The standard Salter-Harris (SH) classification works well for these fractures, especially with regard to treatment and risk of growth arrest. The risk of growth arrest is reported to be between 40% and 52% for all distal femur growth plate fractures.1,2 In a meta-analysis of 564 fractures, growth disturbance occurred in 36% of SH 1 fractures, in 58% of SH 2 fractures, in 49% of SH 3, and in 64% of SH 4 fractures.1 High-energy distal femur growth plate fractures (eg, motor vehicle accident) have a 31% rate of growth disturbance compared with only a 5% rate for low-energy fractures (eg, fall from <10 ft).2 Displaced fractures have a higher incidence of complications (49%) compared with nondisplaced fractures (27%).3 In a retrospective review, the authors recommended subdivision of SH II fractures into those with and without metaphyseal comminution and/or initial displacement >3 mm with loss of contact between the 2 fragments. Those with comminution and displacement had a greater risk of growth arrest (75%) compared with those without (38%).4
Nondisplaced SH I fractures should be suspected when knee tenderness is localized circumferentially to the distal femur growth plate. With the knee in full extension, the equator of the patella usually overlies the growth plate, which helps to guide the examination. Gentle varus/valgus stress to the knee should elicit pain. Radiographic findings can be subtle in all minimally displaced growth plate fractures of the knee. A slight fleck of bone adjacent to the growth plate, a slight widening of the physis, or other irregularity of the growth plate can give a hint of a fracture. Sometimes, the only indication that a distal femur fracture has occurred may be the appearance of periosteal new bone formation about the metaphysis 3 weeks after injury. Stress views of the knee have fallen out of favor because of the severe pain experienced by the patient and the potential growth plate damage incurred when redisplacing a nondisplaced fracture.5 Patients who have tenderness over the growth plate and are unable to bear weight should be treated as having a presumptive growth plate fracture and should be casted for 4 weeks. Magnetic resonance imaging is rarely necessary to confirm the clinical diagnosis of a nondisplaced distal femur growth plate fracture.
Full leg casting up to the groin for 4 weeks is usually sufficient to hold a nondisplaced SH I fracture; however, obese young children may need a hip spica cast.
Displaced SH I fractures need a gentle closed reduction under anesthesia or deep sedation. Salter I fractures are more stable after reduction compared with Salter II-V fractures and may not need internal fixation to supplement casting. Once a SH I fracture is manipulated back into position, it can be held with crossed, percutaneously placed smooth Kirschner (K)-wires. These can be initially placed retrograde through the epiphysis, across the growth plate, and out through the opposite metaphyseal cortex, to exit through the skin in the distal thigh (Fig. 1). This keeps the pins out of the knee joint and helps to minimize the risk of septic arthritis emanating from a pin-tract infection. Percutaneous smooth pins across the growth plate are not associated with growth arrest,2 and healing is usually sufficient to allow removal of pins after 4 weeks to minimize any risk of pin-tract infection. Casting can be discontinued at 4 to 6 weeks postoperatively. A 5- to 10-degree knee flexion contracture may be a subtle early sign of a partial posterior growth arrest. A varus or valgus knee deformity is a more obvious sign of medial or lateral growth arrest.
SH II fractures of the distal femur frequently occur as a result of participation in sports and seem to herald another season of freshman football. Nondisplaced SH II fractures of the distal femur frequently present with moderate knee pain and mild knee swelling. If nondisplaced, they may be treated with cast immobilization, but the surgeon must watch carefully for loss of position on follow up x-rays in the first week. If the fracture shifts, the surgeon may use closed reduction with percutaneous pinning or open reduction and internal fixation within the first week. Mild displacement noticed after the first week is best left to remodeling rather than to remanipulation to correct the alignment.
