- 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. Shelbourne KD, Porter DA, Clingman JA, et al: Orthop Rev 20:995-1004, 1991
-
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:
-
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;
- references:
-
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:
-
reduction:
- 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:
-
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 the problems encountered in peroneal nerve repair following knee dislocations
(or other injuries) is that the location of the nerve injury may be well above the 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;
- 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.
Congenital dislocation of the knee. Its pathologic features and treatment.
The treatment of congenital knee dislocation. A review of nineteen knees.
Traumatic dislocation of the knee. Kremchek TE, Welling RE, Kremchek EJ: Orthop Rev 1989;10:1051-1057.
Dislocation of the knee. Orthop Clin North Am 1987;18:149-156.
Montgomery JB:
Femoral sided fractures dislocation of the knee.
RC Schenck, PLJ McGanity, and JD Heckman.
Surgical Management of Knee Dislocations.
