Transtibial Pull-Out Repair of a Chronic Medial Meniscal Posterior Root Tear With All-Suture Knotless Centralization

Abstract

Background:

Medial meniscus posterior root tears (MMPRTs) are a common form of meniscal tear and are increasingly recognized as one of the most detrimental insults to knee health. Root repairs have mainly focused on reestablishing the biomechanics of the medial knee compartment and preventing joint deterioration; however, meniscal extrusion persists even after the best root repairs and remains an independent risk factor for knee degeneration. Furthermore, chronic MMPRTs are more likely to be associated with significant extrusion, chondromalacia, and fibrotic changes, which make successful repair more challenging. Careful meniscal mobilization and centralization can provide consistent, repeatable results.

Indications:

This technique is indicated for patients with chronic MMPRTs, meniscal extrusion of at least 3 mm, minimal arthritic changes, minimal-to-no varus knee alignment, and the ability to be nonweightbearing for 6 weeks postoperatively.

Technique Description:

The following technique demonstrates the senior author's method of repairing a chronic MMPRT in an anatomic fashion using a 2-tunnel transtibial pull-out repair and footbed anchor fixation. An all-outside centralization is performed using 2 all-suture knotless anchors to address meniscal extrusion and reestablish the biomechanics of the meniscotibial ligament by approximating the posteromedial joint capsule with the rim of the tibial plateau.

Results:

By repairing a chronic root tear and addressing meniscal extrusion, the native biomechanics of the medial compartment are restored, and the meniscus's ability to withstand hoop stress is preserved. Centralization has been shown to lead to favorable improvements in patient-reported and functional outcomes during short-term follow-up and may significantly reduce strain on the root repair construct, thereby improving healing of the meniscal root attachment.

Discussion/Conclusion:

We present our preferred technique for augmenting a chronic MMPRT repair with centralization using all-suture knotless anchors. This method mobilizes fibrotic adhesions and reduces the medial meniscus and peripheral capsule to the rim of the tibial plateau. The advantages include eliminating intra-articular knot-related issues, avoiding the need for an additional tibial tunnel—thereby reducing the risk of tunnel coalition—and offering a streamlined, reproducible approach to minimize meniscal extrusion, with favorable short-term outcomes.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

This video will demonstrate the senior author's (J.C.) technique for anatomic transtibial pull-out repair of a chronic medial meniscal (MM) posterior root tear (MMPRT) with all-suture knotless anchor-based centralization.

Background

It is of utmost importance for orthopaedic surgeons to identify and treat MMPRT, as these are among the most common and most morbid forms of meniscal injury. Up to 20% of all MM tears are classified as a root or radial root equivalent tear, suggesting that this pathology is much more common than previously thought. ³ Perhaps one of the most concerning types of meniscal tears, an unrepaired root tear, is biomechanically equivalent to a total meniscectomy. ¹ They accelerate medial compartment degeneration and are notoriously detrimental to overall knee health. ¹ Over 72% of patients with MMPRT treated by meniscectomy convert to total knee arthroplasty after 10 years and have a 96% clinical failure rate, demonstrating grim outcomes if the root attachment is not preserved. ¹¹ Therefore, it is paramount that orthopaedic surgeons have an in-depth understanding of meniscal anatomy, expertise in root repair techniques, and a keen ability to navigate the challenges these surgeries present to preserve the knee.

MMPRTs accompanied by significant meniscal extrusion require special operative consideration. Extrusion is defined as a disassociation of the meniscus and the tibial plateau, where the meniscus is pushed out of the joint space by horizontal loading vectors. Isolated root tears may lead to meniscal extrusion; alternatively, injuries to the peripheral attachments of the meniscus, such as the meniscotibial ligament, can cause significant extrusion. ⁵ Extrusion >3 mm has been identified as an independent risk factor for progression of chondromalacia, osteoarthritis, and varus deformity, and increases the risk of root repair failure.^5,17 Deichsel et al ⁵ performed a human cadaveric knee study that demonstrated a 200% increase in force on the MMPRT repair construct if the meniscotibial and meniscofemoral ligaments were transected, highlighting the importance of addressing extrusion to promote healing of this biomechanically sensitive repair. ⁵

Indications

This article describes the senior author's technique to address a chronic MMPRT associated with significant MM extrusion. Chronic presentations of this pathology follow a more indolent course than acute presentations, and many patients have no specific injury history and present with more concomitant extrusion, scarring, and chondromalacia, and may have associated spontaneous osteonecrosis of the knee or subchondral insufficiency fractures of the knee.

