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Duke Orthopaedics
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Wheeless' Textbook of Orthopaedics

Traumatic Dislocations of the Knee


 
- Discussion:
    - mechanism of injury:
           - distinguish between high velocity injuries verus low velocity injuries (as this reflects incidence of vascular and nerve injuries);
           - w/ low-velocity knee dislocations occurance of vascular injury is about 5% and nerve injury is about 20%
           - ref: Low-velocity knee dislocation.  
    - classification: 5 types: described w/ tibia in relation to femur;
           - anterior (31%)
                  - occurs from hyperextension of knee (may need > 30 deg of hyperextension to produce this injury);
                  - often the PCL, & ACL will both be torn;
                  - either the MCL or LCL or both will usually be injured;
                  - alternatively, hyper-extension injuries may cause disruption of the ACL and posterior capsule while the PCL is spared;
                  - popliteal artery is tethered proximally at adductor hiatus & distally by arch of soleus;
                          - injury to the popliteal artery may initially manifest as an intimal tear  or intraluminal thrombus (damage is over a longer segment of the artery);  
          - posterior (25%)
                  - there is disruption of both cruciate ligaments
                  - possible extensor mechanism disruption;
                  - avulsion of or complete disruption of of popliteal artery depending on magnitude of injury 
                  - more likely to produce localized injury (isolated transection);
          - lateral (13%)
          - medial (3%)
          - rotary (4% - usually posterolateral)
          - references:
                  - Complete dislocation of the knee without disruption of both cruciate ligaments.
                  - Complete knee dislocation without posterior cruciate ligament disruption. A report of four cases and review of the literature.
                  - Posterior dislocation of total knee arthroplasty.
                  - Knee dislocations with intact PCL.
                  - Knee dislocations: where are the lesions? A prospective evaluation of surgical findings in 63 cases.


- Clinical Findings: 
    - note the frequent occurence that the closed reduction will be performed by EMS, and so the diagnosis at first glance may not be obvious;
    - note the occurrence of an LCL ligament disruption + peroneal nerve palsy = knee dislocation;
    - popliteal artery & vein injury is common; (see management of vascular injuries)
          - its important to note that knee dilocations that have spontaneously reduced may look benign but may lead to thrombosis of the popliteal artery.
    - peroneal nerve injury:
           - occurs in 20% to 40% of knee dislocations & approximately half of these palsies are permanent;
           - note that apparent neurologic injury may in many cases be due to ischemia;
           - typically both cruciates and least one collateral ligament are disrupted;
           - w/ peroneal nerve injury, be highly suspect for vascular injury;
                 - even if pulse returns following reduction, consider need for arteriogram, since incidence of intimal injury is high w/ concomitant nerve injury;
           - reference:
                 - Palsy of the common peroneal nerve after traumatic dislocation of the knee.
    - assessment of ligament injuries:
           - at the earliest opportunity, the patient should have an examination under anesthesia;
                  - this can often be performed during vascular repair or during anesthesia for management of other injuries (abdominal exploration ect);
                  - this allows clinical determination of the ACL, PCL, LCL, Posterolateral corner, and MCL;
    - ref: Examination of the patient with a knee dislocation. The case for selective arteriography.


- Radiographs: 
    - associated radiographic findings: 
          - tibial plateau frx dislocations: 
          - proximal fibular frx
          - avulsion frx of gerdey's tubercle;
          - intercondylar spine frx 
          - avulsion of fibular head; 


- MRI:
          - MRI not only allows assessment of which ligments are intact but also helps determine whether ligament tears are midsubstance or are avulsions (off the femur or tibia);

           

