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Fig 1

FIGURE 1. Medial lateral displacement. A medially displaced Salter Harris II fracture of the distal humeral physis sustained by a 13 year-old in an American football game.

A. Clinical Exam

It forms four projections (from the epiphysis into the metaphysis) called mammillary processes. These stabilize the epiphysis from horizontal shear forces. However, when the physis fails and there is a horizontal shear force it allows the germinal cells on the projections to be injured which can result in osseous bridge formation. The collateral and cruciate ligaments attached to the epiphysis. The medial, gastrocnemius and plantaris muscles arise, however, from the distal metaphysis. The lateral gastrocnemius can arise from both epiphysis and metaphysis. Varus or medial rotational forces on the distal fragment can cause stretching of the popliteal nerve. The joint capsule attaches only to the epiphysis, and thus entire physis is extra-articular.

IV. Classification

It can be classified by physeal types (Le., Salter Harris Types). Types I and II are the most common. Type III is often unappreciated, Type IV is rare and Types V and VI are extremely rare. It also can be classified by displacement: posterior lateral; posterior medial; pure anterior; and pure posterior. There are also special types such as stress fractures which are rare but have been described.4

V. Diagnosis

In the non-displaced fractures the clinical exam may not be quite as diagnostic. There may be point tenderness medially over the medial physeal plate. More often there is associated swelling in the distal thigh musculature (due to intramuscular bleeding from the open physis).

In the clinical exam it may be confused with acute ligamentous disruptions15. There is often severe swelling with

hemarthrosis. Even though the physis is extra-articular, there is usually significant tearing of the capsule resulting in continuity between the joint and fracture site. Medial-lateral displacement of the leg may also be clinically apparent. Varus and valgus laxity can also be present. With these injuries an especially careful vascular assessment and neurological exam of the distal portion of the extremity is mandatory.

FIGURE 2. Anterior displacement. The distal femoral epiphysis in this 10 year-old who fell from a truck is displaced anteriorly, The posterior metaphyseal portion was impinging the popliteal vessels.

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Fig 2

In stress fractures there is a typical history of pain increased with activity and decreased with rest4.

B. Radiographic Exam

In displaced fractures it is often obvious, however, one still needs to look for occult vertical intercondylar fractures. A triplane pattern can occur.

Fig 3

In non-displaced fractures one needs to look at the radiographs more closely. In stress fractures there may not be a hemarthrosis - just a widening of the physeal line. In the non-displaced Salter Harris I and /I fractures hemarthrosis is present. Often if one takes a lateral recumbent radiograph (i.e., cross table lateral) there may be an anterior layering of the fat density in the knee effusion anteriorly (FIGURE 3). Widening of the deep soft tissues in

the distal thigh indicates intramuscular bleeding. Salter Harris III fractures are often undisplaced and may be occuIt.18 The intact medial- collateral ligament and cruciate ligament may prevent displacement of the medial condyle. To determine the presence of a Salter Harris Type III fracture, stress films may be required under general anesthesia or polytomography.

FIGURE 3. Layering of Fat. In this cross talar lateral the anterior layering of the fat density proximal to the super patellar pouch indicated an occult fracture.

What about stress films? If performed, it should be under general anesthesia with traction to prevent further shearing of the mammillary prominences (FIGURE 4).

VI. Treatment

Stress Fractures

These fractures usually undergo rest until pain-free

and there is evidence of healing. In addition there needs to

be a good program of musculoskeletal conditioning.

Fig 4

Non-Displaced Fractures FIGURE 4. Stress Film. Valgus stress film performed under general anesthesia demonstrated a Type I Salter Harris fracture of the distal femoral epiphysis in this 12 year-old athlete.

This usually requires a single hip spica for 2-3 weeks followed by a long-Ieg cast. It is important that total immobilization of the distal physis be achieved as there can be late displacement. The patient can resume active motion once callous is visualized on the metaphysis. If there is a doubt as to the stability, it is

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important to examine under general anesthesia and secure with cross pins,trans metaphyseal or trans epiphyseal screws.

Displaced Fractures.

Medial-Lateral Displaced Fractures.

It is best to gain the reduction by reversing the deformity. One may need to apply longitudinal traction to unlock it first and then correct the angulation (i.e., 90% traction and 10% leverage).

15 It can also be reduced with patient prone and the knee in extension.

Stability needs to be maintained post reduction with a spica cast or a long-leg cast with percutaneous pins to maintain the reduction. If there is a large metaphyseal fragment, then a trans metaphyseal screw plus long-leg cast can be utilized (FIGURE 5).

Posterior Displaced Fractures.

Again, one needs to increase the flexion to unlock and reduce it in extension. The

fracture can be stabilized with cross pins placed in extension and a long-leg cast or spica.

