ANATOMY

Menisci are discs of fibrocartilage interposed between the femoral condyles and tibial plateau. The articular surface of the medial condyle of the tibia is oval, with the longer axis being in the anteroposterior plane (Fig. 6-1). The central portion of the articular surface is not covered by meniscus and represents the articular area. The lateral meniscus plateau is almost circular and less concave. The menisci cover the peripheral two thirds of the tibia, and serve to deepen its articular surface and stabilize the joint. The upper borders of the menisci are concave and the undersurfaces are flat. Peripherally, the menisci thicken and are attached to the synovium and capsule. Centrally, the border is thin and exists as a free edge.

FIGURE 6-1 Axial view of the tibial plateau showing both menisci. Note that the cruciate ligament’s insertion has been removed to allow better visualization (grey rectangle). Transverse ligament, dashed arrow; hiatus popliteus, arrow.

The medial meniscus is oval, 3.5cm in length, and wider posteriorly from its peripheral to its central aspects in the knee. Its anterior horn attaches to the tibial plateau just anterior to the attachment of the ACL. Some posterior fibers originating from the anterior horn cross the knee joint anteriorly, attaching to the lateral meniscus and forming the transverse ligament (see Fig. 6-1). Posteriorly, the meniscus is anchored to the intercondylar fossa of the tibia between the posterior cruciate ligament (PCL) and lateral meniscal attachment. Along its periphery, the medial meniscus is attached to the joint capsule and the deep medial collateral ligament (MCL). The medial meniscus has less mobility than the lateral meniscus, and moves almost 10 mm from extension to flexion.

The lateral meniscus is circular, covering a larger portion of the articular surface than its medial counterpart. It is the same width anteriorly and posteriorly. The anterior horn attaches near the intercondylar spine posterior to the attachment of the ACL, with which it partially blends (Fig. 6-2). The posterior horn attaches just posteriorly to the intercondylar spines, anterior to the attachment of the medial meniscus. The lateral meniscus does not attach to the lateral collateral ligament but is attached loosely to synovium along much of its length. The anterior (ligament of Humphrey) and posterior (ligament of Wrisberg) meniscofemoral ligaments run from the posterior horn of the lateral meniscus to anterior and posterior, respectively, to the PCL attachment on the medial femoral condyle. Moreover, the tendon of the popliteus muscle, on its way to insert into the lateral condyle, crosses the joint through a hole on the lateral meniscus called the hiatus popliteus (see Fig. 6-1). This area along the popliteal hiatus is described as the avascular region.

FIGURE 6-2 Oblique view of the tibia showing the insertion of the ACL. Note how the anterior horn of the lateral meniscus fibers blend with the ACL (arrow).

CLASSIFICATION

A meniscal tear may be classified by its location relative to its blood supply and vascular appearance. The peripheral and central surfaces can be clinically graded as white (relatively avascular) or red (vascular) at the time of arthroscopy. This classification is based on anatomic studies that have depicted a peripheral vascular zone.

A red-red tear is defined as a peripheral capsular detachment, and has the best prognosis for healing. Unfortunately, a significant portion of tears occur in the white-white zone, which lies in the central avascular portion of the meniscus. This area of the meniscus has minimal blood supply, and theoretically is unable to heal. The remainder exist as red-white tears. These are meniscal rim tears through the peripheral vascular zone of the meniscus. The central portion of this tear exists in the avascular zone, so theoretically, these lesions should have sufficient vascularity to heal by fibrovascular proliferation.

Conventional wisdom dictates that meniscal repairs be limited to the peripheral vascular area of the meniscus (i.e., red-red and red-white tears). Both experimental and clinical studies have suggested that white-white tears are incapable of healing, even in the presence of a surgical suturing. This has thus provided the rationale for partial meniscectomy. In an effort to extend the zone of repair more peripherally, techniques such as the creation of vascular access channels by trephination, synovial abrasion, and use of a fibrin clot have been developed.

In addition, meniscal tears can be classified depending on their stability (Box 6-1). A tear is considered unstable when it is more than half the length of the meniscus and subluxes under the femoral condyle when probed with a hook (Fig. 6-3A). This concept is especially important to help decide the treatment options—left alone, trephinated, resected, or repaired.

FIGURE 6-3 A, Unstable longitudinal vertical tear. Note how it subluxes under the femoral condyle when probed. B, Stable incomplete longitudinal vertical tear. Stability should be assessed continuously with the probe. C, Stable complete longitudinal vertical tear. Some tears although complete may also be stable.

Stable tears, which occur particularly in the posterior aspect of the meniscus and do not subluxate into the joint may be left alone (see Fig. 6-3B and C). Fitzgibbons and Shelbourne⁸ have found that of 189 patients whose stable meniscal tears of the posterior horn of the medial meniscus were left alone, no patient was symptomatic at 2.6 years following surgery. Also, a stable longitudinal tear of the lateral meniscus, posterior to the popliteus, may be left alone, even in association with a torn ACL.

