Abstract
Background:
The posteromedial meniscal root is a critical structure in maintaining balanced tibiofemoral contact stresses and joint stability. Studies have shown that posterior root tears are biomechanically equivalent to total meniscectomy and can lead to the rapid development of osteoarthritis. Our presentation focuses on the less common, acute, traumatic posteromedial meniscal root avulsion, although our technique is also applicable to the more common degenerative posteromedial meniscal root tears.
Indications:
Surgical indications include acute tears, as well as chronic or degenerative tears in patients without advanced osteoarthritis. Absolute surgical contraindications include subchondral bone collapse, substantial concurrent meniscal pathology, malalignment of >5°, and advanced knee osteoarthritis.
Technique Description:
Once the tear is identified, the bone at the root insertion is prepared with a meniscal rasp. Two looped sutures are passed through the meniscal root in a cinch-type fashion using a knee scorpion. A tunnel is drilled at the root insertion using a specialized meniscal root repair guide. Approximately, 10 mm of bone are drilled in a retrograde fashion with a flip cutter deployed to 7 mm to decorticate the bone and enhance healing. The drill is then removed and a rubber tube with a retrieval suture is advanced through the drill guide into the joint. The loop suture is retrieved through the anteromedial portal and the repair sutures are passed through the retrieval loop. Under arthroscopic visualization, the root is then reduced to its anatomic insertion and the sutures secured to the tibia using a knotless suture anchor placed 1 cm distal to the transtibial tunnel.
Results:
Several recent studies have shown that meniscal root repair decreases rapid knee degeneration as gauged by meniscal extrusion, progression of Kellgren-Lawrence grade and rate of conversion to total knee arthroplasty (TKA).
Discussion/Conclusion:
Posteromedial meniscal root tears are increasingly being recognized as a distinct meniscal pathology that can lead to rapid arthritis if left unrepaired. Arthroscopic repair techniques continue to improve allowing orthopedic surgeons to more readily address this significant, but treatable pathology.
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.
This is a visual representation of the abstract.
Video Transcript
Arthroscopic transtibial repair of acute posterior medial meniscus root tear presented by Dr James Bradley, clinical professor of Orthopedic Surgery, University of Pittsburgh Medical Center, and head team physician for the Pittsburgh Steelers, along with Michael Nammour, Orthopedic Sports Medicine Fellow.
These are our disclosures.
The posterior meniscal root functions to anchor the posterior meniscal horn to the tibia and provide critical maintenance of proper contact stresses, joint stability, and kinematics. 5 Posterior root tears have a prevalence of 7% to 9% in knee arthroscopy, with two thirds of them being medial root tears.
Posterior meniscal root tears are being increasingly recognized as a cause of early and rapid osteoarthritis development.5,6,8,9 Some studies have also shown that posterior root avulsions are biomechanically equivalent to total meniscectomy. 1 These medial root tears are six times more likely to have articular cartilage defects with a two or greater outerbridge grade. 7 They are usually chronic and degenerative in nature. Also, more than 21% of the population with medial meniscus root tears consists of middle aged women. 8 Lateral root tears, on the other hand, tend to be acute in nature and are 10 times more likely to be associated with an anterior cruciate ligament (ACL) tear. 7
Regarding anatomy and biomechanics, the meniscal roots convert and disperse axial tibiofemoral loads as hoop stresses. This is critical to meniscal function, as 50% to 70% of medial and lateral compartment loads are absorbed by the meniscus. Therefore, disruption of the meniscal root leads to loss of hoop stresses which in turn leaves the articular cartilage exposed to supraphysiologic loads. This leads to increased peak contact pressures, which are nearly equal to those contact pressures experienced by the joint after a total meniscectomy. 1
Typically traumatic tears occur in young active patients are usually lateral and have associated ligamentous injuries, such as an ACL tear. They also tend to be true avulsions. Degenerative tears, on the other hand, are usually medial and account for 70% of posterior root tears. 5 These tears occur due to chronic low energy attritional mechanisms, such as standing from a deep seated position. 8 They also usually present as full-thickness radial tears near the root junction.
On physical examination patients with posterior root tears may present with posterior knee pain, 8 joint line tenderness, 4 pain with full knee flexion, 4 and a positive McMurray tests. 4 Also, pain with varus stress and full extension may be indicative of a posterior root avulsion. 10 Of note, typical meniscal symptoms, such as catching, locking and giving way are less common in these patients.5,8
Typical workup for these patients includes a complete set of knee radiographs including long-standing films to evaluate alignment and a magnetic resonance imaging (MRI). On MRI evaluation, T2 images are the best sequences for the diagnosis of posterior root tears. 5 When evaluating, look for radial tears at the meniscal root, or the absence of meniscal signal in the sagittal plane, which is also known as a ghost sign, as well as for meniscal extrusion. In addition, coronal oblique images can be helpful in tracing the meniscus to its root.
