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Department of Orthopaedic Surgery, Hopital Municipal et Clinique d'Eich, Luxembourg City, LuxembourgSports Medicine Research Laboratory, Luxembourg Institute of Health, Luxembourg City, Luxembourg
Correspondence to Dr Hideyuki Koga, Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University Graduate School of Medical and Dental Sciences, Bunkyo-ku, Tokyo 113-8519, Japan
Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University Graduate School of Medical and Dental Sciences, Bunkyo-ku, Tokyo, Japan
The meniscus is important for load distribution, shock absorption and stability of the knee joint. Meniscus injury or meniscectomy results in decreased function of the meniscus and increased risk of knee osteoarthritis. To preserve the meniscal functions, meniscal repair should be considered as the first option for meniscus injury. Although reoperation rates are higher after meniscal repair compared with arthroscopic partial meniscectomy, long-term follow-up of meniscal repair demonstrated better clinical outcomes and less severe degenerative changes of osteoarthritis compared with partial meniscectomy. In the past, the indication of a meniscal repair was limited both because of technical reasons and due to the localised vascularity of the meniscus. Meanwhile, it spreads today as the development of the concept to preserve the meniscus and the improvement of meniscal repair techniques. Longitudinal vertical tears in the peripheral third are considered the ‘gold standard’ indication in terms of meniscus healing. Techniques for meniscal repair include ‘inside-out’, ‘outside-in’ and ‘all-inside’ strategies. Surgical decision-making depends on the type, size and location of the meniscus injury. Meniscal root tears substantially affect meniscal hoop function and accelerate cartilage degeneration; therefore, meniscus root repair is necessary to prevent the progression of osteoarthritis change. For symptomatic meniscus defects after meniscectomy, transplantation of allograft or collagen meniscus implant may be indicated, and acceptable clinical results have been obtained. Recently, meniscus extrusion has attracted attention due to increased interest in early osteoarthritis. The centralisation techniques have been proposed to reduce the meniscus extrusion by suturing the meniscus-capsule complex to the edge of the tibial plateau. Long-term clinical outcomes of this procedure may change the strategy of treating meniscus extrusion. When malalignment of the lower leg is accompanied with meniscus pathologies, knee osteotomies are a reasonable option to protect the repaired meniscus by unloading the pathological compartment. Advancements in biological augmentation such as bone marrow stimulation, fibrin clot, platelet-rich plasma, stem cell therapy and scaffolds have also expanded the indications for meniscus surgery. In summary, improved repair techniques and biological augmentation have made meniscus repair more appealing to treat that had previously been considered irreparable. However, further research would be necessary to validate the efficacy of these specialised technique.
The menisci have a critical role for shock absorption, lubrication and stability of the knee joint by increasing joint congruity and contact areas on the articular cartilage.
Meniscus injury or meniscectomy decreases meniscal function, followed by the initiation and the development of knee osteoarthritis (OA) in the long-term follow-up.
Therefore, meniscus injury should be treated to preserve as much meniscus function as possible, and ‘saving the meniscus’ is a recent slogan of meniscal surgery.
In addition, the meniscus has a variety of pathologies such as meniscus root tear, meniscus extrusion and meniscus defect after meniscectomy. In this article, a state-of-the-art of the arthroscopic specialised techniques for complex meniscal tear repairs has been provided.
Meniscus anatomy
The meniscus is a crescent-shaped fibrocartilage located between the femoral condyle and the tibial plateau in the medial and lateral tibiofemoral joint. It is triangular in cross-section. The medial meniscus (MM) covers 50%–60% of the medial tibial plateau and the lateral meniscus (LM) 70%–80% of the lateral tibial plateau.
Both menisci have anterior and posterior horns which anchor the meniscus to the underlying subchondral bone of the tibial plateau. The transverse intermeniscal ligament connects the menisci anteriorly. MM is C-shaped and much less mobile during joint motion than LM due to its firm attachment to the joint capsule and medial collateral ligament. The MM root attaches posterior to the apex of the medial tibial plateau, lateral to the apex of the medial tibial eminence and anteromedial to the attachment of posterior cruciate ligament (PCL).
The anterior root of the MM is firmly attached to the tibia anterior to of the anterior cruciate ligament (ACL), near the intercondylar fossa. The LM is almost uniformly circular and more mobile than the MM. Sometimes developmental variations such as discoid lateral meniscus (DLM) are observed. The anterior horn of the LM is attached to the lateral tibial eminence and adjacent to the broad attachment site of the ACL, and the outer fibres from the anterior horn join ACL. The posterior horn is attached posteromedial to the lateral tibial eminence apex, medial to the lateral articular cartilage edge, anterior to the PCL tibial attachment, and is also attached to the medial femoral condyle through the meniscofemoral ligaments of Humphrey and/or Wrisberg.
Attachment area of fibres from the horns of lateral meniscus: anatomic study with special reference to the positional relationship of anterior cruciate ligament.
The inner fibre from the anterior horn constitutes the lateral margin of the ACL attachment, and two crura from the posterior horn constitute the posterior margin of the ACL. The attachment width of the joint capsule at the lateral side of the knee is likely to be disrupted which is gradually tapered towards the posterolateral aspect of the knee.
The popliteus tendon and its fascicles at the popliteal hiatus: gross anatomy and functional arthroscopic evaluation with and without anterior cruciate ligament deficiency.
The major components of the meniscus are water (72%) and collagen (22%). Other constituents include glycosaminoglycan, DNA, adhesion glycoproteins and elastin.
The most critical properties of collagens are the ability for the tensile strength and resistance to compression and shear stress of the meniscus. The majority of collagen fibres are made of type I collagen. They are oriented circumferentially in the deeper layers of the meniscus, parallel to the peripheral border. Radially positioned ‘tie’ fibres are also present in the deep zone. Classification of meniscal cells has been deemed controversial, but three types of meniscal cells are categorised according to the shape and localisation.
