DEFINITION

Irreparable meniscal tears are those for which no healing response is possible.

This may include all or part of a meniscus, prompting partial, subtotal, or total meniscectomy.

Meniscal injuries in the “white zone” (central avascular portion; FIG 1) most often require partial meniscectomy.

This usually involves the inner two-thirds of the meniscus.

Symptomatic tears of discoid lateral menisci also may require partial or subtotal saucerization of the meniscus.

Numerous classifications of tears of the menisci have been proposed based on location or type of tear, etiology, and other factors; most of the commonly used classifications are based on the type of tear found at surgery (FIG 2).

Longitudinal tears

Transverse, radial, and oblique tears

A combination of longitudinal and transverse tears Tears associated with cystic menisci

Tears associated with discoid menisci

The most common type of tear is the longitudinal tear, usually involving the posterior segment of either the medial or lateral meniscus.

More lateral meniscal tears have been diagnosed than medial tears.

Although no definitive study comparing the incidence of medial to lateral tears has been reported, the two types are believed to occur with almost equal frequency.

Most partial-thickness tears involve the inferior rather than the superior surface of the meniscus.

 

 

FIG 1 • Tears in the central avascular portion of the meniscus (white zone) usually require partial meniscectomy, those in the vascular red zone have good healing potential, and those in the red-white zone have limited healing potential.

 

Certain patterns of meniscal tears are associated with mechanical locking.

 

Small longitudinal tears limited to the posterior horn usually are not capable of producing locking but rather cause pain, recurrent swelling, and subjective instability.

 

Extensive longitudinal tears can cause locking by displacing into the intercondylar notch. These unstable tears often are referred to as bucket-handle tears.

 

A pedunculated fragment may result if either the posterior or anterior attachment of the bucket-handle fragment becomes detached.

 

Transverse, radial, or oblique tears can occur in either meniscus but are more common in the lateral, usually at the junction of the anterior and middle thirds.

 

 

Transverse tears also can result from degenerative changes that make the meniscus less mobile. Complex transverse and longitudinal tears may occur with degeneration or repeated traumatic episodes.

 

Meniscal cysts frequently are associated with tears and are nine times more common on the lateral than on the medial side.

 

Discoid menisci are abnormal in terms of both mobility and increased tissue bulk, making them vulnerable to compression and rotary stress.

 

ANATOMY

 

The menisci are crescents that are roughly triangular in cross-section.

 

They cover one-half to two-thirds of the articular surface of the corresponding tibial plateau.

 

They are composed of dense, tightly woven collagen fibers arranged in a pattern, providing great elasticity and ability to

withstand compression.

 

 

The major orientation of collagen fibers in the meniscus is circumferential. Radial fibers and perforating fibers also are present (FIG 3A).

 

The arrangement of these collagen fibers determines to some extent the characteristic patterns of meniscal tears (FIG 3B,C).

 

When meniscal samples are tested by applying a force perpendicular to the fiber direction, the strength is decreased to less than 10% because collagen fibers function primarily to resist tensile forces along the direction of the fibers.6

 

The circumferential fibers act in a similar manner as metal hoops placed around a pressurized wooden barrel: The tension in the hoops keeps the wooden staves in place (FIG 3D,E).

 

Hoop tension is lost when a single radial cut or tear extends to the capsular margin.

 

 

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FIG 2 • Patterns of meniscal tears.

 

 

The peripheral edges of the menisci are convex, fixed, and attached to the inner surface of the knee joint capsule, except where the popliteus is interposed laterally; the peripheral edges also are attached loosely via coronary ligament to the borders of the tibial plateaus.

 

The inner edges are concave, thin, and unattached.

 

 

 

FIG 3 • A. Pattern of collagen fibers within the meniscus. B. Cross-section of meniscus showing horizontal cleavage split. C. Cross-section showing direction of longitudinal tear; direction of tear usually is oblique rather than vertical. D,E. Role of hoop tension in the menisci. D. Hoop tension acts to keep menisci between the bones. E. Single cut in radial edge eliminates hoop tension and allows menisci to move out from between bones. (D,E: Adapted from Grood ES. Meniscal function. Adv Orthop Surg 1984;7:193-197.)

 

 

The menisci are largely avascular except near their peripheral attachment.

 

The inferior surface of each meniscus is flat, whereas the superior surface is concave, corresponding to the contour of the associated bony anatomy.

 

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FIG 4 • Superior view of tibial condyles. Lateral meniscus is smaller in diameter, thicker about its periphery, wider in body, and more mobile than the medial meniscus; posteriorly it is attached to the medial femoral condyle by either the anterior or posterior meniscofemoral ligament, depending on which is present, and to the popliteus muscle.

