How I Manage Physeal Fractures About the Knee

Carl Stanitski, MD, with Carl Sherman

THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 4 - APRIL 97

In Brief: Knee injuries in children and adolescents often involve the growth plate (physis), as well as the adjacent bony areas of the femur, tibia, or patella. Young patients who have injured knees require careful clinical and radiographic assessment to determine the extent of their injuries, with specific management to minimize the potential for growth arrest and resultant deformity. This article discusses distal femoral physeal, proximal tibial physeal, tibial eminence, patellar sleeve, and tibial tubercle fractures in skeletally immature patients.

The knee, a complex, vulnerable joint, is a common site of sports injury in children and adolescents (figure 1) (1). The immature skeletal system is susceptible to a spectrum of injuries distinct from those in adults. When the growth plates (physes) are damaged, there is a risk of growth arrest and subsequent development of deformity, particularly for preadolescent patients who have significant years of growth remaining.

[FIGURE 1] While management of many childhood knee injuries is beyond the scope of the primary care physician, he or she plays an essential role in initial evaluation and referral.

Why are the physes vulnerable to injury?
Before skeletal maturity, the physes, particularly those about the knee, are about one third as strong as the attendant ligaments. Trauma that would result in a ligament injury in an adult is likely to cause a physeal fracture in a child. The relative weakness of the physes is especially evident during periods of rapid growth.

What role should primary care physicians take in treating physeal fractures?
I strongly believe that, except for minor knee contusions, acute knee injuries in general, and physeal fractures in particular, are best treated by someone specialized in the diagnosis and management of these disorders. The physician should immobilize the limb; give the patient crutches and teach a crutch-assisted touch-down gait; then refer the patient to an orthopedic specialist.

Standard-view initial radiographs—anteroposterior (AP), lateral, skyline, and tunnel views —should be obtained. I would not encourage primary care physicians to order a more detailed imaging evaluation, such as magnetic resonance imaging (MRI) or computed tomography (CT). These studies are best ordered, if needed, by the person involved with the ultimate specific care of the injury, so clinical correlation can be done with the imaging study. Prolonged, nonspecific immobilization is to be avoided. As with any injury, a specific diagnosis is required so specific treatment can be initiated, and misuse, disuse, and abuse of the injured area can be prevented.

Distal femoral physeal fractures are a common type of physeal injury. Why?
The distal femoral physis is the largest in the body and is quite vulnerable to medial-lateral, anterior-posterior, and rotational stresses because of its size and topographical morphology. The medial and lateral collateral ligaments attach to the femur at the epiphysis, which is distal to the physis; this leaves the physis, not the ligaments, more likely to be injured.

Distal femoral physeal fractures are about 10 times as common as proximal tibial fractures. They can occur at any age, but are most often seen in boys aged 10 to 14. This age range is a time of significant growth, when the physis is weakest.

The usual cause of these fractures is a direct blow to the sides or front of the knee in a sports or vehicular accident. In sports, the injury classically happens to a young athlete who has one foot planted and is starting to make a turn when someone falls on the outer aspect of the knee of the fixed leg, producing a significant valgus load.

What are the clinical features of distal femoral physeal fractures?
The patient who has this type of fracture usually complains of pain around the knee and is unable to bear weight on the injured leg.

In doing the standard knee physical exam, first assess the uninjured knee for evidence of ligamentous laxity in the anterior-posterior, medial-lateral, and rotational directions. Inherent laxity varies from one individual to another, and one doesn't want to interpret a normal condition as pathological. Then, with the injured knee in extension and at 30° of flexion, see if the application of gentle valgus and varus stress increases pain. I emphasize gentle—this should not be a vigorous maneuver. Assess anterior-posterior stability with the Lachman and drawer tests (anterior and posterior).

Look for effusion in the knee joint. Check for focal tenderness about the knee, at the lateral and medial metaphyseal flare of the femur at the level of the physis as opposed to the joint line below it. In addition, check for focal tenderness at the medial or lateral metaphyseal flare of the tibia.

Check circulation and sensation of the foot to detect possible vascular or neurologic compromise. Damage to the peroneal nerve may occur, particularly with a varus injury mechanism.

What does radiographic assessment show about distal femoral physeal fractures?
Comparison AP and lateral views of the opposite knee may help assess loss of physeal symmetry. Figure 2 shows an abnormal widening of the physis. Follow-up radiographs at 10 days to 2 weeks may also show a periosteal reaction subsequent to fracture healing.

Some people advocate radiographic stress views to demonstrate fracture instability when attempting to rule out a physeal fracture. I feel that this strategy only adds injury to injury. If the fracture is, in fact, displaced, the radiograph will show it. Any new information provided by stressing the knee won't affect management, and the stress maneuver may cause further physeal and epiphyseal damage. If the physis is tender, then an undisplaced fracture can be assumed to have occurred even if the initial x-rays are "normal."

