Issue: November 2021
Source: Choi S-H, et al. Knee Surgery, Sport Traumatol Arthrosc. 2012;doi:10.1007/s00167-011-1794-4.
Disclosures: Larson reports being a consultant for Smith & Nephew and Responsive Arthroscopy and being a shareholder for Responsive Arthroscopy. Dean and Stone McGaver report no relevant financial disclosures.
November 16, 2021
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ACL reconstruction, lateral meniscus root repair technique used in a professional athlete

Issue: November 2021
Source: Choi S-H, et al. Knee Surgery, Sport Traumatol Arthrosc. 2012;doi:10.1007/s00167-011-1794-4.
Disclosures: Larson reports being a consultant for Smith & Nephew and Responsive Arthroscopy and being a shareholder for Responsive Arthroscopy. Dean and Stone McGaver report no relevant financial disclosures.
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A 20-year-old female professional soccer player presented after a noncontact injury during a soccer scrimmage. Examination demonstrated a high-grade Lachman test, a large effusion and an otherwise stable knee.

In cases of ACL deficiency, the posterior root of the lateral meniscus has a significant contribution to lateral compartment joint reactive forces and secondarily controlling anterolateral rotatory instability (ALRI). Therefore, in patients with severely unstable Lachman results and/or higher-grade pivot shifts, concomitant high-grade lateral meniscus injury/root deficiency should be suspected. In a 2021 study, B. Vial and colleagues found 7.1% of primary ACL tears and nearly 40% of revision ACL tears have concomitant lateral posterior meniscal root tears. The patient’s MRI demonstrated an ACL tear with increased signal intensity near the lateral root and a “ghost sign” on sagittal images. The sensitivity and specificity of a “ghost sign,” when the meniscus is not visible posteriorly on sagittal images, for meniscal root tears are reported by S-H Choi and colleagues to be 96.7% and 96.7%, respectively. However, only 33% of lateral root tears diagnosed arthroscopically are originally identified on preoperative MRI according to a study by Aaron J. Krych, MD, and colleagues.

Surgical rationale

A 2014 study by Christopher M. LaPrade, MD, and colleagues showed that tears and avulsions near the lateral root significantly increase contact pressures in the lateral compartment and that these contact pressures can be significantly improved with trans-tibial suture repair. Restoration of lateral meniscal root integrity is also important to help control ALRI, protecting the ACL graft from excessive forces during recovery and return to sports. Moreover, a recent analysis by Scott C. Faucett, MD, and colleagues determined that root repair was associated with a superior quality of life and less cost to the health care system 10 years after the intervention compared with either partial meniscectomy or nonoperative management. When the decision is made to repair the root, it is essential to repair the meniscal root back to an anatomical location, as studies have shown nonanatomic repair positions do not restore the native biomechanics. The root attachment site is 1.5 mm posterior and 4.2 mm medial to the lateral tibial eminence; it is also 4.3 mm medial to the lateral cartilage inflection point and 12.7 mm anterior to the proximal aspect of the PCL attachment site, according to research by A.M. Johannsen and colleagues.

Additionally, several transtibial suture repair techniques have been described using either one or two transtibial tunnels with two or three simple mattress or “luggage tag” nonabsorbable sutures tied over a button, screw and washer or a footprint anchor. Biomechanical evidence in a 2015 study by LaPrade and colleagues suggests that either single-tunnel or two-tunnel techniques can be effective at restoring an anatomical position for the lateral meniscus root.

Surgical technique

Examination under anesthesia confirmed high-grade Lachman and pivot shift tests. There was no significant hypermobility or other ligamentous laxity to the PCL, medial collateral ligament/posteromedial corner or posterolateral corner. A midline incision was made and the middle one-third of the patellar tendon with corresponding bone plugs from the patella and tibia were harvested and prepared as a 9-mm diameter graft. Diagnostic arthroscopy confirmed an ACL tear and lateral posterior meniscal root injury with 90% disruption of the root fibers (Figure 1). The ACL remnant was excised and the femoral and tibial ACL footprints were left visible.

Lateral meniscus root tear
Figure 1. Lateral meniscus root tear (checkered arrow) with 90% tearing, a suture passer device (solid arrow) used to pass a monofilament suture through the meniscus and guide pin (striped arrow) placed in the meniscal root footprint are shown.

Source: Christopher M. Larson, MD

We identified the root footprint and curetted down to a healthy bleeding bone surface. The ACL tibial tunnel guide pin was placed in the center of the ACL footprint. A standard “meniscal root guide” aimer was used to place two guide pins that included an outer metal sleeve (2.8 mm) at the lateral meniscus root footprint (Figure 2). These pins were placed from the lateral proximal tibia, rather than medially, to avoid convergence with the ACL tibial tunnel. We used a suture passer to pass two monofilament sutures through the meniscus root within 10 mm to 12 mm of the root and exchanged these with two #2 nonabsorbable suture tapes in a “luggage tag” fashion (Figure 3). Staying at least 5 mm to 6 mm from the root edge can be helpful to capture more healthy, durable meniscal tissue for the repair. The ACL tibial tunnel was drilled with a 9-mm reamer prior to passing the sutures down the lateral meniscal root tunnels to avoid inadvertent transection of the lateral root pullout sutures. Alternatively, the ACL tibial tunnel can be drilled prior to placing the lateral root guide pin/pins and the arthroscope can be placed up the ACL tibial tunnel to verify that the pins are not visible when drilling.