 

 

The medial meniscus is a C-shaped structure larger in radius than the lateral meniscus, with the posterior horn being wider than the anterior (FIG 4).19,24,30

 

The anterior horn is attached firmly to the tibia anterior to the intercondylar eminence and to the anterior cruciate ligament (ACL).

 

Most of the weight is born on the posterior portion of the meniscus.

 

The posterior horn is anchored immediately in front of the attachments of the posterior cruciate ligament posterior to the intercondylar eminence.

 

Its entire peripheral border is firmly attached to the medial capsule and through the coronary ligament to the upper border of the tibia.

 

The lateral meniscus is more circular in form, covering up to two-thirds of the articular surface of the underlying tibial plateau.

 

 

The anterior horn is attached to the tibia medially in front of the intercondylar eminence.

 

The posterior horn inserts into the posterior aspect of the intercondylar eminence and in front of the posterior attachment of the medial meniscus.

 

The posterior horn often receives anchorage also to the femur via the ligament of Wrisberg and the ligament of Humphrey and from fascia covering the popliteus muscle and the arcuate complex at the posterolateral corner of the knee.

 

 

 

FIG 5 • Kinematics of the menisci with knee flexion, extension, and rotation. Although the lateral meniscus and lateral tibial plateau have a smaller anteroposterior width, the lateral meniscus moves more than the medial meniscus through each range of motion. (Adapted from Tria AJ Jr, Klein KS. An Illustrated Guide to the Knee. New York: Churchill Livingstone, 1992.)

 

 

The inner border, like that of the medial meniscus, is thin, concave, and free.

 

The tendon of the popliteus muscle separates the posterolateral periphery of the lateral meniscus from the joint capsule and the lateral collateral ligament. This tendon is enveloped in a synovial membrane and forms an oblique groove on the lateral border of the meniscus.

 

The lateral meniscus is smaller in diameter, thicker in periphery, wider in body, and more mobile than the medial meniscus.

 

The menisci follow the tibial condyles during flexion and extension; but during rotation, they follow the femur and move on the tibia (FIG 5).

 

Consequently, the medial meniscus becomes distorted.

 

Its anterior and posterior attachments follow the tibia, but its intervening part follows the femur; thus, it is likely to be injured during rotation.

 

However, the lateral meniscus, because it is firmly attached to the popliteus muscle and to the ligament of Wrisberg or of Humphrey, follows the lateral femoral condyle during rotation and therefore is less likely to be injured.

 

In addition, when the tibia is rotated internally and the knee flexed, the popliteus muscle, by way of the arcuate ligament complex, draws the posterior segment of the lateral meniscus backward, thereby preventing the meniscus from being caught between the condyle of the femur and the plateau of the tibia.

 

The vascular supply to the medial and lateral menisci originates predominately from the lateral and medial geniculate vessels (both inferior and superior).

 

Branches from these vessels give rise to a perimeniscal capillary plexus within the synovial and capsular tissue, which supplies the peripheral border of the meniscus throughout its attachment to the joint capsule.

 

These vessels are oriented in a predominantly circumferential pattern, with radial branches directed toward the center of the joint.

 

Arnoczky and Warren6,7 used microinjection techniques to show that the depth of peripheral vascular penetration is 10% to 30% of the width of the medial meniscus and 10% to 25% of the width of the lateral meniscus.

 

The medial geniculate artery, along with a few terminal branches of the medial and lateral geniculate artery, also supplies vessels to the menisci through the vascular synovial covering.

 

The menisci have several proposed functions in the knee joint.

 

 

They act as a joint filler, compensating for gross incongruity between the femoral and tibial articulating surfaces.

 

 

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They are believed to have a joint lubrication function, distributing synovial fluid and aiding the nutrition of the articular cartilage. A study by Ciccotti et al10 appears to confirm this function: In a series of patients undergoing arthroscopy for

meniscal pathology, 85% of 252 patients aged 50 to 59 years and 86% of those aged 60 years or older had articular cartilage changes.

 

They serve as important secondary stabilizers in all planes, especially providing rotary stability to the joint, and allowing for smooth gliding or rotary motion as the knee extends.

 

PATHOGENESIS

 

Meniscal injuries generally have either a traumatic or degenerative cause.

 

 

Traumatic injuries in young, active individuals are often associated with tears of the anterior and posterior cruciate ligaments. Traumatic tears are more common in the lateral meniscus.

 

The most common traumatic tears are vertical longitudinal tears, followed by vertical transverse tears.

