Mechanism of Injury
Two mechanisms have been suggested: “push-off” and “pull-off.” The pull-off or avulsion theory has more advocates than the push-off mechanism.33,72 In early studies,72 this injury was consistently produced in young cadavers by adducting the forearm with the elbow extended and the forearm supinated. The push-off mechanism has also been reproduced in cadavers by applying a sharp blow to the palm with the elbow flexed, causing the radial head to push off the lateral condyle. This push-off injury also can result from a direct blow to the olecranon.
It is likely that both mechanisms can produce this injury. The more common type of fracture, which extends to the apex of the trochlea, probably is a result of avulsion forces on the condyle, with the olecranon’s sharp articular surface serving to direct the force along the physeal line into the trochlea. When a child falls forward on his or her palm with the elbow flexed, the radial head is forced against the capitellum and may cause the less common physeal fracture that courses through the ossific nucleus of the capitellum.
Signs and Symptoms
Compared with the marked distortion of the elbow that occurs with displaced supracondylar fractures, little distortion of the elbow, other than that produced by the fracture hematoma, may be present with lateral condylar fractures. The key to the clinical evaluation of this fracture is the location of soft-tissue swelling and pain concentrated over the lateral aspect of the distal humerus.41 Stage I displacement may produce only local tenderness at the condylar fracture site, which may be increased by flexing the wrist, placing the wrist extensors, which are attached to the fracture fragment, on stretch. The benign appearance of the elbow with some stage I displacements may account for the delay of parents seeking treatment for a child with a minimally displaced fracture. With stage II or III displacement, there often is a hematoma present laterally, and attempted manipulation may result in some local crepitus with motion of the lateral condylar fragment. This obviously would be associated with pain and should be avoided if there is a clear radiographic evidence of a fracture.
The radiographic appearance varies according to the fracture line’s anatomic location and the displacement stage. In the AP view, the metaphyseal fragment or “flake” may be small and seemingly minimally displaced. The degree of displacement may be seen on the true lateral view. In determining whether the articular hinge is intact (i.e., stage I vs. stage II), the relationship of the proximal ulna to the distal humerus is evaluated for the presence of lateral translocation. Oblique views are especially helpful in patients in whom a stage I displacement is suspected but not evident on AP and lateral views.
To determine the importance of the internal oblique view in the radiographic evaluation of nondisplaced or minimally displaced lateral condylar fractures, Song et al.66 compared the oblique view to standard AP views and found that the amount of displacement differed between the two views in 75% of children. They recommended routine use of an internal oblique view to evaluate the amount of fracture displacement and to assess stability if a lateral condylar fracture is suspected.
Three groups of nondisplaced and minimally displaced fractures of the lateral condyle have been described and correlated with the risk of late displacement: stable fractures, fractures with an undefinable risk, and fractures with a high risk of later displacement (Table 19-1).19 Arthrography or MRI evaluation has been suggested to identify unstable fractures in the acute setting and to aid in preoperative planning for those with late displacement, delayed union, or malunion. Although not used with all fractures, MRI can be a very useful diagnostic aid to guiding treatment, especially with delayed unions.
TABLE 19-1 Risk of Subsequent Displacement of Lateral Humeral Condylar Fractures Immobilized in a Cast
A major diagnostic difficulty lies in differentiating a lateral condylar fracture from a fracture of the entire distal humeral physis. In a young child in whom the condyle is unossified, an arthrogram or MRI may be helpful (Figs. 19-2, 19-3, and 19-4).11,27 Ultrasonography, which often can avoid MRI sedation issues, can be used to identify transphyseal separations in young patients.
In fractures of the entire distal humeral physis, the proximal radius and ulna usually are displaced posteromedially (Fig. 19-5A). The relationship of the lateral condylar ossification center to the proximal radius remains intact. In true fractures involving only the lateral condylar physis, the relationship of the condylar ossification center to the proximal radius is disrupted (Fig. 19-5B). In addition, displacement of the proximal radius and ulna is more likely to be lateral because of the loss of stability provided by the lateral crista of the distal humerus.
Lateral condylar physeal fractures can be classified by either the fracture line’s anatomic location or by the amount of displacement.