Tears can be described depending on their morphology and based on their configuration. Under these criteria, tears could be vertical or horizontal, according to whether the line of the lesion goes from superior to inferior (vertical) or from inside to outside (horizontal), commonly called open book or fishmouth tear (Fig. 6-4). Moreover, tears can be described as longitudinal if the pattern is from anterior to posterior (Fig. 6-5; also see Fig. 6-3), or transverse, also called a radial or parrot beak tear (Fig. 6-6). Combinations of these four basic patterns make up the others types of tears; the oblique tear is vertical and radial, and the so-called bucket handle tear is a vertical longitudinal tear that is unstable and subluxes completely under the condyle (Fig. 6-7; also see Fig. 6-3A). Finally, the complex tear is a combination of all of these, usually in a degenerative setting, located in the posterior horn of the medial meniscus (Fig. 6-8).

FIGURE 6-4 Horizontal degenerative tear. These tears may reach the vascular zone (arrow).

FIGURE 6-5 Diagram showing the longitudinal tear.

FIGURE 6-6 Radial tear. This is also called a parrot beak or flap tear.

FIGURE 6-7 Bucket handle tear dislocated into the intercondylar notch.

FIGURE 6-8 Complex tear. These tears are usually located in the posterior horn of the medial meniscus and are associated with degeneration.

Longitudinal vertical tears usually occur in the young patient in association with an anterior ACL tear, and more frequently in the medial meniscus because of its lower mobility. Oblique tears tend to appear in between the medial and posterior thirds of the meniscus. They may cause mechanical symptoms of entrapment and pain caused by the tension on the meniscus–capsular junction.

Horizontal-shaped tears usually begin as intrasubstance degeneration in the middle of the meniscus, and migrate toward the free surface. Often, they also extend to the capsular junction and can cause the formation of a cyst. Because of the increasing size of the cyst over time, the patient may experience pain and tenderness. They usually appear more frequently in the lateral meniscus and are filled with a gel-like substance chemically similar to synovial fluid. These cysts have been reported to be 1% to 10% of meniscal pathology.⁹

Complex tears appear mainly in older patients and are usually associated with cartilage degeneration. They are considered to be part of the process of arthrosis and degenerative arthropathy. Because of their complex pattern, the fragments can be unstable and cause mechanical symptoms. The pain associated with these tears is an added element to the generalized inflammation involved in the osteoarthritic knee. The associated histologic pathology is myxoid degeneration, hyaline acellular degeneration, and dystrophic calcification.¹⁰

Timing is also important in decision making. Tears can be acute, with more likelihood of healing, or chronic, which are usually associated with complex patterns and degeneration. These usually require resection. The time frame to consider a tear to be chronic is generally 8 to 12 weeks after the lesion has occurred.

The cause or mechanism of the tear should be determined. If the tear is traumatic, which usually happens in a young active patient, and is diagnosed acutely, there is an improved chance of success. On the other hand, degenerative complex tears usually occur in older patients and are associated with arthrosis. Whether they are a cause or consequence of the osteoarthritic process is still unknown.

Finally, tears can be classified depending on the side—that is, the medial or lateral meniscus. Metcalf and colleagues¹¹ have observed that 69% of tears affected the medial meniscus, whereas the lateral was affected 24% of the time. In their review, both menisci were torn at the same time in 7% of patients. Moreover, 80% of the tears were vertical or oblique and affected the posterior medial part of the meniscus.

In summary, the most common meniscal tears are as follows:

Chronic, degenerative, horizontal, or complex in the medial meniscus (see Fig. 6-8)

Acute, traumatic, longitudinal, and vertical in the medial meniscus (see Fig. 6-3)

The degenerative horizontal type tear usually occurs insidiously in older patients, and generally requires resection. On the other hand, the traumatic vertical or longitudinal tear is seen more often in the younger patient, and potentially can be repaired.

PATIENT EVALUATION

Physical Examination

The patient is examined for signs of an effusion, loss of quadriceps bulk, and decreased range of motion. Tenderness to palpation along the medial or lateral joint line is among the most sensitive signs of a meniscal tear (Fig. 6-9A). Studies have shown it to be as sensitive as 74%, with a positive predictive value of 50%.¹² The collateral and cruciate ligaments need to be assessed to determine whether additional injury is present. In the setting of an ACL-deficient knee the sensitivity of joint line tenderness has been shown to decrease to approximately 50%.

FIGURE 6-9 A, Palpating for joint line tenderness. This is the most sensitive sign for meniscal tear. B, The McMurray test. As a mnemonic rule, the heel of the foot points toward the injured meniscus. The test is considered positive when the patient feels pain in the appropriate joint line, accompanied by a thud or click.

Special tests for assessing the meniscus, such as the McMurray, Steinmann, and Apley tests, are not conclusive but can aid in the diagnosis. The aim of all these maneuvers is to trap a fragment of meniscus between the tibia and femur, producing pain, a clunk, or both. Because the meniscus itself is fairly aneural, pain is caused by traction at the synovium-meniscal junction.