 

Degenerative meniscal tears occur most often in patients older than 40 years of age, typically with no history of a specific traumatic event and often in association with other degenerative changes in the knee joint.

 

 

Degenerative tears of the menisci are more common in the medial meniscus and have minimal or no healing potential.24 The most common degenerative tear patterns are horizontal cleavage tears, flap tears, and complex tears (see FIG 2).

 

Miller et al22 classified meniscal tears based on their location in three zones of vascularity and use this classification to determine the potential for healing after repair (see FIG 1):

 

Red: fully within the vascular area

 

 

Red-white: at the border of the vascular area White: within the avascular area

 

After injury within the peripheral vascular zone, a fibrin clot forms that is rich in inflammatory cells.

 

 

Vessels from the perimeniscal capillary plexus proliferate throughout this fibrin scaffold and are accompanied by the proliferations of differentiated mesenchymal cells.

 

Eventually, the lesion is filled with cellular fibrovascular scar tissue that glues the wound edges together and appears continuous with the adjacent normal meniscal fibrocartilage.

 

Experimental studies in animals have shown that complete radial lesions of the meniscus are completely healed with a young fibrocartilaginous scar by 10 weeks, although several months are required for maturation to fibrocartilage that appears normal.

 

Controversy exists about the ability of a meniscus or a meniscus-like tissue to regenerate after meniscectomy.

 

 

It is now generally accepted that to have any regeneration, the entire meniscus must be resected to expose the vascular synovial tissue, or, in subtotal meniscectomy, the excision must extend to the peripheral vasculature of the meniscus.

 

The frequency and degree of regeneration of the meniscus have not been determined precisely.

 

Traumatic lesions of the menisci are produced most commonly by rotation as the flexed knee moves toward an extended position.

 

 

 

FIG 6 • Classic bucket-handle meniscal tear.

 

 

The most common location for injury is the posterior horn of the meniscus, and longitudinal tears are the most common type of injury.

 

The length, depth, and position of the tear depend on the position of the posterior horn in relation to the femoral and tibial condyles at the time of injury.

 

Less significant trauma is needed to injure a meniscus that is degenerated or made less mobile from prior injury, previous surgery, disease, or congenital anomaly (ie, discoid meniscus).

 

The menisci are also at increased risk in the presence of joint incongruities, ligamentous instability, profound muscle weakness, or congenitally relaxed joints.

 

As the knee is internally rotated during flexion, the medial meniscus is forced posteriorly. If the peripheral attachment stretches or tears, the posterior part of the meniscus is forced centrally, caught between the femur and tibia, and torn longitudinally as the knee extends.

 

If this longitudinal tear extends anteriorly beyond the medial collateral ligament, the inner segment of the meniscus is caught in the intercondylar notch and cannot return to its former position; thus, a classic bucket-handle tear with locking of the joint is produced (FIG 6).

 

The same mechanism can produce a posterior peripheral or a longitudinal tear of the lateral meniscus.

 

Because of its mobility and structure, the lateral meniscus is not as susceptible to bucket-handle tears, but incomplete transverse tears are more common here than in the medial meniscus.

 

NATURAL HISTORY

 

The effects of meniscectomy on joint laxity have been studied for anteroposterior and varus-valgus motions and rotation.

 

 

These studies indicated that the effect on joint laxity depends on whether the ligaments of the knee are intact and whether the joint is bearing weight.

 

In the presence of intact ligamentous structures, excision of the menisci produces small increases in joint laxity.

 

When combined with ligamentous insufficiency, these increased instabilities caused by meniscectomy are greatly exaggerated.

 

In an ACL-deficient knee, medial meniscectomy has been shown to increase tibial translation by 58% at 90 degrees, whereas primary anterior and posterior translations were not affected by lateral meniscectomy.3

 

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Anatomically, the capsular components that attach the lateral meniscus to the tibia do not affix the lateral meniscus as firmly as they do the medial meniscus.

 

These results indicate that in contrast to the medial meniscus, the lateral meniscus does not act as an efficient posterior wedge to resist anterior translation of the tibia on the femur.

 

Therefore, in knees that lack an ACL, the lateral meniscus is subjected to different forces than those that occur on the medial side.

 

 

Allen et al,3 in a biomechanical study, determined that force in the medial meniscus increased significantly in response to an anterior tibial load after ACL transection, which may account for some of the differences in injury patterns between the medial and lateral menisci in the anterior cruciate-deficient knee.

 

Walker and Erkman29 noted that under loads of up to 150 kg, the lateral meniscus appeared to carry 70% of the load on that side of the joint, whereas on the medial side the load was shared about equally by the meniscus and the exposed articular cartilage.

