orthopedics 5th year, 7th/part two & 8th lectures (dr. ali a.nabi)

Dislocation of the knee joint


Knee dislocation is a relatively rare injury but an important one to recognize because coexistent vascular injury, if missed, often leads to limb loss. In addition, knee dislocation often presents in the context of multisystem trauma or spontaneous relocation, which makes detection more difficult.


The positional classification system was developed by Kennedy and describes 5 major types of positional dislocation,

1. Anterior: Anterior dislocation often is caused by severe knee hyperextension. Approximately 30 degrees of hyperextension is required before dislocation will occur.


1. Posterior: Posterior dislocation occurs with anterior-to-posterior force to the proximal tibia, such as a dashboard type of injury or a high-energy fall on a flexed knee.

2. Medial, lateral, or rotatory: these require varus, valgus, or rotatory components of applied force.


More than half of all dislocations are anterior or posterior, and both of these have a high incidence of popliteal artery injury. Twenty to thirty percent of all knee dislocations are complicated further by open joint injury.


PhysicalMost often, the affected limb has a gross

deformity of the knee with swelling and immobility, but up to 50% of knee dislocations are reduced by the time of ED presentation and may not be obvious.

Many knee dislocations have associated fractures.


The finding of varus or valgus instability in full extension of the knee is suggestive of a spontaneously reduced yet grossly unstable dislocation. In addition, pain out of proportion, or absent or decreased pulses are red flags of such an injury.


A careful vascular examination is required. The popliteal artery may be damaged in all variants of knee dislocation/subluxation, with reported incidence ranging from 7-64%.

Coexistent peroneal nerve injury occurs in 25-35% of patients and must be ruled out.


CausesThe knee is a very stable joint generally

requiring high-energy trauma to produce dislocation. At least 3 major ligaments typically rupture for dislocation to occur.


Common mechanisms of injury include the following: Motor vehicle collisions Auto-pedestrian impact Industrial injuries Falls Athletic injuries


Differential DiagnosesFractures, Femur

Fractures, Knee Fractures, Tibia and Fibula


Imaging Studies Plain radiographs: Plain radiographs are

recommended post reduction and prior to any provocative ligamentous stressing.

Ankle-brachial or arterial-pressure indices: Briefly, the ankle-brachial index compares the Doppler pressure of an arm to a leg to screen for lower limb ischemia.


Duplex/ultrasonography: This is a reliable, noninvasive, low-risk, low-cost option. Duplex ultrasonography appears to be an excellent modality for vascular injury assessment.

CT angiography: CT angiography is another reliable alternative to arteriography without the risk of direct arterial injury.

MRI to show associated ligamental and meniscal injury.


TreatmentPrehospital CarePrehospital personnel should splint the

extremity and provide rapid transport to a medical facility.

Perform field reduction for patients with evidence of vascular compromise.


Emergency Department Care Do not delay reduction in limbs with obvious

vascular impairment. Only patients with good peripheral pulses should undergo prereduction radiographs.

Reduction is straightforward and often easily accomplished in the ED. After adequate sedation, longitudinal traction will relocate the majority of knee dislocations.


Posterolateral dislocations are particularly difficult and often require operative reduction.

After reduction, splint the lower extremity in approximately 20 degrees of flexion to avoid postreduction re-dislocation, apply ice, and keep the knee elevated.


Postreduction radiographs should be obtained, preferably before further ligamentous stressing/assessment.

Postreduction hard signs of arterial injury should prompt emergent vascular surgical intervention that should not be delayed for arteriography.

Dislocation of the patella

Patellar pain is common in both athletic and nonathletic individuals. Among athletes, men tend to present with more patellofemoral injuries, including traumatic dislocations, than women. In the nonathletic population, women present more commonly with patellar disorders.


Because the knee in slight valgus position, there is natural tendency for the patella to pull towards the lateral side when the quadriceps muscle contracts.


Normally the patella is stable because of

1. the patella is seated in the intercondylar groove.

2. the contraction of the quadriceps muscle will pull the patella firmly in the groove.

3. the extensor retinacula and the patellofemoral ligaments guides the patella centerally as tracks in the groove.


Mechanism A common mechanism of patellar injury

and dislocation after direct trauma: when the knee is flexed,

the quadriceps muscle is relaxed; the patella may forced laterally by direct violence.


indirect trauma or force : With sudden changes in direction, usually happened with athletes due to suddon, severe contraction of the quadriceps muscle while the knee is stretched in valgus and external rotation.


The patella usually dislocates laterally and the medial patellofemoral and the retinacular fibers may be torn.

Predisposing factorsgenu valgum. tibial torsion.high riding patella (patella alta).shallow intercondylar groove.patellar hypermobility.


