Revision Anterior Cruciate Ligament Reconstruction: Management of Femoral Tunnel Malposition

Introduction

Revision anterior cruciate ligament (ACL) surgery represents a salvage procedure, and the patient should be counseled that the outcome is not likely to be as good as a primary procedure. The goal of surgery is to provide a stable pain-free knee joint. Return to sport is another goal, but is less predictable. In many cases, the status of the articular cartilage and meniscus are major factors in determining return to sport. ACL reconstruction is currently the sixth most frequently performed orthopaedic surgical procedure. Although more than 200,000 anterior cruciate ligament reconstructions (ACLRs) are performed annually across the world, the failure rate among experienced surgeons is estimated to be 10%–15%. Identification of anatomical femoral ACL footprint after primary ACLR becomes difficult, thus making revision ACLR extremely challenging. Femoral tunnel placement is a key step in having a stable and well-positioned graft. It must be emphasized that incorrect femoral tunnel placement is one of the main causes of failed ACLR and therefore must be considered when undertaking revision surgery. In one study, anatomic femoral tunnel placement demonstrated a higher graft maturation score on second-look arthroscopy, as well as better clinical outcomes than nonanatomically positioned femoral tunnels. In addition, the Multicenter ACL Revision Study (MARS) group found that femoral tunnel malposition was the main reason for failure in almost 50% of the primary ACL revision cases reviewed. The MARS database identifies technical error as the most common reason for primary ACLR failure and indicates femoral tunnel malposition as the most common technical error. While planning for revision tunnel placement, it is important to consider the “divergent tunnel” concept to approach the anatomical femoral or tibial footprint from several extra-articular orientations.

Preoperative Evaluation and Hardware Management

Preoperatively the surgeon should thoroughly document and assess the details of the previous surgery in regard to the type and location of hardware, as it plays an important role while planning for revision tunnel placement and may interfere with the existing femoral tunnel. Furthermore, evaluation through radiographs (lateral view in maximal extension, 45 degrees posteroanterior weight-bearing radiographs) and computed tomography (CT) scan provide significant information about previous reconstruction procedure, tunnel dimensions, and bone defects (e.g., one can identify sclerotic bone margin surrounding the fixation device). Revision ACLR surgery should also address other involved structures with procedures such as osteotomy of the femur or tibia, meniscal allograft reconstruction, and collateral knee ligament surgery. Finally, preoperative patient education is extremely important prior to a revision procedure and the expectations of the patient should be modified.

It is important that the exact hardware is identified (type and manufacturer) in order to plan and prepare instruments for removal. Metal fixation should be removed only if needed. Biodegradable interference screws (IFS) can be drilled through; however, the debris should be carefully washed out or removed to avoid an inflammatory response. If hardware removal will require excessive bone loss, the preferred approach would be to leave the hardware in place and change the orientation of the tunnel while maintaining an anatomic aperture.

Graft Selection and Graft Fixation

Soft tissue or bone-based allograft substitutes offer a good choice; however, many surgeons’ hands are tied due to lack of availability, socioeconomic barriers, and healthcare policies, which varies across the globe. Results show that use of autografts lead to improved function and reduced risks of graft re-rupture at 2-year follow-up. No differences were noted in re-rupture or patient-reported outcomes between soft tissue and bone–patellar tendon–bone grafts.

Several factors, which include local bone stock, tunnel dimension, and type of graft, play a role in choosing the method of graft fixation. Aperture fixation with bioabsorbable screws can be chosen with bone-based grafts, and extracortical fixation can be opted for with soft tissue–based grafts. A bone–patellar tendon graft with conical press-fit fixation can also serve as a good option due to easy and reproducible technique, and it also offers a biological fixation without implant augmentation. Long-term results using this technique in primary ACLR have shown good functional outcomes, stable knees, and good incorporation of the graft. This technique, with its biological advantages, including low postoperative morbidity and a rapid return to sports, and low cost can be applied in revision ACLR, considering the tunnel dimension and local bone quality favors a press-fit fixation. The technical details of the surgery and postoperative images of ACLR done with a conical press-fit technique are described in Fig. 90.1 .

Femoral Tunnel Management

Femoral tunnel creation is key to revision surgery. In some cases, due to compromised bone, it can be very difficult to create a new femoral socket. In addition, the effectiveness of femoral bone grafting has not been well elucidated in the literature. To stratify and find a solution for tunnel revision, the existing tunnel position can be classified using the conventional radiographs (lateral view in maximal extension, 45 degrees posteroanterior weight-bearing radiographs) as:

• 1.

  Correct: The existing femoral tunnel is placed optimally and can be reused for the revision ACLR.

• 2.

  Completely incorrect: The existing tunnel is placed in a completely incorrect position and the new tunnel can be created without contacting the old tunnel.

• 3.

  Partially acceptable: The existing tunnel communicates with the new correctly placed tunnel, which leads to an enlarged tunnel.

Technical Problems Related to Femoral Tunnel Revision

There are several potential problems related to femoral tunnel revision. These situations are discussed as follows.

• 1.

  Revision after failed single-bundle reconstruction:

  The various situations which can be encountered during revision ACLR after a previous single-bundle reconstruction are discussed in Table 90.1 .

  TABLE 90.1

  Technical Problem and Solutions for Femoral Tunnel Revision After a Failed Single-Bundle Anterior Cruciate Ligament Reconstruction

  	Hardware (Out of the Way)	Hardware (In the Way)	Hardware (Broken or Lose)	Hardware Cannot be Removed
  Tunnel Anterior	New tunnel posterior to previous one	New tunnel posterior to previous one + remove hardware + insert new hardware	New tunnel posterior to previous one + remove hardware + insert new hardware	—
  Tunnel Anatomical	—	New tunnel overlapping the existing one + bone-based graft + aperture fixation	Remove hardware + new tunnel overlapping the existing one + bone-based autograft/allograft + aperture fixation	—
  Tunnel Widened	—	Two stage procedure ( Figs. 90.1 and 90.2 ): 1. Débride and bone graft 2. Revision ACLR after 6 months	Two-stage procedure ( Figs. 90.1 and 90.2 ): 1. Débride and bone graft 2. Revision ACLR after 6 months	—
  New Tunnel Impossible	—	—	—	Over-the-top technique or Divergent tunnel technique

  ACLR, Anterior cruciate ligament reconstruction.

• 2.

  Revision after failed double-bundle reconstruction:

  The various situations which can be encountered during revision ACLR after a previous double-bundle reconstruction are discussed in Table 90.2 .

  TABLE 90.2

  Technical Problem and Solutions for Femoral Tunnel Revision After a Failed Double-Bundle Anterior Cruciate Ligament Reconstruction

  	Correct Position	Incorrect Position
  Both Tunnels	—	Staged procedure: Bone grafting + single-bundle ACLR after 6 months
  Single Tunnel	Tunnel is untouched	Hardware removal + single-bundle ACLR
  Tunnel Wall Breached	Single-bundle ACLR (suspensory or aperture fixation)	Staged procedure: Bone grafting + single-bundle ACLR after 6 months

  ACLR, Anterior cruciate ligament reconstruction.