- Management of Knee Dislocations:
    - closed reduction
           - closed reduction is performed as soon as possible (with follow vascular checks); 
           - note that reduction may be complicated by interposed soft tissue;
           - subluxation or recurrent dislocation is common;
                 - immobilize the reduced knee in approximately 20? of flexion with hinged knee brace;
                 - avoid placing in too much extension, since the lax posterior capsule permits subluxation;
           - if adequate reduction is possible but cannot be maintained, then consider external fixation;
                 - it is important that the external fixator pin sites will not interfere with the ACL/PCL tunnel sites (during future ligament reconstruction); 
           - ref:  Two cases of irreducible knee dislocation occurring simultaneously in two patients and a review of the literature.
    - management of vascular injuries in knee dislocation: 
           - expectation is that vascular surgery and compartment fascial release is required;
                 - if pulses are completely normal and symmetric, normal neurological exam, and soft compartments, then in hospital observation is accetable; 
           - compartment syndrome:
                 - compartment syndrome is a frequent complication of knee dislocation, attributable to vascular injury and resultant ischemia;
                 - four compartment fasciotomy is indicated in these situations;
    - nerve injury:
           - peroneal nerve is often disrupted w/ concomitant LCL injuries, but in some cases there will be tibial nerve injury as well;
           - one of problems encountered in peroneal nerve repair following knee dislocations (or other injuries) is that location of nerve injury may be well above knee joint;
                  - in the case of knee dislocation, there may be concomitant tibial nerve division palsy;
           - hence, it should not be assumed that nerve repair (or nerve jump graft) will be possible using a standard posterolateral incision;


- Treatment of Ligament Injuries:
    - timing:
           - if vascular injury has been previously repaired, get clearance from the vascular surgeon to utilize a tourniquet;
           - in cases of intimal flap tears, a loading dose of intravenous heparin is given before tourniquet inflation inorder to minimize the risk of thrombus formation; 
           - for patients that have had an arterial repair, most authors tend to wait two weeks to assure vessel patency;
    - primary repair:
           - PCL avulsions
                  - often the PCL (and sometimes the ACL) will be avulsed from either the femoral or tibial attachement;
                  - in these cases the ligament can be re-attached using a "suture - pull thru" technique;
                  - the ACL tibial guide will faciliate accurate assessment of pull thru drill holes;
                  - in some cases the anterolateral bundle is ruptured but the posteromedial bundle and meniscofemoral ligament is intact; 
           - references:
                   - Primary repair of knee dislocations: results in 25 patients (28 knees) at a mean follow-up of four years.
                   - Re: primary repair of knee dislocations: results in 25 patients (28 knees) at a mean follow-up of four years.
                   - Comparison of Surgical Repair or Reconstruction of the Cruciate Ligaments versus Nonsurgical Treatment in Patients with Traumatic Knee Dislocations
    - reconstruction:
         - surgical reconstruction sequentially adresses ligament tears determined from clinical exam, MRI, and/or arthroscopy (the later may cause
                  compartment syndrome due to capsular disruption);
         - common instability patterns include the ACL/PCL with either the MCL or LCL injured as well; 
         - often the PCL (and sometimes the ACL) will be avulsed from either the femoral or tibial attachement;
                  - in these cases the ligament can be re-attached using a "suture - pull thru" technique; 
                  - the ACL tibial guide will faciliate accurate assessment of pull thru drill holes;
         - note that reconstructing the ACL without reconstructing the PCL can result in a posteriorly displaced tibia;
         - allografts (bone-patella-bone or Achilles tendon) should be available;
     - other considerations:
         - Hinged External Fixation in the Treatment of Knee DislocationsA Prospective Randomized Study
     - postoperative management:
          - early ROM is encouraged to avoid the complication of knee stiffness;
     - references:
          - Comparison of Surgical Repair or Reconstruction of the Cruciate Ligaments versus Nonsurgical Treatment in Patients with Traumatic Knee Dislocations
          - Results after treatment of traumatic knee dislocations: a report of 26 cases.






Traumatic dislocation of the knee joint.
Traumatic dislocation of the knee
Dislocation of the knee
Femoral-sided fracture-dislocation of the knee.
Surgical Management of Knee Dislocations.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, August 6, 2014 8:14 am