MENISCAL TEARSINTRODUCTION

The meniscus consists mainly of circumferential fibers held by a few radial strands. It

is, therefore, more likely to tear along its length than across its width. The split is usually

initiated by a rotational grinding force, which occurs (for example) when the knee is flexed

and twisted while taking weight; hence the frequency in footballers. In middle life, when

fibrosis has restricted mobility of the meniscus, tears occur with relatively little force.

Fibrocartilage discs interposed in femorotibial joints between femoral condyles and

tibial plateaus. Have a triangular cross section thickest at the periphery, then tapering to a thin

central edge. Histologically made up of collagen (mostly type 1, also 2, 3, 5, 6), cells

(fibrochondrocytes), water, proteoglycans, glycoproteins, elastin.

3 layers seen microscopically:

1. Superficial layer: woven collagen fiber pattern

2. Surface layer: randomly oriented collagen fiber pattern

3. Middle (deepest) layer: circumferential (longitudinal) oriented fibers.

Vascular supply from superior and inferior medial and lateral geniculate arteries.

They form perimeniscal plexus in synovium/capsule. Peripheral portion (10-30% medially,

10-25% laterally) is vascular via vessels from the perimeniscal plexus. 3 zones: Red zone:

3mm from capsular junction (most tears will heal), Red/white zone: 3-5mm from capsular

junction (some tears will heal), White zone: 5mm from capsular junction (most tears will not

heal) The central, avascular 2⁄3 of the menisci receive nutrition from the synovial fluid.

Medial meniscus: C-shaped, less mobile, firmly attached to tibia (via coronary

ligaments) and capsule (via deep MCL) at midbody. Lateral meniscus: “circular”, more

mobile, loose peripheral attachments, no attachment at popliteal hiatus (where popliteus

tendon enters joint)

ANATOMY

Gross features

Meniscal anatomy has been extensively studied since Bland-Sutton first described the

meniscus as “the functionless remnants of intra-articular leg muscles. “The anatomy is

important both in the types of meniscal tears and their subsequent treatment. From a gross

anatomic perspective, the menisci are C-shaped or semicircular fibrocartilaginous structures

with bony attachment at the anterior aspects of the tibial plateau. The medial meniscus is C-

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shaped, with the posterior horn larger than the anterior horn in the anteroposterior dimension.

Variation in meniscal morphology and attachments can be observed. Recent studies have

examined anatomic variation in attachments of the anterior horn of the medial meniscus and

the role the transverse intermeniscal ligament plays in medial meniscus stability. Berlet and

Fowler described four types of anterior horn medial meniscus attachments. The type IV

variant has no firm bony attachment and was seen in only 3% (1 of 34) of their specimens.

Nelson and LaPrade found a similar type of attachment in 14% of 47 speciment. In the

majority of speciment , however, a firm anterior bony attachment was observed. The

remainder of the medial meniscus is firmly attached to the joint capsule. The posterior bony

attachment lies anterior to the insertion of the posterior cruriate ligament.

Johnson et al mapped the bony insertion sites of the meniscus in an effort to identify

appropriate landmarks for meniscus transplantation. They noted the location of each insertion

site surface area. The anterior horn of the medial meniscus has the largest insertion site

surface area. The anterior horn of the lateral meniscus, the smallest. The capsular attachment

of the medial meniscus on the tibial side is reffered to as the coronary ligament. A thickening

of the capsular attachment in the midportion spans from the tibia to the femur and is reffered

to as the deep medial collateral ligament.

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The lateral meniscus is also anchored anteriorly and posteriorly throught bony

attachments and has an almost semicircular configuration. It covers a larger portion of the

tibial articular surface than does medial meniscus. Discoid variants have been reported with

an incidence of 3,5% to 5%, most being the incomplete type. the anterior and posterior horns

attach much closer to each other than do those of the medical meniscus, with the anterior

horn inserting adjacent to the anterior cruriate ligament (ACL) and the posterior horn

inserting behind the intracondylar eminence anterior to the posterior horn of the medial

meniscus. A variation in the posterior horn attachment includes the Wrisberg variation of

discoid lateral meniscus, in which the posterior horn bony attachment is absent and the

posterior meniscofemoral ligament of Wrisberg is the only stabilizing structure. this variation

can allow excessive motion and result in posterior horn instability. the anterior

meniscofemoral ligament of Humphry runs from the posterior horn of the lateral meniscus

anterior to the posterior cruciate ligament and inserts on the femur.

