When the anterior cruciate ligament (ACL) graft tears again and revision reconstruction is needed, some patients can complete treatment in one operation, while others need bone grafting first and a second operation several months later.

These two approaches are called one-stage revision and two-stage revision. The choice mainly depends on the bone tunnels left by the first operation, the extent of bone loss, knee stability, and the presence of other factors that increase the risk of another failure.

In patients who meet specific criteria, one-stage revision can provide short- to mid-term functional recovery similar to two-stage revision while reducing the total operative time and treatment cost.

During primary ACL reconstruction, the surgeon creates tunnels in the femur and tibia, passes the graft used to reconstruct the ligament through these tunnels, and secures it.

If the graft later tears again, revision reconstruction involves more than placing a new ligament. The tunnels from the first operation remain and may be poorly positioned, widened, or associated with bone loss. Each of these problems can affect whether the new graft can be fixed in the correct position.

One-stage revision completes the revision reconstruction in a single operation. During the same procedure, the surgeon manages the previous tunnels and failed graft, creates suitable new tunnels, and then performs the new ACL reconstruction.

Two-stage revision requires two phases. The first mainly addresses the old tunnels and bone defects with bone grafting. After the bone graft has healed, ACL reconstruction is performed in a second stage.

Whether treatment can be completed in one stage therefore depends on whether the knee meets the necessary surgical conditions.

After the first ACL reconstruction, tunnels are already present in the femur and tibia. If these tunnels have widened substantially or a large bone defect has formed, secure fixation of a new graft may be difficult.

Placement and fixation of a new tunnel can also be compromised if the old tunnel substantially overlaps the ideal new tunnel.

In this situation, the surgeon may first clear residual tissue and fixation material from the old tunnels and then repair the bone defects with bone graft.

With a staged treatment plan, the first stage uses bone from the patient’s own iliac crest to fill the previous femoral and tibial tunnels. After approximately 6–12 months, CT is used to determine whether the bone graft has healed satisfactorily. The second-stage ACL reconstruction is performed only after suitable tunnel conditions have been confirmed.

This approach requires a longer treatment period, but it can restore a stronger bony foundation for the new ligament reconstruction.

Suitability for one-stage revision must be determined through preoperative imaging and a comprehensive assessment of the knee.

A clinical series compared one-stage and two-stage treatment in patients with graft retear after ACL reconstruction. The 31 patients ultimately included had undergone relatively strict selection. They were 16–45 years old, and preoperative three-dimensional CT showed that femoral tunnel widening did not exceed 12 mm.

These patients also had no marked lower-limb malalignment, posterior tibial slope greater than 12°, severe generalized joint laxity, high-grade pivot shift, or severe osteoporosis. Patients with multiligament injuries requiring simultaneous treatment or more severe cartilage damage were also excluded.

One-stage revision may therefore be considered for selected patients whose previous tunnels have only limited widening and who have no clear factors that increase the risk of another failure.

Standard MRI can show soft tissues such as the ACL graft, menisci, and cartilage, but revision surgery also requires a clear understanding of the bone tunnels left by the first operation.

Three-dimensional CT helps the surgeon assess tunnel diameter, position, and direction and analyze the relationship between the previous femoral tunnel and the ideal reconstruction position.

Femoral tunnels can be divided into three categories:

Among the 31 patients described above, 12 underwent one-stage revision and 19 underwent two-stage revision. Mean follow-up for all patients was approximately 28.5 months.

Knee function improved substantially in both groups after treatment.

At 1 and 2 years after surgery, comparisons using commonly applied knee function scores, including KOOS, Lysholm, and IKDC, found no statistically significant differences between the groups. Knee stability testing at 2 years also showed no clear between-group difference.

MRI at 2 years showed no graft retear in either group.

These results indicate that among carefully selected patients with limited tunnel widening and without the relevant high-risk factors, knee function at around two years is similar after one-stage and two-stage revision.

The two methods cannot be treated as freely interchangeable. One-stage revision is an option only when the patient has the conditions required to complete reconstruction in a single operation.

In this group of patients undergoing one-stage revision, all had received an autologous hamstring tendon graft during their first ACL reconstruction. The revision reconstruction used an autologous quadriceps tendon–bone graft.

The surgeon uses three-dimensional CT to determine the position of the previous femoral tunnel and then decides whether to reuse, adjust, or recreate the tunnel.

On the tibial side, a new anterolateral tunnel is created while the previous anteromedial tunnel is preserved. The new quadriceps tendon–bone graft is passed into the tunnels and secured, after which the surgeon checks for graft impingement as the knee moves through flexion and extension.

This operation requires demanding preoperative planning and tunnel management, so it is not suitable for every patient with an ACL graft retear.

During the first stage, a new ACL reconstruction is temporarily deferred. The surgeon removes the failed ACL graft, manages the previous femoral and tibial tunnels, and harvests the patient’s own iliac crest bone to shape suitable bone blocks that fill the old tunnels.

The implanted bone then needs time to heal. CT is repeated after approximately 6–12 months. If tunnel graft healing meets the required standard, the second-stage operation is performed. New femoral and tibial tunnels are created, and ACL reconstruction is completed using an autologous hamstring tendon graft from the opposite leg.

After an ACL graft retear, MRI, X-rays, and three-dimensional CT can be used to reassess the knee.

When discussing treatment with the surgeon, patients can ask whether the previous femoral and tibial tunnels are positioned appropriately, how much they have widened, whether there is substantial bone loss, whether a new tunnel can avoid the old tunnel, and whether there are problems involving the menisci, cartilage, other ligaments, or lower-limb alignment.

If tunnel conditions are suitable and there are no clear factors that increase the risk of another failure, one-stage revision may avoid an additional operation and several months of waiting.

If the tunnels cannot provide secure fixation for a new graft, bone grafting to restore bone stock before ACL reconstruction may be the more appropriate choice.