The McMurray test is preferred because it is easy, fast, and reliable. In addition, complementary knee tests may be done in the same position. This provocative test is performed with the patient supine, the hip flexed to 90 degrees, and the knee in forced maximal flexion. The foot is grasped by the heel, the knee is steadied, and the joint line is palpated with the other hand. As the knee is slowly brought into extension, an external rotation stress will test the medial meniscus and an internal rotation stress will test the lateral meniscus (see Fig. 6-9B). As a mnemonic rule, the heel of the foot points toward the injured meniscus. The test is considered positive when the patient feels pain in the appropriate joint line, accompanied by a thud or click. When the clunk is present, the test has a sensitivity of 98% but, because it is not always possible to evoke the clunk, its specificity is only 15%.¹³

In conclusion, the hallmarks of a meniscal tear are presence of an effusion, joint line tenderness, and a positive McMurray test. When the history and physical examination are considered together, the overall sensitivity to diagnose a meniscal tear, confirmed with arthroscopy, is approximately 95% and specificity is 88%.¹⁴

TREATMENT

Arthroscopic Technique

If the patient continues to have pain, swelling, and locking or catching symptoms, and is willing to undergo surgical treatment, operative intervention is indicated. There are several surgical principles that should be followed to achieve a good outcome (Box 6-2). First, and following the Hippocratic principle of primum non nocere (“First, do no harm”), do not make the situation worse. If there is a stable, partial or total, vertical tear in a young patient, it should be left alone, and no resection is needed. Second, portal placement should be accurate enough to allow good visualization of the entire meniscus and tear configuration. In addition, portals should allow instruments of desired shapes to be introduced without scuffing the articular surface. Third, when resection is performed, the main objective is to achieve a stable peripheral rim and remove any unstable fragments that could cause mechanical symptoms or pain. During meniscectomy, it is important to contour the edges to have a smooth border and avoid progression to a second tear. The probe should be used continuously to assess stability of the rim. With bucket handle tears, 25% have a secondary tear of the rim that could be overlooked. If a complete meniscectomy is performed, care should be taken to prevent excessive bleeding from the meniscocapsular junction. After meniscectomy, or when the tear is left alone, stimulation of healing would help improve the results. This could be done by rasping the synovium, trephinating the meniscus to allow vascularization, and perforating the notch to cause bleeding. The penetration of the subchondral bone in the notch allows bone marrow mesenchymal cells in the field. Finally, adding autologous plasma rich in growth factors and cytokines may optimize the healing environment.

Box 6-2 Surgical Principles for Meniscectomy

• Primum non nocere (“First, do no harm.”)

• Have good access for viewing and instruments.

• Achieve a stable rim and remove any unstable fragments of meniscus.

• Have a smooth border to contour the edges.

• Use the probe constantly.

• Protect the meniscocapsular junction.

• Stimulate healing by using a rasp, trephination, marrow, and plasma rich in growth factors.

Preparation and Portal Placement

Patient positioning must allow circumferential access to the affected knee. The leg should be prepped and draped to allow posteromedial and posterolateral incisions if they are required in the case of a repair (Fig. 6-10). This can be done with the patient supine so that the break in the table is at the level of the tourniquet and the knee can be flexed to 90 degrees. Alternatively, a leg holder can be used that allows the surgeon to abduct the leg away from the operating table, allowing the knee to flex as needed for access.

FIGURE 6-10 Setup for meniscectomy.

The anterolateral portal is used to place the arthroscope for visualization. This portal is vertical, at the edge of the patellar tendon and at the inferior border of the patella. This high lateral portal allows the arthroscope to be above the fat pad, which avoids putting its tip into the fat pad—”fat padoscopy.” It is also central enough to allow visualization of the posterior notch. A superolateral portal is made in the pouch to allow drainage and lavage to improve visualization.

Diagnostic arthroscopy is performed using a 30-degree arthroscope. This includes an evaluation of the suprapatellar pouch, both menisci, articular cartilage, and cruciate ligaments. After diagnosis, and based on the type of tear, the medial portal is established. With the help of the finger, the medial soft spot is located. A spinal needle is placed to confirm the position of the new portal. The tip of the needle should be able to reach the area of the meniscal tear. The arthroscope is rotated to view the needle. It is essential to avoid cutting the meniscus or damaging the articular surface of the medial condyle. The medial portal is made with a no. 11 blade in an oblique direction to allow increasing the size of the portal, if needed. Making the incision oblique also reduces the potential to cut the articular surface with the blade. After the portals are established, the menisci are probed on the inferior and superior surfaces to identify any tears. In assessing meniscal stability, it is important to realize that the lateral meniscus is normally more mobile, up to 10 mm, than the medial meniscus,. The definition of an unstable meniscal tear is one that is half the length of the meniscus and subluxes under the condyle when probed with a hook (see Table 6-1). Although a tourniquet may be used to improve visualization during the procedure, some surgeons prefer to leave it deflated for the diagnostic arthroscopy to assess the vascularity of the meniscal tear after rasping. Meniscectomy in the medial meniscus is usually done close to extension and with valgus stress. In ACL-deficient patients, is important to take into account that the lateral compartment is usually subluxed anteriorly in internal rotation. The medial spine will obscure the visualization of the posterior horn of the medial meniscus. To get to the posterior horn of the medial meniscus, the assistant should perform external rotation of the tibia by holding the patient’s ankle or the foot. On occasion, in a very tight knee, an 18-gauge needle may be used to “pie crust” the medial ligament over the tibia. When valgus stress is placed on the MCL, a large enough opening will allow access to the posterior horn.