Anatomic Location. The Milch classification, based on whether or not the fracture extends through (type I) or around (type II) the capitellar ossific nucleus, is used infrequently because of its poor reliability and poor predictive value79 and is primarily of historic interest. Salter and Harris59 classified lateral condylar physeal injuries as a form of type IV injuries in their classification of physeal fractures. Because the fracture line starts in the metaphysis and then courses along the physeal cartilage, a lateral condylar humeral fracture has some of the characteristics of both type II and IV injuries. A true Salter–Harris type IV injury through the ossific nucleus of the lateral condyle is rare. Although lateral condylar fractures are similar to Salter–Harris type II and IV fractures, treatment guidelines follow those of a type IV injury: open reduction and internal fixation of displaced intra-articular fractures. The Salter–Harris classification is of little clinical use and is debatable as to the accuracy of terminology, because the fracture exits the joint in the not-yet-ossified cartilage of the trochlea.
Stages of Displacement. The amount of fracture displacement has been described by Jakob et al.33 in three stages (Fig. 19-6).75 In the first stage, the fracture is relatively nondisplaced, and the articular surface is intact (Fig. 19-6A, B). Because the trochlea is intact, there is no lateral shift of the olecranon. In the second stage, the fracture extends completely through the articular surface (Fig. 19-6C, D). This allows the proximal fragment to become more displaced and can allow lateral displacement of the olecranon. In the third stage, the condylar fragment is rotated and totally displaced laterally and proximally, which allows translocation of both the olecranon and the radial head (Fig. 19-6E, F).
Weiss et al.79 modified this classification based on fracture displacement and disruption of the cartilaginous hinge (Fig. 19-7). Type I fractures are displaced less than 2 mm; type II fractures are displaced more than 2 mm but have an intact cartilaginous hinge; and type III fractures are displaced more than 2 mm and do not have an intact cartilaginous hinge. In their series of 158 types II and III fractures, they found that all type II fractures had less than 4 mm of displacement on initial radiographs and all type III fractures had more than 4 mm of displacement. This classification was found to be predictive of complications, with both the major and minor complication rates correlating with fracture type.
Soft-Tissue Injuries. The fracture line usually begins in the posterolateral metaphysis, with a soft-tissue tear in the area between the origins of the extensor carpi radialis longus and the brachioradialis muscle. The extensor carpi radialis longus and brevis muscles remain attached to the distal fragment, along with the lateral collateral ligaments of the elbow. If there is much displacement, both the anterior and posterior aspects of the elbow capsule are usually torn. This soft-tissue injury, however, usually is localized to the lateral side and may help identify a minimally displaced fracture. More extensive soft-tissue swelling at the fracture site may indicate more severe soft-tissue injury,41,54 which may indicate that the fracture is unstable and prone to late displacement.
Displacement of the Fracture and Elbow Joint. The degree of displacement varies according to the magnitude of the force applied and whether the cartilaginous hinge of the articular surface remains intact.31 If the articular surface is intact, the resultant displacement of the condylar fragment is simply a lateral tilt hinging on the intact medial articular surface. If the fracture is complete, the fragment can be rotated and displaced in varying degrees; in the most severe fractures, rotation is almost full 180 degrees, so that the lateral condylar articular surface opposes the denuded metaphyseal fracture surface. In addition to this coronal rotation of the distal fragment, rotation can also occur in the horizontal plane.81 The lateral margin is carried posteriorly, and the medial portion of the distal fragment rotates anteriorly.
Because the usual fracture line disrupts the lateral crista of the trochlea, the elbow joint may be unstable, creating the possibility of posterolateral subluxation of the proximal radius and ulna. Thus, the forearm rotates along the coronal plane into valgus, and there may also be lateral translocation of the lateral condyle with the radius and ulna (Fig. 19-8). This concept of lateral translocation is important in the late reconstruction of untreated fractures.
In physeal fractures, where the fracture line traverses the lateral condylar epiphysis, the elbow remains reasonably stable because the trochlea remains intact. Total coronal rotation of the condylar fragment can occur with this injury. The axial deformity that results is pure valgus without translocation (Fig. 19-8).
This posterolateral elbow instability with the lateral condylar physeal injury has led to a mistaken concept that this injury is associated with a primary dislocation of the elbow,12 which is rarely the case. The posterolateral instability of the elbow is usually a result of the injury, not a cause of it. The displacement of the joint is through the fracture.57
TREATMENT OPTIONS FOR LATERAL CONDYLAR FRACTURES
Fractures involving the lateral condylar physis can be treated with immobilization alone, closed reduction and percutaneous pinning, or open surgical reduction depending on the degree of displacement and amount of instability.
