MENISCI. histology Water( 75%)Collagen type 1Proteoglycans elastin.
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Transcript of MENISCI. histology Water( 75%)Collagen type 1Proteoglycans elastin.
MENISCI
histology
Water( 75%)
Collagen type 1
Proteoglycans
elastin
Collagen fibers
Circumferential fibers(majority)
Radial fibers
Perforating fibers
Role of hoop tension in menisci. Hoop tensiondeveloped in menisci acts to keep them between bones
Radial tear eliminates hoop tension and damages meniscus function
Anatomy
• Attached to the capsule except where the popliteus tendon is interposed laterally
• Loosely attached to the tibial plateaus by the coronary ligaments
• Avascular except near their peripheral attachments
Vascular supply
• lateral and medial geniculate vessels
• 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
FUNCTIONA. act as a joint
filler, compensating for gross incongruity between femoral and tibial articulating surfaces
B. prevent capsular and synovial impingement during flexion-extension
function• joint lubrication• helping to distribute synovial fluid• nutrition of the articular cartilage• Stability especially rotary stabilizer• smooth transition from a pure hinge
to a gliding or rotary motion as the knee moves from flexion to extension
Load bearing
• Cover 1/2-to 2/3 of the articular surface
• Carry40%-70% of weight force
• medial meniscus 50%
• Lateral meniscus 70%
Effects of meniscectomy
Medial meniscectomy
↓contact area by 70%
↑contact stress by 100%
Meniscal movement• The menisci follow the tibial condyles
during flexion and extension• during rotation they follow the femur
and move on the tibia• Medial meniscus:Ant /Post attachments
follow the tibia, but its intervening part follows the femur and becomes distorted
• Lateral meniscus:is firmly attached posteriorly and less likely to be injured
Meniscectomy and joint laxity
• Intact ligaments→little joint laxity
• Ligamentus insufficiency→↑joint laxity
• ACL insufficiency→forces in the medial meniscus increase significantly
• ACL insufficiency+medial meniscectomy:↑AP translation
• ACL insufficiency+lateral meniscectomy:↕AP translation
MECHANISM OF TEAR
• rotational force while the joint is partially flexed
• vigorous internal rotation of the femur on the tibia results in meniscal catching
• meniscus torn longitudinally when the joint is suddenly extended
meniscaltears
• Longitudinal: The most common type usually involve the posterior segment Most involve the inferior rather than . . the superior surface medial meniscus ≈ lateral meniscus• Horizontal/oblique/radial usually lateral meniscus Usually between middle and anterior third
Predisposing factors
• Degeneration• Cyst• Discoid meniscus• Ligament or muscle insufficiency• Knee instability• Abnormal mechanichal axes
DIAGNOSIS• History:• may not be obtained, especially when
tears of abnormal or degenerative menisci in a middle age person
• Locking or no locking: may not be recognized consider absence of normal recurvatum Usually only with longitudinal bucket handle tear• R/O pseudolocking
Giving way
• Is not especific• Results from: Muscle(quadriceps) insufficiency Patellar problems Instability Loose body
Giving way
Giving way due to
meniscal tear
•On rotary movements•With a feeling of subluxation or knee jumping
Giving way due to other
causes
•During flexion against resistance•Walking down stairs
Effusion
• Acute: usually denotes a hemarthrosis, and it can occur when the vascularized periphery of a meniscus is torn
• Late: Tears occurring within the body of a meniscus or in degenerative areas may not produce a hemarthrosis
signs• Quadriceps atrophy
• Joint line tenderness localized to posterolateral or posteromedial(the most important physical finding)
• 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
Mc murray test• Palpate posteromedial/ posterolateral• Rotate leg external or
internal• Move knee from full
flexion to extension• Before 90˚→posterior horn• After 90˚→mid/ant horn
Apley grind testCheck menisci during compression
squat testPain localized to joint line is more important than pain during ext/int rotation
Thessaly test• Knee in 5˚ and
20˚ flexion• Accuracy rate
95%• Always done on
the normal knee first to teach the pt
paraclinic
• X ray: routine AP/LAT/intercondylar/sky line views
• Arthrography• MRI: sensitivity →65% specificity→95%
accuracy→85%
NONOPERATIVE MANAGEMENT
cylinder cast or knee immobilizer worn for 4 to 6 weeks
Strengthen muscles around the knee as well as the hip
criteria
• ZONE• TEAR TYPE• CHRONICITY• SIZE(cm)
A suitable candidate
• NonChronic• Stable( incomplete or could not be displaced
more than 3 mm from the intact peripheral rim)
• Peripheral• <5mm• no other pathological condition
Reparability of Meniscal Tears
• ZONE• TEAR TYPE• CHRONICITY• SIZE(cm)
Ideal indication
• Acute• 1- to 2-cm• Longitudinal• Peripheral• young individual• in conjunction with anterior cruciate
ligament reconstruction
Open or arthroscopic repair
• Open:• posterior horn peripheral tears if posteromedial or
posterolateral capsular reconstructions are being done concurrently
• Arthroscopic: • lateral meniscus• necessary for tears at or near the junction of the vascular and
avascular zones• Medial menisci tears that extend deep to the collateral ligament
DO NOT FORGET• For younger,active patients,ligamentous
stabilizationshould accompany meniscal suture because of thedecreased likelihood of healing and increased risk of re-rupture in a knee with ligamentous laxity
MENISCECTOMY
• Increasing degenerative changes were noted, especially after total meniscectomy
• After subtotal excision degeneration is localized
• degenerative change directly proportional to the amount of meniscus removed
Complete or incomplete
• Complete removal of the meniscus is justified only when it is irreparably torn
• Total meniscectomy is no longer considered the treatment of choice in young athletes
• Subtotal excision is easier by arthroscopy
LATE CHANGES AFTER MENISCECTOMY
• meniscectomy often is followed by degenerative changes within the joint
• after partial medial meniscectomy 88% to 95% of patients reporting good to excellent results.
AUTOGRAFTS AND ALLOGRAFTS• Indications: skeletally mature too young for TKA significant pain and limited function conservative therapy failed mechanical tear no synovial disease younger than 40 years normal mechanical alignment stable knee Outerbridge grade I or grade II articular cartilage changes pain localized to the affected compartment
AUTOGRAFTS AND ALLOGRAFTS
• Contraindications knee instability
varus-valgus malalignment
advanced osteoarthritis is an absolute contraindication
questionsremain about their survivorship and function
THE END