We present a case of a 60-year-old man presenting with right knee pain that began 11 months ago after feeling a pop with deep knee flexion while stepping up and pivoting into his truck. He reports his knee catches. His physical examination demonstrated limited right knee flexion to 120°, a positive McMurray test, medial joint line tenderness, and no signs of ligamentous injury. Radiographs demonstrate mild osteoarthritis. Magnetic resonance imaging (MRI) obtained by the referring physician demonstrated a complex MMPRT, medial tibial plateau bone edema, and a low-grade medial collateral ligament sprain. Notably, he had 3.8 mm of MM extrusion. Given the patient's persistent symptoms and chronicity of his injury, we recommended operative treatment.

Our indications for this technique are a confirmed LaPrade class 2 or 4 MMPRT on MRI, Kellgren-Lawrence grade <2, MM extrusion of ≥3 mm, <5° of varus alignment, and patient ability to be nonweightbearing (NWB) for 6 weeks after surgery. ¹²

Technique Description

The patient was brought to the operating room and placed in the supine position. The ipsilateral thigh was placed into a leg holder, and a nonsterile thigh tourniquet was placed to maintain hemostasis. The contralateral limb was placed in a well-padded stirrup. The patient was prepped and draped in standard sterile fashion.

Anterolateral and anteromedial parapatellar arthroscopic portals were established. A systematic diagnostic arthroscopy revealed a chronic, retracted MMPRT. An arthroscopic grasper was used to assess the posterior horn's mobility, and confirmed scarring of the extruded MM to the posteromedial synovial capsule.

Curved arthroscopic scissors were introduced through the anteromedial portal to release the adhesions along the posterior meniscocapsular junction and the deep portion of the meniscotibial ligament. The dissection was carefully directed along the peripheral margin of the posterior horn to the junction with the meniscal body to fully mobilize the meniscus without damaging the adjacent cartilage or capsule. An arthroscopic grasper confirmed the reducibility of the meniscus. An arthroscopic shaver was then used to remove remaining fibrotic tissue.

The root bed is prepared using a curved ring curette (Meniscal Root Repair System; Smith & Nephew) and an arthroscopic shaver to expose bleeding subchondral bone. This preparation is essential for promoting biological healing by enhancing the vascular interface between the root and tibial bone.

An incision is made over the anteromedial tibia for the transtibial pullout repair. A low-profile, root-specific aiming guide is introduced through the anteromedial portal and positioned at the native root attachment site. A 2.7-mm cannulated sheath with a 2.4-mm guide pin was drilled through the aiming guide at 55° until arthroscopically visualized at the root's anatomic footprint, establishing the first tibial tunnel. This should be flush with the tibial plateau, leaving space for suture placement later. The aiming guide and guide pin were removed, leaving the cannulated sheath in place for suture passage. An offset guide was introduced over the sheath, and a second tunnel was created 5 mm anterior to the first tunnel in a similar fashion.

An arthroscopic cannula (6 mm × 7 cm, Twist-In Cannula; Arthrex) was placed into the anteromedial portal to allow insertion of an arthroscopic suture passer (FirstPass Mini; Smith & Nephew). A No. 2 polyethylene fiber suture (UltraBraid; Smith & Nephew) was passed through the posterior portion of the detached root from the tibial to the femoral side and was then shuttled through the posterior tibial cannula using a nitinol looped passing wire. A second suture was placed at the mid-portion of the detached root anterior to the first in a luggage-tag configuration to capture the radial fibers of the meniscus. It was then shuttled down the anterior tibial cannula. The drill guide and cannulas were removed.

Attention was then turned to address the MM extrusion. A medial accessory portal was created just posterior to the medial collateral ligament (MCL). A curved drill guide and 1.8-mm bit are placed through this portal, and a pilot hole is created through the capsule at the meniscocapsular junction, under the meniscus, and into the rim of the medial tibial plateau (MTP) at the posterior aspect of the meniscal mid-body, immediately posterior to the MCL. A 1.8-mm all-suture knotless anchor (1.8 mm Q-Fix Knotless; Smith & Nephew) was deployed into this pilot hole. In the same fashion, a second anchor was placed in the MTP 1.5 cm posterior to the first to centralize the posterior horn. It is important to maintain the purchase of the drill guide on the MTP rim with forward pressure and to quickly place the Q Fix anchor so proper orientation is not lost. The sutures were crisscrossed and secured outside the capsule in a knotless fashion, creating a suture staple construct that anchors the medial joint capsule to the MTP rim, reestablishing the effect of the meniscotibial ligament and reducing MM extrusion. Native MM mobility within the joint is maintained by anchoring only the capsule to the MTP; thus, surgeons should be careful to avoid capturing the meniscus with the anchor during placement.

After centralization and with the knee flexed to 90°, the 4 suture tag ends were passed through a biocomposite anchor (Footprint Suture Anchor; Smith & Nephew) and fixed to the anteromedial tibia in a footprint style. The detached MM posterior root was anatomically reduced to the prepared footprint under direct arthroscopic visualization. Tension was applied to the sutures sequentially to achieve full contact with the tibial plateau. The anchor device was removed.