Nonoperative Treatment of Lateral Condylar Fractures
Minimally displaced fractures (<2 mm) are stable and have intact soft-tissue attachments that prevent displacement of the distal fragment. About 40% of lateral condylar physeal fractures are nondisplaced, are not at risk for late displacement, and can be treated with immobilization alone.33 If the fracture line is barely perceptible on the original radiographs, including internal oblique views (stage I displacement), the chance for subsequent displacement is low. Immobilization of nondisplaced or minimally displaced (less than 2 mm) fractures in a posterior splint or cast is adequate.4,5,7,10,69 Radiographs are obtained during the first 3 weeks after injury to ensure that rare late displacement does not occur (Table 19-2).
TABLE 19-2 Lateral Condylar Fractures
Operative Treatment of Lateral Condylar Fractures
Closed Reduction and Percutaneous Pinning
When a lateral condylar fracture is displaced more than 2 mm, closed or open reduction is required to restore anatomic alignment of the joint and physis. Several techniques have been described for initial closed reduction, with the recommended elbow position ranging from hyperflexion to full extension. However, clinical experience and experimental studies indicate that closed reduction is best achieved with the forearm supinated and the elbow extended. Placing a varus stress on the extended elbow allows easier manipulation of the fragment. Unfortunately, it is difficult to maintain reduction of a displaced lateral condylar fracture with closed techniques, and thus, closed reduction alone is not generally recommended for treating displaced lateral condylar fractures.
Mintzer et al.46 advocated percutaneous reduction and fixation for unstable, moderately displaced lateral condylar fractures (Jakob type II). Standard closed reduction with thumb pressure on the fracture fragment, elbow flexion, forearm supination, and wrist dorsiflexion usually results in an aligned fracture. An alternative method that is quite reliable is to add percutaneous pin reduction from the lateral column. The smooth pins are then advanced across the fracture site to the opposite cortex to obtain stability.44,46 Anatomic alignment of the joint and fracture stability are confirmed by stress testing and arthrography. If a satisfactory reduction cannot be obtained, then reduction can be achieved and maintained by open reduction and internal fixation.
Expected Outcomes of Percutaneous Reduction and Pinning. Song et al.66 reported good results in 46 (73%) of 63 unstable lateral condylar fractures, 53 of which were treated with closed reduction and percutaneous pinning. They formulated a treatment algorithm based on a five-stage classification system that considered degree of displacement and fracture pattern (Figs. 19-9 and 19-10). Closed reduction was attempted in all fractures, regardless of the amount of displacement. If closed reduction was successful (n = 53), then percutaneous fixation was used. If closed reduction failed to achieve less than 2 mm of displacement, open reduction and internal fixation was performed (n = 10). These authors suggested that open reduction is not necessary for all lateral condylar fractures. They listed three elements as essential to obtaining good results with percutaneous reduction and pinning treatment: (1) accurate interpretation of the direction of fracture displacement (mainly posterolaterally, not purely laterally) and the amount of displacement of the fracture fragment, (2) routine intraoperative confirmation of the reduction on both AP and internal oblique radiographs, and (3) maintenance of the reduction with two parallel percutaneous, smooth Kirschner wires (K-wires).
More recently, Song and Waters67 described closed percutaneous manipulation of 24 completely displaced and rotated fractures (Jakob type III) followed by percutaneous pinning. In this series, closed reduction was successful in 18 (75%). Excellent results were obtained in 17 of the 18 patients; one patient had a good result. It should be noted that this technique is technically difficult, and the authors admit that it has a difficult learning curve; these results have not yet been reproduced at any other institution (Table 19-3).
TABLE 19-3 Lateral Condylar Fractures
Open Reduction and Internal Fixation
Because of the risk of poor functional and aesthetic results with closed reduction methods in unstable fractures, open reduction has traditionally been the advocated treatment method for unstable and irreducible fractures with stage II and stage III displacement.9,10,12,29,33,34,44,47,58,63,68,75,80,84 About 60% of all fractures involving the lateral condylar physis are types II and III fractures.33,79
Open reduction is performed through a lateral incision, usually under tourniquet control. There usually is a large hematoma just beneath the skin that requires superficial subcutaneous exposure for evacuation. The joint is exposed anteriorly through the fracture site, with care taken to preserve the soft-tissue attachments of the posterior extensor–supinator muscle origins. Extensive posterolateral soft-tissue dissection risks osteonecrosis of the condyle and so dissection is performed anteriorly with minimal soft-tissue stripping. Adequate visualization of the trochlea is required for an anatomic reduction of the joint.