Posterior and lateral to the posterior bony insertion of the lateral meniscus lies the

popliteal tendon. The area surrounding this tendon is known as the popliteal hiatus. Simonian

et al have investigated the role that the popliteomeniscal fascicule can result in increased

meniscal motion at the hiatus and may be important in causing hypermobility of the posterior

horn of the lateral meniscus. The remaining attachments of the lateral meniscus to the tibia

are through the capsule but are not as well development allows for increased translation of

the lateral meniscus throughout a range of motion. Using three-dimensional MRI, Thompson

at al, demonstrated 11.2 mm of posterior excursion of the lateral meniscus and 5.2 mm of the

medial meniscus during knee flexion.

Microstructure and biochemistry

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Biochemistry

The fibrocartilaginous structure of the meniscus has a varied architecture of coarse

collagen bundles. Scanning electron microscopy has revealed the orientation of collagen

fibers to be mainly circumferential, with some radial fibers at the surface and within the mid

subtance. This orientation allows compressive loads to be dispersed by the circumferential

fibers, while the radial fibers act as tie fibers to resist longitudinal tearing. at the surface of

the meniscus, fiber orientation is more of a mesh network or random configuration, thought

to be important in the distribution of shear stress. Collagen is 60% to 70% of the dry weight

of meniscus. the majority of collagen (90%) is type I, with types II, III, IV, V, and VI present

in much smaller amounts. Elastin accounts for Approximately 0.6% of the dry weight of the

meniscus and noncollagenous proteins, for 8% to 13%.

the cells of the meniscus have been called fibrochondrocytes because of their

appearance and the fact they synthesize a fibrocartilaginous matrix. The fibrochondrocytes

appear to be of two types, with the more superficial cells being oval or fusiform and the

deeper cells more rounded. Both types contain abundant endoplasmic reticula and Golgi

complexes and few mitochondria.

Blood supply and Neuroanatomic Findings

At birth, the entire meniscus is vascular, by age 9 months, the inner one third has

become avascular. this decrease in vascularity continues to age 10 years, when the meniscus

closely resembles the adult meniscus. The adult blood supply and demonstrated that only the

outer 10% to 25% of the lateral meniscus is vascular. This vascularity arises from the

superior and inferior branches of the medial lateral genicular arteries , which form a

perimeniscal capillary plexus. A synovial fringe extends a short distance over both the

femoral and tibial surfaces of the menisci but does not contribute to the meniscal blood

supply. At the popliteal hiatus, the meniscus is relatively avascular secondary to lack of

penetrating vessels and synovial fringe. Because of the avascular nature of the inner two

thirds of the meniscus, cell nutrition is believed to occur mainly through diffusion or

mechanical pumping. Neural elements are most abundant in the outer portion of the

meniscus, particularly myelinated and unmyelinated nerve fibers. These nerve fibers likely

explain the findings of Dye et al, who did neurosensory mapping of the internal structures of

the knee. On probing, centrally located meniscal tissue gave little or no pain awareness,

whereas more peripheral tissue and the meniscal capsular tissue resulted in slight to moderate

discomfort.

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The anterior and posterior horns of the meniscus are innervated with

mechanoreceptors that may play a role in proprioceptive feedback during extremes of motion.

Their exact role in joint function, however, remains unclear.

FUNCTIONS OF THE MENISCUS

The menisci are important in many aspects of knee function, including load sharing,

shock absorption, reduction in joint contact stresses, passive stabilization, increasing

congruity and contact area, limitation of extremes of flexion and extension, and

proprioception. Many of these functions are achieved through the ability of the menisci to

transmit and distribute load over the tibial plateau. The findings of joint space narrowing,

osteophute formation, and squaring of the femoral condyles after total meniscectomy and led

to investigations of the role of the meniscus in joint function.

The medial and lateral menisci transmit at least 50% to 70% or at times more of the

load when the knee is in extension; this increases to 85% with 90o of knee flexion. Radin et al

demonstrated that these loads were well distributed when the menisci were intact. Removal of

the medial meniscus results in 50% to 70% reduction in femoral condyle contact area and n a

100% increase in contact stress. Total lateral meniscectomy causes a 40% to 50% decrease in

contact area and increase contact stress in the lateral compartment to 200% to 300% of

normal.

