R. Dale Blasier
DEFINITION
Distal femoral physeal fractures involve the femoral condyles distal to the physis.
The fractures may be extra-articular (Salter-Harris types I and II fractures), which are also referred to as distal femoral physeal separations. The fractures may also be intra-articular (Salter-Harris types III and IV) (FIG 1).1
The important things to assess are involvement of the distal femoral growth plate and articular congruity.
ANATOMY
The distal femoral physis is one of the fastest-growing and most important growth plates of the lower extremity (FIG 2). The physis is remarkable for its multiple undulations.
The medial and lateral collateral ligaments originate from the medial and lateral condyles.
The anterior and posterior cruciate ligaments originate in the intracondylar notch.
The peroneal nerve and popliteal artery are close by.
PATHOGENESIS
A direct blow to the knee from medial or lateral may result in avulsion of the distal femoral epiphysis in whole or in part. The distal femoral condylar unit may displace medially or laterally.
A hyperextension injury of the knee may result in distal femoral physeal separation with anterior displacement of the femoral condylar unit.
A direct blow to the flexed knee (dashboard injury) may result in fracturing of the distal femoral epiphysis in a variety of patterns, including the Salter-Harris type IV fracture.
NATURAL HISTORY
While most physeal separations (Salter-Harris type I and II fractures) have an excellent prognosis for healing without growth derangement, fractures of the distal femur are more prone to result in growth problems.
This may result from “shaving off” of the undulations of the growth plate or from “scuffing” of the growth plate by the metaphysis during displacement and replacement of the epiphysis.4
Because this growth plate is rapidly growing and makes an important contribution to the total length of the limb, any derangement here is likely to become symptomatic.2,3,4
Parents must be warned of the possibility of growth derangement (shortening or angular deformity) as a result of physeal damage.
Healing problems and joint stiffness are unlikely.
PATIENT HISTORY AND PHYSICAL FINDINGS
A history is necessary to reveal the direction and magnitude of the injuring force.
Pulses and neural function must be routinely assessed.
Inspection often reveals that the knee is swollen; it may even appear dislocated (FIG 3).
The degree of displacement correlates with the degree of deformity.
True knee dislocation is uncommon in the immature patient; distal femoral physeal separation is not.
The clinician should perform a varus–valgus stress test. Apparent instability suggests that radiographs (with and without stress) should be obtained to differentiate separation from ligament injury.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain film anteroposterior (AP) and lateral radiographs of the distal femur or knee should be obtained (FIG 4A,B).
Truly undisplaced separations may be visualized on stress radiographs (FIG 4C,D).
Displaced intra-articular fractures should be visualized by CT scanning (FIG 4E–H).
If there is suspicion of concomitant intra-articular derangement, MRI should be obtained before the insertion of metallic hardware.
FIG 1 • Patterns of epiphyseal fracture of the distal femur according to the Salter-Harris classification.
FIG 2 • A. AP diagram of knee with physis, collateral ligaments, and cruciate ligaments. B. Lateral diagram of knee with cruciate ligaments.
DIFFERENTIAL DIAGNOSIS
Dislocation of knee
Dislocation of patella
Proximal tibial fracture
Fracture of distal femoral metaphysis
FIG 3 • Picture of swollen knee.
NONOPERATIVE MANAGEMENT
Truly undisplaced fractures can be immobilized in a long-leg cast.
Fractures should be re-evaluated by radiography in a few days to check for displacement.
Fractures that are easily reducible are rarely stable and are not amenable to simple cast immobilization.5
SURGICAL MANAGEMENT
Surgical management should be considered for displaced or irreducible distal femoral physeal separations (Salter-Harris type I or II).
Surgical management should be considered for displaced or unstable intra-articular fractures (Salter-Harris type III or IV).
FIG 4 • A,B. AP and lateral radiographs of knee with physeal separation. C,D. Diagrams of stress radiographs. C. The knee joint opens after collateral injury. D. The physis opens after epiphyseal separation. E. AP radiograph of knee suggests fracture of lateral distal femoral epiphysis. F,G. Coronal and sagittal CT reconstructions show a Salter-Harris type IV fracture of the lateral epiphysis. H. The fracture is well visualized on axial cuts.
FIG 5 • Views from side (A) and foot (B) of operating table, showing the patient's knee flexed over a bump and the C-arm overhead.
Surgical management should be considered for fractures associated with nerve, vascular, or soft tissue injuries that would preclude standard casting.
Preoperative Planning
If manipulative reduction is contemplated, the surgeon should request muscle relaxation from the anesthesia provider after induction.
If distal pulses are diminished before fracture reduction, provision should be made for vascular surgical consultation if the normal pulse is not restored after reduction.
The distal femur must be visualized in AP and lateral views on fluoroscopy.
Intra-articular fractures should be studied by CT scan preoperatively. Fractures that are simply separated may be amenable to percutaneous lag-screw fixation. Fractures that are widely displaced or rotated may require open reduction and internal fixation.
Positioning
Generally patients can be positioned supine on a radiolucent table. However, fractures that are displaced into extension may be best fixed with the knee flexed over a bolster (FIG 5).
Approach
Distal femoral physeal separations will generally be managed by closed reduction and percutaneous fixation.
Fractures that cannot be reduced closed should be managed with open reduction, with the surgical approach on the side (medial or lateral) where the periosteum is torn.
Salter-Harris type I and I fractures with a small Thurston Holland fragment should be fixed with smooth pins across the physis.
Salter-Harris type II fractures with large Thurston Holland fragments should be fixed with transverse screws that lag the Thurston Holland fragment to the metaphysis.
Salter-Harris type III and IV fractures should be anatomically reduced and fixed with lag screws.