Outer zone cells have an oval or fusiform appearance and are classified as fibroblasts. The inner zone cells are more round in shape and behave similar to fibrochondrocytes or chondrocyte-like cells. In the surface of the meniscus, progenitor population cells have been identified. They have a flattened shape, are fusiform and lack cell extensions. At birth, almost of the meniscus is vascularised; however, vascularisation is limited to the peripheral 10%–30% of the meniscus,
and the remaining inner region is avascular in adults. Three regions of the meniscus are classified: the outer red-red zone, the middle red-white zone and the inner white-white zone. One of the essential factors of healing after meniscal repair is the vascularity of the meniscus.
Biomechanical function of the meniscus
Critical functions of meniscus include load distribution, lubrication and joint stability of the knee joint. Fairbank first described the clinical association between joint space narrowing and meniscectomy, indicating an essential function of the meniscus for load transmission.
Several laboratory studies have confirmed that total removal of the meniscus results in a 40%–50% decreased contact area of the compartment and increased peak contact stresses twice or thrice that of the intact knee, which may contribute to increasing stress concentration both in the articular cartilage and in the subchondral bone.
During weight bearing conditions, the LM appears to carry the majority of the load on the lateral compartment, whereas the load is shared approximately equally by the meniscus and the cartilage in the medial compartment. Axial forces loaded on the meniscus during weight bearing are converted into tensile strain through the circumferential collagen fibres of the meniscus, known as hoop stress.
The attachment sites of the anterior and posterior meniscus horns are critical to this function by stabilising the meniscus to the tibia.
The meniscus also plays a remarkable role in controlling knee stability as a secondary restraint. Cadaveric studies have shown that medial meniscectomy in the ACL‐deficient knee causes a significant increase in anterior tibial translation, indicating that the MM is a significant secondary restraint to anteroposterior stability. Moreover, the LM plays a major role as a restraint to anterolateral rotational stability during the pivot shift manoeuvre.
A prospective study for ACL reconstruction showed that deficiency of both MM and LM decreased the survival rate of reconstructed ACL at a follow-up of 2 years.
European Society for Sports traumatology, Knee surgery and Arthroscopy (ESSKA) meniscus consensus group generated the best recommendations for the management of degenerative meniscus tears which is defined as a slowly developing lesion without any history of significant acute trauma in a patient older than 35 years.
Although the natural course of meniscus injury in the long term has not been elucidated, in cases of the definite traumatic episodes, it seems clear that meniscus injury precedes the initiation of OA. On the contrary, sports-related meniscus injuries which are related to repetitive stresses and no sudden traumatic episode may also lead to the progression of OA. Englund et al investigated the elderly people who had no baseline radiographic OA but in whom there was OA progression during a 30-month follow-up period. They had significantly more meniscus injuries at baseline MRI compared with the control who had no progression of OA.
Meniscal tear in knees without surgery and the development of radiographic osteoarthritis among middle-aged and elderly persons: the multicenter osteoarthritis study.
Another cohort revealed that middle-aged population who had the MM injury in MRI at baseline resulted in significantly progressed radiographic OA compared with those without meniscus injury in 10-year follow-up.
Correlation between changes in global knee structures assessed by magnetic resonance imaging and radiographic osteoarthritis changes over ten years in a midlife cohort.
These studies indicate that the meniscus has a key function of the knee joint and that meniscus injury is highly correlated with the initiation of OA. At the same time, the natural course of meniscus injury in adolescent or sports injury remains to be further investigated.
An intact meniscus with extrusion is an important vital meniscus pathology in order to investigate knees with OA. Meniscus extrusion is strongly correlated with OA progression and knee symptoms, although it is still controversial how meniscus extrusion occurs in the absence of an evident lesion of the meniscal body. Hada et al reported that medial tibial osteophyte detected by MRI was frequently observed in the patients with early-stage knee OA, showing close association with MM extrusion.
Association of medial meniscal extrusion with medial tibial osteophyte distance detected by T2 mapping MRI in patients with early-stage knee osteoarthritis.
On the other hand, Krych et al reported that disruption of meniscotibial ligament, which connects the inferior edges of the meniscus to the periphery of the tibial plateau, induced meniscus extrusion.
A 16-year follow-up of meniscectomy with matched controls showed that an isolated meniscal tear treated by meniscectomy induced a high risk of both radiographic and symptomatic knee OA even if the amount of meniscal resection was limited. Worse outcome was correlated with degenerative meniscal tears and extensive resections.
Therefore, meniscal repair is recommended whenever possible to reduce OA in the long term. However, partial meniscectomy is still a standard surgical procedure, especially in middle-aged and elderly patients with knee pain.
A MRI analysis revealed that meniscal tears were observed in 35% of persons older than 50 years of age; however, two thirds of these tears were asymptomatic.
Besides, randomised clinical trial provided no additional benefit to sham surgery or exercise therapy for symptomatic meniscal tears in these populations.
In a randomised clinical trial for symptomatic patients 45 years of age or older with a meniscal tear, there were no significant differences in the improvement of clinical symptoms after 6 and 12 months between patients assigned to arthroscopic partial meniscectomy with postoperative physical therapy and patients assigned to a standardised physical-therapy protocol.
Another randomised clinical trial for degenerative MM tears in middle-aged patients showed that arthroscopic surgery followed by exercise therapy did not result in better objective outcomes than exercise therapy alone at 5-year follow-up. However, 28% in the exercise group had crossed over to the arthroscopic partial meniscectomy group.
These results suggest that unnecessary meniscectomy should be avoided especially in cases with degenerative meniscal tears in elderly patients, as clinical outcomes after meniscectomy are similar to conservative treatment and could initiate the progression of OA. ESSKA consensus group also showed that arthroscopic partial meniscectomy should not be proposed as a first choice of treatment for degenerative meniscus lesions. The benefit of surgical resection of the degenerative meniscus tear is limited; therefore, it should be only applicable after a proper clinical and radiological evaluation and when the improvement of the symptom is marginal.
