OTRAS ABEJAS

Possible contraindications for the use of IM nails for radius and ulna diaphyseal fractures include an older patient or a severely contaminated open fracture. If all growth plates in the forearm are closed, it may be better to use plate-and-screw internal fixation, as the rate of delayed union of the radius and ulna in older teens and adults appears to be higher with IM nail

treatment than if some growth is remaining. If there is a type III open fracture with marked soft-tissue injury and wound contamination, use of an external fixator to facilitate soft-soft-tissue care would be preferred.

PREOPERATIVE PLANNING

Preoperative anteroposterior (AP) and lateral radiographs of the radius and ulna need to include views of the elbow and wrist. This is particularly important at the elbow to prevent the

orthopaedist from not recognizing a possible coexisting Monteggia-type injury at the radial head.

Entry sites for the nail are planned and are to some degree based on the diaphyseal level of the fracture, particularly in the case of the radial fracture. The entire instrument set for inserting

flexible IM nails must be available, and all IM nail sizes from 2 mm to 4 mm need to be sterile and ready for use. Fluoroscopy needs to be set up in the operating room. A radiolucent arm operating table is used.

SURGICAL PROCEDURE

Closed reduction IM fixation of the pediatric forearm is performed in the operating room under general anesthesia. The affected arm is draped to the side on a radiolucent arm table, with the child supine and the shoulder abducted 90 degrees. Antibiotic prophylaxis against infection is given prior to the incision. Usually the bone easiest to reduce is stabilized first. For the ulna, apophyseal and metaphyseal proximal entry sites have both been utilized (Fig. 4-2 ). Because the olecranon

P.35 apophysis does not contribute significantly to the growth of the ulna, most pediatric orthopaedists will pass a small-diameter, smooth rod across the proximal ulnar apophysis, thereby allowing a straight passage of the nail down the ulnar medullary canal. Alternatively, a split is made in the anconeus muscle on the subcutaneous border of the ulna, and an appropriate bend is made in the nail for passing the rod from the proximal to the distal end of the ulna.

Distal entry between the flexor carpi ulnaris tendon and the extension carpi ulnaris tendon has also been used. The size of the nail used depends on the size of the medullary canal on

radiograph. The thinnest diameter of the ulna is located at its distal end; the ulna nail is usually 2 to 3 mm in diameter.

FIGURE 4-2 Intraoperative proximal ulna entry sites for intramedullary fixation: Apophyseal (A) and metaphyseal (B).

If a proximal apophyseal entry point is used, a small incision is made in the skin crease overlying the midportion of the olecranon. The proximal ulnar cortex is entered with fluoroscopic

guidance using a power drill to insert a Steinmann pin into the intramedullary canal. Care must be taken not to penetrate beyond the cortex with this sharp pin, as a false passage may be

created. The Steinmann pin is removed, and the straight elastic nail is then tapped with a mallet down to the fracture site (Fig. 4-3 ). Closed manipulation of the ulna fracture site is performed, and the nail is passed across the ulna fracture. On rare occasions, if interposed tissue prevents anatomic reduction, an open reduction is necessary through a small incision (Fig. 4-4 ). Passage of the pin to a point just proximal to the distal ulnar physis completes the ulnar fixation.

FIGURE 4-3 Intraoperative passage of the ulna rod through the apophysis. A. Power drilling is used for cortical entry only. B. A mallet is then used to pass the IM nail down the medullary canal.

FIGURE 4-4 Incision for open reduction and rod passage is used in difficult reductions to lessen the risk of compartment syndrome.

As mentioned previously, in children between the ages of approximately 8 and 12 years, single-bone fixation may be sufficient to align both single-bones in an acceptable, stable position. More often, however, dual-bone fixation is necessary. Radial IM fixation is performed using a distal nail entry site. Anatomical options include (a) proximal to the Lister tubercle between the third and fourth extensor compartments (Fig. 4-5 ), (b) the radial-side metaphysis proximal to the physis (Fig. 4-6 ), and (c) the ulnar-side metaphysis between the fourth and fifth extensor compartments. For each of these entry sites, the extensor pollicis longus tendon, the radial sensory nerve, and the digital extensor tendons need to be protected. A small incision is usually made at the entry site to avoid iatrogenic tendon or sensory nerve damage during nail

placement.