On the lateral side, the best visualization is obtained with the knee flexed and the leg placed in the figure-of-four position. This position is also key in protecting the peroneal nerve, which lies posterior to the biceps femoris tendon and furthest from the joint capsule with the knee in flexion.

Resection Techniques

The technique is determined by the type of tear. The success of the resection is significantly affected by instrument access to the surgery site. The most common limiting factors are poor portal placement, a tight compartment, and/or instrument geometry. In general, the principles of partial meniscectomy are to remove the least amount of tissue possible to obtain stability of the remaining meniscal rim.

Approach to the Medial Meniscus.

We usually begin at the extreme posterior attachment. To view the resection directly, the arthroscope is passed into the medial compartment. Its tip is kept positioned against the tibia and the telescope is rotated to look up under the condyle. This throws light into the posterior area and prevents scuffing of the condyle with the arthroscope tip. Then, a meniscal up-curved punch, designed to fit under the curve of condyle, is used on tears of the posterior horn of the medial meniscus. When inserting the punch, it should be left closed until it is in place anterior to the meniscal tear and posterior to the curve of the condyle. It is then advanced posteriorly. This way the insertion is easier and iatrogenic lesions to the cartilage are avoided. The next step is to advance the upper jaw of the instrument just above the superior surface of the area intended for resection. Once the selected segment is positioned between the jaws, these are closed, resecting the tear vertically. This step should be repeated circumferentially until the leaflet is resected completely. The side-angled basket is also used as the resection proceeds anteriorly. To prevent the pushing away effect of the basket, certain maneuvers can be performed by the assistant. Our preferred maneuver is to apply digital pressure on the posterior capsule, stabilizing the superior leaflet so it can be seen, and resected if indicated.

Moving to the anterior aspect, a straight large basket is used to resect the length of a segment of approximately 1 cm. Then, the remaining fragments adjacent to the medial collateral ligament are resected with an angled basket. When the midportion of the medial meniscus is approached, it may be resected by changing the arthroscope to the medial portal and inserting the basket through the lateral portal. Between resections with hand instruments, a small-diameter intra-articular shaver can be used to smooth any rough scalloping and to develop a well-contoured rim between resected areas. The shaver with suction also removes semiattached fragments from the rim border to improve visualization and determine whether further resection is needed. Angled small and large baskets can also be used to resect the posterior third. It is advisable to monitor the resection carefully to ensure adequate resection.

Ideally, resection of the posterior medial meniscus leaves an approximate 2- to 3-mm rim. This is gradually beveled through the middle to the anterior third.

If resection of the anterior horn is required, back-biting cutters are available. Alternatively, place the arthroscope in the medial portal and the instruments in the lateral portal. Rotary basket cutters also can be used for resection of the anterior horn. Isolated anterior horn tears are relatively rare, occurring most often in combination with bucket handle tears.

Approach to the Lateral Meniscus.

The arthroscope is inserted through the anterolateral distal portal. The basket cutters are used through the medial portal to resect the midportion of the lateral meniscus. The posterior horn can not be approached this way. Thus, the lateral portal is used for instruments and the medial portal is used for the arthroscope. Resection of the anterior third of the right knee is performed by using the left rotary basket, inserted through the medial portal. The intra-articular shaver is used frequently, interspersed with the left or right rotary basket.

Resecting a Displaced Bucket Handle Tear.

In these cases, the anteriorly displaced fragment (see Fig. 6-7) obscures visualization of the medial compartment and the posterior region of the tear. The rim may be assessed before the tear is reduced to ascertain whether a repair is possible.

The first step is to reduce the fragment with the probe or the blunt trocar from the arthroscope to improve visualization. Valgus stress must be applied to perform the reduction.

Next, use the arthroscopic scissors to cut the posterior horn attachment. Cutting this first avoids the problem of the fragment displacing into the posterior compartment after cutting the anterior horn. The arthroscope may have to be placed into the intercondylar notch and the depth of the cut assessed from there. The anterior attachment is cut as close to the axilla of the tear as possible, leaving a minuscule attachment to prevent the fragment from moving away.

Finally, grasp the end of the fragment and remove it from the joint. The rim should be contoured with the 4-mm shaver. Be sure to hook the remaining rim, because there is a secondary tear in 25% of cases. If there is a tear in the rim. be sure to resect any unstable portion. If it is impossible to reduce the chronic displaced bucket handle on the medial side, the anterior attachment may be cut first. A grasper is used to place tension on the end of the bucket handle fragment, and cutting scissors are inserted through the same portal to cut under the posterior horn attachment. This cut is blind, and careful monitoring of the depth of the cut is important to prevent posterior neurovascular injury. The technique is similar to that for lateral displaced bucket handle tears.