Again, if there is a large metaphyseal fragment

this can be stabilized with a trans metaphyseal

screw.

Anterior Displaced Fractures.

Fig 5A Fig 5 B

One must very carefully apply traction first. This author prefers to reduce the fractures with the patient prone. The surgeon must be careful not to hyperextend the distal

fragment as this can cause further neurovascular injury. The fracture needs to be stabilized with the knee in flexion. These almost always require percutaneous pin or trans metaphyseal screw fixation because of the difficulty of applying the spica cast with the knee in flexion.

FIGURE 5. Metaphyseal Screw. (A) Displaced injury film. (8) Percutaneous stabilization was achieved with a cannulated

trans metaphyseal screw.

Type III or IV Fractures.

The surgeon can reduce the fragment by joysticking the epiphyseal fragment and

then securing it with trans epiphyseal (FIGURE 6) or trans metaphyseal screws.

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It is important that the surgeon always follow clinically for delayed signs of vascular insufficiency and/or compartment (leg-thigh) syndromes. Most nerve injuries (usually peroneal nerve neuropraxia) resolve spontaneously. It is important to maintain external immobilization and non-weight bearing until callous is present along the metaphysis on the radiographs which usually occurs at 3-to-4-weeks. One can start protected motion when metaphyseal callous has formed. This can be in the form of a hinged knee brace or a bivalve cast. Weightbearing can begin at 4 weeks with protection of a hinged knee brace or knee immobilizer. It is important to follow-up closely until skeletally mature to look for delayed growth disturbances.

Post reduction management.

Complications

Growth Arrest

Fig 6A Fig 6 B

FIGURE 6. Epiphyseal Screw. (A)This Salter Harris Type III fracture was stabilized percutaneously with a cannulated trans epiphyseal screw (B).

This physeal injury has the highest incidence of growth arrest either angular

or linear. In a combined series of 186 patients, 90 (48%) had significant growth arrest. 1,2,7,9,

12,16,17 The risk of growth arrest doesn't follow the Salter Harris classification. It is related

more to the degree of displacement and severity of original injury. 7,13

Vascular Injuries

Fortunately, in the present era the incidence is decreased down to about 2%.14 The effects, however, may be delayed, especially with an intimal tear and late propagation of an intravascular clot.

Late Displacement

Some sagittal angulation may remodel in younger patients. Coronal plane angulation never corrects. A late reduction or re-reduction can be accomplished up to 10-13 days. This, however, is a double edged sword, since remanipulation increases the risk of physeal damage. One has to weigh the degree of displacement, i.e. is it acceptable with the risk of growth arrest, creating possibly a greater deformity. Age is also a factor in the decision-making as to whether to re-reduce.

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This is very rare with a 1 % incidence at the most. Only a few series are reported.1,3,4,6 Fifty percent occur as a result of athletic injuries.8 Most are Salter Harris Type II fractures with Salter Harris Type III being the next most common.5 Again, it is more common in adolescents.

Mechanism of Injury

Again, as in distal femoral epiphysis, there is a valgus or varus bending force or a hyperextension injury. In the more common valgus injury (FIGURE 7) there is first an avulsion of the medial periosteum and superficial medial collateral ligament. The deep medial collateral may remain intact. 2

As the bending force progresses, there is propagation of the fracture line through the lateral epiphysis producing a Salter Harris Type III fracture pattern. At the same time there is a compression of the lateral physis which can produce a subsequent growth arrest. The epiphysis is usually displaced laterally with an associated fracture of the proximal fibula as well. The same mechanism can occur with hyperextension of the knee resulting in anterior displacement of the epiphysis, and posterior displacement of the metaphysis.

Anatomical Considerations

Anteriorly the tibial tubercle projects distally. The physeal line is concave to fit the adjacent convex metaphyseal surface. Only the deep medial collateral ligament attaches directly to the epiphysis. The superficial medial collateral ligament attaches distally to the metaphysis. The lateral collateral ligament attaches to the fibula. Thus the proximal tibial physis and epiphysis are relatively protected from avulsion collateral ligament stresses. This probably accounts for the rarity of this fracture.

Bony Structural Relationships

The configuration of the proximal epiphysis plus the fibula tend to force this fragment most commonly anterior laterally with the metaphyseal fragment being forced posterior medially.

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FRACTURE OF THE PROXIMALTIBIAL PHYSIS & EPIPHYSIS

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Incidence

FIGURE 7. Valgus forces on proximal tibia. A valgus force was applied to the knee of this 13 year-old producing a rupture of the medial collateral ligaments (curved areas) from tension forces and a Salter Harris Type III fracture of the lateral tibial epiphysis from the lateral compressive forces (straight

arrows).

Fig 7