Updated: 2/26/2017

Posterior Approach to Knee

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Introduction
  • Overview
    • primarily a neurovascular approach
    • pathology related to posterolateral and posteromedial corners of the knee should be approached using lateral and medial approaches to knee respectively
  • Indications
    • neurovascular repair in traumatic injury
    • PCL avulsion repair
    • gastrocnemius recession in knee contractures
    • hamstring lengthening
    • Baker's / popliteal cyst excision
    • tibial nerve compression by soleus
Key Anatomy
  • Muscles
    • gastrocnemius 
    • semimembranosus 
    • semitendinosus 
  • Nerves
    • medial sural nerve
  • Vessels
    • small saphenous vein
    • popliteal artery and vein
    • genicular vessels (two superior, two inferior, one middle)
Internervous Plane
  • The is no true internervous plane
Preparation & Positioning
  • Preparation
    • table
      • use radioopaque table when performing fixation (PCL avulsion)
    • tourniquet
      • used in most cases except when a vascular repair is being performed
      • may delay exsanguination until vein is identified
  • Position
    • patient is placed prone
Approach
  • Incision
    • identify superficial landmarks
      • gastrocnemius
      • semimembranous
      • semitendinosus
      • biceps femoris
    • make lazy-S incision running
      • from lateral biceps femoris
      • to medial head of gastrocnemius muscle and into calf
  • Superficial Dissection
    • make subcutaneous skin flaps
      • generous skin flaps will facilitate closure
    • identify small saphenous vein and medial sural nerve
      • medial sural nerve runs on lateral side of vein
      • small sapheneous vein can assist in locating the medial sural nerve
      • the medial sural nerve is a branch of the tibial nerve and can be used as a guide and  into popliteal fossa
    • incise fascia of popliteal fossa
      • make fascial incision just medial to small saphenous vein
    • disect to apex of popliteal fossa
      • use tibia nerve as a guide to apex of popliteal fossa
      • apex is formed by semimembranous (medial) and biceps femoris (lateral)
    • mobilize common peroneal nerve
      • branches from tibial nerve at apex of popliteal fossa
      • runs along posterior border of biceps femoris
    • mobilize popliteal artery and vein
      • lies deep and medial to tibial nerve
      • popliteal vein lies medial to artery as it enters the fossa, then it curves and lies directly posterior to the artery at the midpoint in the fossa
      • must identify and ligate at least one of the five genicular branches in the posterior knee that include
  • Deep Dissection
    • evaluate posteromedial joint capsule
      • faciliated by detaching medial head of gatrocnemius at origin
    • evaluate posterolateral corner of joint
      • develop plane between lateral head of gastrocnemius and biceps femoris
      • faciliated by detaching lateral head of gatrocnemius at origin
Dangers & Complications
  • Medial sural cutaneous nerve injury
    • avoid injury by entering fossa medial medial to small saphenous vein (nerve lies lateral)
    • injury make lead to painful neuroma or anesthesia
  • Tibial nerve injury
    • injury at this level leads to paralysis of foot and toes flexors
  • Common peroneal nerve injury
    • injury at this level leads to paralysis of extensors and evertor of the foot
  • Popliteal artery
    • origin before knee
      • a continuation of the superficial femoral artery
      • transition is at hiatus of adductor magnus muscle
      • anchored by insertion of adductor magnus as enters region of posterior knee
    • course in posterior knee
      • relation to anatomy structures of knee
        • lies posterior to the posterior horn of the lateral horn of the lateral meniscus
          • lies directly behind posterior capsule
    • branches within knee
      • at supracondylar ridge gives branches the provide blood supply to the knee
        • above knee joint branches include
          • medial and lateral sural arteries
          • cutaneous branch
          • middle genicular artery
        • at level of knee joint branches include
          • medial genicular artery
          • lateral genicular artery
    • exit of knee
      • anchor
        • as artery exits knee it is anchored by soleus tendon (originates form medial aspect of tibial plateau)
      • distal branches
        • branches into anterior and posterior tibial arteries at distal popliteus muscles
 

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