Resection of a Radial Lateral Meniscus Tear.

The radial tear of the lateral meniscus is approached with instruments from the medial portal. The straight basket is used to resect the posterior edge and the 90-degree basket is used to resect the anterior edge. The small shaver is used to contour the meniscus further. This has to be resected back to a normal-appearing rim. The body of the meniscus will often have a degenerative mucoid appearance that must be resected.

Resection of Lateral Meniscal Tears Associated with a Cyst.

This tear is approached in much the same fashion as described for the radial tear (see earlier). The entrance to the cyst is usually below the meniscus and can be entered with a small shaver. Digital palpation of the cyst externally will cause some ganglion-like fluid to enter the joint through the entrance made by the shaver. The suction on the shaver is used to evacuate the cyst. No external excision of the cyst is necessary if the meniscectomy is adequate.

Resection of the Discoid Lateral Meniscus.

Often, the central tear of the discoid meniscus will be difficult to visualize. The center of the meniscus is probed with a hook and the delamination or tear is then palpated. The basket forceps is brought through the medial portal and the central portion is resected back to a normal-appearing rim of lateral meniscus. It is important to probe the rim to be certain that it is attached, and not unstable. Rarely, a Wrisberg type of lateral meniscus will be encountered that does not have any peripheral attachments, and a suture repair of the rim must be performed.

Baker’s Cyst and Degenerative Medial Meniscal Tears.

In most cases, once the degenerative medial meniscus is resected, the recurrent effusions are controlled and the symptoms of pain and swelling caused by the Baker’s cyst will improve. Occasionally, with a very large symptomatic cyst and a degenerative medial meniscal tear associated with degeneration of the medial compartment, the Baker’s cyst must be addressed. A posteromedial portal is made with the arthroscope in the lateral portal and then advanced into the posteromedial compartment. The overlapping flaps of the Baker’s cyst are identified and, with a shaver through the posteromedial portal, the inferior flap is resected to leave an opening into the cyst. The cyst will then drain into the joint and remain decompressed. Once the joint effusion is controlled, the Baker’s cyst will gradually reduce in size.

Occasionally, with a chronic Baker’s cyst, the shaver may have to be introduced into the cyst through a separate percutaneous puncture and the cyst walls resected. The arthroscope is introduced into the cyst through the opening made in the posterior capsule to monitor the progress of the cyst wall excision.

Special Considerations: Anterior Cruciate Ligament Reconstruction and Meniscectomy

Facing a meniscal tear during ACL surgery is not an uncommon situation. In some series, the incidence can be as high as 57%,¹⁹ whereas some others have reported an incidence of approximately 30%.²⁰ A predominance of lateral meniscal tears has been demonstrated with acute ACL rupture, whereas the incidence of medial meniscal tears increases significantly with chronic ACL insufficiency. This suggests that lateral meniscal tears occur at the time of injury to the ACL or very soon after injury, whereas medial meniscal tears are acquired after the knee has been ACL-deficient.

A treatment decision is especially important in this scenario. Deciding to leave certain types of tears alone can result in saving time in these long procedures, with good outcomes. Definition of stability during arthroscopy, a tear that does not sublux under the condyles, or one less than 10 mm long, would be helpful in clarifying which tears could be saved. The bleeding environment along with the stable knee facilitates healing after surgery. Taking that into account, some surgeons consider that the radial tear of the lateral meniscus can also be saved in the setting of ACL reconstruction. Shelbourne¹⁹ has advocated leaving alone the vertical tear located posterior to the popliteus tendon and the posterior horn avulsion, and has shown in a long-term follow-up that they are asymptomatic. In their series of stable peripheral vertical tears of the medial meniscus treated with trephination and abrasion, Shelbourne and Rask²¹ have reported a 94% success rate.

Recently, Pujol and Beaufils²² have proposed to leave alone those stable tears placed on the lateral side, based on a systematic review of the literature. On the other hand, they advised that tears in the medial meniscus, including the stable ones, should be repaired or resected because of the undesirable outcomes in the published series. This advice is based on literature results on medial meniscus tears left alone, which have been shown to fail in about 50% of cases. Failure is considered to be pain, locking, or any other clinical meniscal symptoms, along with proof of nonhealing in any image test, such as arthroscopic MRI, normal MRI, or arthroscopy.

In the setting of ACL reconstruction with a tear in the lateral meniscus that could not be left alone, more emphasis should be put on repairing it over resection because of its important role in stability. A repaired lateral meniscus has a potential role in reducing anterior translation and thus protecting the graft from undesirable stresses that could lead to failure.