 

Medial meniscectomy decreases contact area by 50% to 70% and increases contact stress by 100%.

 

Lateral meniscectomy decreases contact area by 40% to 50% but dramatically increases contact stress by 200% to 300% because of the relative convex surface of the lateral tibial plateau.

 

Presumably, the menisci provide mediolateral stability where the load is supported by the entire width of the tibial articular surface. Without the menisci, the load is supported centrally on each plateau, diminishing the lever arm of load support.

 

Radiographic changes apparent after meniscectomy include narrowing of the joint space, flattening of the femoral condyle, and formation of osteophytes.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Mechanical symptoms, such as catching, popping, and locking, usually occur only with longitudinal tears and are much more common with bucket-handle tears, usually of the medial meniscus.

 

Locking of the knee is not pathognomonic of a bucket-handle tear of a meniscus: Other conditions such as loose body, patellar maltracking, and intra-articular tumor can cause similar findings.

 

The following clues can be important in the differential diagnosis:

 

 

 

Sensation of giving way Effusion

 

Atrophy of the quadriceps

 

Tenderness over the joint line (or the meniscus)

 

Reproduction of a click by manipulative maneuvers during the physical examination

 

Probably, the most important physical finding is localized tenderness along the posteromedial or posterolateral joint line, which is most commonly caused by reactive synovitis.

 

A history of specific injury may not be obtained, especially when tears of abnormal or degenerative menisci have occurred.

 

A patient without locking typically gives a history of several episodes of trouble referable to the knee, often resulting in effusion and a brief period of disability but no definite locking.

 

A sensation of giving way or snaps, clicks, catches, or jerks in the knee may be described, or the history may be even more indefinite, with recurrent episodes of pain and mild effusion in the knee and tenderness in the anterior joint space after excessive activity.

 

The injured knee should be compared with the opposite knee, which can exhibit 5 to 10 degrees of physiologic recurvatum. In this case, the injured knee can be locked and still extend to neutral position.

 

Regardless of its cause, locking that is unrelieved after aspiration of the hemarthrosis and a period of conservative treatment may require surgical treatment.

 

A serious error would be failure to distinguish locking from false locking.

 

False locking occurs most often soon after an injury in which hemorrhage about the posterior part of the capsule or a collateral ligament with associated hamstring spasm prevents complete extension of the knee.

 

Aspiration and a short period of rest until the reaction has partially subsided usually will differentiate locking from false locking of the joint, and magnetic resonance imaging (MRI) can confirm the diagnosis.

 

A sensation of giving way is often present but is not specific to meniscal tear.

 

Effusion indicates that something is irritating the synovium; therefore, it has limited specific diagnostic value.

 

 

The sudden onset of effusion after an injury usually denotes a hemarthrosis, and it can occur when the vascularized periphery of a meniscus is torn.

 

Tears occurring within the body of a meniscus or in degenerative areas may not produce a hemarthrosis.

 

Repeated displacement of a pedunculated or torn portion of a meniscus can produce sufficient synovial irritation to produce a chronic synovitis with an effusion of a nonbloody nature.

 

The absence of an effusion or hemarthrosis does not rule out a tear of the meniscus.

 

Atrophy of the musculature about the knee suggests a recurring disability of the knee but does not indicate its cause.

 

Clicks, snaps, or catches, either audible or detected by palpation during flexion, extension, and rotary motions of the joint, can be valuable diagnostically, and efforts should be made to reproduce and accurately locate them.

 

Numerous manipulative tests have been described, but the McMurray test is most commonly used. Although other tests cannot be considered diagnostic, they are useful enough to be included in the routine examination of the knee.

 

For the McMurray test, with the knee completely flexed, the examiner palpates the joint line with one hand and uses the other hand to rotate the foot internally while extending the knee. The maneuver is repeated with the foot externally rotated. If a meniscal tear is present, a click may be heard or felt in the joint line of the affected side during this maneuver.

 

The grinding test, as described by Apley,5 is another test for isolating meniscal pathology. With the patient prone, the knee is flexed to 90 degrees and the anterior thigh is fixed against the examining table. Traction on the foot is used to distract the joint and the foot is rotated. Next,

 

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with the knee in the same position, the foot and leg are pressed downward and rotated as the joint is slowly flexed and extended.

 

Another useful test, the squat test, consists of several repetitions of a full squat with the feet and legs alternately, fully internally and externally rotated as the squat is performed. Reproduction of pain on the medial or lateral side of the knee is suggestive although not diagnostic of meniscal tear.

 

The hip and back should be carefully examined because pathology in these areas can manifest as referred knee pain.