With the decrease in contact area within the joint, stresses are increased and are

unevenly distributed. This results in increased compression and shear across the joint. Along

with the biomechanical changes that can occur with meniscectomy, the results of some

studies suggest that biochemical activity of cartilage is also affected. The improved joint

congruity, which occurs through meniscus contact, is thought to play a role joint lubrication

and cell nutrition.

The meniscus also plays a role in shock absorption. Compression studies using bovine

menisci have demonstrated that meniscal tissue is approximately one half as stiff as articular

cartilage. In oone study, the shock absorption capacity of the normal knee was reduced by 20

% after meniscectomy.

The menisci also play a key role in enchancing joint stability. Medial meniscectomy

in the ACL-intact knee has little effect on anteroposterior motion, but in the ACL-deficient

knee, it results is in an increase in anterior tibial translation of up to 58% at 90% of flexion.

Shoemaker and Markolf demonstrated that the posterior horn of the most important structure

resisting an applied anterior tibial force in the medial meniscus of the ACL-deficient knee

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increasedby 52 % in full extension and by 197%, at 60o of flexion under a 134-N load.

Although the inner two thirds of the meniscus is important in maximizing joint contact area

and increasing shock absorption, the integrity of the peripheral one third is essential for both

load transmissions and stability.

EPIDEMIOLOGY

The mean annual incidence of meniscal tears is 60 to 70 per 100.000. Meniscal tears

are more common in males; the male:female ratio ranges from 2,5:1 to 4:1. In a study by

Poehling et al, slightly more than one third of all tears were associated with an ACL injury.

The peak incidence for this group was in men 21 to 30 years old and in girls and women in 11

to 20 years old. Degerative types of meniscal tears commonly occur in men in their fourth,

fifth, and sixth decades. Meniscal pathology in women is rather constant after the second

decade of life. Younger patients are more likely to have an acute traumatic event as the cause

of their meniscal pathology.

In patients with acute ACL injury, lateral meniscus tears occur more frequently then

do medial meniscus tears. In patients with chronic ACL-deficient knees, however, medial

meniscus tears are more prevalent. Meniscal injury is also frequent in the setting of tibial

plateau fracture, with 17 of 36 patients (47%) in one study having a meniscal tear associated

with the fracture. Femoral shaft fractures also have been associated with concurrent meniscal

injury and the presence of hemarthrosis should increase the index of suspicion for

ligamentous or meniscsl injury in this setting.

CLASSIFICATION

Meniscal tear classification can be based on the pattern of the tear seen at athroscopy

or on the etiology of the meniscal injury. The two etiologic categoric are tears from excessive

application of force to a normal meniscus and tears occurring from normal forces acting on a

degenerative structure.

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Commonly described patterns of meniscal tear include vertical longitudinal, oblique,

complex (including degenerative), transverse (radial), and horizontal. The incidence of these

tear patterns has been evaluated by Metcalf et al, who found that 81% of tears were oblique

or vertical longitudinal. With increasing age, degenerative complex tears are more frequently

seen, with most meniscal pathology found in the posterior horns.

Vertical longitudinal tears can be complete (ie, bucket handle tears) or incomplete and

most often occur in younger individuals. The medial meniscus is more commonly affected,

likely because its more secure attachments to the tibial plateau make it susceptible to shear

injury.

Oblique tears, often called flap or parrot beak tears, can occur at any location but are

most often found at the junction of the posterior and middle thirds of the meniscus. Complex

or degenerative tears occur in multiple planes and are more common in older age group (>40

years). Occurring in the posterior horn and midbody, they are often associated with

degenerative changes of articular cartilage inn the knee and represent part of the pathology of

degenerative arthritis.

Transverse or radial tears occur in isolation or in conjunction with other tears. They

are typically located at the junction of the posterior and middle thirds of the medial meniscus

or near the posterior attachment of the lateral meniscus.

Horizontal tears are believed to begin near the inner margin of the meniscus and

extend toward the capsule. They tend to occur in the plane of the horizontally oriented middle

perforating collagen fiber bundles and are thought to be the result of shear forces generated

by axial compression. They are also commonly seen in the lateral menisci of runners.

