Diagnosis of Concomitant Posterior Lateral Meniscus Root Tears in Anterior Cruciate Ligament−Related Radial Lateral Meniscal Injuries: The “2R” Lesion

Abstract

Avulsion of the posterior root of the lateral meniscus have been commonly Technical Note since they are biomechanically equivalent to complete meniscectomies. The technique we describe in this study consists of identifying a posterior root tear of the lateral meniscus after detecting a radial tear in the body segment of that same meniscus. By having such a systematic approach, we ensure that posterior root lateral meniscus tears associated with meniscal body radial tears are not missed in anterior cruciate ligament−deficient patients, enabling appropriate repair and potentially reducing the risk of instability, meniscal extrusion, and early osteoarthritis.

Posterior lateral meniscal root tears (PLMRTs) consist of a disruption of the meniscotibial ligament that normally attach the posterior root of the lateral meniscus (PRLM) to the tibial plateau.¹ More prevalent after a traumatic event, they have been frequently associated with anterior cruciate ligament (ACL) injuries (7%-18% of patients with ACL tears depending on the chronicity of the lesion).1, 2, 3 In fact, they are 10 times more frequent than medial meniscus posterior root tears in patients with a traumatic ACL injury.^1,2,4,5

Because they compromise the ability of the meniscus to transmit the joint loads properly, they are biomechanically equivalent to a total meniscectomy.^2,3 Furthermore, anterior tibial translation and pivoting activities are affected since the PRLM is crucial for maintaining joint stability. It is therefore critical to correctly identify these lesions to avoid instability and cartilage degeneration.^2,4

When a lateral meniscus body partial radial tear was identified on arthroscopy during ACL reconstruction (ACLR), we often found a PLMRT, regardless of what was mentioned on the preoperative magnetic resonance imaging (MRI). We present in this article our surgical technique to a systematic arthroscopic exploration of the lateral meniscus in patients with ACL injuries. The purpose is to identify and repair a PLMRT after finding a radial tear in the body of that meniscus.

Surgical Technique

Every ACLR in Mérignac-center is completed by using a 4-strand semitendinosus graft, with or without an antero-lateral ligament reconstruction using a 2-strand Gracilis tendon graft. The ACL graft is fixed both at the femur and the tibia with cortical adjustable suture button PULLUP (SBM, Lourdes, France) as per Colombet and Graveleau.⁶ Right after drilling the tibial tunnel (outside-in technique), and just before completing the femoral tunnel, we proceed with a systematic check of both menisci. For the lateral meniscus, the limb of the patient is placed in a figure-of-four position.

We systematically start by checking the body of the lateral meniscus (Video 1). Whenever we find a radial tear (Fig 1), we systematically have a high index of suspicion of finding an associated PLMRT. The latter is confirmed by a positive lift-off sign on probing, revealing the disruption of the root fibers^7,8 (Fig 2). To best visualize the PRLM, we place the arthroscope via the antero-lateral portal, and variate the flexion of the knee at different angles.⁷ One should always remember the anatomy of the PRLM’s footprint, positioned anteriorly to the insertion of the posterior horn of the medial meniscus, medially to the articular margin of the lateral tibial plateau, and posterior to the tibial insertion of the ACL.¹ For an even better visualization, we advise to switch the camera from the anterolateral to the anteromedial portal. Even though we systematically confirm the integrity of the meniscofemoral ligaments, we always proceed with reinsertion of the PRLM independently of the meniscofemoral ligaments’ findings, which varies across other practices.¹

Fig 1.

Arthroscopic view (from anterolateral portal) of the lateral meniscus in a left knee showing the radial tear in the body segment (black arrow). During an anterior cruciate ligament reconstruction, whenever in front of such a lesion, it is crucial to properly inspect the posterior root of the lateral meniscus. a. lateral femoral condyle, b. lateral tibial plateau, c. lateral meniscus.

Fig 2.

Arthroscopic view (from anterolateral portal) of the lateral meniscus in a left knee showing a positive lift-off test which confirms the posterior root avulsion of the lateral meniscus. (A) Before pulling with the probe on the posterior root. (B) After pulling with the probe on the posterior root. After seeing the radial tear in the body of the lateral meniscus, it is paramount to switch the 30° viewing-scope from anterior to posterior, and place a probe under the root of the lateral meniscus. By pulling upwards (hook test), we evaluate the integrity of the meniscotibial ligament. If they are not intact, we can confirm the avulsion of the posterior root of the lateral meniscus a. lateral femoral condyle, b. lateral tibial plateau, c. posterior root of lateral meniscus, d. probe.

The PLMRT is either an oblique split within 1 cm from the root insertion (Fig 3), or a complete root avulsion (Fig 2). The technique of repair varies depending on the injury pattern. We perform a side-to-side repair technique using 2 anchor sutures (SBM) for PLMRT with oblique patterns.¹ However, if the root is completely avulsed, we proceed with a trans-osseus tibial reinsertion of the root into the ACL tibial tunnel, as Hercé et al.³ previously described (Fig 4). Finally, the radial tear of the lateral meniscus body is levelled by performing a partial meniscectomy.

Fig 3.

The lesion on the posterior root can also have an oblique tear pattern, which is shown on this arthroscopic view (from anterolateral portal) of the lateral meniscus in a left knee (black arrow). a. lateral femoral condyle, b. lateral tibial plateau, c. posterior root of the lateral meniscus.

Fig 4.

Once the posterior root avulsion is confirmed, we proceed with its reinsertion like shown on this arthroscopic view (from anterolateral portal) of the lateral meniscus in a left knee with 2 FiberWires (Arthrex). a. lateral femoral condyle, b. lateral tibial plateau, c. posterior root of the lateral meniscus, d. FiberWire.