 

The diagnosis of internal derangement of the knee caused by a meniscal tear can be difficult to make even for an experienced orthopaedic surgeon, but a careful history and physical examination combined with appropriate imaging studies help to limit errors in diagnosis and unnecessary arthroscopy.

 

During an injury, damage to other structures of the knee such as the ligaments and articular cartilage is common. For simplicity, tears of the menisci are discussed here as though they were isolated injuries, but evidence of other injuries always must be sought.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Imaging includes standing anteroposterior, 45-degree posteroanterior, and patellofemoral views to exclude other causes of knee pain such as joint degeneration, loose bodies, and osteochondritis dissecans.

 

Other noninvasive diagnostic studies, such as ultrasonography, scintigraphy, computed tomography (CT), and MRI, have been shown to improve diagnostic accuracy in many knee disorders.

 

Compared with arthroscopy, MRI has been shown to have 98% accuracy for medial meniscal tears and 90% for lateral

meniscal tears.

 

Others have reported that MRI had a positive predictive value of 75%, a negative predictive value of 90%, a sensitivity of 83%, and a specificity of 84% for pathologic changes in the menisci.

 

MR arthrography may be useful in evaluating knees with prior meniscectomy or meniscal repair.

 

High-resolution CT has been reported to have a sensitivity of 96.5%, specificity of 81.3%, and accuracy of 91%, but we usually use this study to evaluate the patellofemoral joint.

 

DIFFERENTIAL DIAGNOSIS

 

 

Ligament injury Chondral injury

 

 

Osteochondral loose body Pathologic plica

 

 

Patellar maltracking Intra-articular tumor

NONOPERATIVE MANAGEMENT

 

An incomplete meniscal tear or a small (5 mm) stable peripheral tear with no other pathologic condition, such as a torn ACL, can be treated nonoperatively with predictably good results. Many incomplete tears will not progress to complete tears if the knee is stable.

 

Small stable peripheral tears have been observed to heal after 6 to 8 weeks of protection.

 

Stable vertical longitudinal tears, which tend to occur in the peripheral vascular portions of the menisci, have been reported to heal with nonoperative treatment.

 

Meniscal tears that cause infrequent and minimal symptoms can be treated with rehabilitation and restricted activity.15,31 Yim

et al31 found similar improvements in pain relief and function with meniscectomy and physical therapy in a group of 102 patients with similar meniscal pathology.

 

Tears associated with ligamentous instabilities can be treated nonoperatively if the patient defers ligament reconstruction or if reconstruction is contraindicated.

 

Nonsurgical management consists of activity modification, nonsteroidal anti-inflammatories, and physical therapy.

 

If symptoms recur after a period of nonoperative treatment, surgical repair or removal of the damaged meniscus may be necessary.

 

The most important aspect of nonoperative treatment, once the acute pain and effusion have subsided, is restoration of the normal knee range of motion and muscle strength. This can be accomplished through a regular program of progressive exercises to include the quadriceps, hamstrings, hip flexors, and hip abductors.

 

SURGICAL MANAGEMENT

 

Indications for surgical treatment of meniscal tears include the following1,16,20,22,25:

 

 

 

Symptoms that affect sports participation or activities of daily living or work (locking, giving way, frequent effusions) Failure of nonoperative treatment

 

 

Absence of other causes of knee pain (based on complete clinical and imaging evaluations) Meniscectomy is categorized into three types depending on the amount of meniscus removed:

 

Partial meniscectomy, in which only loose, unstable meniscal fragments are excised and a stable and balanced peripheral rim of healthy meniscal tissue is preserved (FIG 7)

 

Subtotal meniscectomy, in which the type and extent of the tear require excision of a portion of the peripheral rim, usually leaving most of the anterior horn and a portion of the middle third intact

 

Total meniscectomy

 

Historically, the indications and surgical techniques for excision of torn menisci have been controversial.

 

 

Some have advocated total excision of torn menisci, whereas others have proposed subtotal excision.

 

 

 

FIG 7 • Partial meniscectomy: Loose unstable fragments are excised and a stable and balanced peripheral rim of healthy meniscal tissue is preserved.

 

 

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Justification for total excision often was based on shortterm, functional recovery criteria; however, longer followup showed associated degenerative changes.

 

Removal of even one-third of the meniscus has been shown to increase joint contact forces by up to 350%.

 

The amount of degenerative change in the articular cartilage appears to be directly proportional to the amount of meniscus removed.

 

If meniscal pathology produces almost daily symptoms, frequent locking, or repeated or chronic effusions, the pathologic portion of the meniscus should be removed because the problems caused by the present disability far outweigh the probability or significance of future degenerative arthritis.