Meniscal cysts are often associated with horizontal tears and can be symptomatic because of

localized swelling.

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Meniscal cysts represent 1% to 10% of meniscal pathology. They are highly

correlated with meniscal tears and most often occur in the lateral meniscus. Pathologically,

these cysts appear directly connected to the meniscus and are filled with a gel-like material

biochemically similar to synovial fluid. Symptoms include joint line pain, and the cysts are

often palpable on physical examination at or below the joint line.

DIAGNOSIS

History

The diagnostic of meniscal tear can frequently be made from a careful history,

physical examination and appropriate diagnostic tests. The onset of symptoms and

mechanism of injury are often clues to the diagnosis. Patient age may be a factor with regard

to the likelihood of surgical repair as well as the presence of associated chondrosis or other

joint damage. In isolation, meniscal tears often occur during a twisting injury or hyperflexion

event, and they may present with acute pain and swelling. Complaint of “locking” or

“catching” may be present but also may be secondary to other pathology, such as chondral

injury or patellofemoral chondrosis. Loss of motion with a mechanical block to extension is

commonly the result of a displaced bucket handle meniscal tear and usually requires acute

surgical treatment. Degenerative tears of the meniscal tend to occur in older patient (>40

years), frequently with an atraumatic chronic history of mild joint swelling, joint line pain,

and mechanical symptoms. These tears are often associated with some degree of chondral

damage.

Physical Examination

A complete examination of the lower extremity is required for any pasien suspected of

having meniscal pathology. An inspection should be done to asses for joint effusion,

quadriceps muscle atrophy, and any joint line swelling that may occur with a perymeniscal

cyst. Range of motion must be assessed to deternain whether a mechanical block to extension

or loss of flexion is present.

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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. If these noises are localized to the joint

line, the meniscus most likely contains a tear. Similar noises originating from the patella, the

quadriceps mechanism, or the patellofemoral groove must be differentiated. Numerous

manipulative tests have been described, but the McMurray test and the Apley grinding test

probably are most commonly used. All basically involve attempts to locate and reproduce

crepitation that results as the knee is manipulated.

The McMurray’s test is probably best known and is carried out as follows. With the

patient supine and the knee acutely and forcibly flexed, the examiner can check the medial

meniscus by palpating the posteromedial margin of the joint with one hand while grasping the

foot with the other hand. Keeping the knee completely flexed, the leg is externally rotated as

far as possible and then the knee is slowly extended. As the femur passes over a tear in the

meniscus, a click may be heard or felt. The lateral meniscus is checked by palpating the

posterolateral margin of the joint, internally rotating the leg as far as possible, and slowly

extending the knee while listening and feeling for a click. A click produced by the McMurray

test usually is caused by a posterior peripheral tear of the meniscus and occurs between

complete flexion of the knee and 90 degrees. Popping, which occurs with greater degrees of

extension when definitely localized to the joint line, suggests a tear of the middle and anterior

portions of the meniscus. Thus the position of the knee when the click occurs may help locate

the lesion. A positive McMurray click localized to the joint line is additional evidence that

the meniscus is torn; a negative McMurray test does not rule out a tear.

McMurray’s test is performed at varying angles of flexion.

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The grinding test, as described by Apley, is carried out as follows. With the patient

prone, the knee is flexed to 90 degrees and the anterior thigh is fixed against the examining

table. The foot and leg are then pulled upward to distract the joint and rotated to place

rotational strain on the ligaments; when ligaments have been torn, this part of the test usually

is painful. Next, with the knee in the same position, the foot and leg are pressed downward

and rotated as the joint is slowly flexed and extended; when a meniscus has been torn,

popping and pain localized to the joint line may be noted. Although the McMurray, Apley,

and other tests cannot be considered diagnostic, they are useful enough to be included in the

routine examination of the knee. The grinding test relaxes the ligaments but compresses the meniscus – it causes pain with meniscus lesions.