TECHNIQUES
CLOSED REDUCTION AND PERCUTANEOUS PINNING
Fracture Reduction
Reduction should be done as soon as possible and certainly within a week of injury or the fracture may not be reducible.
Optimal anesthetic technique includes maximum muscle relaxation before fracture reduction.
Extension injuries are best reduced with the knee in flexion (TECH FIG 1).
Separations displaced medially or laterally are reduced by a medial or lateral force opposite to the direction of displacement.
Fixation
Smooth Kirschner wires are placed under fluoroscopic control after reduction of the fracture. Stout wires should be used (greater than 2 mm in diameter). Two pins are used.
One starts in the medial epiphysis and is advanced across the separation out the medial femoral metaphysis (TECH FIG 2A–C).
TECH FIG 1 • Lateral diagrams of distal epiphysis displaced into extension (A) and reduced (B).
TECH FIG 2 • AP diagrams. A. Pin starting in medial femoral condyle drilled retrograde. B. Pin starting in medial femoral condyle drilled retrograde across proximal contralateral metaphysis and out skin. C.Pin drilled retrograde from proximal until distal end of pin is buried in the epiphysis. D. Pin starting in lateral femoral condyle drilled retrograde across proximal contralateral metaphysis and out skin. E.Drilled retrograde across proximal contralateral metaphysis and out skin. F. Pins cut and left outside the skin proximally.
The second starts in the lateral epiphysis and is advanced across the separation into the lateral metaphysis (TECH FIG 2D,E).
Pins left protruding distally may provide a portal to seed the knee joint with bacteria. For this reason, consideration should be given to advancing the pins proximally out the contralateral metaphysis and out the skin of the thigh. The pins are grasped proximally and drilled retrograde until the distal end disappears into the knee joint and the epiphysis of the distal femur. Pins are left protruding proximally (TECH FIG 2F).
A cast or splint is applied with the knee in a comfortable degree of flexion.
CLOSED REDUCTION AND PERCUTANEOUS SCREW FIXATION
This technique is satisfactory for type II epiphyseal separations with a substantial Thurston Holland fragment or for type III and IV fractures that are not widely displaced or rotated.
The fracture is reduced by closed manipulation (TECH FIG 3A,B). Guidewires for cannulated screws (usually 4.5 mm) are passed percutaneously using fluoroscopic guidance. The guidewires should be passed perpendicular to the plane of the fracture and parallel to the physis (TECH FIG 3C).
Fluoroscopy confirms wire placement. Overdrilling precedes placement of lag screws (TECH FIG 3D). Generally two screws are placed (TECH FIG 3E).
Stability of fixation is tested. Hardware is added if needed.
A splint or cast is applied.
TECH FIG 3 • AP diagrams. A. Displaced Salter-Harris type II fracture of distal femur. B. Reduced SalterHarris type II fracture of distal femur. C. Guidewires placed across Thurston Holland fragment, parallel to physis. D.Drill over guidewires. E. Lag screws in place.
OPEN REDUCTION AND INTERNAL FIXATION
Extra-articular Fractures
A tourniquet should be applied to the thigh and inflated after exsanguination.
Irreducible epiphyseal separations should be approached from the side on which the periosteum is torn (TECH FIG 4A).
An incision is made medially or laterally over the physis. Interposed soft tissue, usually periosteum, is removed and the fracture is reduced (TECH FIG 4B).
TECH FIG 4 • AP diagrams of displaced Salter-Harris type II fracture. A. Fracture of distal femur with interposed soft tissue. B. Interposed soft tissue removed. C. Interposed soft tissue removed and screws placed.
Fixation is then placed as for the above procedures (TECH FIG 4C).
Intra-articular Fractures
Salter-Harris type III or IV fractures that cannot be reduced closed should be approached by a parapatellar arthrotomy on the same side of the fracture.
Hematoma is evacuated.
The fracture is reduced under direct vision and lagged in place with cannulated screws (TECH FIG 5).
Closure and splinting or casting are routine.
TECH FIG 5 • AP diagrams of a displaced Salter-Harris type III fracture (A) that has been lagged together (B).
POSTOPERATIVE CARE
The splint or cast is left for 1 month.
Straight-leg raising is encouraged.
Weight bearing is not allowed.
Pins are pulled at cast removal.
Motion is allowed after cast removal.
Screw removal is optional after complete healing.
OUTCOMES
Healing is not a problem and can be expected in all cases.
The knee will be stiff when the cast is removed, but range of motion is usually quick to return.
Up to one third of patients may develop late growth derangement. Assessment of the physis with plain radiographs and in most cases MRI is important because the rate of growth arrest is so high. An MRI at 4 to 6 months may show the first signs of physeal arrest.
COMPLICATIONS
Nerve or vessel injury
Malreduction
Pin tract infection
Growth derangement
REFERENCES
1. Beaty JH, Kumar A. Fractures about the knee in children. J Bone Joint Surg Am 1994;76A:1870–1880.
2. Graham JM, Gross RH. Distal femoral physeal problem fractures. Clin Orthop Relat Res 1990;255:51–53.
3. Lombardo SJ, Harvey JP Jr. Fractures of the distal femoral epiphyses—factors influencing prognosis: a review of thirty-four cases. J Bone Joint Surg Am 1977;59A:742–751.
4. Riseborough EJ, Barrett IR, Shapiro R. Growth disturbances following distal femoral fracture-separations. J Bone Joint Surg Am 1983;65A:885–893.
5. Thomson JD, Stricker SJ, Williams MM. Fractures of the distal femoral epiphyseal plate. J Pediatr Orthop 1995;15:474–478.