 

 

If a significant portion of the peripheral rim can be retained by subtotal meniscal excision, the long-term result is improved. Partial meniscectomy by arthroscopic technique has sufficient support and clinical results to indicate its routine use.

 

Subtotal meniscectomy is justified only when it is irreparably torn, and the meniscal rim should be preserved if at all possible.

 

Total meniscectomy is no longer considered the treatment of choice in young athletes or other people whose daily activities require vigorous use of the knee.

 

Preoperative Planning

 

A discussion regarding meniscal repair versus removal should be conducted preoperatively. The patient should understand the risks, benefits, alternatives, and potential complications of both, as well as the variations in postoperative recovery time and rehabilitation.

 

The patient also should understand the potential for recurrent meniscal tear and long-term consequences of meniscectomy.

 

A discussion also should be held about the treatment of additional pathology, such as chondral lesions, that may be a source of continued symptoms postoperatively.

 

The necessary equipment should be present to treat whatever meniscal or chondral pathology might be encountered.

Positioning

 

The patient is placed supine with the nonoperative leg in a leg holder that brings the extremity into flexion at the hip and knee (FIG 8A).

 

The use of a proximal leg holder for the operative knee places the patient's foot on the surgeon's iliac crest, eliminating the need for an assistant to hold the leg.

 

 

 

FIG 8 • A. Patient positioning for meniscectomy. B. Surgical landmarks are outlined; operative extremity is clearly identified and surgeon has “signed the site.” C. Arthroscopic probe used to determine extent of meniscal tear.

 

 

The use of a tourniquet for less than 30 minutes has been shown to have no adverse effect on rehabilitation, return to activity, or muscle damage and to make surgery 13% quicker.28

Approach

 

After an examination under anesthesia, joint lines and soft tissue and bony landmarks are drawn on the skin before joint distention (FIG 8B).

 

Typically, these are the outlines of the patella and patellar tendon, the medial and lateral joint lines, and the posterior contours of the medial and lateral femoral condyles.

 

Standard and optional arthroscopic portals are marked (see Chap. 39).

 

 

A small outflow, needle-type cannula can be placed superomedially or superolaterally, with inflow through the arthroscope, but this often is not needed for meniscectomy.

 

A two-portal or three-portal technique can be used (see Chap. 39).

 

 

The anterolateral and anteromedial portals are most commonly used with the two-portal technique.

 

Occasionally, a posteromedial, accessory medial, or central portal is used to assist in removal of displaced meniscal fragments.

 

Thorough, systematic arthroscopic examination of the knee joint must be done before the decision is made for partial or subtotal meniscectomy (see Chap. 39).

 

An arthroscopic probe should be used to examine the meniscal tear to determine its anterior and posterior extents (FIG 8C). The probe should be used to palpate the superior and inferior extents of the meniscus.

 

When an irreparable meniscal tear is identified, all mobile fragments that can be pulled past the inner margin of the meniscus into the joint should be removed and the remaining meniscus contoured to reduce the risk of leaving a defect that can propagate into a larger tear.

 

The meniscal rim does not need to be perfectly smooth, and the amount of meniscus removed and contouring of the rim must be weighed against the risk of degenerative changes (the risk of degenerative changes is directly proportional to the amount of meniscus removed).

 

The goal is to remove the tear entirely while removing as little meniscus as possible.

 

 

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TECHNIQUES

• Arthroscopic Partial Meniscectomy for Conventional Tears

   

  The goals of surgery are to remove the mobile segment at the meniscal base and to contour the remaining meniscus to leave as wide a rim as possible.

   

  Any tags or pieces of meniscus that may catch in the joint or can be displaced into the center of the joint are resected with meniscal forceps, baskets, scissors, or graspers (TECH FIG 1).

   

   

   

  TECH FIG 1 • A. Meniscal scissors. B. Meniscal basket. C. Meniscal grasper.

   

   

  Full-radius resectors and motorized suction shavers are used to remove damaged cartilage, smooth the meniscal rim, and remove loose pieces of meniscus and cartilage.

   

  Various ablation devices can be used to contour tears; however, care must be taken not to damage adjacent articular cartilage.

   

  For horizontal cleavage tears, one or both “leaves” can be resected, depending on surgeon preference. No definitive study has shown that preserving either the superior or inferior leaf improves results.

• Arthroscopic Partial Meniscectomy for Bucket-Handle Tears

   

  A probe or blunt trocar is used to reduce the fragment to its normal position (TECH FIG 2A).

