摘要
- ACL grafts are secured inside bone tunnels or sockets using fixation devices such as buttons, loops or screws.
- An adjustable loop allows the surgeon to draw the graft into the femoral socket and adjust its position during surgery.
- Fixation holds the graft in place while it gradually heals into the surrounding bone.
- Most fixation implants remain in the knee and do not routinely need to be removed.
- Graft type and surgical technique determine how fixation and rehabilitation are planned.
When an ACL is reconstructed, positioning the new graft correctly is only part of the job. It also needs to be held firmly in place at both ends while it goes through the slower process of healing into the bone.
Orthopaedic surgeons have a few ways to achieve this, such as the adjustable loop fixation. This method uses a small button and an adjustable suture loop to anchor the graft securely against the bone.
What Happens During ACL Surgery?
During an ACL reconstruction surgery, the damaged ligament is replaced with graft tissue positioned along the course of the original ACL.
The graft may come from your own hamstring, quadriceps or patellar tendon, with the choice depending on factors such as your anatomy, activity demands and your surgeon’s assessment.
Why the Torn Ligament Is Replaced, Not Stitched
A complete ACL tear is commonly reconstructed rather than simply stitched back together because the ligament does not heal in a way that restores the stability required for an active knee.
The graft acts as a replacement for the damaged ligament, connecting the femur (thigh bone) to the tibia (shin bone).
Not every ACL injury requires reconstruction. Surgery is considered according to the type of tear, knee stability, associated injuries and your activity goals.
Preparing the Graft
Once the graft has been harvested, it is prepared to the appropriate length and diameter.
Its ends are also prepared for the fixation method being used. With suspensory fixation, the graft is connected to a strong suture loop and small cortical button that will help hold it in position.
The exact preparation differs depending on whether the graft is made entirely of tendon or contains a small bone block.
Creating the Tunnels and Sockets
If there are bones involved, your surgeon creates carefully positioned tunnels or sockets in them. The graft is then passed into them so that it sits across the knee in the intended position.
A tunnel passes through the bone, while a socket is a shorter, blind-ended opening. Some ACL reconstruction techniques use sockets to accommodate the ends of the graft without drilling a full-length tunnel of the same diameter.
How Is the Graft Anchored at Each End?
Immediately after ACL surgery, the graft has not yet biologically attached to the surrounding bone. Fixation devices therefore help to hold it securely while healing takes place.
Fixation at the Thigh Bone
One option used at the femur is cortical suspensory fixation, where a small button anchors the graft against the outer surface of the femur. With an adjustable loop, the loop length can be changed during surgery to help position the graft within the socket.
Fixation at the Shin Bone
The tibial end can be secured using several methods, including interference screws, buttons or other fixation devices depending on the graft and surgical technique.
An interference screw works differently from a suspensory button. Rather than suspending the graft from the outer cortex, the screw is placed alongside the graft within the tunnel to secure it against the surrounding bone.
Your surgeon chooses the fixation method according to the graft being used and the requirements of the reconstruction.
Why the Two Ends Are Handled Differently
The femur and tibia have different anatomy, tunnel orientations and forces acting on the graft.
As a result, ACL reconstruction does not require identical fixation at both ends. Your surgeon can select the combination that allows the graft to be positioned, tensioned and secured appropriately for your knee.
Understanding Adjustable Loop Fixation
What the Button and Loop Actually Are
The button is a small implant designed to rest against the outer cortex of the femur.
Attached to it is a loop made from high-strength suture material. The graft is connected to this loop, allowing it to be suspended inside the femoral socket.
Unlike a fixed-loop device, where the loop has a predetermined length, an adjustable-loop device allows your surgeon to change the loop length during surgery.
How the Loop Is Tightened During Surgery
Once the button has passed through the femur, it is positioned against the outer surface of your bone.
Your surgeon then shortens the adjustable loop, which draws the graft further into the socket. This allows its final position and tension to be adjusted during fixation.
Some adjustable-loop systems can also be re-tensioned after the other end of the graft has been secured.
Why a Shorter Socket Can Be Used
A fixed-loop button requires enough tunnel length for the button to pass through the bone before it can be turned into position.
An adjustable loop changes this because the surgeon can shorten the loop after the button has been positioned. This reduces the additional tunnel length required for button deployment while allowing more of the available socket to be occupied by the graft.
This can be particularly useful when the surgeon is working with a shorter femoral socket.
What Happens to the Graft Over the Following Months?
The fixation device provides immediate mechanical support, but that is only the beginning of the graft’s relationship with the knee.
Over the following months, biological changes take place both within the bone tunnels and within the graft itself.
How the Graft Bonds With the Bone
The healing process differs depending on what sits inside the tunnel.
With a soft-tissue graft, new tissue develops at the interface between tendon and bone before progressively becoming incorporated. A graft containing a bone block undergoes a different bone-to-bone healing process.
These changes take place over weeks and months rather than immediately after surgery. The way a graft incorporates within the bone tunnel also varies according to graft type.
Why Early Rehabilitation Is Kept Controlled
A securely fixed graft still needs time to heal.
Early rehabilitation aims to restore movement, quadriceps function and normal walking without placing inappropriate demands on the reconstruction. Loading is gradually increased as recovery progresses.
Your rehabilitation plan may also differ if another procedure, such as a meniscus repair, was performed at the same time.
Have questions about how your ACL will be reconstructed or which graft and fixation method may be used? Contact us to arrange a consultation.
Common Questions About the Implant
Knowing that a button, screw or another device may remain inside the knee naturally raises questions about what happens to it after the graft has healed.
Whether the Implant Is Ever Removed
ACL fixation implants are generally intended to remain in place and do not routinely need to be removed once healing has occurred.
However, fixation devices come in different materials and designs. Removal may occasionally be considered if an implant causes a specific problem or as part of another operation.
Your surgeon can tell you exactly which implants have been used in your knee.
Airport Scanners and Metal Detectors
A small metallic fixation implant may sound like something that would cause problems at airport security, but orthopaedic implants do not automatically trigger every metal detector.
Whether a device is detected can depend on its material, size and the security equipment being used. If you are concerned before travelling, ask your surgeon what type of implant you have and whether you need to carry any medical documentation.
Future Scans and Revision Surgery
Having an ACL fixation implant does not automatically prevent you from having future medical imaging.
Magnetic resonance imaging (MRI) compatibility depends on the specific implant and material, so you should tell the radiology team about your previous ACL reconstruction before a scan.
Fixation also matters if revision ACL surgery is required. Your surgeon will assess the existing tunnels, graft and implants when planning the revision and decide whether previous hardware needs to be removed or can remain in place.
Book an ACL Graft Assessment in Singapore
How an ACL graft is secured depends on the graft, your knee anatomy and the reconstruction technique being used. Adjustable loops are one fixation option, but the implant is only one part of a successful reconstruction.
At Alps Orthopaedic Centre, we can assess your ACL injury and discuss ACL surgery in Singapore, including graft selection, fixation and what to expect during rehabilitation.