Clinical features the patient got tearing sensation and feeling

that the knee has gone ‘out of joint’. the patient fall or collapsed on the ground. pain. swelling. deformity. Patella will seated in the lateral

aspect of the knee.


active and passive movement are impossible. patella may reduced spontaneously. There will

be only pain and swelling without deformity. bruising and tenderness haemoarthrosis. symptoms are less marked in recurrent

dislocation.


Imaging anteroposterior, lateral and skyline x-ray

views are needed.MRI to evaluate soft tissue like medial

patellofemoral ligament.


Treatment closed reduction is usually easy and may not

need anasthesia. haemoarthrosis should be aspirated, cast splint is indicated for2-3 weeks. open reduction is only indicated if the

dislocated patella entraped intra articularlly. ligamental injury and recurrent dislocation

need surgical repair.

Fractures of the tibia and fibula

Lower leg fractures include fractures of the tibia and fibula. Of these two bones, the tibia is the only weight bearing bone. Fractures of the tibia generally are associated with fibula fracture, because the force is transmitted along the interosseous membrane to the fibula.


The skin and subcutaneous tissue are very thin over the anterior and medial tibia and as a result of this; a significant number of fractures to the lower leg are open. Even in closed fractures, the thin, soft tissue can become compromised. In contrast, the fibula is well covered by soft tissue over most of its course with the exception of the lateral malleolus.


Mechanism Mechanisms of injury for tibia-fibula

fractures can be divided into 2 categories: Low-energy injuries such as ground levels

falls and athletic injuries (indirect force). High-energy injuries such as motor vehicle

injuries, pedestrians struck by motor vehicles and gunshot wounds (direct force).


Pathological anatomyThe behavior of these fractures and the

choice of treatment will depend onThe state of soft tissue.The risk of complications and the

progress to fracture healing are directly related to the amount and type of soft tissue damage.


Close fractures are classified according to the state of soft tissue coverage by Tscherne’s classification (1984)

Type I – no skin lesion. Type II – no skin laceration but contusion. Type III – circumscribed degloving. Type IV – extensive, closed degloving. Type V – necrosis from contusion. Open fracture classified according to Gustilo’s

(1990).


The severity of the bone injury. High energy fractures are more damaging and take longer time to heal than low energy one.

Stability of the fracture. Spiral fractures are the most stable while the comminuted fractures are the least stable.


Clinical featuresPatient may report a history of direct

(motor vehicle crash or axial loading) or indirect (twisting) trauma.

Patient may complain of pain, swelling, deformity and inability to ambulate with tibia fracture.

Ambulation is possible with isolated fibula fracture.


Tibial shaft fractures usually present with a history of major trauma. An exception to this is a toddler's fracture, which is a spiral fracture that occurs with minor trauma in children who are learning to walk.


O/E swelling, bruises, echymosis, blisters, deformity, tenderness, crepitus, and painful restricted movements.

Always be alert for sign of compartmental syndrome.

Wound can be seen if the fracture is open.


X – Ray role of twos.


Treatment The goal is toLimit soft tissue damage and preserve

skin cover.Prevent compartment syndrome.Reduce and hold fracture.Start early weight bearing.Start early joint movement.


Initially, all tibial shaft fractures should be stabilized with a long posterior splint with the knee in 10-15° of flexion and the ankle flexed at 90°. Admission to the hospital may also be necessary to control pain and to monitor closely for compartment syndrome.


Closed fractures with minimal displacement or stable reduction may be treated nonoperatively with a long leg cast, but cast application should be delayed for 3-5 days to allow early swelling to diminish. The cast should extend from the mid thigh to the metatarsal heads, with the ankle at 90° of flexion and the knee extended. The cast increases tibial stability and can decrease pain and swelling.


Early ambulation with weight bearing as tolerated should be encouraged. Tibial shaft fractures treated with casting must be monitored closely with frequent radiographs to ensure that the fracture has maintained adequate alignment. Adequate callus formation generally takes 6-8 weeks before cast therapy can be discontinued.


Despite proper casting techniques and adequate follow-up, not all nonoperatively treated tibial shaft fractures heal successfully. In addition, 6 weeks without knee motion often results in a stiff joint.


The patellar tendon–bearing cast, used early in treatment of tibial shaft fractures in place of the long leg cast.


In general, however, better results are reported with internal fixation of displaced tibial shaft fractures than with nonoperative treatment. The results of nonoperative treatment of displaced tibial shaft fractures were not as satisfactory as those with intramedullary nailing.


open fractures are usually treated as follow Antibiotics. Debridement. Stabilization usually by external

skeletal fixation. Soft tissue coverage. Rehabilitation


ComplicationsI – early Vascular injury.Compartment syndrome.Nerve injury especially common

peroneal nerve.Infection Gangrene


II – late Malunion.Delayed union.Non-union.Joint stiffness.Osteoporosis.Alygodystrophy. Osteomyelitis

orthopedics 5th year, 7th/part two & 8th lectures (dr. ali a.nabi)

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