For meniscus deficiency after meniscectomy, replacement with allografts or—as a potential alternative—the use of artificial meniscus implants is an acceptable option, although the availability of those materials is different among countries. Additional surgical procedures may also become necessary to improve clinical outcome.
Meniscal allograft transplantation
Multiple clinical articles on meniscal allograft transplantation (MAT) have been performed in a painful meniscectomised knee and it has become an accepted surgical option for knee with meniscus deficiency which had previous subtotal or total meniscectomy.
Commonly, the periphery of the meniscal allograft is sutured to the remaining peripheral rim or the joint capsule, and the meniscal horns are fixed with bone plug or soft tissue fixation with sutures. A corrective osteotomy and ligament reconstruction should be considered in patients with malalignment and/or unstable knee due to ligament failure. Coronal malalignment tends to exert abnormal pressure on the allograft leading to graft failure. Verdonk et al reported that total meniscal replacement with allograft is one of the valuable alternatives with a satisfactory long outcome in total resection of the meniscus, and good healing of the peripheral rim to the joint capsule was observed in second-look arthroscopies.
A systematic review showed that good early and midterm results of MAT could be achieved in a relatively young patient with only mild chondromalacia (lower than Outerbridge grade 3) at the time of transplantation, and radiological examination showed its chondroprotective effect.
On the other hand, poor outcome predictors such as malalignment, advanced chondromalacia and knee instability had been indicated, and it is unclear whether MAT can delay the initiation of OA after meniscectomy. In addition, meniscus extrusion after MAT has been reported, which is associated with the development of OA.
Meniscus implant (collagen meniscus implant, other artificial materials and so on)
Meniscus implant represented as collagen meniscus implant (CMI) or polyurethane implant are emerging as a promising alternative to MAT after meniscectomy. CMI is a meniscal scaffold composed of collagen type I fibres isolated from bovine Achilles tendon. Zaffagnini et al showed improvements in clinical symptoms and radiological findings with the use of a CMI compared with partial medial meniscectomy through a minimum 10-year follow-up of non-randomised cohort study with MM injuries.
In addition, clinical evaluation of arthroscopic collagen meniscus implantation for LM at a minimum 2-year follow-up showed improved knee function and decreased pain in patients with a CMI compared with their preoperative status. Besides, significantly increased meniscal tissue in the CMI group was observed compared with that seen after partial meniscectomy in second-look arthroscopy done at 1 year. Toanen et al reported the safety and clinical outcome of biodegradable polyurethane scaffold for meniscus at 5-year follow-up, and significant clinical improvements were obtained compared with baseline. MRI evaluation of the scaffold showed the smaller size and higher signal intensity compared with that of the native meniscus.
However, some challenges should be necessary to obtain ideal meniscal scaffolds which have compressive and tensile properties of the native meniscus, and to explore a new technique to fix the implant to the tibia and joint capsule to minimise extrusion.
Current state of the art: surgical treatment of complex meniscus tear and disease
To save the meniscus, the first surgical option for a meniscus injury should be meniscal repair. Despite apparently high revision rates after a meniscal repair, satisfactory mid-term or long-term clinical results have been obtained compared with meniscectomy.
Recently, the ratio of meniscal repair against meniscectomy increased in some countries, following the development of the concept to preserve the meniscus and the improvement of meniscal repair techniques.
This initiative has led to innovative approaches for meniscus repair and the description of new conditions of meniscus damage which have hardly been considered for repair previously. Among these lesions are meniscus root and ramp lesions and conditions like meniscus instability, extrusion or deficiency. Notably, a high percentage of LM posterior root tears (LMRPTs) are often missed and nearly impossible to diagnose with imaging techniques.
In the case of acute MM root tears, surgical repair may appear to become more necessary in comparison to other meniscus injuries due to the high risk of progression of cartilage degeneration
Non-operative management of medial meniscus posterior horn root tears is associated with worsening arthritis and poor clinical outcome at 5-year follow-up.
For meniscus extrusion, a new concept of meniscal centralisation has recently been developed. When malalignment of the lower leg is present, it is difficult to improve clinical symptoms only by a surgical procedure against meniscus pathologies. Knee osteotomy may, therefore, be considered as a possible combination with meniscus surgery. Finally, recent advancements in biological augmentation have expanded the surgical options of meniscus repair. However, given their innovative character, compelling scientific evidence is still lacking to support these surgical trends.
Meniscus tear
Meniscus injury has various morphological tear patterns including longitudinal tear, radial tear, horizontal tear and flap tear;
however, a good indication of meniscal repair had been historically limited to the longitudinal tear within the vascular area of the meniscus. The surgical technique of approach for meniscal repair can be divided into three procedures: inside-out, outside-in and all-inside technique, where a technique be applied depending on the location and type of meniscus injury. Care should be taken not to injure neurovascular structures mainly while repairing posterior horn/root of the LM using all-inside devices. Saphenous nerve injury for MM repair and peroneal nerve injury for LM repair should also be avoided when using the inside-out technique. The author's preferred technique in terms of location is the inside-out technique for middle and posterior based tears, the outside-in technique for anterior tears and the all-inside for tears isolated to the posterior horn. Meniscal cyst formation was reported after meniscus repair, and the incidence was 1.7%–40.0%, especially after all-inside repair.
Paxton et al reported that isolated partial meniscectomies had a reoperation rate of 1.4% whereas meniscal repairs had a 16.5% reoperation in the short-term follow-up of 0–4 years period.
In addition, on a follow-up period of 4–10 years, partial meniscectomies required a reoperation in only 4.7%, whereas meniscal repair had a reoperation rate of 30.1%. However, 78% of meniscal repairs had no radiographic degenerative radiographic changes compared with 64% of partial meniscectomies after more than 10 years' follow-up. In another retrospective comparative study of 32 patients with a mean follow-up of 10.6 years, the functional score was significantly better with meniscal repair than meniscectomy and the radiological scores correlated closely as well.
