Stable Slipped Capital Femoral Epiphysis
Eduardo N. Novais
Percutaneous In Situ Fixation
Operative Indications
In situ fixation is the mainstay of treatment for stable slipped capital femoral epiphysis (SCFE). However, because of the low potential for remodeling and high risk of femoral acetabular impingement (FAI) following in situ pinning for moderate and severe stable SCFE, we prefer to perform in situ fixation for mild, stable SCFE.1,2 Another indication for percutaneous in situ fixation is the prophylactic treatment of the contralateral hip in patients presenting with unilateral SCFE. Nevertheless, given the potential risk of complications,3 our indication for contralateral prophylactic fixation includes patients younger than 10 years, endocrine or metabolic disorder, and patients with open triradiate cartilage for whom appropriate follow-up with close surveillance is not reliable.
Alternative Treatment
Stable SCFE requires surgical treatment because the natural history involves slip progression and a severe deformity of the proximal femur associated with FAI, cartilage damage, and osteoarthritis4
Equipment
Cannulated screw system
Although in situ fixation can be performed with smooth pins and an expandable screw that allows the femoral neck to grow, our preference is to use a single fully threaded cannulated screw
Bone biopsy needle
Classical teaching suggests that the guidewire from one of the commercially available cannulated screw systems should be advanced freehand from the anterolateral aspect of the proximal femoral metaphysis toward the center of the epiphysis. However, we have observed that the freehand technique can often be frustrating and discouraging because the guidewire skives out of the femoral cortex as we adjust its position. We have also found a high risk of guidewire bending when we try to obtain the lateral view of the femur. Finally, the freehand technique often leads to multiple readjustment perforations that increase the risk of an iatrogenic subtrochanteric fracture. Therefore, our technique involves the application of a bone biopsy needle to establish the entry point of the screw in the anterolateral aspect of the proximal femoral metaphysis
Radiolucent table (preferable) or fracture table
C-arm fluoroscopy
Positioning
In situ fixation can be performed using a fracture table. However, our preference is to perform the surgery on a flat-top radiolucent table. We position the patient supine with a bump under the ipsilateral scapula, which helps to straighten the lower extremity in neutral rotation. The lower extremity should be prepared and draped entirely free, including the hemipelvis.
Surgical Approach
In situ fixation of stable mild SCFE is performed percutaneously.
Technique in Steps
Determine the Incision Site
Position C-arm fluoroscopy in the anteroposterior (AP) view to mark the trajectory of the screw by placing a guidewire in the anterior aspect of the thigh in alignment with the center of the epiphysis
Percutaneously Dissection Down to the Femur
A small incision is made in the anterolateral aspect of the thigh in line with the skin mark
We use a long Schnidt clamp to dissect through the subcutaneous tissue and the fascia lata down to the anterolateral aspect of the proximal femur
Establish the Entry Point of the Screw Fixation
Although the entry point for screw fixation can be established using only the guidewire, the wire often skives anteriorly. Additionally, there is a risk of bending the wire when the leg is positioned for the lateral view of the proximal femur
The bone biopsy needle is a very helpful tool to establish the entry point. We first establish the entry point in the AP view (Figure 19.1)
Gentle twisting maneuver and tapping allow for the bone biopsy needle to penetrate to about 2 or 3 mm into the anterolateral cortex of the femur
The hip is flexed, and the C-arm is rotated to about 45° to 60° into a lateral position. Achieving a satisfactory lateral projection of the femur does not require a figure-of-4 position (flexion-external rotation-abduction). Instead, we only flex the hip and rotate the C-arm around
Under C-arm fluoroscopy control, the bone biopsy needle can be introduced, aiming toward the center of the epiphysis in the lateral projection. Often, we need to drop the bone biopsy needle handle toward the floor to aim the tip of the needle slightly anteriorly toward the epiphyseal center (Figure 19.2)
The C-arm fluoroscopy is moved back to the AP view, and the hip is positioned in extension. The bone biopsy needle is advanced into the femur by gentle twisting motion and taping with a mallet
 Figure 19-1 ▪ Intraoperative picture showing the insertion of an 8-gauge bone marrow biopsy needle (Harvest Terumo BCT, Lakewood Colorado) in line with a previously drawn skin mark. Top left panel shows the corresponding intraoperative fluoroscopy imaging. (Courtesy of Children’s Orthopaedic Surgery Foundation.) |
