The menisci play a vital role in knee joint stability, load distribution, and lubrication, protecting the joint surfaces from degenerative change. Meniscal repair protects the joint from increased loading and when successful reduces progression of osteoarthritis. Successful repair involves accurate surgical techniques, guarded postoperative rehabilitation, and potential use of additional biologics to promote healing. An integrated approach to meniscal surgery is required as part of an overall strategy to preserve and restore knee function, preserving meniscal tissue whenever possible. This article reviews the repair techniques: procedures, indications, and rehabilitation for meniscal repair.
Key points
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The menisci have a primary role of improving congruency between the convex surface of the distal femur and the surfaces of the proximal tibia.
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The menisci play a vital role in knee joint stability, load distribution, and lubrication, protecting the joint surfaces from degenerative change.
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Meniscal repair protects the joint from increased loading and when successful reduces progression of osteoarthritis.
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Successful repair involves accurate surgical techniques and guarded postoperative rehabilitation An integrated approach to meniscal surgery is required as part of an overall strategy to preserve and restore knee function, preserving meniscal tissue whenever possible.
Video content accompanies this article at http://www.sportsmed.theclinics.com .
Introduction
Meniscal tears are common, with a yearly incidence of 60 to 70 per 100,000 population. Loss of meniscal tissue predisposes the knee joint to degenerative change and symptoms of activity related knee pain that can develop over a variable length of time. Repair is an important option for meniscal tears with the intention of improving symptoms and reducing the risk of subsequent arthritis. Sutures or devices to repair the meniscus can be delivered via inside-out, outside-in, or all-inside techniques. The tear location and orientation determine the optimal technique for suture placement. This article reviews current techniques for meniscal repair specifically focusing on all-inside, inside-out, and outside-in techniques. Repair of ramp lesions and root tears are not addressed in this review.
Consequences of meniscal deficiency
Long-term follow-up of meniscal deficient patients after partial or total meniscectomy has demonstrated increased risk of osteoarthritis (OA). In a systematic review of risk factors for OA, Papalia and colleagues reported a 7 times increase in the radiologic diagnosis of OA at 5 to 30 years of follow-up after surgical management of meniscal tears. The incidence was 40% in the operated knee and 6% in the contralateral/control knee, with a higher incidence following lateral compared with medial meniscal surgery and with total compared with partial meniscectomy. In a single cohort follow-up study of adolescents who underwent total meniscectomy at a mean age of 16 years, Pengas and colleagues reported a 132-fold increase in the incidence of knee arthroplasty at mean 40 years follow-up compared with geographic- and age-matched controls.
Menisci have a primary role of improving congruency between the convex surface of the distal femur and the surfaces of the proximal tibia. They enhance stability and help to distribute load evenly across the knee, reducing load on the articular cartilage, effectively being load distributors while also contributing to proprioception, cartilage nutrition, and lubrication.
Relevant anatomy when considering meniscal repair
The medial meniscus has a slightly asymmetrical C-shaped structure with larger posterior than anterior horn ( Fig. 1 ). It covers 50% ± 6% of the medial plateau and is firmly attached to the periphery via the deep medial collateral ligament, which has both meniscofemoral and meniscotibial attachments. This makes it relatively immobile with only about 5 mm anterior–posterior translation during knee flexion–extension.
The lateral meniscus is more symmetric and a tighter C shape. It is similar in volume to the medial meniscus but covers a relatively larger proportion of the lateral tibial plateau—59% ± 7%. Being less firmly attached to the periphery, it is more mobile with approximately 11 mm posterior translation during knee flexion. The medial meniscus bears about 50% of load, whereas the lateral meniscus bears up to 70% through its respective compartment.
The predominantly circumferential arrangement of the collagen fibers is vital to meniscal function, resisting extrusion on compression. Weight bearing after repair therefore compresses the healing area while flexion under load applies a shear force to the repairing area. At full extension, the femur has a large contact area with the tibial plateaus pressing anteriorly on the meniscal horns. As the knee flexes, tibial internal rotation occurs and contact moves posteriorly toward the posterior meniscal horns owing to femoral roll-back. Contact area with the tibial plateau is decreased as the lesser radii of curvature of the femoral condyles sequentially come into contact. The center of contact on the medial side remains relatively constant, whereas the lateral condyle rolls posteriorly toward the posterior horn of the mobile lateral meniscus and thus tibial rotation occurs mainly about a medial axis, with the center of rotation medial to the knee joint in the axial plane ( Fig. 2 ). The result is that meniscal load increases in flexion to as much as 85% and without a meniscus the tibiofemoral contact area is decreased by 50% to 75% and the peak contact pressure is increased by 200% to 300%.
Meniscal vascularity is crucial to the chances of a repair being successful. The lateral meniscus is vascularized in only the outer 10% to 25% of its width and the medial meniscus in the outer 10% to 30% in adults, although this percentage is higher in less than 12 years of age.