These findings indicate that meniscal repair may protect against OA progression in a long-term follow-up, although further prospective randomised studies are required to establish the evidence. Based on these findings, indications for meniscal repair have been expanding to the following tear types.
Vertical longitudinal tears
Vertical longitudinal tears disrupt radial fibres in line with the circumferential fibres. The tear usually separates the meniscus into inner and outer fragments. A small peripheral vertical tear of <10 mm or incomplete tear are considered stable and can be left in situ with a high rate of healing in a stable knee, but tears of >10 mm resulted in unstable and increased risk of reoperation.
When the tear is large enough and the central flap displaces into the notch, it results in a ‘bucket-handle tear’. On sagittal images of MRI, the fragment of the bucket-handle tear is observed as a dark band anterior to the PCL and this is called the ‘double PCL sign’. For this tear pattern, the inside-out suturing technique has been widely performed. However, concerns for saphenous nerve injury or surgical time have led to the development of an all-inside technique. Biomechanical testing has demonstrated similar loads to failure using the all-inside technique compared with traditional the inside-out technique.
Drawbacks of the all-inside technique include damage of the meniscus and cartilage, migration of the implant, larger needle perforations of the meniscus and foreign body reactions. Overall, a systematic review showed that there were no significant differences in clinical outcomes or anatomic failure rates between the inside-out and the all-inside repairs.
Horizontal tears run parallel to the tibial plateau, which separates the meniscus into upper and lower fragments. Koh et al reported that horizontal tears did not result in the notable change to the total contact surface area or contact pressures; in contrast, resection of the inferior leaf of a horizontal cleavage tear resulted in increased contact pressure.
On the other hand, Beamer et al reported that horizontal tear significantly increased average peak contact pressure and reduced average contact area. They also reported that meniscal repair of horizontal tear restored peak contact pressure and areas similar to the intact state, although partial meniscectomy resulted in a significant increase in the average peak contact pressure and decrease in average contact area.
These findings indicate that attempts should be made to preserve both leaflets during repair, especially for the LM. Although horizontal tears are considered to have minimal healing capacity due to its vascularity and concomitant degenerative change,
a systematic review stated that success rate of repairs of horizontal tears was 77.8%, which is a comparable success rate to repairs of other types of meniscal tears.
Radial tears transect the meniscus from the inner free edge of the meniscus to the peripheral, completely disrupting the circumferential collagen fibres. The hoop stress transmission is interrupted, thereby increasing tibiofemoral contact pressures.
Radial tears had previously been considered irreparable, but it has been reported that partial meniscectomy of radial tear further increased contact pressure on the tibial plateau, whereas repairing the radial tear could recover the contact pressure to nearly normal conditions.
A representative case of meniscal repair for radial tear is shown in figure 1.
Figure 1Meniscal repair for the radial tear of the LM. (A, B) The preoperative MRI showed a LM tear in coronal (A) and a sagittal (B) views (arrows). (C) Arthroscopic findings showed a radial tear of the LM at the middle segment (arrows). (D) The radial tear of the LM was repaired using the tie-grip suture technique.
Meniscus ramp lesions are characterised by a tear or disruption of the peripheral meniscocapsular attachments of the posterior horn of the MM and present as superior meniscocapsular ligament tear, inferior meniscotibial ligament tear or both.
Epidemiological evaluation of meniscal ramp lesions in 3214 anterior cruciate ligament-injured knees from the SANTI study group database: a risk factor analysis and study of secondary meniscectomy rates following 769 ramp repairs.
Epidemiological evaluation of meniscal ramp lesions in 3214 anterior cruciate ligament-injured knees from the SANTI study group database: a risk factor analysis and study of secondary meniscectomy rates following 769 ramp repairs.
Diagnostic performance of magnetic resonance imaging for detecting meniscal ramp lesions in patients with anterior cruciate ligament tears: a systematic review and meta-analysis.
They may also be called ‘hidden lesions’, because they cannot be reliably diagnosed through the classic anterior arthroscopy. Indeed 40% of ramp lesion could be missed arthroscopically by standard anterior view. Therefore, routine arthroscopic assessment via a transcondylar view and a posteromedial portal is necessary to confirm their presence, extension and type.
Epidemiological evaluation of meniscal ramp lesions in 3214 anterior cruciate ligament-injured knees from the SANTI study group database: a risk factor analysis and study of secondary meniscectomy rates following 769 ramp repairs.
Ramp lesions of the medial meniscus are associated with a higher grade of dynamic rotatory laxity in ACL-injured patients in comparison to patients with an isolated injury.
A recent biomechanical cadaver study revealed increased external rotation and anterior translation in an ACL deficient knee with concomitant ramp lesion, and only the restoration of both injuries restored the normal knee kinetics.
Likewise, patients with ramp lesions have shown a higher degree of pivot shift. The residual instability with the unstable ramp lesion at the time of ACL reconstruction could lead to graft failure and secondary OA. When ramp lesions are repaired using a suture hook from posteromedial portal, the overall clinical success has been high with a secondary partial meniscectomy rate of only 10.8%.
Epidemiological evaluation of meniscal ramp lesions in 3214 anterior cruciate ligament-injured knees from the SANTI study group database: a risk factor analysis and study of secondary meniscectomy rates following 769 ramp repairs.
On the other hand, a prospective randomised controlled trial showed that the stable ramp lesion treated with abrasion obtained the similar clinical outcome and meniscal healing to those treated with repair.
Is it necessary to repair stable ramp lesions of the medial meniscus during anterior cruciate ligament reconstruction? A prospective randomized controlled trial.
Degenerative tears indicate the quality of the meniscus as fibrillation or degeneration and can be accompanied by OA change without any history of significant trauma. The tear pattern is usually horizontal, radial or complex, while longitudinal tears are rarely observed.
Most degenerative tears are an indication for non-operative therapy focusing on non-steroidal anti-inflammatory drugs and physical therapy, by which pain relief and improvement of mechanical function are obtained. Meniscus tears in patients older than 40 years have decreased cellularity of the meniscus and are more vulnerable to retear after repair compared with menisci of younger patients.
