Lister (which approximates the distal metaphyseal–diaphyseal junction) to the proximal base of the bicipital tuberosity. The shaft of the ulna corresponds to these same points on the radius (FIG 1).5,6
In unfractured bones the normal orientation of the radial styloid and bicipital tuberosity is slightly less than 180 degrees from one another, while the ulnar styloid and coronoid process come closer to a true 180-degree relationship.
Classically, forearm shaft fractures are divided into distal third (pronator quadratus region), central third (pronator teres region), and proximal third (biceps and supinator region). These anatomic relationships offer insight into the deforming forces acting on the fractured forearm (FIG 2).
PATHOGENESIS
Forearm shaft fractures most commonly occur secondary to a fall on an outstretched arm and usually involve both bones. Forward falls tend to involve a pronated forearm and backward falls a supinated forearm.
Single-bone forearm shaft fractures should raise significant suspicion regarding the presence of a Galeazzi or Monteggiatype injury (see Chap. PE-52).
Mechanisms of injury that involve little rotational force result in forearm fractures at nearly the same levels, while greater rotational force results in fractures at rather different levels.
NATURAL HISTORY
The remodeling potential of the pediatric forearm shaft has been well documented and is considered to be most predictable in children less than about 8 to 10 years of age.
Spontaneous correction and improvement of malaligned shaft fractures are considered to occur in young children via three mechanisms:
Adjacent physes produce “straight bone” via normal growth.
Physeal orientation tends to “right its horizon” via the Hueter-Volkmann law.
True shaft remodeling occurs via Wolff's law.9
PATIENT HISTORY AND PHYSICAL FINDINGS
The clinician should gather as much pertinent information as possible regarding the mechanism of injury (eg, a fall from the bottom step of the playground sliding board may be much different from a fall from the top step of the same sliding board).
The clinician should determine whether the patient has any other complaints of pain beyond the forearm shaft region (eg, wrist or elbow tenderness). Any perceived deformity or pain to palpation should trigger dedicated radiographs of the problematic region.
The clinician should elicit any past history of fracture or bone disease in the patient or the patient's family.
Physical examination of the skin of the child's forearm should be performed to rule out the presence of an open fracture. Any wound, no matter how small or seemingly superficial, should be carefully evaluated. Persistent bleeding or oozing from a small suspicious wound should be considered an open fracture until proven otherwise.
The environment of the injury has special significance for open fracture management. For instance, farm-related injuries may alter the treatment regimen for the patient.
Multiple trauma or high-energy trauma scenarios dictate that a screening orthopaedic examination be performed to help rule out injuries to the other extremities as well as the spine.
Brachial, radial, and ulnar pulses should be palpated and distal capillary refill should be assessed.
Sensory examination should include, at minimum, light touch sensation testing (or pin prick testing if necessary) of the autonomous zones of the radial, ulnar, and median nerves. Older children may be able to comply with formal two-point discrimination testing.
FIG 1 • The radial diaphysis extends from the most proximal aspect of the tubercle of Lister to the proximal base of the bicipital tuberosity. The ulnar diaphysis corresponds to these same points on the radius.
FIG 2 • Forearm shaft fractures are divided into distal third (pronator quadratus region), central third (pronator teres region), and proximal third (biceps and supinator region).
It has been said that you need only a thumb to test the motor function of all three major nerves: radial nerve = extensor pollicis longus, ulnar nerve = adductor pollicis, median nerve = opponens pollicis.
Peripheral nerves in the fractured extremity are assessed with the “rock-paper-scissors” method.
The radial nerve (really the posterior interosseous nerve in the forearm) is tested with “paper”—extension of the fingers and wrist well above a zero-degree wrist position. The autonomous zone is the dorsal web space between the thumb and index finger. There is a risk of iatrogenic injury during surgical exposure of the proximal radial shaft.
The ulnar nerve is tested with “scissors”—adducted thumb, abducted fingers, and flexor digitorum profundus function to ring and pinky. The autonomous zone is palmar tip pinky finger. This is the most common iatrogenic nerve injury after internal fixation of forearm shaft fractures.