In terms of timing of ACL surgery with a concomitant meniscal tear, it is advisable to perform the procedure before the third month postinjury, considering the findings of Papastergiou and associates.²⁰ They showed that the prevalence of a meniscal tear needing treatment increases significantly after this period. In their study, the prevalence of meniscal tear in the first 3 months after the traumatic injury was approximately 45%, increasing up to 69% after the sixth month. Considering that the prevalence of medial meniscal tears increases with time, they concluded that ACL reconstruction in the early period would reduce the risk of secondary meniscal tears.

PEARLS

PEARLS

• Use drainage from the superolateral portal to improve visualization.

• Use vertical oblique incisions in case portal augmentation will be needed.

• Use external rotation to get to the post horn of the medial meniscus.

• Use the figure-of-four position for the best approach to the lateral compartment, and use the probe constantly.

• Use the “pie crust” technique on the MCL to open the medial compartment.

OUTCOMES

The menisci were once considered a vestigial tissue, without any role in the knee.²⁷ At that time, total open meniscectomy was considered the definitive treatment for its pathology. The short-term results of total meniscectomy are good because it eliminates the mechanical symptoms of locking immediately and achieves fast pain relief. On the other hand, the clinical results worsen with time, and osteoarthritis of the involved compartment appears sooner than age-matched controls without total meniscectomy.²⁸ In addition, total meniscectomy is associated with more radiographic osteoarthritis over time than partial meniscectomy.¹⁶

Because of the increasing information about meniscal function, surgical procedures have evolved with the objective of preserving as much tissue as possible. Thus, partial meniscectomy has become the elected treatment when repair is not possible. The American Academy of Orthopaedic Surgeons estimates that 636,000 arthroscopic procedures of the knee are performed each year in the United States.²⁹

With the help of optical magnification and minimally invasive instruments, arthroscopic partial meniscectomy has become the gold standard over open surgery.³⁰ Numerous reports have commented on the beneficial effect of the use of arthroscopy over open surgery.

The advantages related to arthroscopic surgery are day surgery without the need of hospital admission, less recovery time, less pain caused by the minimally invasive surgery, less global morbidity, improved visualization with more accurate resections, resulting in better long-term outcomes, fewer complications, and lower cost for the patient and/or the system.

When analyzing partial meniscectomy results, various methods of determining surgical outcome have been used, ranging from clinical examination to patient satisfaction and radiographic measurements. In general, in the literature, uniformly good to excellent results have been documented in 80% to 95% of patients within the first 5 years after partial meniscectomy. Rockborn and coworkers³¹ have reported a mean Lysholm score of more than 84 in the first year after meniscectomy. It has been shown that allowing the patient to watch the arthroscopic procedure increases his or her overall understanding and satisfaction in the early postoperative period. In addition, it decreases the anxiety and worries about the surgery and the postoperative period significantly.³²

Clinical outcomes in the long term are also satisfactory. Burks and colleagues³³ have published overall Lysholm scores of 94 and average satisfaction index of 8.8. Moreover, the Tegner change of desired versus actual activity level was 0.3. This means that the subjective results were satisfactory 15 years after meniscectomy.

Higuchi and associates,³⁴ based on the criteria of Tapper and Hoover and the International Knee Documented Committee’s evaluation form (IKDC), rated their results after 12.2 years postmeniscectomy as being excellent and good in 71% of their series.

Because of the variety of measuring tools used in the different studies, it is difficult to compare their results. Addressing that issue, the University of Western Ontario has developed, and validated the WOMET.³⁵ This is a simple, disease-specific tool designed to evaluate health-related quality of life in patients with meniscal pathology to be used in research or in clinical practice uniformly.

Meniscectomy is a well-known risk factor for secondary osteoarthritis (OA) of the knee. Traditionally considered as a result of joint injury and increased cartilage contact stress caused by the loss of meniscal tissue, wear and tear is a straightforward explanation for secondary knee OA. In addition, there is proof of an interaction between primary heritable OA and exogenous secondary OA caused by meniscectomy.³⁶ Moreover, there is a sixfold increased relative risk for the development of radiographic osteoarthritis after total meniscectomy compared with nonoperated controls.² However, as expected, partial meniscectomy induces less radiographic OA over time than does total meniscectomy.¹⁶

Is important to note that radiographic changes do not clearly correlate with clinical symptoms.³⁷ Thus, radiographic outcome appears to be a poor determinant of overall outcome from surgery.

Degenerative tears of the menisci have been associated with osteoarthritis. Whether degenerative tear is a cause or consequence of osteoarthritis is still unknown. Some studies have suggested that a degenerative tear could be the first sign of arthritis in the knee. Patients suffering a degenerative tear experience worse clinical outcomes than those with a traumatic lesion.³⁸ Partial meniscectomy of degenerative tears is associated with a high risk of radiographic and symptomatic tibiofemoral arthritis at 16-year follow-up.² Evaluating for pain after exercise at 8.5 years follow-up, patients with flap or horizontal tears had worse clinical outcomes after meniscectomy than those with bucket handle tears.³⁹

Data regarding medial versus lateral partial meniscectomy are controversial. Although in vivo studies have not clearly shown significant differences between sides, laboratory studies have proven that lateral partial meniscectomy is more dangerous than the same procedure performed in the medial compartment. Englund and Lohmander¹⁶ published worse radiographic outcomes in association with lateral meniscectomy 22 years after surgery than medial meniscectomy. The lateral meniscus carries a higher load in the knee compared with the medial meniscus. Consequently, its loss may result in increased cartilage contact stress.