Pauli et al reported that meniscus in older patients demonstrated decreased cell density or diffuse hyper cellularity along with cellular hypertrophy and abnormal cell clusters.
Therefore, enhancement of meniscal repair for degenerative meniscus may be necessary to achieve successful meniscus healing in such cases.
Posterior root repair
Posterior root tears severe affect biomechanics of the knee joint, and pathologies of LMPRT and medial meniscus posterior root tear (MMPRT) are quite different. LMPRT is often accompanied with an acute ACL injury,
In a matched cohort study investigating the results of isolated ACL reconstruction versus combined treatment of ACL and LMPRT without repair, there were no significant differences in clinical outcomes. However, joint space narrowing of the lateral compartment was obvious with a combined LMPRT in a mean follow-up of 10.6 years.
LM posterior root also has an important role as a secondary restraint to pivot shift in ACL-deficient knees. A cadaveric study showed that LMPRT increased pivot shift significantly in ACL-deficient knees. Clinically, it has also been shown that LMPRT is associated with larger pivot shift grade in ACL injured knees,
Therefore, in cases with LMPRT accompanied with an ACL injury, LMPRT should be repaired simultaneously at the time of ACL reconstruction.
On the other hand, MMPRT typically occurs in middle-aged and elderly patients, with acute pain after minor trauma such as tripping on stairs. MMPRT dramatically increases contact pressure on medial tibial plateau, which often induces subchondral insufficiency fractures and early progression of knee OA.
Non-operative management of MMPRT is associated with worsening arthritis and poor clinical outcome, with 31% resulting in total knee arthroplasty at a mean of 30 months after diagnosis and an overall 87% of patients failing non-operative treatment.
Non-operative management of medial meniscus posterior horn root tears is associated with worsening arthritis and poor clinical outcome at 5-year follow-up.
Faucett et al compared meniscal repair, meniscectomy and non-operative treatment of MMPRT, showing that incidence of OA was 53.0%, 99.3% and 95.1% and total knee replacement rate was 33.5%, 51.5% and 45.5%, respectively.
Meniscus root repair vs meniscectomy or Nonoperative management to prevent knee osteoarthritis after medial meniscus root tears: clinical and economic effectiveness.
Lee et al reported that partial meniscectomy for MMPRT in varus osteoarthritic knees led to unfavourable outcome with significant higher rate of total knee arthroplasty (TKA) conversion than that in well-aligned non-arthritic knees.
Therefore, decision making for treatment of MMPRT is quite crucial. Appropriate indications for MMPRT repair were proposed including (1) acute, traumatic root tears without OA change, for the prevention of future arthritis and (2) chronic symptomatic root tears in young or middle-aged patients without definite OA change.
The most common techniques for meniscus root repair include transosseous suture repair and suture anchor technique under arthroscopy. For the transosseous technique, the basic principle of this technique is to reattach the meniscus by placing sutures through the meniscus root and pulling them through a transtibial tunnel. For MMPRT using transtibial technique, Chung et al reported a high clinical survival rate of transtibial pullout repair, with a survival rate of 99% at 5 years and 95% at 7 years, when failure was defined as conversion to TKA or poor final Lysholm score.
On the other hand, meniscus extrusion was increased after the surgery in 59% of patients, and residual meniscus extrusion was correlated with both clinical and radiographic findings.
Lee et al reported improved outcomes after MMPRT repair at mean follow-up duration of 40.6 months, and second-look arthroscopy revealed that 69.7% were classified as stable and healed, however, although the medial joint space became significantly narrower. Feucht et al reported that healing status was rated as complete in 62% and partial in 34% by second-look arthroscopy, whereas meniscus extrusion was reduced only in 56% by MRI.
Arthroscopic transtibial Pullout repair for posterior medial meniscus root tears: a systematic review of clinical, radiographic, and second-look arthroscopic results.
Further improvement in surgical procedures is required especially in terms of reducing meniscus extrusion and thereby preventing progression of OA. A representative case of MMPRT repair is shown in figure 2.
Figure 2Meniscal repair for the MMPRT. (A) MMPRT was confirmed arthroscopically (arrows). (B) Guide wire was inserted through the tibia. (C) Tibial tunnel was created with 6 mm diameter. (D) After suture passage, the MM posterior root was pulled through the tibial tunnel. MFC, medial femoral condyle; MM, medial meniscus; MMPRT, medial meniscus posterior root tear; PCL, posterior cruciate ligament.
DLM is the most common congenital anatomic variation of the meniscus in the knee joint. DLM is a possible cause of knee pain and functional limitations, but most of them remain asymptomatic and require no treatment. For symptomatic DLM with failed conservative treatments, surgical treatments such as total meniscectomy or subtotal meniscectomy had been performed. However, it would dramatically increase contact pressure on the lateral compartment and cause degeneration of articular cartilage and/or osteochondritis dissecans,
Therefore, recent trends have been towards preservation of the peripheral part of the DLM by saucerisation with repair of the remaining meniscus. A systematic review comparing saucerisation and total meniscectomy showed similar clinical results in short-term follow-up, but superior clinical outcome was obtained by saucerisation than total meniscectomy.
Wasser et al reported that patients with a saucerisation procedure and suture repair had significantly better clinical results than a simple saucerisation procedure alone,
However, degenerative changes are already observed on preserved peripheral zone in most cases and DLM originally has less hoop function by disorientation of collagen fibre. Matsuo reported that DLM appeared extrusion after a partial meniscectomy with repair, and function of the meniscus might not be maintained properly.
Further development in the treatment of DLM is necessary for better clinical outcomes. A representative case of saucerisation and meniscus repair for DLM is shown in figure 3.