The median nerve is tested with “rock.” The autonomous zone is palmar tip index finger. The median is the most commonly injured nerve after closed or open forearm shaft fractures.
The anterior interosseous nerve is tested with the “okay” sign. Flexion of the distal interphalangeal of the index finger and the interphalangeal of the thumb herald flexor digitorum profundus and flexor pollicis longus function of these digits. This is a motor branch only (it has no cutaneous innervation, only articular). Isolated palsy has been reported secondary to constrictive dressings and after proximal ulna fracture.
IMAGING AND OTHER DIAGNOSTIC STUDIES
AP and lateral radiographs (two orthogonal views) that include the entire radius and ulna are essential for proper diagnosis of forearm shaft fractures in children (FIG 3). If suspicion exists for compromise of the distal or proximal radioulnar joints (Galeazzi or Monteggia injuries), dedicated wrist and elbow radiographs are also indicated.
FIG 3 • AP and lateral radiographs of boy age 9 years and 11 months with a forearm shaft fracture.
If fracture angulation is noted on both orthogonal forearm views, the true fracture angulation exceeds that measured on either individual view (FIG 4).
FIG 4 • A. Out-of-plane AP and lateral views of a 45-degreeangulated iron pipe. B. True AP and lateral views of the same pipe.
The radiographs should be used to classify the forearm fracture in a practical fashion with respect to “2 bones, 3 levels, 4 fracture patterns” (Table 1). This is akin to describing bone tumors in terms of matrix, margins, and so forth.
DIFFERENTIAL DIAGNOSIS
Galeazzi injury (concomitant distal radioulnar joint disruption)
Monteggia injury (concomitant proximal radioulnar joint disruption)
Coexisting distal humeral fracture (eg, supracondylar humeral fracture, also known as floating elbow)
Open fracture (the clinician must be beware of small, innocuous-appearing wounds)
Compartment syndrome (more common in setting of floating elbow and extended efforts at indirect reduction of difficult-to-reduce fractures)
NONOPERATIVE MANAGEMENT
Nonoperative (closed) fracture management is used in the vast majority of pediatric forearm shaft fractures.
Successful nonoperative treatment requires an eclectic mix of anatomic knowledge, skillful application of reduction techniques, appreciation for remodeling potential, and respect for the character of the soft tissue envelope.
Greenstick fracture patterns retain a degree of inherent stability; intentional completion of these fractures is not recommended. Davis and Green reported a 10% loss of reduction rate with greenstick fractures and a 25% rate with complete fractures.2
Greenstick fracture patterns often involve variable amounts of rotational deformity such that when the forearm is appropriately derotated, reduction of angulation occurs simultaneously.
Apex volar greenstick fractures are considered to represent supination injuries that require a relative degree of pronation to effect reduction.
Apex dorsal greenstick fractures are considered to be pronation injuries that require supination to aid reduction.
Classic finger-trap and traction reduction techniques are probably best reserved for complete both-bone fracture patterns. When dealing with complete both-bone shaft fractures, respect should be paid to the level of the fractures when choosing a relatively neutral, pronated, or supinated forearm position.
Price has suggested that estimated rotational malalignment should not exceed 45 degrees.8 The related concepts of maintenance of an appropriate amount of radial bow and interosseous space on the AP radiograph must also not be forgotten, but precise criteria do not exist at this time.
Initial above-elbow cast immobilization is the rule for all forearm shaft fractures, as this appropriately controls pronation–supination as well as obeying the orthopaedic maxim of immobilizing the joints above and below the fracture. An extra benefit of above-elbow immobilization relates to the activity limitation it imposes; in some instances this may increase the chances of maintaining a satisfactory reduction in an otherwise very active customer.
SURGICAL MANAGEMENT
Flexible intramedullary nail treatment of pediatric forearm shaft fractures focuses predominantly on displaced complete fractures, many of which may have minor comminution (butterfly fragments usually less than 25% of a shaft diameter).