To be able to inform the patient about expectations after surgery, it is important to be familiar with the predicting factors affecting the results. Intuitively, one might think that they would include the following: the compartment involved (lateral meniscectomy resection is worse than medial); the amount of resection (more removed equals more risk); the type of resection (radial resection of even a small portion may destroy the hoop stress function and probably is the equivalent of a near-total meniscectomy); associated conditions (ACL insufficiency and chondral pathology are probably overall even more significant indicators of probable degenerative progression); tibiofemoral alignment (varus alignment risk for medial meniscus, lateral for valgus); and body habitus, patient age, and activity level.

However, only some factors have proven to affect the outcome significantly. In the short term, only female gender and previous OA are associated with a slower rate of recovery from arthroscopic partial meniscectomy, whereas age, body mass index, depth of meniscal excision, involvement of one or both menisci, and extent of meniscal tear show no association.¹⁵ In the long term, contributing risk factors for arthritis development after meniscal resection are similar to risk factors for common knee osteoarthritis. Systemic and local biomechanical factors interact. Younger patient age predicts a better long-term prognosis after meniscectomy, whereas, obesity, female gender, and preexisting early-stage OA are features associated with poor self-reported and radiographic outcomes.¹⁶

COMPLICATIONS

The overall complication rate of knee arthroscopy is relatively low.⁴⁰ It has been estimated in retrospective large series of 118,590 and 395,566 arthroscopies to be 0.8%⁴¹ and 0.5%,⁴² respectively. In those series, complications were more likely to occur with more complex procedures, such as meniscal repair, synovectomy, and intra-articular reconstruction of both the ACL and PCL. In a prospective study reviewing 10,262 procedures, Small⁴³ has found an overall complication rate of 1.68%. The most common complications in this study were hemarthrosis (60.1%), infection (12.1%), thromboembolic disease (6.9%), anesthetic complications (6.4%), instrument failure (2.9%), complex regional pain syndrome 1 (CRPS 1; 2.3%), ligament injury (1.2%), and fracture or neurologic injury (0.6% each).

In general, arthroscopic meniscectomy is an innocuous procedure. However, complications can arise during surgery or in the postoperative period. Operative complications are usually iatrogenic and may be avoided with careful surgical technique. During surgery, several structures may be damaged, such as the medial collateral ligament, neurovascular structures, and meniscal and cartilage tissues.

Medial collateral injury during arthroscopic maneuvers may occur. Leg holders or posts are commonly used to aid exposure, particularly of the posterior horn of the medial meniscus. To achieve better exposure, valgus force is applied. If force is not used judiciously, a medial collateral ligament injury may result. This is especially possible in a tight medial compartment in a middle-aged or older patient in whom the soft tissues are likely to be less flexible. Small⁴² has reported a 0.003% incidence of medial collateral injury; ninety % of them were attributed to the use of the leg holder. Treatment is normally conservative by functional bracing, with initial restriction of extension.

Neurologic damage can occur during arthroscopic meniscectomy. Rodeo and coworkers have reported four possible mechanisms: (1) direct trauma; (2) pressure secondary to a compartment syndrome caused by extravasation of fluid; (3) damage related to the use of a tourniquet) and (4) dysfunction caused by the ill-understood condition of CRPS 1. Nerve injury to the sensitive branches innervating the knee can cause numbness and/or neuropathic pain. This can happen in the anterior part of the knee when preparing the portals. Occasionally, formation of a neuroma can be troublesome and it is possible that a relatively minor nerve injury can lead to CRPS 1.

On the medial side, the infragenicular branches of the saphenous nerve (IGBSN) can be affected more commonly. Sherman and colleagues⁴⁴ have reported an incidence of 22.2% of sensory changes in the distribution of the IGBSN after standard portals had been used. Although safe zones have been advocated, the wide variability in the course of the nerve precludes the absolute avoidance of damage. Mochida and associates⁴⁵ have recommended that arthroscopic portals should be positioned close to both the patella and patellar tendon if injury to the IGBSN is to be avoided. On the lateral side, there has been a report of injury to the common peroneal nerve during lateral meniscectomy,⁴⁶ but this complication usually occurs during meniscal suture.

A temporary paresis may occur after prolonged inflation of the tourniquet. In the series of Sherman and coworkers,⁴⁴ the incidence of complications was directly related to age and tourniquet time. However, the higher risk for major complications was in the group in which the tourniquet time was longer than 60 minutes regardless of age, with a predicted complication rate of 14.3%. To avoid this type of complication, it is important that regular checks be made on the accuracy of tourniquet pressure, which should be deflated after a maximum of 2 hours.