 Figure 19-2 ▪ Intraoperative picture with the hip positioned in neutral rotation and flexion to about 45° while the C-arm fluoroscope is turned 45°. Top left panel shows the corresponding intraoperative fluoroscopy imaging in the lateral view: the bone marrow biopsy needle is properly placed aiming toward the center of the femoral head. (Courtesy of Children’s Orthopaedic Surgery Foundation.) |
 Figure 19-3 ▪ Intraoperative picture showing the placement of the cannulated system guidewire through the bone marrow biopsy needle that serves as a cannula for soft-tissue protection preventing bending of the guidewire. In the top left corner, the corresponding fluoroscopy view shows the long guidewire introduced through the biopsy needle. (Courtesy of Children’s Orthopaedic Surgery Foundation.) |
Insertion of the Guidewire, Drilling, and Cannulated Screw Placement
The bone biopsy needle trocar is removed, and the needle can be used as a soft-tissue guide and protection for the cannulated system guidewire. The use of the bone biopsy needle is beneficial because it avoids the guidewire to bend while the lateral radiograph is obtained
The guidewire is further advanced under C-arm fluoroscopy control in the AP and then in the lateral projection (Figure 19.3)
The guidewire should penetrate the growth plate ideally in the center of the epiphysis in both the AP and lateral view. We do not typically recommend placing the guidewire in the subchondral bone to avoid the risk of penetrating through the articular cartilage of the femoral head. Instead, we advanced the guidewire just beyond the physis
The length of the screw is measured based on the guidewire plus 5 mm as we do not introduce the wire down to the subchondral bone. Then the cannulated drill is used. The drill passes into the physis under direct C-arm visualization carefully to avoid excessively pushing the guidewire proximally and perforate the femoral head
The drill is removed, and a fully threaded cannulated screw is introduced through the guidewire. For patients, younger than 10 years, we employ a 6.5-mm, fully threaded screw. For patients older than 10 years, we use a 7.3-mm fully threaded cannulated screw (Figure 19.4)
Figure 19-4 ▪ Final intraoperative C-arm fluoroscopy reveals optimal position of the screw in center of the femoral head with 5 threads passed the through physis. A, Anteroposterior view. B, Frog-leg lateral view. (Courtesy of Children’s Orthopaedic Surgery Foundation.)
Before wound closure, it is essential to be sure that the screw does not penetrate the joint. The approach and withdrawal technique helps to assess the appropriate distance between the tip of the screw and the subchondral bone
The wound is instilled with local anesthetic and closed with absorbable sutures
Surgical Pearls
Five screw threads should engage in the epiphysis
The tip of the screw should be at least 5 mm away from the subchondral bone to avoid penetration of the screw through the femoral head. It is important to note that C-arm fluoroscopy can underestimate the actual distance from the tip of the screw to the subchondral bone
The screw should be inserted in the center of the epiphysis to avoid penetration of the epiphyseal tubercle. Protection of the epiphyseal tubercle and the metaphyseal socket increases the stability of the screw fixation. On the contrary, screw penetration of the epiphyseal tubercle may lead to lucency around the screw, increasing the risk of screw failure and breakage
In situ fixation for moderate or severe SCFE requires particular attention to avoid joint penetration by the screw. Injection of contrast (ioversol) through the screw is a helpful technique to assess whether the screw has penetrated the joint. If there is a perforation of the epiphysis, a hip arthrogram will be obtained, and the screw needs to be pulled or exchanged
Postoperative Care
For mild, stable SCFE, we recommend a toe-touch weight-bearing with crutches for at least 6 weeks postoperatively. Crutches are then discontinued, and another clinic visit at 3 months with repeated AP and lateral x-rays is planned. Full return to activities depends on the healing; however, sports participation is not allowed for a minimum of 6 months and sometimes for up to 1 year. We routinely measure the serum levels of vitamin D because low vitamin D may delay the healing of SCFE after in situ fixation10
We recommend patients to be followed until skeletal maturity because of the risk of FAI. In unilateral SCFE, we recommend routine follow-up every 3 months for the first year after in situ fixation and then twice a year during the second year
The decision to perform a contralateral fixation depends upon the patients’ age, the status of the triradiate cartilage, associated comorbidities, and the morphology of the uninvolved femur.11 Obese and younger patients with increased posterior epiphyseal tilt and decreased superior epiphyseal extension are at higher risk of subsequent SCFE.12,13,14 Although highly controversial, we prefer surveillance to monitor the contralateral hip in patients with unilateral SCFE to avoid the risk of iatrogenic complicationRelated posts:
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