When efforts at closed fracture management do not achieve and maintain fracture reduction within accepted guidelines, surgical treatment is indicated.
When complete fractures occur in children younger than about 8 to 10 years of age with angulation of at least 20 degrees in the distal third, 15 degrees in the central third, or 10 degrees in the proximal third, risk–benefit discussions are appropriate regarding further efforts at fracture reduction and possible internal fixation.3,10
Lesser measured angulation associated with significant forearm deformity (as defined in a discussion between the orthopaedic surgeon and the parents) may also prompt intervention in selected children.
Complete forearm shaft fractures in children older than 8 to 10 years of age should be evaluated very critically with the intention to accept no more than 10 degrees of angulation at any level.3,10 Compromise (loss) of interosseous space should also be considered, as well as rotational malalignment (difficult to assess precisely) when debating the merits of continued cast treatment versus flexible intramedullary nail fixation.
Preoperative Planning
Rotational alignment of the radius and ulna should be assessed and estimated using the guidelines mentioned in the Anatomy section. Concern is increased if greater than 45 degrees of rotational malalignment is judged to be present.
Measurement of the narrowest canal diameter of the radius (usually midshaft) and ulna (usually distal third) will aid in the selection of appropriately sized intramedullary nails. Implants 2 mm in diameter or smaller are commonly used, and the same-sized nail is used in each bone. It is far worse to select implants that are too big rather than too small.
Assessment of existing or impending comminution is prudent. Significant comminution may lead the surgeon to choose plate fixation over intramedullary fixation for one or both bones.
Assessment of the soft tissue envelope of the forearm is important. Tense swelling of the forearm certainly increases suspicion for compartment syndrome, and the surgeon should be prepared to measure compartment pressures accordingly.
FIG 5 • My preferred operating room set-up, with the injured arm on the radiolucent hand table and the C-arm properly positioned.
Positioning
The patient is placed in a supine position on the operating room table with the involved extremity positioned on a sturdy hand table to allow easy, unobstructed radiographic visualization of the entire forearm (FIG 5).
In general, the monitor for the portable fluoroscopy unit should be positioned near the end of the operating table, opposite the imaging unit (C-arm).
A nonsterile tourniquet may be applied about the upper arm (near the axilla) before preparation and draping, but it is not routinely inflated.
The limb is appropriately prepared and draped, with care being taken to ensure that the first layer is a sterile impervious one (eg, blue plastic U-drape). The C-arm is also appropriately protected with a C-arm sterile plastic drape and an additional sterile skirt (usually a sterile paper half-sheet). Without this sterile skirt certain limb positions and certain surgical maneuvers occur far too close to nonsterile territory.
Approach
Physeal-sparing distal radial entry is routinely obtained via the floor of the first dorsal compartment (alternately, the interval between the second and third dorsal compartments near the proximal base of the tubercle of Lister may be used).
Physeal-sparing proximal ulnar entry is typically achieved via an anconeus starting point just off the posterolateral ridge of the olecranon. The true tip of the olecranon is avoided as an entry point because it needlessly violates an apophyseal growth plate, and a subcutaneous nail in this region often leads to painful olecranon bursitis.
In complete both-bone fractures the radius is routinely approached first as it is considered to be the more difficult bone to reduce.
No power instruments are required for completion of the procedure. Key instruments are a stout sharp-tipped awl and T-handled chucks that achieve a firm grip on the flexible nail such that it can be rotated as needed (FIG 6).
FIG 6 • Valuable tools for intramedullary nailing of pediatric forearm fractures.
DISTAL RADIAL ENTRY POINT (PHYSEAL-SPARING)
Using fluoroscopy (C-arm), a physeal-sparing distal radial incision is fashioned overlying the first dorsal compartment (TECH FIG 1A).
Care is taken to protect branches of the superficial radial nerve. A short portion of the first dorsal compartment is opened.