Assessment of meniscal tears when considering repair
The European Society of Sports Traumatology, Knee Surgery and Arthroscopy (ESSKA) and the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) Classification (2006) is based on tear depth (full/partial thickness), residual rim width (<3 mm, 3-5 mm, >5 mm), and location (posterior, mid-body, anterior). Residual rim width is a proxy for meniscal function, because lesions with less than 3 mm of rim remaining compromise the circumferential fibers and the ability of the meniscus to resist hoop stress, effectively defunctioning the meniscus. Tear classifications are summarized in Figs. 3 and 4 .
Meniscal Vascularity
Understanding meniscal vascularity has led to the mainstay of assessment. Red–red tears, as popularized after the anatomic description by Arnoczky and Warren, are in the peripheral vascularized area (0-3 mm from the rim) and have the best chance of healing. White–white tears in the inner avascular zone (5-7 mm from the rim) have the lowest healing potential and tears in the intermediate zone (3-5 mm from the rim) are termed red–white, and have intermediate potential for healing, being more favorable in the younger patient.
Tear Orientation and Fiber Disruption
Vertical tears can be longitudinal, producing a bucket handle type tear or a flap, or radial in direction disrupting the circumferential fibers (see Fig. 4 ). Vertical oblique tears disrupt a mixture of both radial and circumferential fibers.
Horizontal tears (see Fig. 4 H) occur in the plane of the meniscus parallel to the articular surface and in general do not disrupt the radial or circumferential fibers. Such tears are associated with meniscal degeneration and with parameniscal cyst development. Contact surface area and contact pressures are not altered and pain probably arises from peripheral capsule irritation. Removal of the inferior leaf reduces contact area by 59% and produces peak pressures similar to dual leaflet resection.
Complex tears (see Fig. 4 I) include a mixture of horizontal and vertical components and are most commonly degenerate in etiology, resulting from repetitive physiologic forces leading to gradual attrition of the menisci. Such tears are often accompanied by OA.
Tear repairability
Repairability of a tear depends on several factors and these are all taken into account when considering technique and repair.
Vertical Longitudinal Tears
Acute, peripheral, vertical longitudinal tears demonstrate good capacity for healing (72% to 94% reported). Repaired tears in the red–red or red–white zones lead to good and excellent clinical midterm results. As a rough guide, such repairable tears include those less then 4 mm from the meniscal rim. Tears less than 10 mm long can be left unrepaired because they have good healing potential. Fig. 5 demonstrates a stable undersurface tear of the lateral meniscus not needing resection or repair while Fig. 6 shows an unstable lateral meniscal tear requiring repair and closure if the anterior aspect of the popliteofibular hiatus.
Radial Tears
Radial tears extending to the peripheral zone cause complete loss of meniscal function. Because the periphery is vascular these tears can be repaired, but specific suture or anchor techniques are required to tolerate the high forces in the rim. The authors prefer the method using tie-grip sutures as a vertical configuration before placing horizontal sutures to draw the edges together, and in this way the sutures do not pull out through the circumferential fibers of the meniscus ( Figs. 7 and 8 ).
Horizontal Tears
These tears were once thought to have minimal healing capacity, because they are associated with degenerative changes and OA. In young patients, however, healing similar to other tear patterns has been observed, with a healing rate of 78% reported in a systematic review of 9 studies. Preliminary results are encouraging, demonstrating better results in terms of functional scores and secondary meniscectomy. Although complex, this treatment has to be compared with resection, which will inevitably expose the joint to increased risk of early OA. Fig. 9 demonstrates use of vertical suture loops in closing a horizontal tear in a young patient.
Age of the Tear
It is difficult to define or quantify repairability in terms of age of the tear but there is clinical dogma that fresh tears have a higher chance of healing after repair. A figure of 4 weeks is often quoted, but a tear in the peripheral red zone where the fragment has not been damaged should still be considered for repair even after several months. This notion is supported by Van der Wal and colleagues who studied 238 meniscal repairs and found that the interval between trauma and meniscal repair had no influence on the failure rate.
Age of the Patient
It has been suggested that the older the patient the less the intrinsic healing capability of the meniscus owing to decreased cellularity and reduced healing response. Eggli and colleagues in their series of 56 arthroscopic meniscal repairs found patients aged less than 30 had better healing potential at an average 7.5 years follow-up. More recently, however, investigators have not found age to be a significant factor in the failure of the meniscus to heal. Contemporary attitudes toward meniscal repair seem to place more importance on the macroscopic appearance, location, size, and orientation of the tear, and less so on the chronicity of the tear or the age of the patient.
All-inside meniscal repair technique
All-inside meniscal repair involves insertion of a suture through the meniscus and fixation inside the knee without involving perforation through the skin. Techniques involving manual tying of knots inside the joint have evolved into use of fixation devices that implant anchor devices in the peripheral tissue with a self-tying slipknot in-between. There are now several commercial variations available and the range has been grouped in Table 1 .
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