ANTERIOR CRUCIATE LIGAMENT - DNB Orthopaedics MS Orthopedics MRCS Exam GUIDE - Orthodnb.com

DNB Orthopaedics  MS Orthopedics  MRCS Exam GUIDE - Orthodnb.com

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Friday, 27 April 2018

ANTERIOR CRUCIATE LIGAMENT

ANTERIOR CRUCIATE LIGAMENT 2


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Treatment
  1. non surgical
  • in those who are willing to make life style changes – avoid the activities of recurrent instability
  • in cases of stable knee
  • muscle strengthening – braces
  • risk of meniscal tears high
  1. repair of ACL
  • 50% failure within 5 years
  • primary repair indicated only in bony avulsion of ACL
  • more tibial avulsions than femoral ( except skiers with low velocity injuries)
  • avulsed bony fragment replaced, fixed sutures through trans osseous drill holes/screws
  • post op 3 wks – up to 900 flexion allowed in brace – 6 wks crutches – 8wks full range motion- 3 months exercises continued
  1. reconstruction of ACL
  • Extra articular
  • intra articular

Image result for ANTERIOR CRUCIATE LIGAMENT
Extra articular procedures
  • create a restraining band on lateral knee – from lat femoral epicondyle to gerdy tubercle – line parallel with ACL
  • use iliotibial band
  • stress depends on the changes of femoral fixation points – so transfer should be anchored high on femur – proximal to attachment of LCL
  • decreases the anterolateral rotatory subluxation – do not recreate normal anatomy – high chance of failure when used alone
  • used along with intra articular reconstruction
  • Techniques
    • Macintosh technique (iliotibial band tenodesis)
      • 1.5 cm band strip dissected from mid portion – at 16 cm from distal insertion – passed through hiatus created in distal inter muscular septum – passed deep to fibular collateral ligament – fixed to gerdy tubercle with staples or sutures
    • Losee modification of Macintosh technique
      • 18cm long, 1.5 cm wide strip of iliotibial band – distally attached to gerdy tubercle – passed through an osseous tunnel created in anterolateral femoral condyle – through the femoral attachment of lateral inter muscular septum and lateral head of gastrocnemius – fixed to gerdy tubercle with suture/ staple
    • Andrew's technique
      • anterolateral 10cm hockey stick incision exposing iliotibial tract
      • longitudinal division of tract – 10cml long at 4 cm anterior to posterior margin of tract
      • separated into two bundles – fixed to femur by sutures – passed through tract – through 2 parallel holes to distal femur – fixed to each other at medial side of femur beneath vastus medialis
      • anterior bundle tight in flexion – posterior bundle tight in extension
Intra articular reconstruction
  • arthroscopically or small arthrotomy incision
  • Graft selection
    • autografts – allografts – synthetic grafts
    • autografts – low risk of inflammation – no risk of disease transmission
    • most common choices
      • bone - patellar tendon -bone graft
        • 8-11mm wide
        • central third patellar tendon with adjacent patellar and tibial bone block
        • strength – 2977 N
      • quadrupled tendon graft
        • quadruple stranded semitendinosus graft or quadruple stranded semitendinosus – gracilis tendon graft
      • quadriceps tendon graft
        • harvested with patellar bone or entirely soft tissue graft
    • ACL strength – 1750 N - strength of graft decreases to half when fully taken up – so initial strength of graft should be 2x1750 N
  • Graft placement
    • femoral site more important – closer to the center of axis of knee motion
    • femoral tunnel – too anterior – intra articular distance lengthens in flexion – leads to knee capturing or loss of flexion – failure of graft
    • posterior placement of tunnel – graft taut in extension and lax in flexion – produces an acceptable result – ACL cause knee stability is in the end of extension – clinical examination negative Lachman and Ant drawer but posterior drawer +
    • isometric placement of tunnel is preferred location – that limits changes in length and tension in movement
      • posterior portion of ACL tibial insertion near the posterolateral bundle location – best reproduction of intact ACL function – decreases graft impingement against roof of intercondylar notch in extension ( as in an anterior placement)
    • tibial bone plug – triangular – patellar - trapezoidal
    • Notch plasty – widening of the intercondylar notch – prevent impingement – posterior tibial placement requires minimal notch plasty
      • needed in c/c ACL deficiencies, intercondylar notch stenotic w/ osteophytes
      • limited notch plasty improves visualization – assist in proper placement of tunnel
      • anterior aspect of notch deepened by 2-3cm – depends on size of graft
      • tapered posteriorly – so no bone is removed at femoral insertional site
      • bony ridge / resident's ridge – anterior to femoral attachment of ACL removed – hinders proper identification and placement of tunnel
      • posterosuperior apex of the notch at 12'o' clock – funnel canal should be at 11'o'clock in right knee and at 1'o'clock in left knee
  • Graft tension
    • that much needed to obliterate Lachman test
    • less tendon needed for b-pt-b graft than semitendinosus graft – tendon portion in b-pt-b is short and stiffer
  • Graft fixation
    • early post op – weak ling is fixator not graft tissue
    • direct fixation – interference screws, staples, washers, cross pins
    • indirect fixation – polyester tape – titanium button, suture
    • interference screws popular for b-pt-b graft
      • complications are
        • inadvertent graft advancement unless graft fixed correctly while inserting the screw
        • screw laceration of passing suture – place at least one suture on opposite side of bone plug ( side which has no contact with screw threads)
        • screw thread laceration of tendon – if tip protrudes out of bone
    • screws parallel to bone plug and tunnel wall – ensured by using cannulated screw system
    • bioabsorbable screws – good alternative to metal screws
    • bone to bone healing in b-pt-b graft is 6 wk – bone to tendon is 8-12 wks – rehab during this period gives additional stress of 450N – this period fixation strength determines the failure – once graft taken up graft strength limits failure

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