Thessaly test. This test is based on a dynamic reproduction of load transmission in the

knee joint under normal or trauma conditions. With the affected knee flexed to 20 degrees

and the foot placed flat on the ground, the patient takes his or her full weight on that leg while

being supported (for balance) by the examiner (Fig. 20.9). The patient is then instructed to

twist his or her body to one side and then to the other three times (thus, with each turn,

exerting a rotational force in the knee) while keeping the knee flexed at 20 degrees. Patients

with meniscal tears experience medial or lateral joint line pain and may have a sense of

locking. The test has shown a high diagnostic accuracy rate at the level of 95 per cent in

detecting meniscal tears, with a low number of false positive and negative recordings.Picture

showing how the patient is positioned during the Thessaly test.

Tears of one meniscus can produce pain in the opposite compartment of the knee. This

is most commonly seen with posterior tears of the lateral meniscus. This phenomenon is not

understood. The use of MRI has minimized initial exploration of the wrong compartment.

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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.

Pain usually is produced on either the medial or lateral side of the knee, corresponding to the

side of the torn meniscus. Pain in the internally rotated position suggests injury to the lateral

meniscus, whereas pain in the external rotation suggests injury to the medial meniscus. The

localization of the pain to either the medial joint line or the lateral joint line, however, is a

much more dependable localizing sign than the position of rotation.

Additional Examination

Plain X-Ray

Before any further diagnostic studies are undertaken, plain radiographs should be

obtained. A standard series will include a 30o or 45o posteroanterior flexion weight-bearing

view of both knees, a true lateral radiograph, and a Merchant or sky line view. Although

these radiographics views cannot confirm the diagnosis of meniscal tear, they are extremel

y important in defining bony pathology and evaluating the knee for joint space

narrowing. Because articular cartilage wear often is more advanced in the posterior aspects of

the femoral condyles, the 30o or 45o posteroanterior flexion weight bearing view is more

sensitive than standard standing views for detecting early joint space narrowing. Unweight

radiographs are of little value in this regard. Patient with joint space narrowing need to be

counseled regarding chondrosis and degenerative joint disease as likely causes of knee pain

when meniscal tear is being considered as the diagnosis. The Merchant view is helpful in

evaluating the patellofemoral joint is often a source of medial knee pain.

Magnetic Resonance Imaging

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The advantages of MRI in evaluating patient with a suspected meniscal tear include

its noninvasive nature, the ability to assess the knee in multiple planes, the absence of

ionizing radiation, and the capacity to evaluate other structures within the joint. The

limitations are its relatively high cost and the potential for misinterpretation or error because

of technical inadequacies of the study or variability in interpretation. Early studies evaluating

MRI technology often conducted with magnets of low field strength. Accuracy for detecting

meniscal tears was commonly reported at 80%-90%. With improved technology and

increased experience in reading these scans, the accuracy of detection is now considered to be

approximately 95% or better.

The normal appearance of the meniscus on MRI is that of a uniformly low signal

structure. Areas of increased signal within the meniscus occur in children and increase with

age in adult. These intrasubstance change are see frequently and are a common cause of over-

reading a meniscus tears on MRI scans.

Normal Meniscus (left: Medial Meniscus, right: Lateral meniscus

Although MRI is a powerful tool in the detection of meniscal pathology, the entire

clinical picture must be evaluated in deciding on treatment. In a study of MRI findings in

asymptomatic patient between the ages of 18 and 39 years with a normal physical

examination.

Polly et al., in a prospective study comparing the accuracy of MRI with arthroscopic

findings, reported 98% accuracy for medial meniscal tears, 90% for lateral meniscal tears,

100% for posterior cruciate ligament tears, and 97% for anterior cruciate ligament tears if the

ligament was inspected thoroughly.

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(Left: posterior horn of the medial meniscus, Right: complex tear of medial meniscus)

Glashow et al. reported a prospective, double-blind study that compared MRI

diagnosis of anterior cruciate ligament and meniscal lesions with subsequent arthroscopic

findings. They found 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 pathological changes in the

menisci. For complete tears of the anterior cruciate ligament, the positive predictive value

was 74%, the negative predictive value 70%, the sensitivity 61%, and the specificity 82%.(Bucket Handle Tears (Left: Coronal view, Right: Sagital views)

