The pediatric humerus, particularly toward the proximal end where 80% of the humeral growth is generated, has significant remodeling potential.1 Fracture alignment recommendations for closed treatment of pediatric humeral fractures vary; however, generally accepted guidelines include <30 degrees for proximal fractures, <20 degrees for diaphyseal injuries, and <15 degrees for distal fractures.2–5 The amounts of acceptable angulation can be considerably larger for much younger patients and still result in excellent remodeling and functional outcome. Furthermore, fracture displacement and shortening are quite well tolerated by pediatric patients. The more proximal the fracture, the larger the amount of malunion that is acceptable, because the shoulder provides a very large, multiplanar range of motion and the proximal humeral physis provides significant remodeling power.
As with many fractures in children, treatment has traditionally involved closed management with traction, casts, splints, and braces. Over time, the desire for more anatomic alignment, shorter hospitalizations, quicker return to activity, and improved pain control has resulted in more frequent surgical treatment of many pediatric long-bone fractures. The pediatric humeral shaft has been 1 exception to this trend, and many studies and textbooks continue to recommend nonoperative treatment of these fractures.5–8 Well-aligned pediatric proximal humeral fractures often can be managed with a simple sling, or a hanging arm cast if the fracture requires gradual reduction over time. Humeral shaft fractures often can be managed with a coaptation splint initially and then transitioned to a functional brace when early fracture callous is seen on radiographs.
Despite generally good results with nonoperative methods, surgical treatment is occasionally indicated for these fractures. The options for stabilization are many, including external fixation, rigid internal fixation with plates and screws, closed manipulation and percutaneous pinning, and intramedullary fixation. External fixation probably is best reserved for fractures with large associated soft-tissue injuries that require multiple repeat surgical debridements.5–8 Rigid internal fixation is best for older patients who are at, or near, skeletal maturity, especially in patients with polytrauma who will need the arm for transfers and mobilization.5–8 Percutaneous fixation is appropriate for the most-proximal and most-distal fractures that are unstable following closed manipulation. Flexible intramedullary implants can be a good option for certain situations based on both fracture-specific factors, such as location and morphology, as well as patient factors, such as age or associated injuries.5–8
The early enthusiasm for flexible intramedullary nailing (FIN) of humeral shaft fractures began in Europe in the early 90s, and much of the literature on the topic is from that region, particularly experience with the flexible nail that originated at the University of Nancy, France. As pointed out previously, the popularity of this technique has grown in North American and other parts of the world in other long bones, such as the femur, tibia; and, to a lesser extent, the forearm. But there is a paucity of literature originating in North American on the use of FIN in pediatric humeral fractures.9–11
PRINCIPLES OF MANAGEMENT
FIN work by applying a balanced 3-point force on the intramedullary cortical bone.12,13 This is particularly powerful in length-stable diaphyseal fractures, but proximal and distal fractures or those with comminution or a long oblique fracture pattern also can be managed successfully with this implant with careful attention to detail, supplemental splinting or casting, and close follow-up.
Indications for FIN of Pediatric Humeral Fractures
The literature on the use of FIN for pediatric humeral fractures can be divided into small groups of similar series based on a particular indication. The most commonly described humeral fractures treated with FIN include those of the surgical neck (proximal third), distal third above the supracondylar region, supracondylar region, and shaft in patients with polytrauma or a floating elbow. There also are a number of published series on the use of FIN in prophylactic stabilization of large diaphyseal humeral bone cysts.
A number of studies have reported good outcomes, including rapid and reliable union, pain relief, and return to normal function with the use of retrograde FIN in the treatment of proximal pediatric humeral fractures (Fig. 1 and Table 1).14–18 Comparisons of retrograde FIN to closed manipulation and percutaneous pinning have reported similar union rates and ability to achieve and maintain acceptable alignment.11,19 Hospitalization and time to implant removal were longer for the FIN groups, but complications were more frequent in those with percutaneous pinning. Surgical times were mixed between the 2 studies. Both studies’ authors concluded that either treatment can produce a favorable and comparable result.
Two recent studies reported good healing rates, acceptable alignment, and reliable functional recovery after treatment of fractures of the distal metaphyseal-diaphyseal junction with FIN (Fig. 2).20,21 Ge et al20 compared FIN to Kirschner-wire fixation for 19 metaphyseal-diaphyseal junction fractures and reported better postoperative alignment, shorter operative times, less blood loss, and faster union with FIN.
Other authors have reported the use of antegrade FIN for the treatment of pediatric supracondylar humeral fractures (Fig. 3).22–24 Kannellopoulos and Yiannakopoulos24 described the use of this technique in 2 adolescents with T-condylar fractures of the distal humerus, and Lacher et al22 in 127 children with AO types II, III, and IV supracondylar humeral fractures. Suggested advantages of antegrade FIN over Kirschner-wire fixation include avoidance of iatrogenic ulnar nerve injury, cast-free treatment, and early evaluation of clinical motion.
Shaft (Polytrauma and Floating Elbow) Fractures
The ability to limit the amount of casting or splinting and rapid mobilization are 2 of the potential benefits of FIN in patients with polytrauma or an ipsilateral floating elbow injury (Fig. 4). High union rates and good functional outcomes have been reported.9,12,25
FIN frequently is used for prophylactic stabilization of the humeral shaft at the time of treatment of large benign diaphyseal bone cysts or after pathologic fracture (Fig. 5).26–30 While the tumor may recur, radiographic union of pathologic fractures is the norm.
