Dislocation of knee,what to know?
Knee Dislocation, what to know?
The knee joint allows for flexion and extension. These functions allow the body to perform activities like walking, running and sitting. Knee dislocations occur as a result of violent trauma. The femur and tibia are not articulating with each other. The bones of the knee are held together by strong ligaments. For a knee dislocation to occur, 3 out of 4 of these ligaments have to become ruptured. Types of knee joint dislocations: •Anterior •Posterior •Medial-lateral •Rotary: usually posterolateral. The medial femoral condyle can button-hole through the medial soft tissues resulting in a “dimple sign”. It is often irreducible. Posterior dislocation/ dashboard injury Most common mechanism of injury includes exaggerated hyperextension of the knee and dashboard injuries. Posteriorly directed force with the knee flexed in 90 degrees. The peroneal nerve is tethered at the fibular neck. The incidence of nerve injury ranges from 14% to 35%. Arterial injury •Vascular damage is most common in anterior and posterior dislocations in approximately 40% of the cases. Arterial damage in approximately 20-40% of all knee dislocations. Knee dislocation is associated with a high incidence of popliteal artery injury. •With an established popliteal artery and resultant ischemia, blood flow must be restored within 6 hours. •Posterior tibial and dorsalis pedis pulses should be carefully evaluated and compared to the other side in any patient with a knee dislocation. •Look for any evidence of ischemia, diminished blood flow, or compartment syndrome. •Urgent reduction of the knee dislocation is mandatory •Be aware of spontaneously reduced knee dislocations and its associated pathology. •Reevaluate circulation after reduction, if pulses are normal, serial follow-up up to 48 hours with clinical examination and non-invasive studies (ABI). If ABI is 0.9 or more, then the patient will not have an arterial injury. If pulses are abnormal or different, do arteriography. If no pulses then do an immediate exploration in the OR. Treatment •Arterial injury is treated with excision of the damaged segment and reanastmosis with a reverse saphenous vein graft and prophylactic fasciotomy. •Early surgery if ligament avulsion is present- important ligament to reconstruct is the PCL- if posterolateral corner disruption. •After reduction, the patient is placed into a knee immobilizer or external fixator. •Delayed elective reconstruction of the knee ligaments is usually done at a later date. •The PCL is an important ligament to reconstruct.
source---https://www.youtube.com/watch?v=G9MPgxiZnoc
The knee joint allows for flexion and extension. These functions allow the body to perform activities like walking, running and sitting. Knee dislocations occur as a result of violent trauma. The femur and tibia are not articulating with each other. The bones of the knee are held together by strong ligaments. For a knee dislocation to occur, 3 out of 4 of these ligaments have to become ruptured. Types of knee joint dislocations: •Anterior •Posterior •Medial-lateral •Rotary: usually posterolateral. The medial femoral condyle can button-hole through the medial soft tissues resulting in a “dimple sign”. It is often irreducible. Posterior dislocation/ dashboard injury Most common mechanism of injury includes exaggerated hyperextension of the knee and dashboard injuries. Posteriorly directed force with the knee flexed in 90 degrees. The peroneal nerve is tethered at the fibular neck. The incidence of nerve injury ranges from 14% to 35%. Arterial injury •Vascular damage is most common in anterior and posterior dislocations in approximately 40% of the cases. Arterial damage in approximately 20-40% of all knee dislocations. Knee dislocation is associated with a high incidence of popliteal artery injury. •With an established popliteal artery and resultant ischemia, blood flow must be restored within 6 hours. •Posterior tibial and dorsalis pedis pulses should be carefully evaluated and compared to the other side in any patient with a knee dislocation. •Look for any evidence of ischemia, diminished blood flow, or compartment syndrome. •Urgent reduction of the knee dislocation is mandatory •Be aware of spontaneously reduced knee dislocations and its associated pathology. •Reevaluate circulation after reduction, if pulses are normal, serial follow-up up to 48 hours with clinical examination and non-invasive studies (ABI). If ABI is 0.9 or more, then the patient will not have an arterial injury. If pulses are abnormal or different, do arteriography. If no pulses then do an immediate exploration in the OR. Treatment •Arterial injury is treated with excision of the damaged segment and reanastmosis with a reverse saphenous vein graft and prophylactic fasciotomy. •Early surgery if ligament avulsion is present- important ligament to reconstruct is the PCL- if posterolateral corner disruption. •After reduction, the patient is placed into a knee immobilizer or external fixator. •Delayed elective reconstruction of the knee ligaments is usually done at a later date. •The PCL is an important ligament to reconstruct.
source---https://www.youtube.com/watch?v=G9MPgxiZnoc
Management
The first step in management involves immediate reduction of obviously dislocated knee, especially if neurovascular compromise exists, without radiographs. Neurovascular status should be documented before and after attempting reduction. Prior to reduction evaluate the patient for signs of a posterolateral dislocation (ie “dimple sign”), as these dislocations are not amenable to closed reduction. An anteromedial skin furrow, or “dimple sign” at the medial joint line, is suggestive of a posterolateral dislocation, which are irreducible. Attempts at closed reduction may compromise the thin veil of skin overlying the prominent femoral condyle in posterolateral dislocations leading to skin necrosis.
The initial approach to reducing all knee dislocations is to apply longitudinal traction to the extremity. This is usually all that is required to reduce a knee. Anterior knee dislocations may require additional lifting of the distal femur, whereas posterior dislocations may require lifting of proximal tibia to complete reduction. After reduction, the knee should be immobilized in a long leg posterior splint with the knee in 15-20 degrees of flexion.
Vascular examination at bedside following a knee dislocation is of limited accuracy. Controversy exists regarding the necessity of angiography in all patients with knee dislocations to screen for the presence of popliteal artery injury. All patients with weak/absent pulses or hard signs for vascular injury should have angiography performed along with emergent vascular surgery consultation. It is recommended that patients with ABI < 0.9, asymmetric pulses, or abnormal doppler ultrasound obtain angiography (or comparable vascular study such as a CTA) in consultation with vascular surgeon to evaluate integrity of popliteal artery (8). Some studies have shown that vascular injury can be reliably excluded in patients with low-energy knee dislocations, a normal physical examination with Doppler US, and ABI > 0.9. However, these patients should receive close monitoring with serial examinations (9-11).http://www.emdocs.net/
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