Another complication that can occur during portal preparation is iatrogenic section of the anterior horns of the menisci, which are especially vulnerable. This can be avoided by palpating the soft point for the anterolateral portal and creating the anteromedial portal under direct arthroscopic visualization. It is advisable to cut upward with the knife, away from the meniscus, rather than downward.

Iatrogenic lesions to the cartilage can also occur when inserting the different instruments. It is important not to use a sharp trocar to introduce the arthroscope into the knee. A portal of adequate size should be made so that a blunt obturator can be used. One way to avoid cartilage damage during the arthroscopic procedure is always to direct any instrument to the intercondylar notch gently. After that, use the arthroscope to control its position and then direct the instrument where needed under arthroscopic control.

Apart from intraoperative complications, postoperative complications may also occur, such as joint effusion, residual pain, infection, and thromboembolism. Joint effusion after surgery can be caused by hydrarthrosis or hemarthrosis. Hydrarthrosis is usually a consequence of synovitis. This could be caused by the presence of previous knee osteoarthritis or by aggressive use of the joint during rehabilitation or daily activities. On the other hand, hemarthrosis is usually a consequence of extended meniscal excisions reaching the vascular zone or even the capsule. This can cause intense pain and loss of ROM in the knee. If the joint is under high tension, evacuation might be needed. Infiltrating with local anesthetic and adrenalin may be helpful. Rarely, a second-look arthroscopy is needed to cauterize the bleeding vessel. To avoid this complication, some surgeons do not use a tourniquet or deflate it before finishing the arthroscopy. In this way, bleeding points can be controlled and cauterized with the aid of electrical devices. In addition, preserving as much of the meniscal tissue as possible, mainly the rim, and avoiding sectioning the capsule are also efficacious methods to prevent bleeding. Joint effusion, in general, is managed with evacuation, rest, elevation, and ice. If it is persistent, the judicious use of an injection of cortisone is indicated.

If postoperative pain is well managed, residual pain after surgery is usually related to the preexisting condition of the knee. The previous state of the femoral, tibial, and patellar cartilage plays a key role. The more wear the cartilage has had before the surgery, the less likely is it possible to achieve complete pain relief in the short term or long term. Moreover, the presence of mechanical symptoms such as locking after surgery can be also be attributed to the incongruence of the worn joint instead of an incomplete resection. The clinical situation of persistent pain can be evaluated with a contrast MRI. The dye may demonstrate a persistent cleft into the remaining rim, indicating incomplete resection.

Infection rates of arthroscopic meniscectomy are similar to those of other basic arthroscopic procedures. Kirchhoff^46a has reported an incidence of infection in elected arthroscopy of 0.42%. In knee arthroscopy, Sherman and colleagues⁴⁴ have reported an incidence of 0.1%, DeLee⁴¹ of 0.08%, D’Angelo and Ogilvie-Harris⁴⁷ of 0.23%, and Armstrong and associates⁴⁸ of 0.42%. This severe complication may be avoided with the use of antibiotic prophylaxis. Bert^47a has shown that routine antibiotic administration does not reduce the rate of postoperative septic arthritis. Although some institutions do not routinely use antibiotic prophylaxis in arthroscopic meniscectomy procedures, D’Angelo and Ogilvie-Harris⁴⁷ have recommended its use based on their cost-effective analysis. On the other hand, the appearance of septic arthritis of the knee postmeniscectomy is a devastating complication that should be treated aggressively. The most common infecting organism is Staphylococcus aureus. In the treatment protocol, arthroscopic débridement, along with intravenous antibiotics, should be included. Continuous passive motion is recommended as soon as the patient tolerates it.

The overall incidence of thromboembolic disease in knee arthroscopy is approximately 0.1%. Thromboembolism is even more infrequent after meniscectomy because of the short duration of the procedure and the possibility of immediate mobility after surgery. There is no indication for routine thromboprophylaxis in arthroscopic surgery, but the operating and tourniquet times should be kept to a minimum and postoperative mobilization should be as rapid as possible. Chemoprophylaxis should be considered only for high-risk patients, particularly those with previous thromboembolism.

Some exceptional complications have been reported. Berndt and coworkers⁴⁹ have reported the appearance of heterotopic ossification of the medial portal after partial meniscectomy. Furthermore, MacDessi and colleagues⁵⁰ have reported a series of eight cases of osteonecrosis after meniscectomy. They attributed the cause to subchondral fractures and suggested that this complication should be treated successfully with arthroplasty.

CONCLUSIONS

The arthroscopic technique offers advantages and better outcomes over the open procedure, as does partial over total meniscectomy. In general, the literature has documented uniformly good to excellent results in 80% to 95% of patients who have undergone arthroscopic partial meniscectomy in the short term. In the long term, results are more controversial.

Although meniscectomy is still the most frequent current procedure, there is an increasing interest in preserving techniques because of more information about the role of the menisci. Moreover, new biologic enhancing techniques, along with tissue engineering, may be the future of the treatment of meniscal pathology.