The tendons within the first dorsal compartment are retracted and protected before the awl engages the distal radius (TECH FIG 1B).
After fluoroscopic confirmation of starting awl position, partial right and left rotations (not full turns) are used to gain satisfactory distal radial entry. A two-handed awl technique is used.
TECH FIG 1 • Repair of forearm fracture of the patient in Figure 3. A. Physeal-sparing incision fashioned with fluoroscopic assistance. B. The surgeon must identify and protect the abductor pollicis longus and extensor pollicis brevis. C,D. AP and lateral fluoroscopic confirmation of entry point. E. Well-seated and slightly angulated awl.
Satisfactory intramedullary awl position is confirmed by a gentle “bounce” against the far cortex as well as fluoroscopic AP and lateral projections (TECH FIG 1C–E).
The awl is temporarily left in its intraosseous position before insertion of the radial flexible intramedullary nail. Thus, the surgeon's ability to judge both the portal location and the angle of nail entry will be facilitated by immediate sequential awl removal and nail tip insertion.
Reduction and Nail Passage Within the Radius
The flexible nail for the radius is contoured such that it will re-establish appropriate radial bow. Nail contouring is gradual, smooth, and substantial. Acute bends in the nail should not be apparent (TECH FIG 2A–C).
Entry into the distal radius entry site should be directly visualized, and the feel of the nail within the intramedullary canal offers distinct tactile feedback called “scrape.” Entry is further confirmed fluoroscopically (TECH FIG 2D).
The radial nail is gently advanced up to the level of the fracture. Reduction is achieved via a combination of longitudinal traction and judicious use of AP compression with a radiolucent tool such as a vinyl Meyerding mallet (TECH FIG 2E).
The nail is rotated to optimize nail passage across the fracture site (TECH FIG 2F–H), and then it is advanced to an appropriate depth within the proximal fragment (TECH FIG 2I).
TECH FIG 2 • Insertion and passing of the radial nail. A. Gentle contouring of the distal aspect of the radial nail is important, as overbending effectively increases the diameter of the implant and may lead to nail incarceration. B.The “channel bender” is an effective tool for creating a properly contoured radial nail. C. The apex of the contoured nail should be placed so as to recreate appropriate radial bow (slightly distal of midshaft radius). D. Under direct visualization, the contoured radial nail is manually inserted into the previously prepared entry point. Distinctive intramedullary tactile feedback (“scrape”) should be detected and the implant advanced as far as possible using only the surgeon's hands. Note the trajectory of the nail (tip points radially), as this nail orientation should be maintained during most of the procedure. E. Appropriate longitudinal traction needs to be applied by an assistant, as well as supplemental reduction forces such as that provided by the broad flat surface of a vinyl Meyerding mallet. F. The bent tip of the nail (the “fang”) approaches the fracture site after being advanced as far as possible without using a hammer. “Manual forces only” should be used as much as possible to advance the nail within the canal using a properly tightened T-handle or similar chuck. G. As the fang crosses the fracture site, proximal fragment intramedullary canal entry is often facilitated by nail rotation. At this point finesse is much, much more important than brute strength. H. Once the nail properly enters the proximal fragment, the position is radiographically confirmed and the nail is rotated back toward its “entry trajectory.” I.The nail is advanced to an appropriate level in the region of the radial neck and rotated so as to properly recreate radial bow. Restoration of radial bow can be quite striking when visualized under live C-arm imaging. When radial nail contouring is preserved during the insertion process, the nail should be rotated 180 degrees such that the fang points in an ulnar direction. If this position does not optimize radial bow, then live C-arm imaging will allow the surgeon to choose the nail rotation that does.
TECHNIQUES
PROXIMAL ULNA ENTRY POINT (PHYSEAL-SPARING)
An entry point is selected on the lateral edge of the subcutaneous border of the proximal ulna. The skin is touched but not pierced by the awl (TECH FIG 3A).
Once correct position is confirmed fluoroscopically, the awl is used to gain percutaneous entry to the intramedullary canal of the proximal ulna (TECH FIG 3B).
