Knee Dislocation

  • Associated with significant incidence of neurovascular injury – popliteal artery injury & peroneal nerve palsy (20-40%)
  • May look benign because spontaneously reduces but still has risk of arterial injury
  • knee dislocations that have spontaneously reduced may look benign but may lead to thrombosis of the popliteal artery
  • Both cruciates & least one collateral ligamentare usually disrupted

Classification

  • Direction of displacement
    • Anterior (31%)
    • Posterior (25%)
    • Lateral (13%)
    • Medial (3%)
    • Rotary (4 % – usu posterolateral)
  • Open vs closed
  • High energy vs low energy

Associations

Ligament Injuries

  • may involve ACL, PCL, MCL, LCL , PLC
  • depending on injury pattern, a ligament may be spared

Nerve Injuries

  • 30% incidence
    • peroneal
  • nerve exploration of little value unless preparations made with a surgeon capable of group-fascicular repair

Vascular Injury

  • 30% of cases
  • artery is tethered:
    • proximally by adductor hiatus
    • distally by soleus arch (where it bifurcates into anterior & posterior tibial arteries
  • mechanism of injury:
    • stretch
    • contusion by posterior rim of plateau
    • intimal damage
    • arterial spasm in not an appropriate diagnosis
    • insufficient collateral circulation distally with an occluded popliteal pulse

Investigations

X-Rays

  • Associated radiographic findings
    • Tibial plateau fracture
    • Proximal fibula fracture
    • Avulsion fracture of Gerdy’s Tubercle
    • Intercondylar spine fracture
    • Avulsion of Fibular Head

Arteriogram

  • indications unclear
  • if ABI < 0.9
    • consult vascular surgeon
    • angiography required
    • circulation must be restored within 6-8 hours
    • if vasc. Injury strongly suspected, angio preferably in OR to avoid delay

MRI

  • allows assessement of posterolateral corner injury as well as ACL & PCL
  • assess which structures of the posterolateral corner are injured & whether the injuries are mid-substance or whether they have been avulsed from the fibula or femur

Management

Initial assessment

Angiography

  • hard signs of arterial injury
    • no pulse
    • cold/white foot
    • pulsatile bleeding or mass
    • expanding hematoma
  • diminished pulses
  • If ABI < 0.9
    • consult vascular surgeon
    • angiography required
    • circulation must be restored within 6-8 hours
    • if vasc. Injury strongly suspected, angio preferably in OR to avoid delay

Treatment

Initial

  • EMST
    • Treatment of life threatening injuries
    • Treatment of limb threatening injuries

Emergency

  • reduce ASAP in ER – reduction may be blocked by interposed soft tissue
  • assess neurologic status carefully
  • assess vascular status carefully – including ABI
  • assess ligamentous injuries – clinical exam, EUA & MRI
  • Reduction
    • in ER
    • do not reduce a posterolateral dislocation with a ‘dimple sign’ in which the medial femoral condyle has buttonholed the anteromedial capsule (transverse groove in skin at medial joint line from invagination of part of medial capsule). Should be reduced operatively because high risk skin necrosis
    • External fixation – it is important that the external fixator pin sites will not interfere with the ACL/PCL tunnel sites (during future ligament reconstruction)
  • Vascular Inuries
    • worst error to make is to underestimate the need to promptly treat these injuries
  • Nerve injury
    • location of the nerve injury may be well above the knee joint
    • nerve exploration of little value unless preparations made with a surgeon capable of group-fascicular repair
  • Assessment of ligament injuries
    • EUA

Definitive

  • Nonoperative
    • historical Tx, or for old sedentary persons
    • -6 weeks in cast
  • Operative
    • Principles
      • delay for vascular monitoring, ↓ swelling
      • can delay up to 2 to 3 weeks
      • do not perform reconstruction if fasciotomy needed (additional soft tissue trauma & risk of infection)
      • arthroscopy contraindicated due to capsular tear & ↑ risk compartment syndrome
      • if vascular injury has been previously repaired, get clearance from the vascular surgeon to utilize a tourniquet
    • Technique
      • assess ACL & PCL through anteromedial arthrotomy
      • repair PCL peel-off or reconstruct midsubstance tear
      • delay ACL reconstruction (good results for delayed reconstruction)
      • medial ligament complex can be reached through extended anteromedial incision with leg in figure four
      • lateral structures & peroneal nerve reached from additional lateral incision
    • Repair
      • procede from the deepest structures to the most superficial structures
      • lateral meniscus repair
      • Capsular repair
      • Reattach popliteus to its femoral attachment (bone anchor) & to its fibular head attachment (pull thru sutures)
      • Arcuate ligament
        • reconstruction/repair of this structure is necessary to avoid excessive tibial rotation, especially as the knee moves from extension to flexion
        • remember that the biceps tendon, LCL , & arcuate complex all insert on the fibular styloid, & that if there is a fibular styloid avulsion, osseous reattachement will restore all three structures
        • Achilles tendon allograft may be indicated
        • main goal is to create a checkrein to external rotation
      • LCL repair / advancement on its femoral attachment
      • Biceps Tendon
      • IT Band
        • note that the posterior 1/3 of the IT band attaches to the femoral epicondyle; – if this attachement is deficient, it should be repaired to help restore lateral stability
  • no vascular injury, adequate CR
    • get MRI to determine extent of injury
    • place in hinged knee brace
    • refer to knee specialist
    • closely monitor vascular status
  • no vascular injury, irreducible
    • needs to go to OR for open reduction using medial parapatellar approach & spanning ex fix with pins in distal femur & proximal tibia
    • ID injured ligaments
    • MRI postop
    • refer to knee specialist
  • vascular injury but no repair required
    • monitor for 2-3 days to ensure that injury doesn’t thrombose
    • hinged knee brace
    • MRI to assess ligamentous damage
    • check with vascular surgeon about timing of repair & use of tourniquet
    • refer to knee specialist
  • vascular injury requiring repair
    • allow vascular surgeon to do repair
    • if > 6 hrs of ischemia »
      • fasciotomies
    • hinged knee brace & MRI postop
    • check with vascular surgeon about timing of repair & use of tourniquet
    • refer to knee specialist

Repair/reconstruction of multiple knee ligament injuries

  • always fix PCL to prevent anterior subluxation of tibia with ACL reconstruction
  • ACL can be reconstructed at a later date
  • open procedures because capsule torn & ↑ risk of compartment syndrome with arthroscopy
  • PCL
    • direct repair
      • thru bone holes if pull off injury
    • reconstruct
      • with hamstring tendons or quads tendon or allograft Achilles tendon
    • can be done thru anterior approach
  • ACL
    • direct repair
      • thru bone holes if pull off injury
    • reconstruct
      • with hamstring tendons
    • can be done thru anterior approach
  • MCL
    • direct repair & look for meniscal injuries thru anterior approach
  • LCL & PLC
    • direct repair (can use suture anchors to reattach to fibula)
    • will likely need 2nd incision so beware of skin bridges
    • can reinforce LCL with biceps tendon

Victorian Orthopaedic Registrar presentation