Figure 3Saucerisation with suture repair for the DLM. (A) The preoperative MRI showed the anterior shift of the DLM (arrows). (B) Displacement of the DLM (arrows) was confirmed arthroscopically. (C) After the saucerisation, the remaining meniscus was repaired with inside-out and outside-in technique. (D) The postoperative MRI showed the triangular shape of the remaining meniscus. ACL, anterior cruciate ligament; DLM, discoid lateral meniscus; LFC, lateral femoral condyle.
Meniscus extrusion is critical pathology to consider the strategy for the early stage of OA and new developments in imaging diagnosis attract the attention.
Meniscus extrusion occurs in knees with disruption of the hoop stress such as posterior root tears or radial tears, after meniscectomy, after saucerisation of discoid meniscus and as a complication after meniscal transplantation. Extrusion of the meniscus can also be frequently accompanied by OA.
Meniscus body position, size, and shape in persons with and persons without radiographic knee osteoarthritis: quantitative analyses of knee magnetic resonance images from the osteoarthritis initiative.
Meniscus body position, size, and shape in persons with and persons without radiographic knee osteoarthritis: quantitative analyses of knee magnetic resonance images from the osteoarthritis initiative.
Therefore, a surgical procedure that can reduce the displacement of meniscus could lead to preserving the meniscal function, thereby preventing the progression to OA. Koga et al reported arthroscopic centralisation of an extruded LM to maintain meniscal functions.
This technique was indicated for patients with LM extrusion, as well as symptomatic torn discoid meniscus to prevent extrusion after saucerisation. Meniscus extrusion was reduced by suturing the capsule attached to the meniscus to the edge of the tibial plateau using suture anchors. At 2-year follow-up, satisfactory clinical results were obtained, as indicated by Knee injury and Osteoarthritis Outcome Score (KOOS) and Lysholm score, and MRI evaluation showed a significant reduction in the meniscus extrusion width.
The radiographic lateral joint space width on a standing 45° flexion view was also significantly increased at 3 months after the surgery and was maintained for 2 years.
Utilization of transtibial centralization suture best minimizes extrusion and restores Tibiofemoral contact mechanics for anatomic medial meniscal root repairs in a cadaveric model.
in terms of improvements in load distributing function and reduction of meniscus extrusion. A representative case of centralisation for extruded LM is shown in figure 4.
Figure 4Centralisation for the extruded LM. (A) The preoperative MRI showed extrusion of the LM more than 3 mm (arrows). (B) Extrusion of the LM was confirmed arthroscopically. (C) Suture anchor was inserted on the lateral edge of the lateral tibial plateau. (D) The displaced meniscus was centralised after centralisation. LFC, lateral femoral condyle; LM, lateral meniscus; LTP, lateral tibial plateau.
When malalignment of the lower leg is present, it is challenging to improve clinical symptoms only by a surgical procedure against meniscus pathologies. Nakayama et al reported that patients with varus deformity (% of mechanical axis less than 30%) showed inferior outcomes after meniscal repair for degenerated MM tear.
Therefore, the combination of around the knee osteotomy is a possible option to protect the repaired meniscus by unloading the pathological compartment. Around the knee osteotomy has regained attention for joint preservation, and among them, high tibial osteotomy (HTO) is the most common surgical procedure for the medial compartment OA due to varus alignment, and good clinical results were obtained. The most commonly used surgical techniques of HTO are medial opening wedge HTO and lateral closed wedge HTO. A systematic review has shown that the majority of patients undergoing HTO return to sport and work within 1 year after the operation and approximately two-thirds of patients return to an equal or greater level of physical work.
The aim of HTO is to realign the mechanical axis of the lower extremity to shift weight-bearing zones from the pathological compartment to the healthy compartment, and decreased loading to the damaged cartilage reduces pain, improves function and potentially delays the need for arthroplasty. Although several studies have investigated additional cartilage restoration techniques such as microfracture, autologous chondrocyte implantation, osteochondral autograft and osteochondral allograft in combination with HTO, not so much attention had been given to the associated meniscus pathology. Only a few studies reported combined meniscus surgeries such as MAT and meniscus substitution with a polyurethane scaffold, and no clinical outcomes were provided to support these procedures combined with HTO. On the other hand, in cases with MMPRT with varus alignment, combination of centralisation augmentation and HTO with MMPRT repair could have the potential to further improve both clinical and radiological outcomes.
Suture anchor repair for a medial meniscus posterior root tear combined with arthroscopic meniscal centralization and open wedge high tibial osteotomy.
Nevertheless, further studies are required to validate the effectiveness of combined meniscus surgeries with HTO. A representative case of HTO with MMPRT repair and centralisation is shown in figure 5.
Figure 5Open wedge high tibial osteotomy for the MMPRT with varus alignment. (A) The preoperative MRI showed MMPRT (arrows). (B) MMPRT was confirmed arthroscopically. (C) Extrusion of the MM was confirmed arthroscopically. (D) MMPRT was repaired by transosseous technique. (E) Extrusion of the MM was reduced by centralisation technique. (F) The postoperative radiograph after OWHTO, repair of MMPRT and centralisation. (G) Healing of the posterior root of the MM was confirmed in second-look arthroscopy. (H) Centralised MM was also confirmed by second-look arthroscopy. MFC, medial femoral condyle; MM, medial meniscus; MMPRT, medial meniscus posterior root tear.
Healing after meniscal repair is significantly restricted without an adequate blood supply even when the meniscal repair technique is able to stabilise the tear. To enhance the healing after meniscal repair, biological augmentation techniques appear to have significant potential especially in avascular zones.
Bone marrow stimulation
It has been well known that the success rate of meniscal repair in conjunction with ACL reconstruction is higher compared with meniscal repair alone. Paxton et al reported that the reoperation rate of isolated meniscal repair was 16.5% in the short-term follow-up period (0–4 years), and 30.1% over the long-term follow-up period (4%–10%).
A systematic review showed that the average failure rate including reoperation or clinical failure was 23.1% in the overall population of meniscal repair at greater than that of 5-year follow-up.