Other authors strongly advocate that all displaced SH type II, III, and IV fractures should be treated with open reduction and internal fixation, which they maintain produces better results compared with closed reduction and casting.6 We believe that displaced SH II fractures of the distal femur should undergo closed or open reduction with smooth K-wire pinning, if the metaphyseal fragment is small. If the metaphyseal fragment is large, one or two 4.5- to 7.3-mm cannulated screws with washers are placed transversely through the metaphyseal fragment into the bone of the femoral shaft (Fig. 2). This fixation is usually supplemented/neutralized with a long leg cast. It is important to ensure that the screws engage the fracture, as the metaphyseal fragment may be primarily anterior or posterior, and it is difficult to determine on lateral view. If the metaphyseal fragment is primarily anterior, a transverse screw that starts posteriorly may appear in excellent position on the anteroposterior view but may completely miss the distal metaphyseal fragment. Healing takes about 4 to 6 weeks. Growth should be monitored for 6 to 12 months to rule out growth arrest. The screws and washers may need to be removed because of soft tissue irritation. To minimize the need for removal, at the time of surgery make sure to incise and release the iliotibial band or the medial retinaculum so that these structures are not bound down by the screw.
SH III and IV
Only those fractures that are radiographically occult (identified only on magnetic resonance imaging) are safe for nonoperative treatment.
All nondisplaced and displaced SH III and IV fractures should undergo operative fixation. Even minimally displaced fractures can be unstable and can shift position during the first several weeks.
We recommend obtaining a computed tomography (CT) scan preoperatively on all SH III and IV fractures to help plan fixation with percutaneous cannulated screws. Plain x-rays can be deceptive and may underestimate the articular surface gap and step-off, leading to undertreatment.7 Oblique x-rays can improve the accuracy of plain films.8 It is strongly recommended that the surgeon make a medial or lateral parapatellar incision about 3 cm long over the intercondylar fracture line to allow direct palpation of the fracture during reduction and fixation. The fluoroscopic image can severely underestimate the step-off and gap at the fracture site. A single transverse 7.3- or 6.5-mm cannulated screw placed through the epiphyseal triangle is sufficient for fixation (Fig. 3). This “epiphyseal triangle” is seen on a lateral fluoroscopic view and is formed by the shadows of (1) the physis; (2) the superior arch of the intraconylar notch (the Blumensaat line); and (3) the trough of the trochlear groove (Fig. 4).
Tips: The anteroposterior fluoroscopic view often misses the over penetration of a screw tip into the opposite cortex and the fact that it is sitting proud outside the bone. This will impinge on the soft tissues and cause pain with knee motion. To avoid this complication, rotate the leg under fluoroscopy to catch the screw at its longest apparent length outside the bone. Just before the screw head and washer are seated on the cortex, incise the deep soft tissues longitudinally and use a hemostat to elevate the medial or lateral soft tissue out from under the screw head and washer.
Arthrographic and arthroscopic visualizations are alternatives to direct palpation and visualization of the joint surface through an arthrotomy during SH III and IV fracture reduction and fixation. Although these techniques are minimally invasive, they may not allow the most accurate confirmation of reduction. Figure 5A shows an intraoperative arthrogram of a SH III fracture that failed to clearly identify a residual fracture gap and step-off. This led to a minor malunion as seen in Figure 5B. Figure 6 shows a major malunion in a patient who underwent an arthroscopically assisted reduction and fixation. This patient developed posttraumatic arthritis within a year of surgery. A 3-cm arthrotomy is very well tolerated in a young patient and allows the surgeon to be sure that the reduction is perfect in the operating room, especially if the intracondylar fracture line is palpated on the anterior and inferior surfaces. Verifying reduction by palpating the trochlear groove and the notch surface/weight bearing surfaces of the intra-articular fracture, which are at 90 degrees to each other, ensures anatomic reduction of the entire fracture fragment.