A mildly contoured (ie, nearly straight) flexible nail is inserted into the proximal ulna intramedullary canal (TECH FIG 3C).
Proper position within the proximal ulna is confirmed fluoroscopically (TECH FIG 3D).
Reduction and Nail Passage Within the Ulna
The ulna is reduced and the nail is passed across the fracture site in a manner similar to the radius. If open reduction becomes necessary, a simple Mueller (AO-type) approach to the ulna is used (exploiting the interval between the extensor carpi ulnaris and the flexor carpi ulnaris).
The ulnar nail is cut such that it is subcutaneous yet easily palpable.
TECH FIG 3 • Insertion and passing of the ulnar nail. A. As opposed to the radial entry point, where a true incision is very important to allow protection of nerves and tendons, true percutaneous entry is an option for the anconeus starting point (distal to olecranon physis and just lateral off the ridge of the ulna). B. Radiographic confirmation of an acceptable awl entry point as well as awl trajectory is necessary. Anconeus entry is preferred over true tip-of-theolecranon entry for two reasons: the anconeus entry point avoids unnecessary physeal injury and also decreases the likelihood of large painful olecranon bursae. C. The ulnar nail is contoured in a far more gentle fashion as the ulna is a predominantly straight bone compared to the radius. After manual nail entry, the ulnar nail is advanced with the use of a chuck. Note the 90-degree-flexed position of the elbow and the 90-degree external rotation of the shoulder. D. Similar nail advancement technique is used for the ulna, with the exception of any dramatic nail rotation maneuver at the end of nail insertion.
FINAL ROTATION AND CUTTING OF THE RADIAL NAIL
The precontoured radial nail is rotated so as to optimize and normalize the anatomic bow of the radial shaft. This step is most dramatic when performed under several seconds of live fluoroscopic imaging.
Appropriate full-length forearm imaging must be performed at the end of the case to ensure an acceptable rotational relationship between the radial styloid and the bicipital tuberosity, as well as the ulnar styloid and the coronoid process.
Care must be taken when cutting the radial nail. If the nail is too short, removal will be difficult and dorsal compartment tendons adjacent to a sharp nail edge will be at risk. Thus, the nail should be cut to protrude beyond the tendons while still remaining subcutaneous.
CLOSURE, DRESSING, SPLINTING, AND AFTERCARE
Closure of the radial entry site is performed with absorbable subcutaneous and subcuticular suture and SteriStrips. Care is taken to protect branches of the superficial branch of the radial nerve (TECH FIG 4A,B).
Light Xeroform, sterile gauze, and Tegaderm dressings are applied to the surgical sites (TECH FIG 4C–E).
A removable forearm fracture brace may also be applied to increase patient comfort (TECH FIG 4F).
TECH FIG 4 • My preferred closure, dressing, and splinting technique. A. Several interrupted absorbable sutures (typically 3-0 Vicryl) are used for closure of the subcutaneous and subcuticular portion of the radial wound. Steri-Strips are added for final wound closure (B), followed by Xeroform and sterile gauze (C), and a Tegaderm dressing (D). E. A similar dressing consisting of Xeroform, sterile gauze, and Tegaderm is applied to the proximal ulnar wound. F. A removable Velcro forearm fracture brace is applied at the end of the procedure.
POSTOPERATIVE CARE
Other than patients with open fracture, flexible nailing of the forearm can be performed as a outpatient procedure so long as there are absolutely no concerns about swelling or compartment syndrome.
Oral prophylactic antibiotics may be continued for several doses postoperatively if desired, but usually an appropriately administered preoperative intravenous antibiotic (within 2 hours of the surgical incision) is all that is required.
The patient is allowed immediate active elbow and hand motion. Concerns about rotational stability after flexible nail stabilization seem to have been vastly overstated, and aboveelbow immobilization is not required.
As there are no sutures to remove, outpatient follow-up may occur in 4 to 6 weeks (FIG 7A,B).
