TIS

Chapter 12
Meniscal Injuries


  1. Introduction

  2. Epidemiology

  3. Structure

  4. Function
    1. load transmission: 30-70% of load across knee
      • 50% medially and more laterally
      • increasing flexion increases ineniscal loads (85% at 90 degrees flexion)
      • partial and total meniscectomy decrease contact area and increase peak local contact stresses; removal of 16-34% of meniscus increases joint surface contact forces by 350%
    2. shock absorption
      • meniscectomy decreases 20%
    3. joint congruity
    4. joint stability
      • decreases A/P translation
      • in an ACL deficient knee, the posterior horn of the MM decreases anterior translation [cause of MMT's in ACL deficient knees, and failure of post horn MMT repairs in ACL deficient knees (as high as 95%)]
    5. lubrication
    6. nutrition - articular cartilage

  5. History and Mechanism

  6. Meniscal Surgery
    1. Total meniscectomy - no longer routinely performed
      • Fairbank 1948: changes following total meniscectomy included: marginal femoral osteophytic ridge, flattening of MFC, narrowing of joint space
      • many subsequent studies in the 1960's, 1970's documenting DJD, pain and articular cartilage changes
      • amount of DJD correlated with the amount of meniscus excised
    2. Partial meniscectomy
      • better than total
      • Ferkel (1985): 86% good/excellent results at 2-5 years follow-up; results were worse with:
        • chondral changes, medial, lateral or PF
        • degenerative tears
        • work-related injuries
      • Baratz (1986) cadaver study looked at contact area decreases and peak local stress increases following total or partial meniscectomy:
        • partial: | contact area 10% & | PLS 65%
        • total: | contact area 75% & | PLS 235%

      Rehabilitation following partial meniscectomy:

      Key Issues/risk factors:

      • amount & location of associated injury/pathology: ACL?, DJD?
      • previous injuries/surgeries
      • body weight
      • muscle mass/quadriceps tone
      • activity level and type

      ** BOTTOM LINE: THE KNEE MUST ADAPT TO CHANGES IN THE LOADING PATTERN AT THE KNEE; AREAS WILL NOW BE LOADED IN A DIFFERENT PATTERN AND AT A HIGHER LEVEL THAN PREVIOUSLY. THE KNEE MUST BE GIVEN TIME TO ALLOW THIS ADAPTATION TO OCCUR. If not, other parts of the knee will become overloaded, placing them at risk for another injury. This is especially true in those with high risk factors. The knee must be taken through a series of progressive activities including an impact loading series and functional progression to assure safe returns!

      Early:
      • ROM
      • swelling
      • maintain quadriceps tone

      Intermediate:
      • quadriceps strength & endurance
      • quadriceps strength & endurance
      • quadriceps strength & endurance
      • balance & proprioception

      * watch swelling as program progresses; this will tell you appropriate pace of program

      * progress from open chain to controlled, progressive loading via closed chain

      * work closed chain in multiple planes

      Late:
      • quadriceps strength & endurance maintenance
      • progressive impact loading
      • functional progression
      • quadriceps strength & endurance maintenance

    3. Meniscal repair
      • which tears are repairable?
      • depends upon who you ask
      • can be done open or through the scope; open allows for better visualization of associated capsular injuries (tibiomeniscal lig)
      • arthroscopic techniques include: inside-out, outside-in and all-inside

      Stable Tears:
      • often occur acutely with ACL tears
      • they can be full thickness (<7-10 mm) or partial (<1.5 mm); frequently they are peripheral and longitudinal tears
      • generally leave stable tears alone unless symptomatic, or rasp to facilitate healing
      • Weiss (1989) 2-10 year R/U of 80 tears in 75 pts
          46/52 were asymptomatic; all of the 6 who were symptomatic were failures upon re-scope
          32 repeat scopes (for other reasons) demonstrated:
            17/26 longitudinal healed
            1/6 radial healed

      Indications for repair:
      • Henning felt that 98% of tears were repairable
      • Others: peripheral longitudinal tears in the vascular zone that are unstable to probe or are symptomatic
        • patients under 40 yrs
        • STABLE KNEE
        • flap and radial tears less suitable for repair

      Results:
      1. DeHaven (1989): 2-9 yr R/U (avg 5 yr) 80 with open repair
        • 11% retear; mostly associated with ACL deficiency
        • 40/41 normal x-rays
        • 42/44 no limitations
        • new 10 year R/U: 22% retear rate

      2. Cooper, Arnoczky, Warren (1991): outside-in
        • 75-80% heal completely
        • 15% partial healing (<50%)
        • 5-10% failure
        • 50% failure without ACL reconstruction
        • 5% failure with ACL reconstruction
        • 23% failure with intact ACL

      3. Morgan, Wojtys (1991): second look scope, outside-in in 74/353 pts
        • asymptomatic healing in 84%: 65% complete, 19% incomplete
        • symptomatic failures in 16%: all were ACL deficient
        • 11/12 failures occurred in posterior horn of MM

      BOTTOM LINE: INCREASED RISK OF FAILURE IN ACL DEFICIENT KNEE. MENISCUS SHOULD NOT BE REPAIRED IN ACL DEFICIENT KNEE WITHOUT CONCURRENT ACL RECONSTRUCTION.


      Rehabilitation following meniscal repair:

      Key issues/risk factors:
      • concommitant injury: ACL, PCL, PL corner
      • same issues as post-meniscectomy: loading joint and repair
      • know extent and location of tear
      • preservation of motion is key
      • rehab is getting more aggressive

      Early:
      • TTWB x 4 weeks in knee immobilizer or brace:
        • peripheral to midzone: 0-90 degrees
        • peripheral anterior or posterior zone: 20-90 degrees
        • white zone: 20-70 degrees
      • passive motion minimum TID
      • open chain SLR's in slight flexion, submaximal quad sets (to maintain patellar mobility and quad firing), heel slides, etc.
      • caution with excessive semimembranous firing secondary to MM attachment

      Intermediate:
      • progress to FWB from weeks 3-6 by - 25%/week; white zone repairs should progress over weeks 4-8; DC brace
      • biking
      • PRE 0-90 degrees; quad strength
      • progressive loading of meniscus, with slow progressive loading of repaired area
      • pool activities
      • balance & proprioception activities

      Late:
      • progressive loading of joint; closed chain activities
      • quadriceps strength maintenance
      • progressive impact loading program; beginning at 4 months
      • balance & proprioception activities

      Mensicus repair with ACL reconstruction:
      • follow protocol for ACL reconstruction

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