Any physeal fracture of the distal femur can be complicated by a growth arrest. Distal femur growth plate fractures, along with distal tibia and distal ulnar growth plate fractures, have the highest rates of growth disturbance of all bones in the body. SH fractures of the distal femur are reported to have a 30% to 70% incidence of growth arrest.4,9 A complete growth arrest of the distal femur, the fastest growing growth plate in the body, can produce up to a 12 cm leg length difference in a 6-year-old boy. Even worse, a partial growth arrest can produce 25 degrees of angulation about the knee. SH III and IV fractures that heal with displacement can produce posttraumatic arthritis because of their joint surface involvement. In operatively treated cases of distal femur growth plate fractures, there was a higher incidence of complications when hardware crossed the physis.3 Another study found that, although there is a greater incidence of growth disturbance in patients who were treated with fixation (58% vs. 63%), there was a decreased incidence of significant growth disturbance (37% vs. 27%).1
Vascular injury can also complicate these distal femur growth plate fractures, especially with anterior displacement of the epiphysis (Fig. 7). This pattern is similar to an anterior knee dislocation in an adult. If there is a diminished distal pulse compared with the opposite side, an ankle-brachial index should be checked. The cuff systolic blood pressure at the ankle should be >90% of the arm’s (brachial) systolic blood pressure. The ankle-brachial index is more reliable for detecting an arterial injury than for obtaining a “dopplerable pulse.” If the ankle’s cuff systolic pressure is <80% to 90% of the arm’s cuff systolic pressure, further work-up with a flow Doppler ultrasound or arteriogram may be indicated.10 Compartment syndrome has been noted in 1.3% of SH fractures of the distal femur and peroneal nerve palsy has been observed in 7.3%.11 Knee ligament laxity is associated with 8% to 38% of distal femur fractures.9 Loss of knee range of motion has been reported at 25% in SH II fractures of the distal femur.4
A 9-year-old boy was struck from the side during a football game. He experienced immediate pain, deformity, and swelling around his knee. He arrived in the emergency room and his x-rays showed a displaced SH II fracture of the distal femur with a small metaphyseal fragment (Fig. 7). The patient underwent closed reduction and percutaneous pin fixation with smooth crossed K-wires placed antegrade through the joint and across the fracture (Fig. 8). The pins were left outside the skin at the knee. At 4 weeks postoperatively, the fracture position was maintained and healing was evident (Fig. 9). At 10 weeks postoperatively, the distal femur growth plate appeared to have a partial physeal bar on CT scan (Fig. 10). This case illustrates the high risk of growth arrest with distal femur fractures even with anatomic reduction.
A 15-year-old boy was struck at the side of the leg during a football tackle. He experienced severe knee pain and was unable to stand. In the emergency room, he was noted to have knee tenderness and an effusion. His x-rays demonstrated a minimally displaced SH III fracture of the medial femoral condyle (Fig. 11). The patient was splinted and referred to an orthopaedic surgeon who placed him in a long leg cast. Radiographs were taken weekly and showed no change in position. After 3 weeks in a cast, follow-up x-rays showed minimal healing and a slightly larger intercondylar gap (Fig. 12). A CT scan was obtained and revealed a 3- to 5-mm fracture gap (Fig. 13). The patient then underwent open reduction through a small incision placed over the intercondylar portion of the fracture. At the time of surgery, which was 4 weeks after the original injury, the surgeon noted that there was full mobility of the fracture fragment and no apparent healing. The fracture was anatomically reduced and palpated with the surgeon’s finger. A 7.3-mm cannulated compression screw was placed transversely across the intercondylar fracture line in the distal femoral epiphysis. The patient’s injury healed quickly and he returned to play football the next season.
Failure to anatomically reduce the articular surface anatomically of Salter III and IV fractures may lead to early osteoarthritis. To maximize the anatomic reduction and to minimize complications in these difficult SH III and IV fractures:
- Directly palpate the intercondylar fracture line with your finger through a 3-cm parapatellar incision during reduction and fixation.
- Place a transverse screw across the intercondylar fracture targeting the center of the epiphyseal triangle.
- Obtain a preoperative CT scan to visualize the exact fracture pattern, which is difficult to visualize on preoperative x-rays and intraoperative fluoroscopy.
These 3 tips will help ensure an anatomic fracture reduction and minimize the risks of growth arrest and posttraumatic arthritis in Salter III and IV distal femur fractures.
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