Most investigators recommend fixation with smooth K-wires in children or screws and/or plates in adolescents nearing skeletal maturity. A report from Germany showed better maintenance of reduction with the use of compressive (threaded) K-wires (“screw-wires”) than with standard K-wires.82 Use of compressive K-wires is not widespread, and further study is necessary to determine their efficacy and safety (Table 19-4).
TABLE 19-4 Lateral Condylar Fractures
Expected Outcomes of Pin or Screw Internal Fixation. Smooth pins are the most frequently used method of fragment fixation.7,22,33,69,75,80,84 The passage of a smooth wire through the physis does not result in any growth disturbance,18,40 which may be due to the fact that the cross-sectional area of the pins is small relative to the surface area of the physis and because only 20% of humeral growth occurs through the distal humeral physis.
The pins should start in the metaphysis if the metaphyseal fragment is large enough and diverge as much as possible to enhance the stability of fixation. When there is only a small metaphyseal fragment, the pins can be safely placed across the physis.
When adequate reduction and internal fixation are carried out within the first few days after the injury, the results are uniformly good. The key, however, is to be sure that the reduction of the joint is anatomic. Surgery alone does not ensure a good result unless an anatomic reduction is obtained and the fixation is secure enough to maintain the reduction.
Early surgical intervention is essential, because organization of the clot with early fibrin development makes it difficult to achieve a reduction without extensive soft-tissue dissection in fractures that are treated late. The pins can be buried or left protruding through the skin with a low incidence of infection. Leaving pins buried requires a second operative procedure, even though it usually can be accomplished with a local anesthetic or outpatient sedation. A recent comparison of pins left outside or below the skin found that, while exposed pins had a slightly higher infection rate, buried pins had higher rates of pin migration, symptomatic implants, and protrusion through the skin and increased treatment cost.39
Screw fixation has been used less frequently in children because of concerns about growth arrest. Sharma et al.60 reported painless, full range of elbow motion in 36 of 37 children who had displaced lateral condylar fractures fixed with partially threaded 4-mm AO cancellous screws. In a series of 62 patients, Li and Xu39 found lower rates of infection (0% vs. 17%), lateral prominence (13% vs. 37%), and loss of motion (6% vs. 30%) in patients treated with open reduction and fixation with cannulated screws compared to those treated with K-wires. Although the two groups were similar, the type of fixation was not randomized.
AUTHOR’S PREFERRED TREATMENT FOR LATERAL CONDYLAR FRACTURES
If the fracture is minimally displaced on all three radiographic views (i.e., the metaphyseal fragment is less than 2 mm from the proximal fragment on AP, lateral, and internal oblique views) and the clinical signs also indicate there is reasonable soft-tissue integrity, we immobilize the elbow in a long arm cast with the forearm in neutral rotation and the elbow flexed 60 to 90 degrees. Radiographs are taken within the first week after the fracture with the cast removed and the elbow extended. If there is no displacement, the radiographs are repeated once again during the next 1 to 2 weeks. Immobilization is continued until fracture union is apparent, usually between 4 and 6 weeks after injury.
In some fractures with more than the allowable 2 mm of displacement (type II injury), the fracture pattern is such that the articular cartilage appears intact. If there is any question about the stability at the time of the fracture, MRI can be obtained or the extremity can be examined with the patient under general anesthesia. If examination is performed in the operating room, gentle varus stress views with the forearm supinated and the elbow extended should be taken to determine if the fracture displaces significantly. Intraoperative arthrography can also be used to determine the stability of the nonossified articular cartilage. Usually in these circumstances, percutaneous pins are placed to maintain articular alignment until healed.
For fractures with stage II displacement (2 to 4 mm), reduction and percutaneous pin fixation are done because open reduction often is not necessary in these circumstances and closed reduction alone is too risky for redisplacement (Fig. 19-11). If there are concerns about reduction or stability after percutaneous pinning, varus stress radiography and elbow arthrography are performed.