On the other hand, better outcomes were obtained in meniscal repair combined with ACL reconstruction rather than in repair alone. Wasserstein et al reported that the rate of meniscal reoperation was significantly lower in the meniscal repair and combined ACL reconstruction group (9.7%) than in the meniscal repair alone group (16.7%) at 2-year follow-up.
The lower failure rate in meniscal repair combined with ACL reconstruction may be explained by biological factors released while drilling the bone tunnel, and the concentration of platelet-derived growth factor, insulin-like growth factor and vascular endothelial growth factor were the candidates of the effect.
Outcomes after biologically augmented isolated meniscal repair with marrow Venting are comparable with those after meniscal repair with concomitant anterior cruciate ligament reconstruction.
To enhance the healing of repaired meniscus, bone marrow stimulation procedures with drilling of the intercondylar notch have been performed after isolated meniscal repair.
Dean et al demonstrated a minimum 2-year follow-up comparative study which showed no significant difference in outcomes in isolated meniscal repair with marrow venting technique at the intercondylar notch and meniscal repair performed with concomitant ACL reconstruction, providing the potential for enhancement of meniscal healing by biological augmentation technique.
Outcomes after biologically augmented isolated meniscal repair with marrow Venting are comparable with those after meniscal repair with concomitant anterior cruciate ligament reconstruction.
Fibrin clot derived from peripheral blood contains growth factors and enhances meniscus healing. In the series of isolated meniscal repair, Henning et al reported an 8% failure rate using exogenous fibrin clots compared with a 41% failure rate without fibrin clot.
They prepared the tubular-shaped fibrin clot which can be used to wrap or package autogenous meniscal fragments. Follow-up arthroscopy revealed the regeneration of meniscus-like tissue at 6 months after the surgery. This technique may have advantages in tissue regeneration with native meniscal tissue and growth factors obtained from fibrin clot. However, these reports include only small size of clinical studies or technical note without a control group, suggesting no evidence of superiority of adding fibrin clot use to meniscal repair.
Platelet-rich plasma
Platelet-rich plasma (PRP), which is obtained from whole blood by centrifugation, has been widely used for injury of tendon, muscle and ligament; however, its efficacy in meniscal repair is still a matter of controversy. Pujol et al reported that meniscal repair of horizontal tears extending into the avascular zone was effective enough at a minimum of 2 years postoperatively, but addition of PRP increased slightly healing of meniscus on MRI.
Griffin et al reported that outcomes after meniscal repair augmented with and without PRP appeared similar in terms of reoperation rate and in the proportion of return to work or sports activity at a minimum of 2 years.
Evenhart et al reported that PRP had a substantial protective effect in terms of the risk of isolated meniscal repair failure over 3 years, but in the setting of concomitant ACL reconstruction, PRP does not reduce the risk of meniscal repair failure.
Platelet-rich plasma reduces failure risk for isolated meniscal repairs but provides no benefit for meniscal repairs with anterior cruciate ligament reconstruction.
Further evaluation of PRP augmentation should be addressed with a longer follow-up.
Stem cell therapy
Stem cell therapy is used to enhance the ability of healing and regeneration of meniscus. Whitehouse et al reported a first-in-human study where autologous bone marrow mesenchymal stem cells (MSCs) embedded in a collagen scaffold was placed into the avascular meniscus tear prior to meniscal repair, and three of five patients were asymptomatic at 2 years follow-up with improved clinical score and MRI findings.
Repair of torn avascular meniscal cartilage using undifferentiated autologous mesenchymal stem cells: from in vitro optimization to a first-in-human study.
Vangsess et al reported that patients who had injections of 50 million or 150 million allogeneic bone marrow-derived MSCs after partial meniscectomy experienced a significant reduction of pain compared with the control who had an injection of hyaluronic acid for up to 24 months, and there were significantly increased meniscal volume in the MSC group.
Adult human mesenchymal stem cells delivered via intra-articular injection to the knee following partial medial meniscectomy: a randomized, double-blind, controlled study.
Synovial MSCs have the potential to enhance the healing of repaired meniscus due to its high proliferative and chondrogenic ability and its same origin of the intra-articular tissue. Good clinical results and MRI findings were reported 2 years after transplantation of synovial MSCs on to repaired menisci for degenerative tears.
Additional use of synovial mesenchymal stem cell transplantation following surgical repair of a complex degenerative tear of the medial meniscus of the knee: a case report.
A representative case of transplantation of synovial MSCs after meniscal repair for torn meniscus is shown in figure 6.
Figure 6Transplantation of synovial mesenchymal stem cells after meniscal repair for torn meniscus. (A) Arthroscopic findings showed a torn MM. (B) Meniscal repair was performed. (C) Suspension of synovial MSCs was transplanted on the repaired meniscus 2 weeks after the surgery (arrows). (D) Healing of repaired meniscus was confirmed in second-look arthroscopy 1 year after the transplantation. LTP, lateral tibial plateau; MFC, medial femoral condyle; MM, medial meniscus.
whereas in other countries, meniscectomy is still the majority. This may be reflective of the focus on physician education about the importance of meniscus preservation and an increase in the number of publications regarding the topic. In the USA, there may be a biased perception by patients that a prolonged recovery for meniscus repair is not worth the advantages of the longer-term result.
In some countries such as Japan, the use of allograft is minimal; therefore, treatment against meniscus defect after meniscectomy is difficult. Further development of meniscus reconstruction surgeries or enhancement of meniscus repair technique to prevent the loss of meniscus is especially important in such countries.
Conclusion
To preserve meniscal function, meniscus tears should be repaired as much as possible, as long-term outcomes show that meniscal repairs provide better clinical outcomes and less OA changes compared with partial meniscectomy. For meniscus defect after meniscectomy, transplantation of allograft or CMI provides acceptable clinical results. The centralisation technique has been proposed to reduce the meniscus extrusion. Advancements in surgical techniques, combined with around the knee osteotomy and biological augmentation, have expanded the surgical indications for addressing the meniscus pathology. Further, validated evidence should be established for meniscus repair in degenerative knee conditions.