Arthroscopy

The gold standard of confirming the diagnosis of meniscal tears is an arthroscopic

examination. During arthroscopy, the meniscocapsular junction can be probed and the

superior and inferior surfaces examined. Placement of the arthroscope in the posteromedial or

posterolateral compartment may be necessary to assure that peripheral posterior horn tears are

not missed. At the popliteal hiatus, direct probing will help assess hypermobility, which can

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occur after popliteomeniscal fasciculi disruption. With a careful, systematic approach,

arthroscopic evaluation should be the definitive means of detecting meniscal tears.Medial Meniscus (Left: Normal, Right: Torn medial meniscus)

Normal Lateral Meniscus

(Left: Horizontal tear of lateral meniscus, Right: Oblique tear posterior horn of lateral meniscus)

DIFFERENTIAL DIAGNOSE

a. Loose bodies

Loose bodies in the joint may cause true locking. The history is much more

insidious than with meniscal tears and the attacks are variable in character and intensity.

A loose body may be palpable and is often visible on x-ray.

b. Recurrent dislocation of the patella

Recurrent dislocation of the patella causes the knee to give way; typically the

patient is caught unawares and collapses to the ground. Tenderness is localized to the

medial edge of the patella and the apprehension test is positive.

c. Fracture of the tibial spine

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Fracture of the tibial spine follows an acute injury and may cause a block to full

extension. However, swelling is immediate and the fluid is blood-stained. X-ray may

show the fracture.

d. Partial tear of the medial collateral ligament

A partial tear of the medial collateral ligament may heal with adhesions where it is

attached to the medial meniscus, so that the meniscus loses mobility. The patient

complains of recurrent attacks of pain and giving way, followed by tenderness on the

medial side. Sleep may be disturbed if the medial side rests upon the other knee or the

bed. As with a meniscus injury, rotation is painful; but unlike a meniscus lesion, the

grinding test gives less pain and the distraction test more pain.

e. Torn anterior cruciate ligament

A torn anterior cruciate ligament can cause chronic instability, with a sense of the

knee ‘giving way’ or buckling when the patient turns sharply towards the side of the

affected knee. Careful examination should reveal signs of rotational instability, a positive

Lachman test or a positive anterior drawer sign. MRI or arthroscopy will settle any

doubts.

TREATMENT

Dealing with the locked knee

Usually the knee ‘unlocks’ spontaneously; if not, gentle passive flexion and rotation

may do the trick. Forceful manipulation is unwise (it may do more damage) and is usually

unnecessary; after a few days’ rest the knee may well unlock itself. However, if the knee does

not unlock, or if attempts to unlock it cause severe pain, arthroscopy is indicated.

If symptoms are not marked, it may be better to wait a week or two and let the

synovitis settle down, thus making the operation easier; if the tear is confirmed, the offending

fragment is removed.

Conservative treatment

Nonsurgical treatment of meniscal tears is generally limited to smaller, incomplete

tears involving the posterior horns. These tears may be painful but do not catch in the joint so

the patient does not feel popping or catching. Such tears are usually found in stable knees.

Treatment includes modification of activity to avoid cutting and pivoting sports that may

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aggravate symptoms, stretching, and quadriceps and hamstring strengthening. Such treatment

often works best in older individuals as arthritis rather than the meniscal tear may be the

cause of their symptoms. Small (<10 mm) stable longitudinal tears, partial-thickness tears on

the superior or inferior surface, or small (<3 mm) radial tears may heal spontaneously or

remain asymptomatic.

If the joint is not locked, it is reasonable to hope that the tear is peripheral and can

therefore heal spontaneously. After an acute episode, the joint is held straight in a plaster

backslab for 3–4 weeks; the patient uses crutches and quadriceps exercises are encouraged.

Operation can be put off as long as attacks are infrequent and not disabling and the patient is

willing to abandon those activities that provoke them. MRI will show if the meniscus has

healed.

Operative treatment

Surgery is indicated (1) if the joint cannot be unlocked and (2) if symptoms are

recurrent. For practical purposes, the lesion is often dealt with as part of the ‘diagnostic’

arthroscopy. Tears close to the periphery, which have the capacity to heal, can be sutured; at

least one edge of the tear should be red (i.e. vascularized).

Types of Meniscal Excisions

O'Connor separated meniscal excisions into three categories depending on the amount of meniscal tissue to be removed.