   

  Partial division of the posterior attachment of the meniscal fragment is done with basket forceps, scissors, or an arthroscopic knife. The cut should go almost completely through the posterior attachment of the mobile fragment at its junction with the remaining normal meniscal rim (TECH FIG 2B).

   

   

   

  TECH FIG 2 • Meniscectomy for a bucket-handle tear. A. Displaced fragment is reduced into normal position with a

  probe. B. Posterior attachment is almost transected with a meniscal biter. C. Anterior attachment is transected with a meniscal biter or knife. D. Fragment is grasped and rotated to avulse the few remaining strands of meniscal tissue. (Adapted From Scott N. The Knee. St. Louis: Mosby, 1994.)

   

  To avoid damage to the normal meniscus or articular cartilage, this cut should not be made blindly. Exposure can be aided by passing the arthroscope through the intercondylar notch to view the posterior horn of the meniscus while cutting.

   

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  Alternatively, a posteromedial portal can be made for direct observation.

   

  A small tag of meniscal tissue is left intact posteriorly to prevent the meniscus from becoming a loose body in the joint after anterior release.

   

  The anterior horn attachment is divided with angled scissors, basket forceps, or an arthroscopic knife. The release should be made flush with the intact anterior rim so that no stump or dogear remains (TECH FIG 2C).

   

  If access to the anterior horn attachment is difficult through the ipsilateral portal, changing portal sites and approaching from the contralateral portal with the instrument often makes this easier. Rarely, a midpatellar portal is necessary so that both anterior portals can be used for instruments.

   

  A hemostat is used to enlarge the capsular incision before attempting meniscal removal.

   

  A grasping clamp is inserted through the ipsilateral portal to grasp the meniscal fragment as close to its remaining posterior attachment as possible. With the fragment in view, the grasping forceps are twisted and rotated while applying traction to avulse the few remaining strands of meniscus, and the fragment is removed from the joint (TECH FIG 2D).

   

  Occasionally, the meniscal fragment cannot be detached with the grasping forceps alone. With a grasper through the lateral portal for traction on the meniscus, an arthroscopic scissor can be passed through the same portal to complete the resection. If necessary, an accessory portal can be made for the scope so that the two anterior portals can be used for instruments.

   

  A motorized meniscal shaver is used to smooth the remaining rim.

• Arthroscopic Partial Meniscectomy and Meniscal Cyst Decompression

   

  The meniscus is carefully probed to identify the extent of the meniscal tear. Radial tears are trimmed to a stable peripheral rim. For stable horizontal tears, only the inferior leaf is resected and the superior leaf is gently trimmed.

   

  The cyst is palpated externally, which may push the cyst material into the joint and decompress the cyst, allowing identification of the cyst communication.

   

  If this is not successful, a spinal needle can be inserted percutaneously through the cystic mass to help locate the track between the cyst and the meniscus. Punch forceps passed through the tear and tracked into the cyst may widen the track enough for the contents of the cyst to be evacuated into the joint.

   

  If necessary, a small, motorized shaver or curette is inserted into the cyst to break up loculations, assist in cyst decompression, and stimulate inflammation and scarring of the cyst.

• Arthroscopic Partial Excision of Discoid Lateral Meniscus

 

The following principles can be applied to all three types of discoid lateral menisci, including incomplete, complete, and Wrisberg types.

 

In young patients with small knees, a 2.7-mm arthroscope and small-joint instruments should be used.

 

In older individuals, the standard 4-mm arthroscope is used. In addition to standard technique, anteromedial and lateral portals can be used for instrumentation while viewing through a medial midpatellar portal.

 

TECH FIG 3 • A. Knee is placed in figure-4 position for resection of discoid meniscus. B. Discoid meniscus with radial tear.

With the knee in a figure-4 position, basket forceps are used to begin the central resection of the discoid tissue (TECH FIG 3A).

With the discoid meniscus under direct observation, resection is planned so that a healthy peripheral meniscus about 8 mm wide remains.

When the desired amount of meniscal tissue has been removed and the rim is balanced, the thickness of the inner edge is much greater than that after routine partial meniscectomy (TECH FIG 3B).

For a Wrisberg-type discoid meniscus, a repair with saucerization is recommended; however, if an inadequate posterior tibial attachment is present, total meniscectomy may be indicated.

