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Updated: Sep 21 2023

Meniscal Tears

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  • summary
    • Meniscal tears are common sports-related injuries in young athletes and can also present as a degenerative condition in older patients.
    • Diagnosis can be suspected clinically with joint line tenderness and a positive Mcmurray's test, and can be confirmed with MRI studies.
    • Treatment can be nonoperative versus operative (partial meniscectomy versus repair) depending on the morphology of the meniscus tear, root involvement, patient symptoms, and patient activity demands. 
  • Epidemiology
    • Incidence
      • very common
        • most common indication for knee surgery
    • Risk factor
      • higher risk in ACL deficient knees
  • Etiology
    • Pathophysiology
      • medial tears
        • more common than lateral tears
          • the exception is in the setting of an acute ACL tear where lateral tears are more common
        • degenerative tears in older patients usually occur in the posterior horn medial meniscus
      • lateral tears
        • more common in acute ACL tears
  • Anatomy
    • Anatomy of meniscus
  • Classification
    • Descriptive classification
      • location
        • red zone (outer third, vascularized)
        • red-white zone (middle third)
        • white zone (inner third, avascular)
      • position (anterior, middle, posterior third, root)
      • size
      • pattern
        • vertical/longitudinal
          • common, especially with ACL tears
          • repair when peripheral
        • bucket handle
          • vertical tear which may displace into the notch
        • oblique/flap/parrot beak
          • may cause mechanical locking symptoms
        • radial
          • complete radial tears that extend to the meniscocapsular junction are biomechanically equivalent to posterior root tears
        • horizontal
          • more common in older population
          • may be associated with meniscal cysts
        • complex
        • root
          • functionally equivalent to a total meniscectomy
          • lateral root tears associated with ACL tears
          • medial root tears associated with chondral injuries
  • Presentation
    • Symptoms
      • pain localizing to medial or lateral side
      • mechanical symptoms (locking and clicking), especially with squatting
      • delayed or intermittent swelling
    • Physical exam
      • joint line tenderness is the most sensitive physical examination finding
      • effusion
      • provocative tests
        • Apley compression
          • prone-flexion compression
        • Thessaly test
          • standing at 20 degrees of knee flexion on the affected limb, the patient twists with knee external and internal rotation with positive test being discomfort or clicking.
        • McMurray's test
          • flex the knee and place a hand on medial side of knee, externally rotate the leg and bring the knee into extension.
          • a palpable pop / click + pain is a positive test and can correlate with a medial meniscus tear.
  • Imaging
    • Radiographs
      • Should be normal in young patients with an acute meniscal injury
      • Meniscal calcifications may be seen in crystalline arthropathy (ex. CPPD)
    • MRI
      • indications
        • MRI is most sensitive diagnostic test, but also has a high false positive rate
      • findings
        • MRI grade III signal is indicative of a tear
          • linear high signal that extends to either superior or inferior surface of the meniscus
        • parameniscal cyst indicates the presence of a meniscal tear
        • bucket handle meniscal tears indicated by
          • "double anterior horn" sign
        • meniscal extrusion or "ghost sign," may indicate meniscal root tear
    • MCL sprain
      • pain with valgus stress at 30° knee flexion, which isolates the superficial MCL
      • gapping of medial joint line
    • Plica syndrome
      • pain is typically in the medial parapatellar region
      • may have palpable medial parapatellar cord
    • Osteochondral lesions
      • may present very similarly
      • differentiated with imaging (MRI)
  • Treatment
    • Nonoperative
      • rest, NSAIDS, rehabilitation
        • indications
          • indicated as first line treatment for degenerative tears
        • outcomes
          • improvement in knee function following physical therapy
          • "noninferior" when compared to arthroscopic partial meniscectomy
    • Operative
      • partial meniscectomy
        • indications
          • tears not amenable to repair (complex, degenerative, radial tear patterns)
          • repair failure >2 times
        • outcomes
          • >80% satisfactory function at minimum follow-up
          • 50% have Fairbanks radiographic changes (osteophytes, flattening, joint space narrowing)
          • predictors of success
            • age <40yo
            • normal alignment
            • minimal or no arthritis
            • single tear
      • meniscal repair
        • indications
          • best candidate for repair is a tear with the following characteristics
            • peripheral in the red-red zone (vascularized region)
            • lower rim width correlates with the ability of a meniscal repair to heal 
              • rim width is the distance from the tear to the peripheral meniscocapsular junction (better blood supply).