How do you manage distal femoral physeal fractures?
Management depends on the type of fracture. (Figure 3 shows the Salter-Harris classifications.) Type I fractures involve only the physis. If there is no displacement with a type I fracture, I apply a cylinder or long leg cast, with use of crutches and protective weight bearing for 4 weeks, followed by rehabilitation to restore motion and strength.

Type II fractures involve the metaphysis as well as the physis. If patients have type I or type II fractures with displacement, reduction is required. This can usually be done closed, by manipulation. A displaced type II fracture usually needs internal fixation to provide stability after reduction.

Type III fractures involve the physis, epiphysis, and joint; and type IV fractures involve the physis, epiphysis, metaphysis and joint. If displaced, these injuries require open reduction and internal fixation to restore physeal and joint congruity.

What is the outlook for patients who have had distal femoral physeal fractures?
Even an innocuous-looking type I or type II distal femoral physeal fracture can be a bad actor, potentially resulting in deformity because of the morphology of the distal femoral physis. There is a significant amount of interdigitation between the physis and metaphysis, which provides stability. A fracture shears this junction, damaging the growing area.

If areas are involved asymmetrically, as in type II, type III, and type IV fractures, the damaged portion of the physis may be "spot welded" and stop growing, producing a spectrum of deformities. A peripheral closure causes angular deformity in which one side grows and the other does not. Central physeal arrests tend to cause leg length inequality. Remember that the distal femoral physis contributes two thirds of the adult length of the femur, and just over one third of the length of the lower extremity.

The long-term effects of distal femoral physeal fractures depend in part on the age of the patient at the time of the injury. In a patient who is close to skeletal maturity, the concern is not as great as it would be for someone younger. In a younger patient who has significant growth remaining, the potential for deformity is high if asymmetrical physeal closure occurs.

The take-home message: Patients who have had distal femoral physeal fractures require long-term evaluation after the acute phase to watch for subsequent asymmetrical growth. Future leg length equalization and deformity corrective procedures may be necessary.

When do you suspect a proximal tibial physeal fracture?
This is a rare injury. It most often occurs in preteens, and is generally caused by a direct blow to the knee, which causes physeal displacement. This type of fracture can occur when the knee is struck head-on, as when a child runs into something knee first.

[FIGURE 4] The patient typically complains of pain. I look for point tenderness at the physis and joint line. I also assess knee stability, as well as motor, circulatory, and sensory function distal to the injury. This type of fracture will usually be revealed by AP and lateral radiographs of the knee (figure 4). Comparison radiographic views of the uninjured knee often resolve doubts in cases of an undisplaced fracture.

How do you manage proximal tibial physeal fractures?
Treatment depends on the fracture pattern and amount of displacement. These fractures, if unstable, can usually be reduced by manipulation and internally fixed percutaneously. With a type III or type IV fracture, arthroscopic assessment is helpful to document anatomic articular reduction and to detect other intraarticular injuries such as meniscal tears. In cases of a nondisplaced or minimally displaced fracture, arthroscopy is unnecessary—radiography or CT scans are usually adequate for detecting the injury.

These patients do well overall. There seems to be less potential for growth arrest and subsequent deformity than with fractures of the distal femoral epiphysis.

What complications do you look for in patients who have proximal tibial physeal fractures?
This injury is usually due to anterior-posterior forces, so there is a heightened risk of neurologic or vascular compromise, with the potential for the development of a compartment syndrome as well.

After reduction of the fracture, it is advisable to admit the child to the hospital and observe him or her for indications of progressive neurologic or vascular damage, as well as for loss of pulses and sensory changes distal to the injury. Slowly increasing leg pain, especially with motor paralysis, often indicates the development of a compartment syndrome.

How do you identify tibial eminence fractures?
These fairly common fractures are considered the same as anterior cruciate ligament (ACL) injuries; however, in contrast to ACL injuries, which are intraligamentous, these injuries are bone avulsions. I teach that any 8- to 11-year-old child who falls from a bicycle and injures a knee has a tibial eminence fracture until proven otherwise. This hyperflexion injury to the knee damages the chondroepiphysis, the mostly cartilaginous secondary ossification center of the proximal tibia.

The patient will typically have knee pain, with significant effusion, and will refuse to move the knee. If he or she is cooperative enough for a clinical knee examination, it may show evidence of increased anterior translation: The tibia can be pulled forward more on the injured side than on the other side, because the tibia has lost the check rein effect of the ACL.