Guide pins placed in the lateral meniscus root
Figure 2. Guide pins placed in the lateral meniscus root footprint (arrow) are shown.
Two #2 nonabsorbable suture tapes placed in a “luggage tag” fashion
Figure 3. Two #2 nonabsorbable suture tapes placed in a “luggage tag” fashion through the meniscus root is shown.

The inner root tunnel guide pins were removed and one limb of each suture was passed down each of the metal sheaths using a monofilament suture. The metal sheaths were removed and the sutures were tied over the tibia using an endobutton (Figure 4) with the knee in 70° to 90° flexion while directly visualizing the meniscus and meniscal reduction (Figures 5 and 6). If the construct has some laxity after securing the sutures and is not fully reduced, these sutures can be placed through a distal footprint anchor and tensioned further. Care should be taken to avoid over-tensioning the meniscus, which could increase the risk for failure as higher degrees of postoperative flexion are obtained postoperatively. The ACL femoral tunnel is drilled with the surgeon’s preferred technique in the center of the femoral ACL footprint (low anteromedial portal or, alternatively, two-incision rear entry technique). The ACL graft is passed and secured with appropriate fixation. We prefer a rear entry guide while visualizing the femoral ACL footprint via the anteromedial portal. The graft is passed and secured with a metal interference screw on the femur. The graft is cycled, tensioned and secured with another metal interference screw in the tibial tunnel with the knee in full extension. Impingement-free motion and good ACL stability was confirmed.

final intraoperative radiograph after ACLR and meniscus root repair
Figure 4. A final intraoperative radiograph after ACLR and meniscus root repair tied over an endobutton on the lateral tibia (arrow) is shown.
Meniscal root sutures after passage down the root tunnels prior to tensioning
Figure 5. Meniscal root sutures after passage down the root tunnels prior to tensioning are shown.
Reduction of the lateral meniscus root after the sutures are tied over an endobutton
Figure 6. Reduction of the lateral meniscus root after the sutures are tied over an endobutton on the lateral tibia is shown.

Contraindications to the lateral meniscus root repair include advanced lateral compartment osteoarthritis (Kellgren-Lawrence grade 3 or 4), uncorrected osseous malalignment or the inability of the patient to follow the prescribed rehabilitation program and non-weight-bearing precautions.

Rehabilitation

After the procedure, the patient was placed in a hinged knee brace locked in extension and instructed to remain non-weight-bearing for 6 weeks. Zero degrees to 90° flexion is allowed for the first 2 to 3 weeks and the patient is gradually progressed thereafter. At 6 weeks postoperatively, the patient was allowed partial weight-bearing and progressed to full weight-bearing during the next 2 to 3 weeks. Weight-bearing flexion beyond 70° was restricted for 3 months or longer to protect the root repair, however full passive motion was not limited. Ultimately, the patient returned to unrestricted professional soccer at 9 months postoperatively.

Surgical outcomes

Previous studies have shown surgical outcomes following anatomic lateral posterior meniscus root repair with ACL reconstruction (ACLR) have a significant improvement in subjective patient-reported outcomes compared with preoperative scores based on research by Robert F. LaPrade, MD, and colleagues. A study by Hongwu Zhuo and colleagues evaluated the stability of lateral posterior meniscus root repair using a suture pull-out technique on both second-look arthroscopy and through patient-reported outcome scores at 2 years postoperatively. They reported stable healing in 18/23 knees and lax healing in 5/23 knees in patients who elected to undergo second-look arthroscopy for endobutton removal at a mean of 17 months. They also showed less lateral compartment cartilage degeneration in patients who underwent lateral meniscal root repair. Finally, this study reported that concomitant ACLR was found to positively influence healing of the repaired lateral posterior meniscus root.

Tips and pearls

  • Lateral meniscal root tears are frequently associated with an ACL tear in young athletic patients;
  • MRI can miss lateral meniscal root tears, so a high index of suspicion is required;
  • A more generous notchplasty posteriorly can aid meniscal root visualization, if needed;
  • At least two to three #2 sutures placed 5 mm to 6 mm away from the torn meniscal edge and within 10 mm to 12 mm of the root allows for ideal strength of repair;
  • A lateral tibial entrance point for lateral meniscal root repair tunnel placement helps to avoid convergence with the ACL tibial tunnel;
  • Reaming the ACL tibial tunnel prior to pulling the meniscal root sutures down the tunnel will help avoid inadvertent disruption of the root repair; and
  • Six to 8 weeks of strict non-weight-bearing is critical to optimize root healing potential.