FIGURE 4-5 Intraoperative radial entry site proximal to Lister tubercle.

FIGURE 4-6 Intraoperative radial entry site proximal to physis on the radial side.

P.36 P.37 With the radial elastic nail, three-point bending is necessary to maintain the radial bow and radial fracture alignment (Fig. 4-7 ). The degree of bend should lead to overall filling of the intramedullary canal at the thinnest portion of the radius, which is in the mid-diaphyseal region.

The bend in either an elastic or a stainless pin should be sufficient to avoid impaling the opposite cortex during insertion. The cortical entry site should be widened to allow for better control of nail passage during insertion. Again, insertion with a power drill should be used only at the entry site and not beyond to prevent creating a troublesome false passage. The nail is inserted from distal to proximal with a mallet, all the time controlling the nail's rotational position. Passage across the fracture site can usually be performed by twisting the rod tip.

Confirmation of successful placement of the nail across the fracture is made with fluoroscopy.

The nail is then tamped into the proximal radial neck region.

FIGURE 4-7 (A, B) Intramedullary fixation of radius and ulna fractures with elastic titanium nails that were precontoured prior to placement.

Approximately 5% to 10% of radius and/or ulna fractures require an open reduction. This is usually because the surgeon is unable to obtain an anatomic reduction to allow for nail passage percutaneously across the fracture site; rarely is it because the surgeon selected a nail of too large a diameter. With repeated attempts at closed manipulation, the risk of compartment syndrome increases. Therefore, excessive or overzealous attempts at achieving percutaneous reduction and fixation should be avoided. Difficulty in attaining radial reduction is most often due to interposed periosteum or extensor muscle in the fracture site. With open reduction, the surgeon should not only be mindful of the posterior interosseous nerve location when exposing the midproximal radius but also be prepared for the possibility of a displaced neurovascular bundle when exposing the ulna. All open fractures require irrigation and debridement of the fracture site and, thus, open reduction. Intramedullary nail fixation can be used to stabilize open radial and/or ulna fractures, unless marked wound contamination exists.

POSTOPERATIVE MANAGEMENT

The decision of whether to bury the tips or leave the end of the IM nail exposed depends on the length of time the surgeon plans to leave the IM fixation in place. Surgeon preference also

influences the chosen site of nail insertion. Intramedullary forearm fixation has been removed as early as 4 to 6 weeks and as late as 1 year following fracture. Surgeons who prefer to remove the IM nails after approximately 6 weeks of healing will usually leave the tips exposed (Fig. 4-8 ), avoiding skin breakdown over buried pins and possible infection, especially with proximal ulnar apophyseal pins. Early nail removal may require additional cast or brace treatment until there is full fracture healing. Surgeons who worry about early refracture or a loss of fracture alignment usually leave the IM fixation in place for approximately 6 months or until there is clearly

complete healing. These buried pins can cause problems with irritation of the extensor tendon, sensory nerves, or the skin.

FIGURE 4-8 A, B: Displaced, unstable radius and ulna diaphyseal fractures treated with

intramedullary fixation (can be either elastic titanium nails or Kirschner smooth wires), with pins left external for early removal (C, D).

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The use of postoperative cast, splint, or brace immobilization also varies widely among surgeons.

There is no clear evidence for the superiority of one technique over another. The less

conservative surgeon will splint the forearm only temporarily for soft-tissue injury, excessive pain, or a comminuted fracture pattern at higher risk for loss of fracture alignment. The more conservative surgeon will use a cast or splint until sufficient healing is seen radiographically in order to prevent nail migration, nail bending, fracture malalignment, or delayed bone healing.

A summary of the treatment principles using forearm IM nails is presented in Table 4-2 . Fracture stability and alignment

Minimal incisions, as compared with plating Periosteum resists torsional forces

First fix the bone easiest to reduce

Small-diameter nails, typically 2–3 mm in diameter (not canal filling; ~1/3 canal fill) Maintenance of anatomic radial bow

Physeal sparing entry sites, if possible