Pediatric Anterior Cruciate Ligament Femoral Fixation: The Trans-Iliotibial Band Endoscopic Portal for Direct Visualization of Ideal Button Placement

Abstract

Pediatric and adolescent anterior cruciate ligament reconstruction is a commonly performed procedure that has been increasing in incidence. Multiple techniques for graft fixation have been described. Button-based femoral cortical suspension fixation of the anterior cruciate ligament graft allows for fast, secure fixation with strong load-to-failure biomechanical properties. The biomechanical properties of button-based femoral cortical suspension fixation are especially beneficial with soft-tissue grafts such as hamstring autografts. Confirmation of a successfully flipped button can be achieved with intraoperative fluoroscopy or indirect viewing; however, these techniques do not provide direct visualization of the flipped button. Our trans-iliotibial band endoscopic portal allows the surgeon to safely and directly visualize the flipped button on the lateral femoral cortex and ensure that there is no malpositioning in the form of an incompletely flipped button or from soft-tissue interposition between the button and the lateral femoral cortex. This portal therefore allows for direct visual confirmation that the button is fully flipped and resting flush against the femoral cortex, deep to the iliotibial band and vastus lateralis.

Pediatric anterior cruciate ligament (ACL) reconstruction continues to be a commonly performed procedure. Investigating the hospital records over a 12-year period at The Children's Hospital of Philadelphia, the incidence of ACL ruptures in children and adolescents was found to have increased by 400%.¹ A further study of adolescent soccer and football athletes showed that approximately 14 patients will sustain an ACL injury (Fig 1) per 100,000 athletic exposures.² Given the increasing number of ACL reconstructions performed, advances in surgical techniques that improve safety, operative efficiency, and thereby improve value for the patient are increasingly important.

Fig 1.

Arthroscopic image showing complete ACL rupture viewed from anterolateral portal. (LFC, lateral femoral condyle.) (© The Children's Hospital of Philadelphia)

Button-based femoral cortical suspension fixation of ACL grafts allows for fast, secure fixation.³ However, there are several case reports of button malpositioning^4,5 due to the inability to visualize the “flipped” button and guarantee that it is fully flipped and positioned flush against the femoral cortex. Button migration can also occur as a result of soft-tissue interposition when the button does not sit directly on the lateral femoral cortex.⁶

Current surgical techniques do not allow for direct visualization of the button in its final position, ensuring that it is both fully flipped and not lodged superficial to the iliotibial (IT) band or the vastus lateralis. Therefore a method to directly visualize a flipped button can prevent such malpositioning and decrease the potential for graft migration and loosening over time as the patient cycles the knee.

Button-based fixation can remain an excellent choice for femoral graft fixation. Studies have shown that femoral ACL fixation with interference screws has less ideal biomechanical properties when used for soft-tissue grafts. These biomechanical deficits include graft slipping and decreased ultimate failure loads.⁷ Given the potential benefits of soft-tissue grafts, button-based fixation remains valuable—especially if known potential technique complications can be virtually eliminated.

Several techniques have been proposed to enhance ideal button placement and lessen the probability of button malpositioning. Some surgeons have advocated for intraoperative fluoroscopy to assess the position of the button and its relation to the femoral cortex. However, this increases operative time; exposes the patient to potentially unnecessary radiation, albeit small levels; increases operative costs; and requires additional personnel. In addition, fluoroscopy does not permit direct visualization of the seated button. Other surgeons have proposed monitoring the button as it passes through the femoral tunnel arthroscopically and using a guide pin to provide a controlled force for button passage.⁸ However, this technique does not allow for direct visual confirmation of the flipped button resting on the femoral cortex, potentially again allowing for a falsely secure femoral fixation.

We describe the use of the femoral guide pin incision on the lateral femur as an endoscopic portal, termed the trans-IT band portal. Our portal allows for direct visualization of the flipped button, thereby eliminating the need for intraoperative fluoroscopy and further eliminating the potential of femoral ACL graft fixation failure due to improperly flipped and secured buttons (Table 1).

Table 1.

Pearls and Pitfalls of Trans-IT Band Endoscopic Portal for ACL Reconstruction

Indication The trans-IT band endoscopic portal should be considered when using button-based femoral cortical suspension fixation for ACL grafts to ensure proper graft placement and positioning. Pearls 1. The trans-IT band portal should be created by sharply incising the skin and IT band at the site of the femoral guide pin insertion. Blunt dissection is used to reach the lateral femoral cortex to prevent injury to the lateral superior genicular artery. 2. While inserting the graft, the button should be visualized using the arthroscope in the anteromedial portal. Slowly advance the graft until the button just exits the guide pin hole on the femoral cortex. 3. Short bursts of fluid inflow can be used to clear the tip of the arthroscope to allow easy visualization of the flipped button. 4. A small probe can be inserted alongside the arthroscope to help seat a mal-reduced button. Pitfalls 1. Failure to confirm that the IT band and vastus lateralis are both superficial to the button will result in tissue interposition and potential graft loosening. 2. The arthroscope inflow should be switched off while the lateral trans-IT band portal is being used, apart from short bursts to clear the tip of debris. Although the portal should be used briefly for simple visual confirmation, excessive introduction of fluid could increase the risk of compartment syndrome. 3. The lateral superior genicular artery runs in the substance of the vastus lateralis. To avoid injury, use blunt dissection through the substance of the vastus lateralis to reach the lateral femoral cortex.