It is important to be alert for damage to other knee structures. Tenderness, especially at the joint line, suggests mid- to posterior meniscal injury.

What will radiography show about tibial eminence fractures?
An accurate lateral view of the knee is necessary to see the tibial eminence well: If the view is not a true lateral, one can be misled and think there is no injury (figure 5).

A tunnel view of the knee (figure 6) may be helpful to supplement, but not replace, the lateral one. This specialized view outlines the femoral notch and tibial eminence.

How do you manage tibial eminence fractures?
Management depends on the amount of displacement and comminution of the fragment. An undisplaced (type I) fracture can simply be immobilized. Aspirating the joint may make the patient more comfortable and able to extend the knee farther. If he or she can't extend the knee fully, there may be a mechanical block, perhaps from a malrotated fracture fragment or a trapped meniscus.

A slightly or completely displaced (type II or type III) fracture can usually be reduced under arthroscopic control. Fixation is required for the displaced fragments once they are reduced.

These patients generally do well if the fracture has been reduced appropriately, and other injuries—to the meniscus, for example—are managed properly. There is often mild anterior translation on follow-up examination, but this does not result in functional instability.

How do patellar sleeve fractures occur?
These fractures usually involve the inferior portion and/or, rarely, the proximal portion of the patella. In this injury, the chondral part of the osseous patella is pulled off by the patellar tendon, usually by a hyperflexion injury.

The typical patient is a preteen who fell on a flexed knee. He or she is unable to move the knee, and pain is localized at the site of injury. The physician can sometimes palpate a gap between fracture fragments. The patella rides high (proximally), compared with the uninjured side.

Why are patellar sleeve fractures frequently missed?
Even an appropriate radiograph—a good lateral view of the knee—may show what looks like a little patellar "chip fracture," and the knee is just put in a splint. Ten days or so may pass before it becomes evident that there's a displaced fracture. It's important to realize that what is visible on the radiograph represents only a small portion—the ossified part—of the whole fragment.

With a high index of suspicion, the diagnosis can be made on clinical grounds. When I find focal tenderness at the junction of the distal patella and proximal patellar tendon, a gap, and an inability to extend the knee, I think of a sleeve fracture.

How do you manage patellar sleeve fractures?
The fracture can sometimes be reduced by putting the knee in extension. If there is significant displacement that is not reduced this way, it must be managed operatively, with direct reduction of the fracture fragment and the articular patellar surface, and fixation of the osseous fragment.

The outlook for the patient with a patellar sleeve fracture is generally good if the diagnosis is made promptly.

Why are tibial tubercle avulsion fractures different from other types of physeal fractures?
Patients who have tibial tubercle avulsion fractures are usually near the end of adolescence. The typical patient is a muscular, well-developed athlete who has almost reached skeletal maturity. The injury nearly always occurs in a jumping sport, most commonly basketball. As the athlete prepares to jump or starts to land, the knee begins to flex, with the quadriceps muscle and patellar tendon pulling hard on the tubercle. The tubercle, which is not fully fused, is pulled off with the tendon.

What is the clinical presentation in patients who have tibial tubercle avulsion fractures?
In the case of a minimally displaced fracture that involves the tubercle only (type I in the Ogden-Tross-Murphy classification), pain is the predominant symptom. The patient may have trouble going up and down steps. When the fracture extends from the tubercle to the tibial epiph-ysis (type II) or through the secondary epiphysis and into the joint (type III), quadriceps insufficiency makes walking difficult.

The physical exam shows focal tenderness at the site of the injury, often with significant ecchymosis and swelling. In displaced fractures, the patella rides high (proximally) compared with the other side. The patient will be unable to bear weight on the leg or extend the knee because of pain and disruption of the quadriceps mechanism.

How do you manage tibial tubercle avulsion fractures?
Management is dependent on the fracture type. AP and lateral radiographic views of the knee will usually tell the story—in particular, they will show the amount of displacement. For nondisplaced type I fractures, I would immobilize the knee using an immobilizer or a cast for 10 days to 2 weeks, for comfort and to allow healing. The patient should avoid jumping activities for 4 additional weeks. More complex injuries require open reduction and fixation. The knee is immobilized for 3 weeks after surgery, followed by progressive rehabilitation. It is usually 2 to 3 months before the patient returns to full athletic activity after an open reduction.

Patients who have had tibial tubercle avulsion fractures usually do well. There's no real danger of physeal arrest since skeletal growth is, in almost all cases, complete.

References

Edwards PH, Grana WA: Physeal fractures about the knee. J Am Acad Orthop Surg 1995;3(2):63-69

How I Manage Physeal Fractures About the Knee

Carl Stanitski, MD, with Carl Sherman

References

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