            • vertical and longitudinal tear
              • rather than radial, horizontal or degenerative tear
              • bucket handle meniscus tear
            • 1-4 cm in length
            • acute repair combined with ACL reconstruction
              • traditional literature report higher healing rates with concurrent ACL reconstruction
              • current literature shows no difference in healing for 2nd generation all-inside repairs with/without concomitant ACL reconstruction
        • outcomes
          • 70-95% successful
          • highest success when done with concomitant ACL reconstruction (90%)
          • modest result when done with an intact ACL (60%)
          • poor results with untreated ACL-deficiency (30%)
      • meniscal transplantation
        • indications
          • controversial
          • young patients with near-total meniscectomy, especially lateral
        • contraindications
          • inflammatory arthritis
          • instability
          • marked obesity
          • grade III and IV chondral changes
          • malalignment (if not concurrently addressed)
          • diffuse arthritis
        • outcomes
          • requires 8-12 months for graft to fully heal
          • return to sports by 6-9 months
          • 10 year follow-up showed:
            • persistent improvement in subjective pain and function scores
            • most had radiographic progression of degenerative changes
          • re-tears or extrusion are common
      • total meniscectomy
        • of historical interest only
        • outcomes
          • 20% have significant arthritic lesions and 70% have radiographic changes three years after surgery
          • 100% have arthrosis at 20 years
          • severity of degenerative changes is proportional to % of the meniscus that was removed
  • Techniques
    • Rest, NSAIDS, rehabilitation
      • technique
        • PWB, ROM as tolerated
    • Partial Meniscectomy
      • approach
        • standard arthroscopic approach
      • technique
        • minimize resection (DJD proportional to amount removed)
        • do not use thermal (heat probes)
      • postoperative
        • early active range of motion
        • prolonged immobilization (10 weeks) is detrimental to healing in a dog model
    • Meniscal repair
      • approach
        • inside-out technique
          • considered gold standard
          • medial approach to capsule
            • expose capsule by incising the sartorius fascia
            • retract pes tendons / semimembranosus posteriorly
            • developing plane between the medial gastrocnemius and capsule
          • lateral approach to capsule
            • develop plane between IT band and biceps tendon
            • then retract lateral head of gastrocnemius posteriorly
        • all-inside technique (suture devices with plastic or bioabsorbable anchors)
          • most common
          • allows tensioning of the construct
          • many complications (device breakage, iatrogenic chondral injury)
        • outside-in repair
          • useful for anterior horn tears
        • open repair
          • uncommon except in trauma, knee dislocations
      • technique
        • vertical mattress sutures are strongest because they capture circumferential fibers
        • healing is enhanced by rasping
        • knee flexion beyond 90 degrees should be avoided postoperatively
      • risks
        • saphenous nerve and vein (medial approach)
        • peroneal nerve (lateral approach)
        • popliteal vessels
    • Meniscal Transplantation
      • technique
        • bone to bone healing with plugs at each horn or a bridge between horns
        • peripheral vertical mattress sutures
        • correct sizing of the allograft is essential (commonly based on radiographs, within 5-10% error tolerated)
          • oversizing leads to meniscal extrusion
          • undersizing results in poor congruity and increased load transmission
  • Complications
    • Saphenous neuropathy (7%)
    • Arthrofibrosis (6%)
    • Sterile effusion (2%)
    • Peroneal neuropathy (1%)
    • Superficial infection (1%)
    • Deep infection (1%)
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