Seil R, Becker R. Time for a paradigm change in meniscal repair: save the meniscus! Knee Surg Sports Traumatol Arthrosc. 2016 May;24(5):1421–3.
2.
Englund M, Roemer FW, Hayashi D, Crema MD, Guermazi A. Meniscus pathology, osteoarthritis and the treatment controversy. Nat Rev Rheumatol. 2012 Jul;8 (7):412–9.
3.
Paxton ES, Stock MV, Brophy RH. Meniscal repair vs partial meniscectomy: a systematic review comparing reoperation rates and clinical outcomes. Arthroscopy. 2011 Sep;27(9):1275–88.
4.
Nepple JJ, Dunn WR, Wright RW. Meniscal Repair Outcomes at Greater Than Five Years A Systematic Literature Review and Meta-Analysis. J Bone Joint Surg Am. 2012 Dec 19;94a(24):2222–7.
5.
Woodmass JM, LaPrade RF, Sgaglione NA, Nakamura N, Krych AJ. Meniscal Repair: Reconsidering Indications, Techniques, and Biologic Augmentation. J Bone Joint Surg Am. 2017 Jul 19;99(14):1222–31.
6.
Sonnery-Cottet B, Praz C, Rosenstiel N, et al. Epidemiological Evaluation of Meniscal Ramp Lesions in 3214 Anterior Cruciate Ligament-Injured Knees From the SANTI Study Group Database: A Risk Factor Analysis and Study of Secondary Meniscectomy Rates Following 769 Ramp Repairs. Am J Sports Med. 2018;46(13):3189–3197.
7.
LaPrade CM, James EW, Cram TR, Feagin JA, Engebretsen L, LaPrade RF. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;43(2):363–369.
8.
Koga H, Muneta T, Watanabe T, et al. Two-Year Outcomes After Arthroscopic Lateral Meniscus Centralization. Arthroscopy. 2016;32(10):2000–2008.
9.
Dean CS, Chahla J, Matheny LM, Mitchell JJ, LaPrade RF. Outcomes After Biologically Augmented Isolated Meniscal Repair With Marrow Venting Are Comparable With Those After Meniscal Repair With Concomitant Anterior Cruciate Ligament Reconstruction. Am J Sports Med. 2017;45(6):1341–1348.
10.
Verdonk R, Volpi P, Verdonk P, et al. Indications and limits of meniscal allografts. Injury. 2013;44 Suppl 1:S21-27.
Tips and tricks for successful surgical treatment of complex meniscus tear and disease
1.
Vertical longitudinal tears are the best indication for meniscal repair, but other types of tears should also be repaired whenever possible. Meniscectomy should be avoided as much as possible not to initiate/progress osteoarthritis.
2.
No significant differences in clinical outcomes or anatomic failure rates between inside-out and all-inside repairs, but surgical technique should be individualised according to types, size and location of the meniscus tears.
3.
Medial meniscus posterior root tear is recommended to be treated surgically because non-operative management is associated with worsening arthritis and poor clinical outcomes.
4.
For meniscus defect, transplantation of allograft or collagen meniscus implant is a surgical option. Surgical procedures depend on the individual situations including sex, age, religion and countries.
5.
In cases with malalignment, alignment correction by around the knee osteotomy should be considered to protect the repaired meniscus.
Major pitfalls of surgical treatment of complex meniscus tear and disease
1.
Care should be taken not to injure neurovascular structures especially while repairing posterior horn/root of the LM using all-inside devices.
2.
Saphenous nerve injury for MM repair and peroneal nerve injury for LM repair should also be avoided when using inside-out technique.
3.
Meniscal repair without alignment correction in cases with malalignment would result in inferior clinical outcomes.
4.
Considering high reoperation rate after isolated meniscal repair, biological augmentation techniques should be attempted to enhance the healing after meniscal repair.
Longer-term follow-up is necessary to confirm the effects of meniscal repair on clinical outcomes as well as prevention of OA.
2.
Dealing with meniscus extrusion seems to be critical for prevention of OA, and so far centralisation technique can be one option to reduce meniscus extrusion. Long-term clinical outcomes of this procedure may change the strategy against meniscus extrusion.
3.
For meniscus defect after meniscectomy, transplantation of allograft or collagen meniscus implant provides acceptable clinical results. Several other implants have been tried in animal models, and accumulating evidence is necessary to apply new substitutes in clinical situations.
4.
Advancements in surgical techniques and biological augmentation have expanded the surgical option for the meniscus pathology. Further evidences should be established for the advancement of the meniscus treatment.
Acknowledgments
We thank Dr Megha Agrawal for English editing.
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Non-operative management of medial meniscus posterior horn root tears is associated with worsening arthritis and poor clinical outcome at 5-year follow-up.
Epidemiological evaluation of meniscal ramp lesions in 3214 anterior cruciate ligament-injured knees from the SANTI study group database: a risk factor analysis and study of secondary meniscectomy rates following 769 ramp repairs.
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Utilization of transtibial centralization suture best minimizes extrusion and restores Tibiofemoral contact mechanics for anatomic medial meniscal root repairs in a cadaveric model.
Suture anchor repair for a medial meniscus posterior root tear combined with arthroscopic meniscal centralization and open wedge high tibial osteotomy.
Outcomes after biologically augmented isolated meniscal repair with marrow Venting are comparable with those after meniscal repair with concomitant anterior cruciate ligament reconstruction.
Platelet-rich plasma reduces failure risk for isolated meniscal repairs but provides no benefit for meniscal repairs with anterior cruciate ligament reconstruction.
Repair of torn avascular meniscal cartilage using undifferentiated autologous mesenchymal stem cells: from in vitro optimization to a first-in-human study.
Adult human mesenchymal stem cells delivered via intra-articular injection to the knee following partial medial meniscectomy: a randomized, double-blind, controlled study.
Additional use of synovial mesenchymal stem cell transplantation following surgical repair of a complex degenerative tear of the medial meniscus of the knee: a case report.
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