Knee Dislocation- Review

Knee Dislocations

• Traumatic knee dislocations are uncommon, account for <0.02% of all orthopaedic injuries.
• It commonly results in multidirectional instability due to involvement of stabilising soft tissues (usually a combination of disruption of Acl, Pcl, Mcl, Lcl.

Knee dislocation can be acute (<3 wks) or chronic (>3 wks).It can be classified anatomically based on position of displaced tibia (anterior, posterior, medial, lateral), anterior being the most common (40%).

• Anterior: Forceful knee hyperextension beyond -30 degrees (most common)
• Posterior: Posteriorly directed force against proximal tibia flexed knee
• Lateral: Valgus force
• Medial: varus force
• Rotational: Varus/valgus with rotatory component

 

Schenck’s Anatomic Classification

 

I	Single cruciate + collateral	ACL + collateral PCL + collateral
II	ACL/PCL	Collaterals intact
IIIM	ACL/PCL/MCL	LCL + PLC intact
IIIL	ACL/PCL/LCL + PLC	MCL intact
IV	ACL/PCL/MCL/LCL + PLC
V	Fracture-dislocation
C	Arterial injury
N	Nerve injury

• It is also associated with neurovascular injuries. Popliteal artery is injured in 30% cases and most common with posterior dislocations. There may be distal pulses and capillary refill due to collateral circulation but it doesn’t maintain limb viability.
• Common peroneal nerve injury(16-40%)  associated with postero-lateral dislocations.

EVALUATION :

• 20 to 50% dislocations spontaneously reduce and hence may present with normal looking X-rays.

• The ACL and PCL are disrupted in most cases, with a varying degree of injury to the collateral ligaments, capsular elements, and menisci.
• Any three-ligament injury should be considered and treated as knee dislocation.
• Associated fractures of the distal femur or tibial plateau are seen in 60% cases
• CT Angiogram is considered to be the gold standard in evaluating patients with clinical evidence of vascular injury
• Vascular examination

o     Dorsalispedis and posterior tibial artery pulses should be evaluated.

o     Pulse absent

–        Consider immediate closed reduction.

–        If pulse returns, consider CT angiogram versus observation.

–        If still absent, explore the artery.

o     Pulse present

–        If the Doppler ankle-brachial pressure index (ABPI) is >0.9, observe the patient.

–        If the ABPI is <0.9, proceed with CT-angiogram and/or exploration.

• Slight widening of the joint space may be a subtle evidence of a knee dislocation. The presence of rim/avulsion fractures, subtle tibiofemoral subluxation maybe indicative of a reduced knee dislocation
• Presence of a ‘dimple sign’ on examination may be evidence of a posterolateral dislocation, and is a contraindication to closed reduction due to risk of skin necrosis.

Treatment

Initial management:

• Vascular status of the limb must be determined quickly and managed appropriately.
• If the limb is obviously ischemic, the knee should be reduced immediately through gentle traction-counter traction.

 

Reduction methods:

a)    Anterior: longitudinal limb traction is combined with lifting of the distal femur.

b)    Posterior: longitudinal limb traction is combined with extension and lifting of the proximal tibia.

c)    Medial/lateral: longitudinal limb traction is combined with lateral/medial translation of the tibia.

d)    Rotatory: longitudinal limb traction is combined with derotation of the tibia.

Definitive management

Closed Reduction:

• It consists of closed reduction and immobilization in extension for 6wks
  • Once closed reduction is obtained immobilisation is maintained in a splint or a brace

Operative Treatment

•    Indications of operative treatment

–   Unsuccessful closed reduction

–   Residual soft-tissue interposition (especially in postero-lateral dislocation)

–   Open injuries

–     Vascular injuries: when vascular repair is done, simultaneous prophylactic fasciotomies are recommended and external fixation is done to maintain reduction and access to soft tissue

–     If Operative treatment is performed for knee dislocation, immobilization using an external fixation is preferred.

 

Operative:

• Ligament reconstruction may be delayed to allow vascular monitoring and also to reduce the risk of arthrofibrosis, though posterolateral structures, capsular lesions and avulsion fractures may be repaired acutely if a vascular repair is being undertaken
• Controversy exists over early repair Vs delayed reconstruction of the PLC.(Stannard AJSM 2005)
• Multiligamentous reconstruction maybe performed if the soft tissues are amenable to surgical intervention and if the patient is able to undergo an extensive rehabilitation protocol.
• For ACL reconstructions, single bundle reconstructions are preferred because of the need for numerous tunnels in a multi ligamentous injured knee.
• Double bundle techniques have been proposed for the PCL in this setting, but no level 1 studies are available to support this.
• Autografts are preferred over allografts and potential sources include patellar, quadriceps, hamstring, either from the ipsilateral knee or the contralateral knee
• Allografts have a potential for disease transmission especially HIV, with a reported incidence of 1 in 1.6 million.
• MCL injuries: For delayed reconstruction the Bosworth technique is used. The Bosworth technique has been modified to detach the tendon proximally and secure it to the femur at the MCL origin, with the remaining portion of the graft secured to the tibia distally.
• PLC: the preferred technique for reconstructing the PLC is by using a Achilles tendon bone allograft with two sockets created on the femoral side and one through the fibula, reconstructing the tendinous portion of the popliteus, popliteofibular ligament and the FCL.

Postoperative Regimen:

• A postoperative regimen described by Fanelli et al, has demonstrated excellent long term results
• Patients are immobilized in full extension for the first 3 weeks after surgery and then allowed to progress to pain-free prone passive ROM. Weight bearing is allowed only after 6 weeks.
• Open kinetic chain exercises are best avoided
• Patients continue in a range of motion knee brace for upto 1 year after reconstruction

Further Reading:

1. Stannard JP, Brown SL, Farris RC, McGwin G Jr, Volgas DA, The posterolateral corner of the knee: Repair Vs Reconstruction  Am J Sports Med 2005; 33(6), 881-888
2. Fanelli GC, Edson CJ, Arthrosopically assisted combined anterior and posterior cruciate ligamentous reconstruction in the multiple ligament injured knee, Arthroscopy 2002; 18(7); 703-714