While the surgical technique is easy to describe, it can be challenging to implement. Intraoperative imaging of the humerus can be challenging, because orthogonal views of the proximal humerus can be difficult to obtain. The anatomy, particularly related to the location of nail insertion, may not be as familiar to the pediatric orthopaedist as the anatomy of other bones where FIN is more commonly used. An understanding of humeral anatomy is of paramount importance because many neurovascular structures lie in close proximity to each of the described nail insertion points. Journeau and Annocaro23 and Gordon and Garg10 have provided detailed descriptions of the surgical technique. Those are summarized here.
For Retrograde Insertion
- The patient is positioned supine or in the lateral decubitus position on a radiolucent table. A bump under the ipsilateral scapula can be helpful.
- Adequate anteroposterior and lateral images of the fracture and planned nail insertion site are essential.
- The entire upper extremity, including the shoulder, is fully prepared and draped.
- For fractures in the mid-diaphysis or proximal third, dual lateral entry nailing can be used. The incision is made just above the lateral condyle and just anterior to the triceps. Although this should be well distal to the crossing radial nerve, careful dissection down to the bone is recommended.
- For more distal fractures, both medial and lateral entry holes are recommended. Care should be taken to appropriately identify and protect the ulnar nerve during insertion of the medial nail.
- An awl or drill of appropriate diameter should be used to create the entry hole. For those unfamiliar with the bony anatomy in this region, cannulated drill may be used. The guidepin can be placed first and adjusted or confirmed by image intensification before a large-diameter entry hole is created.
- The entry hole should angulate proximally to facilitate nail insertion.
- For dual lateral entry, 2 separate holes are recommended rather than 1 large oblique hole.
- Rods should be chosen so that their combined diameter is 70% to 80% of the canal diameter. The rods should be of the same size to avoid a progressive angular deformity postoperatively.
- The rods are bent in “C” and “S” configurations for dual lateral entry, and both nails are bent in a “C” configuration for medial and lateral entry. The contours of the bend should follow the prebent nail tip.
- The nails are best inserted with an inserter and mallet rather than with forceful pushing and twisting.
- The fracture is reduced and held with a combination of traction and local fracture manipulation. Then the nails are advanced across the fracture site. Ideally, the bends of the nail will be in opposite directions at the level of the fracture.
- Care should be taken to avoid twisting the nails around one another. If the nail is rotated to aid in insertion, it should be rotated back in the opposite direction rather than 360 degrees.
- The nails are impacted to the desired level in the proximal humerus. For more proximal fractures, it might be necessary to cross the physis to achieve stable fixation.
- The nails are backed out 1 to 2 cm and are cut short at the level of the skin before reinsertion with a tamp and mallet. If the implants are to be removed, they should be left prominent; if they are to be left in place, they should be impacted to the surface of the bone to prevent implant prominence.
- A brief period of immobilization in a splint or sling is used for pain control and soft-tissue healing.
For Antegrade Insertion
- Antegrade insertion may be used for the most-distal factures including supracondylar fractures.
- Patient positioning is similar to that for retrograde insertion.
- An incision is made 1 to 2 cm below the tip of the acromion, and the deltoid and rotator cuff are split along their fibers.
- “C” and “S” rod bends are used. The entry holes can be made in the tuberosity and cross the physis or just distal to the physis in the proximal humeral metaphysis. Careful dissection, exposure to the periosteum, and soft-tissue protectors for the entry drill are important to prevent injury to the axillary nerve.
- In more distal fractures, it is difficult to achieve stability with the 3-point bend of the nails. Rather, stability is achieved by impacting the nail tips into the medial and lateral columns on either side of the olecranon fossa.
Shoulder and elbow stiffness are both common after upper extremity trauma in children.5–7 Temporary splinting or casting should be used for only 1 or 2 weeks after FIN to allow earlier motion and prevent stiffness.
The most commonly reported complication of FIN in pediatric humeral fractures is implant prominence.31,32 There is no consensus in the literature as to whether or not these implants must be removed. If removal of the implant is planned, the optimal timing remains unknown. If removal is planned, the implants should be impacted as far as possible to still allow easy extraction. Length-unstable fracture patterns are likely to settle in the postoperative period, which could cause worsening of implant prominence. Although no consensus exists on timing of nail removal, it probably is safe to remove the nails when ample bony callous is present at the fracture site, particularly if the implants are painful or tenting the skin. If early implant prominence is not an issue, the nails are ideally removed between 6 and 12 months.5–7,33
While some malunion can be tolerated in the healed pediatric humeral fracture, it is best if it is avoided altogether. To prevent malunion, nails should have the same diameter, should be widely opposed at the level of the fracture, and should fill 70% to 80% of the canal diameter. Rods that bend in the same direction at the fracture site or have a mismatch in size can result in an angular deformity.
Iatrogenic nerve injury is a rare but devastating complication.34 This can be avoided by adequate exposure at the nail insertion sites, use of soft-tissue guides for the reamers, and anatomic fracture reduction to lessen the chance of nerve entrapment at the fracture site. If anatomic reduction cannot be achieved by closed means or if there is concern for nerve entrapment, open reduction may be required.
Most pediatric humeral fractures can be treated successfully by closed means; however, certain fractures, such as those near the proximal or distal end or in patients with polytrauma or ipsilateral forearm fractures, may be better treated with FIN. Attention to detail can limit the complications of this procedure.
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