The originators of this procedure have suggested that the nails be removed by about the sixth postoperative month (FIG 7C,D).
FIG 7 • Postoperative AP and lateral radiographs at 4 weeks (A,B) and 1 year (C,D) of the patient in Figure 3 and all Techniques Figures.
OUTCOMES
At this time no randomized trials comparing flexible intramedullary nailing of forearm shaft fractures versus cast treatment have been conducted.
A systematic review of English-language reports comparing flexible nailing to cast treatment found a significantly lower risk of forearm stiffness with nailing (25% stiffness with casting versus 5% with flexible nailing). This comes at the price of a higher rate of minor complications (21%) with surgery versus casting (6%).5
The largest published series4 of pediatric forearm shaft fractures treated using flexible intramedullary nailing showed 92% excellent results with full range of motion at an average of 3.5 years of follow-up.4
COMPLICATIONS
Sensory neurapraxia (usually the superficial branch of the radial nerve) occurs at a rate of at least 2% after flexible intramedullary nailing. These deficits are almost always temporary, resolving over weeks to months.
The deep infection rate (osteomyelitis) after flexible intramedullary nailing of pediatric forearm shaft fractures is less than 0.5%; this can be compared to the reported 5% rate of osteomyelitis after plate fixation of similar fractures.5
Extensor tendon injury (especially the extensor pollicis longus) has been reported by multiple authors and may occur during nail insertion or nail removal as well as when tendons repetitively glide past a sharp nail tip (slowly sawing the tendon in two). Radial entry through the floor of the first compartment may minimize this complication (versus entry between the second and third compartments).
In the clinical setting of forearm shaft fractures coexisting with ipsilateral humeral fracture (floating elbow), the incidence of compartment syndrome may be as high as 33%. When longer operative times are required (about 2 hours), a 7.5% rate of compartment syndrome has also been reported.
Delayed union and nonunion are decidedly rare after flexible intramedullary nailing of pediatric forearm fractures. If either delayed union or nonunion occurs, there is usually some explanation, such as a technical error (eg, too large an intramedullary implant distracting the ulnar fracture site), infection, or neurofibromatosis.
There should be a 5% or less chance of long-term forearm stiffness after flexible intramedullary forearm shaft fixation.
REFERENCES
1. Cheng JCY, Ng BKW, Ying SY, et al. A 10-year study of the changes in the pattern and treatment of 6,493 fractures. J Pediatr Orthop 1999;19:344–350.
2. Davis DR, Green DP. Forearm fractures in children: pitfalls and complications. Clin Orthop Relat Res 1976;120:172–183.
3. Johari AN, Sinha M. Remodeling of forearm fractures in children. J Pediatr Orthop B 1999;8:84–87.
4. Lascombes P, Prevot J, Ligier JN, et al. Elastic stable intramedullary nailing in forearm shaft fractures in children: 85 cases. J Pediatr Orthop 1990;10:167–171.
5. Mehlman CT, Wall EJ. Injuries to the shafts of the radius and ulna. Chapter 10 in Beaty JH, Kasser JR, eds. Rockwood and Wilkins' fractures in children, ed 6. Philadelphia: Lippincott Williams & Wilkins, 2006:399–441.
6. Mehlman CT. Fractures of the forearm, wrist, and hand. Orthopaedic Knowledge Update 9. Rosemont, IL: AAOS, 2008.
7. Mehlman CT, Greiwe M, Wall EJ, et al. Stiffness in displaced pediatric both-bone forearm fractures. Paper #46 presented at 2007 European Pediatric Orthopaedic Society Meeting.
8. Price CT, Scott DS, Kurzner ME, et al. Malunited forearm fractures in children. J Pediatr Orthop 1990;10:705–712.
9. Schock CC. The crooked straight: distal radial remodeling. J Ark Med Soc 1987;84:97–100.
10. Younger ASE, Tredwell SJ, Mackenzie WG, et al. Accurate prediction of outcome after pediatric forearm fracture. J Pediatr Orthop 1994;14:200–206.