Finally, an arthroscopic probe was used to verify adequate repair of the MMPRT, confirming that the MM was fully centralized within the MTP rim.

Postoperatively, patients should be placed in a hinged knee brace locked in extension and should be made NWB. NWB is mandatory, as any weightbearing demonstrates unrecoverable biomechanical loosening of the repair construct, causing deleterious effects on the repair and predisposing the patient to failure. ¹⁵ They are allowed to passively range the knee from 0° to 90°, with a focus on achieving full extension. Patients should avoid squatting and hamstring contraction as the semimembranosus attaches to the posteromedial joint capsule and moves the meniscus posteriorly. At 6 weeks, the brace is gradually unlocked, and the patient can be weaned from crutches; they may work toward 120° of active flexion, aiming for full range of motion by 10 weeks postoperatively. After 12 weeks, gradual closed-chain quadriceps and hamstring strengthening can begin, and patients can gradually increase squat depth. A medial unloader brace may be used during strengthening sessions. Once patients are 6 months out from surgery, they can work on further strengthening to meet their lifestyle goals.

Results and Discussion

Repairing MMPRTs is the gold standard for properly selected patients and results in improved patient-reported outcomes, knee biomechanics, and delays osteoarthritis progression. ¹⁴ However, there is no consensus on which technique is best and whether a 2-tunnel or single-tunnel transtibial pull-out technique is better.^4,13,18 Both tunnel approaches demonstrate equal displacement upon axial joint loading and equal load to failure. However, with a 2-tunnel technique, it is expected that more of the MM root can be reduced to the native footprint, allowing for more robust healing. ¹³ Healing of MMPRTs remains one of the most challenging aspects of a repair, and patients with partial healing and associated persistent extrusion go on to have significant cartilage degeneration after 2 years of follow-up.^6,7,9 This stresses the importance of a nuanced approach to not only repairing the root, but treating each patient's concomitant pathologies so they have the best chance of knee preservation.

Studies have found that meniscal extrusion independently degrades the knee and persists even after the best MMPRT repairs in certain patients, making it clear that we must do more to understand and treat extrusion when present.^6,14,16 According to Thamrongskulsiri et al, ¹⁶ repairs performed without a centralization technique showed only a minimal reduction in extrusion, from 4.1 ± 0.8 mm preoperatively to 3.6 ± 0.9 mm postoperatively. ¹⁶ In chronic cases, the extruded meniscus and surrounding capsule may become adherent to the tibial plateau, positioned peripheral to the native meniscal margin, causing fibrous resistance to reduction. Centralization is used to reposition the meniscus into the joint and further reduces postoperative extrusion compared with repair alone.^2,16 Boksh et al ² reported a recent 2025 systematic review and meta-analysis evaluating the effects of meniscal centralization on meniscal extrusion, joint biomechanics, and clinical outcomes. The review included 15 studies, comprising biomechanical tests on cadaveric and animal knees and clinical studies involving 158 patients. Biomechanical findings demonstrated that centralization significantly reduced meniscal extrusion and contact pressure while improving contact area, thereby restoring joint mechanics closer to the native state. ² Clinically, meniscal centralization resulted in significant improvements in patient-reported outcomes, such as the Knee injury and Osteoarthritis Outcomes Score and Lysholm scores, and it maintained extrusion reduction over time while preserving knee motion. ² Meniscal centralization performed here in the senior author's technique aims to mitigate the likelihood of residual extrusion after surgery, reducing strain on the MMPRT repair construct and improving medial compartment biomechanics.

Other authors have created similar techniques utilizing suture anchors. Koga et al ⁸ previously introduced a centralization technique for the MM, performed in conjunction with MMPRT repair using all-suture anchors and intra-articular knot tying. ⁸ While this technique effectively reduces MM extrusion, even as an isolated procedure, intra-articular knot tying is technically difficult and may limit native meniscal motion while ranging the knee. On the other hand, the Krych et al ¹⁰ technique employs a similar centralization technique with repair of the meniscotibial ligament. However, this is performed in an all-inside fashion and relies on a pulley configuration to reduce extrusion. Similar to our presented technique, this anchors only the joint capsule, not the meniscus itself, allowing native motion. Our technique improves upon this by requiring fewer steps and avoiding intra-articular suture complications. Future research should focus on evaluating biomechanical outcomes of various centralization techniques to determine which is most effective.

In this video, we present our preferred technique for augmenting a chronic MMPRT repair with centralization using all-suture knotless anchors. This method mobilizes fibrotic adhesions and reduces the MM and peripheral capsule to the rim of the tibial plateau. The advantages include eliminating intra-articular knot-related issues and avoiding the need for an additional tibial tunnel—thereby reducing the risk of tunnel coalition—and offering a streamlined, reproducible approach to minimize meniscal extrusion, with favorable short-term outcomes.