Tricks and pitfalls are cited in Table 1. The postoperative protocol consists of partial weight-bearing for 45 days with 2 crutches, and limitation of knee flexion to 90° for the first 6 weeks postoperatively. Pivot contact sports are prohibited for at least 6 months.

Table 1.

Surgical Steps, Tricks, and Pitfalls

Surgical Steps	Pearls	Pitfalls
Check the body of the lateral meniscus: confirm the partial radial tear	Switching of portals to visualize the PRLM from the anteromedial portal	Difficulty of encompassing the whole meniscus in a single visualization through the arthroscope
Probe the root and inspect the meniscotibial attachment	Figure-of-four position while variating knee flexion	Tighter lateral compartment with no possibility to pie-crust the LCL
If oblique lesion, repair with suture anchors. If root avulsion, proceed with transosseus tibial reinsertion	Probe the PRLM to assess for a lift-off sign

LCL, lateral collateral ligament; PRLM, posterior root of the lateral meniscus.

Discussion

This article highlights the importance of a thorough systematic arthroscopic inspection of the posterior meniscal root whenever a radial tear of the lateral meniscus body is found during an ACLR. This inter-relationship should be an alerting sign to go probe the PRLM to not miss a lesion of the meniscotibial attachment.

Because these tears lead to anterior laxity and possible meniscal extrusion, they compromise the convergence of the axial loads into the radial tangential stresses, or hoop stresses.^8,9 This pushes us to always repair a PLMRT, whether anchoring the meniscus to the tibial plateau, or by repairing it with simple anchor sutures to the remaining attached meniscal root.^1,2,8,10 We believe that this should be done regardless of the presence or absence of a rupture of the meniscofemoral ligaments.

We acknowledge that MRI is the imaging modality of choice to diagnose PLMRTs.^1,2 The so-called “ghost sign” on sagittal T2 sequences showcases the absence of a normal dark meniscal sign, and is a direct sign of a PLMRT.^1,2,4 The vertical linear tear termed “cleft sign” on coronal T2 sequences also constitute a direct sign of a PLMRT, whereas parameniscal cysts, subchondral bone marrow edema, and meniscal extrusion of more than 3 mm are all indirect signs of a PLMRT.^2,11 Nevertheless, MRI still has a 69% sensitivity and 88% specificity of diagnosing an arthroscopically confirmed PLMRT.⁷ This is related only to the diagnosis of avulsed posterior roots, which emphasizes the importance of a thorough systematic arthroscopic evaluation of the PRLM during an ACLR.

In our center, we opt for a transtibial pullout repair technique as described by Hercé et al.³ for PLMRTs. The end goal is to restore meniscus stability and knee kinematics, which is why a transtibial pullout repair technique is considered the gold standard.² Leyes et al.¹² described their technique to repair a PLMRT during a concomitant ACLR by placing a suture anchor on the lateral meniscus root footprint through the outside-in ACL femoral tunnel. By doing so, they avoid complications such as chondral iatrogenic damage and tunnel coalescence. We prefer to adopt the technique described by Hercé et al. as it confers an anatomic reduction by creating a bony groove between the tibia and the meniscal root that increases the likelihood of healing. This technique also avoids tibial tunnel coalition and avoids additional implants since the sutures that are passed through the PRLM are tied directly on the tibial suspensory cortical plate of the ACLR.

In a systematic review and meta-analysis published by Wu et al.¹³ in 2022, many risk factors for PLMRTs have been described such as age <30 years old, male gender, greater body mass index, greater lateral posterior tibial slope, deep sulcus sign, bone bruises on lateral femoral condyle, lateral meniscal extrusion, medial meniscal tears, and medial RAMP lesions. There was no mention of a concomitant PLMRT with a radial tear of the lateral meniscus body. We believe that this finding could be attributed to the torsional energy that goes through the lateral meniscus during an ACL injury, with an entry point at the meniscal body that translates into a radial tear, and an exit point at the posterior root with subsequent avulsion. More biomechanical studies should be conducted to verify this inter-relationship.

The main advantages of our technique (Table 2) are the improved detection of previously undiagnosed posterior root tears, the standardization of meniscal assessment in ACL surgeries, which therefore conveys a better correlation between MRI and arthroscopic findings and helps refining the diagnostic protocols. In contrast, this technique could increase surgical time, with a potential of overtreatment of a minimally relevant root tear that might lead to an unnecessary intervention. This could increase equipment and costs. Furthermore, the weight-bearing restrictions will prolong the postoperative rehabilitation compared with an isolated ACLR. Nevertheless, we believe the advantages of this technique outweigh the disadvantages, particularly in preventing missed diagnoses and optimizing treatment strategies.

Table 2.

Advantages and Disadvantages

Advantages	Disadvantages
Improved detection of hidden PRLMTs	Relative increased surgical time
Standardization of meniscal assessment	Potential for overtreatment in minimally relevant root tears
Better correlation between MRI and arthroscopy	Increased technical demands and costs
	Altered postoperative rehabilitation

MRI, magnetic resonance imaging; PRLMT, posterior lateral meniscal root tear.

A limitation in our technique is the variability of the arthroscopic diagnosis. Because the detection of the PLMRT depends on the surgeon’s expertise and technique, an interobserver variability is introduced. Moreover, small or incomplete root tears can still be undetected during the arthroscopy.

Disclosures

All authors (J.T., N.B., A.M., N.G.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Data

Video 1

Systematic arthroscopic evaluation of a posterior lateral meniscal root tear after identifying a body radial tear in an anterior cruciate ligament−deficient patient: surgical technique video applied on a left knee viewed by an anterolateral portal, then switched to a view by an anteromedial portal.