Technique

Preparation of ACL Femoral Tunnel

The femoral tunnel is prepared in the standard fashion for button fixation. An ACL guide is placed through the anterolateral portal and centered on the ACL femoral footprint. Before drilling the guide pin through the lateral femoral cortex, the surgeon makes a small longitudinal incision through the skin and IT band at the guide pin entry site, just large enough to allow for passing the arthroscope. This incision will be the trans-IT band endoscopic portal.

After establishing the portal, we use a FlipCutter (Arthrex, Naples, FL) to drill a femoral socket. A 5- to 7-mm cortical bony bridge should be left on the lateral femoral cortex.

Preparation of ACL Tibial Tunnel

The tibial tunnel is prepared in the preferred fashion. The tibial insertion of the graft is anatomically positioned at the footprint of the native ACL.

Preparation of ACL Graft

We prefer to use hamstring autograft; however, a button can be used for femoral fixation for multiple types of grafts including both bone-tendon grafts and allografts. We use the ACL TightRope RT (Arthrex), which incorporates a femoral cortical button and suspension fixation. However, our technique is applicable to all types of button-based fixation.

ACL Graft Passage and Securing of Femoral Fixation

The sutures for the ACL TightRope RT are fed through the tibial tunnel and femoral tunnel and out through the lateral trans-IT band portal incision. Once the sutures are passed, the arthroscope is placed in the anteromedial portal to directly visualize the femoral tunnel (Fig 2, Video 1). Under arthroscopic visualization, the graft is gently advanced until the button just exits the femoral cortex through the guide pin hole. The button is flipped under arthroscopic visualization. Next, the arthroscope is inserted into the trans-IT band portal (Fig 3). The arthroscope is advanced through the IT band and the vastus lateralis. The surgeon then identifies the button, making sure it is fully through the tunnel and flat against the femoral cortex (Fig 4, Video 1). If the button is entrapped in the vastus lateralis or superficial to the IT band, a probe can be introduced through the same portal to help manipulate it into the proper position.

Fig 2.

Arthroscopic image of femoral tunnel for graft fixation. The femoral fixation button is passing through the guide pin hole. The arthroscope is placed through the anteromedial portal to view the lateral femoral tunnel. (© The Children's Hospital of Philadelphia)

Fig 3.

Arthroscopic image looking through trans-IT band portal, viewing sutures for femoral fixation. The IT band is split, and the button is deep to the IT band, resting on the lateral cortex of the femur. (© The Children's Hospital of Philadelphia)

Fig 4.

Deeper view through trans-IT band portal. The button is fully flipped and flush against the femoral cortex. (© The Children's Hospital of Philadelphia)

Completion of Graft Fixation

The knee is cycled to tension the graft. The preferred tibial fixation is placed. We use a bioabsorbable interference screw with bony ingrowth properties, the BioComposite GraftBolt (Arthrex), as well as backup fixation with PushLock BioComposite arthroscopic anchors (Arthrex).

Discussion

Our novel trans-IT band endoscopic portal bridges the gap between advances in surgical technology and patient safety, allowing for safer femoral fixation of ACL grafts using a biomechanically advantageous button technique. Our technique eliminates the need for increased operative time or patient radiation exposure as is required for intraoperative radiographic imaging to attempt confirmation of a flipped button. The surgeon can directly visualize the flipped button on the lateral aspect of the distal femur, ensuring that there is no soft-tissue interposition. Furthermore, this direct visual confirmation is possible without requiring an open technique.

The additional trans-IT band portal is located on the lateral aspect of the distal femur and is large enough only to allow insertion of the arthroscope. This is a relatively safe zone in which to make an incision; however, the main structure at risk is the lateral superior genicular artery. The skin and the IT band should be sharply dissected; however, blunt dissection through the vastus lateralis should be performed to minimize risk of arterial injury.

Because the trans-IT band portal is not an intra-articular portal, the surgeon should switch off the arthroscopic inflow to prevent unwanted soft-tissue fluid extravasation. Short bursts of fluid inflow can be used to clear any fat or blood from the tip of the arthroscope if needed.

Although all causes of graft failure cannot be entirely eliminated, the described technique significantly decreases the possibility of graft failure due to an improperly flipped or malpositioned button associated with previous indirect techniques to confirm proper button placement. By allowing biomechanically secure fixation with direct visual confirmation of the button's position, our trans-IT band endoscopic portal can enhance both operative time and safety in pediatric ACL reconstruction.

Supplementary Data

Video 1

Arthroscopic visualization of button passing through femoral tunnel to seat onto femoral cortex, and endoscopic visualization of flipped button resting flush on lateral femoral cortex. The clip begins deep as the arthroscope is drawn superficially, showing the vastus lateralis and the IT band, both of which are superficial to the button.