 

 

P.376

 

PEARLS AND PITFALLS

Patient ▪ The leg holder or post is placed about 10 cm above the superior pole of the patella. positioning ▪ If too proximal or distal, the surgeon cannot obtain sufficient valgus stress to open the medial joint for inspection.     Portal ▪ The number of portals should be minimized. placement ▪ With multiple portals, there is a risk of fluid extravasation. The knife blade is directed medially or laterally away from the patellar tendon for horizontal portals and superiorly away from the anterior of the menisci for vertical portals.     Arthroscopic ▪ Systematic approach to evaluation to identify/treat any pathology examination Anterior compartment (suprapatellar region, patellofemoral joint [including tracking], lower trochlea) Medial and lateral gutters Medial and lateral compartments Posterior compartment (by directing arthroscope medial to posterior cruciate ligament)   Menisci are probed superiorly and inferiorly. The posterior horn of the medial meniscus can have up to 5-mm physiologic excursion, and the posterior horn of the lateral meniscus can have up to 10-mm physiologic excursion. Knee is inspected for pathologic plicae that may mimic meniscal tear. Inspection and probing are done to identify any displaced meniscal fragments, which may be

 

 

 

	submeniscal or in the posterior compartment (FIG 9).         FIG 9 • Displaced meniscal fragment (A), which must be located and removed (B).

 

POSTOPERATIVE CARE

 

No brace or range-of-motion restrictions

 

 

Immediate full weight bearing with crutches as needed Cold therapy

 

Nonsteroidal anti-inflammatories at 2 weeks if not contraindicated

 

 

Active, passive, and active-assisted range of motion immediately postoperatively Straight-leg raise exercises immediately

 

Return to sports when full range of motion is regained, no effusion is present, and strength is 80% of uninjured side (usually 4 to 6 weeks minimum)

 

 

OUTCOMES

The knee can function well without the meniscus, sometimes for the rest of a patient's life, but late degenerative changes within the joint sometimes occur, and the loss of the meniscus undoubtedly plays some part in producing these changes.2,4,9

In addition to the condition of the meniscus, numerous other factors can influence long-term function, such as joint alignment, laxity of the capsular or ligamentous structures, and incomplete rehabilitation of the musculature about the knee. A recent study found that patients with moderate or significant obesity (body mass index [BMI] >26) have inferior

short-term outcomes compared with nonobese patients.11

Fairbank12 described three changes he had observed in the knee, alone or in combination, in patients who had had a meniscectomy, at intervals ranging from 3 months to 14 years after the surgery:

The development of an anteroposterior ridge that projected distally from the margin of the femoral condyle Flattening of the peripheral half of the articular surface of the condyle

Narrowing of the joint space

These changes have been reported in 40% to 90% of patients with meniscectomy in ACL-deficient knees. Considerable evidence indicates that meniscectomy often is followed by degenerative changes within the joint, but whether the injury, the damaged meniscus itself, or its excision led to the degenerative changes cannot be determined with certainty in most of these studies. Probably, all these factors, and others as well, have an

influence.4,9

Partial meniscectomy has been proven to have significantly better outcomes than total meniscectomy (90% and 68%

good results, respectively, reported in comparison study).

Generally, outcomes after medial partial meniscectomy (80% to 100% good to excellent results) have been better than after lateral partial meniscectomy (54% to 92% good to excellent results). A review of the literature, however, reported that there were consistently no significant differences in radiographic or functional outcome between medial and lateral

meniscal injury in the studies included in their analysis.21

P.377

Reported results of partial meniscectomy for discoid meniscus in children are generally good (87% to 100% good to excellent results).13,18,23

Results tend to deteriorate with time because of degenerative changes in the knee joint; however, continued good to excellent results have been reported with follow-up as long as 10 to 20 years.27

Two primary factors associated with worse results of partial meniscectomy are preexisting osteoarthritis and ACL deficiency. Other factors suggested to predispose to poor outcomes are age older than 35 years, female gender,

presence of medial cartilage degeneration, resection of the posterior third of the meniscus, and meniscal rim resection.8 Preoperative participation in sports has been shown to be a predictor of a better outcome.9

 

 

COMPLICATIONS

The complication rate after arthroscopic meniscectomy (2.8%) is lower than that for posterior cruciate ligament reconstruction (20%), ACL reconstruction (9%), meniscal repair (7.6%), and chondroplasty (3.6%).26

Possible complications after partial or total meniscectomy are the same as those after any arthroscopic procedure on the knee17 (see Chap. 39).

Postoperative complications, including pyogenic arthritis, deep vein thrombosis, and pulmonary embolism, are more frequent in patients 65 years of age and older.14

Patients should be informed of the risks of infection, deep vein thrombosis (with or without pulmonary embolism), recurrent effusions, incomplete tear removal, synovial-cutaneous fistula, arteriovenous fistula, popliteal pseudoaneurysm, and compartment syndrome.

 

 

REFERENCES

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