Fig. 48-15  Types of meniscal excision. A, Partial meniscectomy. B, Subtotal meniscectomy. C, Total meniscectomy. (Redrawn from Shahriaree H: O'Connor's textbook of arthroscopic surgery, Philadelphia, 1984, JB Lippincott.)

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Partial Meniscectomy

In this type of meniscal excision, only the loose, unstable meniscal fragments are

excised, such as the displaceable inner edge in bucket-handle tears, the flaps in flap tears, or

the flaps in oblique tears. In partial meniscectomies, a stable and balanced peripheral rim of

healthy meniscal tissue is preserved.

Subtotal Meniscectomy

In this type of meniscectomy, the type and extent of the tear require excision of a

portion of the peripheral rim of the meniscus. This is most commonly required in complex or

degenerative tears of the posterior horn of either meniscus. Resection of the involved portion

by necessity extends out to and includes the peripheral rim of the meniscus. It is termed

subtotal because in most cases most of the anterior horn and a portion of the middle third of

the meniscus are not resected.

Total Meniscectomy

Total removal of the meniscus is required when it is detached from its peripheral

meniscosynovial attachment, and intrameniscal damage and tears are extensive. If the body of

the peripherally detached meniscus is salvageable, total meniscectomy is not warranted, and

meniscal suture should be considered.

General Principles

Partial meniscectomy is always preferable to subtotal or total meniscectomy. Leaving

an intact, balanced, peripheral rim of meniscus aids in the stability of the joint and protects

the articular surfaces by its load-bearing functions. Total meniscectomy removes all of the

actual load-bearing protection and reduces stability of the joint, especially if a concomitant

ligamentous relaxation already exists. Partial meniscectomy, although desirable, is not always

possible if the tear extends to the periphery of the meniscus. In such cases, subtotal excision

is preferable to complete excision, even though the contoured anterior meniscal tissue left

may be subject to subsequent tears or degeneration.

To determine accurately the type of meniscectomy required, the meniscal lesion must

be carefully probed and classified. Failure to classify, probe, and explore accurately and

thoroughly the extent and various planes of the tear before proceeding with the meniscal

resection often results in needlessly sacrificing healthy meniscal tissue.

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When the meniscal tear has been probed and classified, the surgeon should mentally

formulate the methods and steps required to excise the necessary portion of the meniscus.

The surgeon should be able to visualize the tissues to be removed and the subsequent contour

of the peripheral meniscal rim. The objective is to remove the torn, mobile meniscal fragment

and contour the peripheral rim, leaving a balanced, stable rim of meniscal tissue.

Excision of the pathological tissue can be done either with en bloc resection of the

mobile fragment or by morcellization of the fragments and subsequent removal. Sharp

excision of the major mobile fragments usually is preferable to morcellization to minimize

the potential debris within the joint. When the tear has been removed, the remaining

peripheral rim must be carefully probed to ensure that there are no additional tears and that

the rim is balanced and stable. When a contoured, balanced, stable peripheral rim is present,

the joint should be thoroughly lavaged and suctioned to remove any small meniscal

fragments or debris that may have dropped into the joint as a result of the resection.

In appropriate cases the success rate for both open and arthroscopic repair is almost

90 per cent. Tears other than those in the peripheral third are dealt with by excising the torn

portion (or the bucket handle). Total meniscectomy is thought to cause more instability and

so predispose to late secondary osteoarthritis; certainly in the short term it causes greater

morbidity than partial meniscectomy and has no obvious advantages.

Arthroscopic meniscectomy has distinct advantages over open meniscectomy: shorter

hospital stay, lower costs and more rapid return to function. However, it is by no means free

of complications (Sherman et al.,1986). Postoperative pain and stiffness are reduced by

prophylactic non-steroidal anti-inflammatory drugs. Quadriceps-strengthening exercises are

important.

(a) Removal of a torn medial meniscus.

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b) Repair is appropriate if at least one edge of the tear is vascularized. This can be done arthroscopically.

Outcome

Neither a meniscal tear by itself nor removal of the meniscus necessarily leads to

secondary osteoarthritis. However, the likelihood is increased if the patient has (a) a pre-

existing varus deformity of the knee, (b) signs of cruciate ligament insufficiency or (c)

features elsewhere of a generalized osteoarthritis.

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DAFTAR PUSTAKA

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