Surgical indications for posterior root tears include acute tears, chronic or degenerative tears without substantial confirmed meniscal pathology, or tears in active patients without advanced osteoarthritis. 5 The absolute surgical contraindications include subchondral bone collapse, substantial concurrent meniscal pathology, malalignment >5°, and Kellgren-Lawrence Grade 3 to 4 changes. Relative contraindications include a body mass index (BMI) >30 or malalignment <5° as these can lead to increased stresses on the repair construct. In cases with significant malalignment, an osteotomy can be performed to correct the alignment and meniscal root repair can be performed after the alignment correction.
For our case, we will discuss a 20-year-old male football player who sustained a tackle to his right knee during a game. He experienced a pop during the injury, and he has pain and swelling as well as difficulty with weight bearing. His past medical history is significant for asthma. On physical examination, he has an antalgic gait and a decreased range of motion of his right knee compared with his unaffected left knee. He has quadriceps atrophy as well as an effusion. He has medial joint line tenderness and a positive McMurray test.
On ligamentous examination, he has a 1A Lachman and negative pivot shift and negative anterior and posterior drawer tests. He does have a Grade 2 opening to valgus stress at 30° and a negative varus stress. He is neurovascularly intact. Radiographs of the right knee are normal, and there is no significant malalignment on long leg films. MRI of the right knee demonstrates a Grade 2 medial collateral ligament (MCL) tear on the tibial attachment as well as a bone bruise pattern consistent with a hyperextension injury. There is a medial meniscus posterior root tear as indicated by the yellow arrow. On the sagittal views, one can see that the ACL is intact. The posterior root is highlighted by the yellow circle. The coronal oblique sequences are also useful in identifying the meniscus root tear as shown by that yellow arrow. This case highlights an uncommon presentation of meniscal root tears as it is an acute posteromedial root tear in a young athlete.
On diagnostic arthroscopy, the medial meniscus posterior root tear is identified and probed. In this case, visualization is easier due to the concurrent MCL injury. If there is inadequate visualization then pie crusting of the MCL can be performed. The bone is then prepared for repair with a meniscal rasp. A grasper is then used to test the mobility and reduction of the meniscal root.
To assist in the repair, a portal cannula is inserted into the anteromedial portal. We prefer to use a meniscal repair guide to aid in our tunnel placement given that it has a hook that helps the stability of the guide and its curve allows for appropriate visualization. The markings also allow the guide to be adjusted for anatomic pin placement. We then pass 2 loop sutures with a suture passing device. This technique is advantageous, in that, it requires only a single pass and research has shown that this suture configuration has increased pullout strength compared with simple sutures.
The tibial tunnel is then drilled with a flip cutting drill, and the guide is then removed. The flip cutting drill is then carefully inserted into the joint with enough clearance for the cutter to deploy. One can see that the tunnel is at the root’s anatomic insertion. Once the flip cutter is deployed, approximately 10 mm of bone are drilled in a retrograde fashion. The markings on the drill can be used in conjunction with a guide to gauge drilling length. This step is done to decorticate the bone and enhance healing of the repair. The drill is then carefully removed, and the guide is left in place to not lose the drill hole so that the rubber tube with the sutures can be shuttled transtibially into the joint. The loop suture is then retrieved through the anteromedial portal. The meniscus repair sutures are then passed through the tibial suture loop. The sutures are then shuttled from the tibial tunnel and the posterior root is then reduced to its anatomic location. Here you can see excellent reduction of the posterior root. To finalize the repair, a drill is used for an anchor hole and the sutures are then loaded into an anchor and the anchor is then malleted and screwed into place with the appropriate tension at 30° of knee flexion.
Postoperatively, in the initial 6-week period, the patient is toe touch weight bearing in full extension with the brace. Knee range of motion is limited from 0° to 90°. At 6 weeks, the brace is discontinued and the patient may begin progression to full weight bearing and can have unrestricted knee range of motion when the knee is unloaded. At 3 months, there is a gradual increase in activities. At 4 months, knee loading flexion angles >90° begins. At 4 to 6 months, once normal strength and gait are achieved, the patient may begin gentle sporting activities. 5
Regarding outcomes, studies have shown that for posterior root tears, surgical intervention helps to decrease arthritis progression. A study showed that only 14% of 37 meniscal root repair patients had a 2 unit or greater progression of arthritis on the Kellgren-Lawrence grade. 2
In a follow-up study, only 1% of 91 patients had converted to a TKA after root repair at 7.1 years postoperatively. 3 Another study showed that healing of root tears is associated with decreased meniscal extrusion, whereas incomplete healing can lead to increased extrusion and eventual early osteoarthritis. 4
These are our references.
Thank you for your attention.
Footnotes
Submitted January 3, 2023; accepted March 17, 2023.
One or more of the authors has declared the following potential conflict of interest or source of funding: J.W.A. receives research and educational support from Arthrex, Inc. and is a board or committee member for AOSSM and American Shoulder and Elbow Surgeons. J.P.B. receives royalties from Arthrex, Inc. and DJO and is a board or committee member for AOSSM. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
