Floating Knee

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Introduction

• The term ‘floating’ has been used quite vaguely in the literature to describe various injury patterns /surgical procedures and even congenital anomalies. When the term is used to describe an injury pattern, it commonly implies that a joint/bone has lost its continuity at adjacent ends either as a result of fractures, fracture dislocations or pure disloca-tions and hence has become ‘floating’ 
  
•  Floating Knee is the term applied to the flail knee joint segment resulting from a fracture of the shaft or adjacent metaphysis of the ipsilateral femur and tibia. The fractures range from simple diaphyseal to complex articular types. This complex injury has increased in proportion to population growth, number of motor vehicles on the road, and high speed traffic. Although the exact incidence of the floating knee is not known, it is an uncommon injury. 

              

Epidemiology

• Most of the patients are in their third decade
• Preponderance of males.

Etiology

Road traffic accident (RTA) accounts for majority of the cases and this is followed by fall from height (FFH) 1-5

Presentation / Complications

• Floating knee injuries must be included in assessment and treatment protocols for patients with polytrauma. 
• Damage to the vessels (mainly the popliteal and posterior tibial arteries) and lesions of the nerves (eg, peroneal nerve) are common. Vascular injury is common and may be limb threatening if not recognized and addressed. Often, the vascular injury is to the anterior tibial artery and does not result in ischemia and is not treated with vascular repair or reconstruction. However, vascular status needs to be assessed and addressed as appropriate. Traction usually causes neurapraxia, which often resolves, but complete resolution cannot always be anticipated.
• The incidence of open fractures is high, approaching 50-70%, at 1 or both fracture sites. The most common combination is a closed femoral fracture with an open tibial fracture.
• A well-documented finding is injury to the knee ligaments that occur in association with ipsilateral femoral and tibial fractures. Anterolateral rotatory instability is the most common pattern of instability. Knee ligament injury is not always suspected, and joint swelling due to hemarthrosis should not be mistaken for a sympathetic effusion. The ipsilateral femoral and tibial shaft fractures and knee ligament injury appear to be part of a continuum of combined injuries resulting from complex, high-energy forces 
• In skeletally immature patients, floating knee is uncommon. Few studies of this injury have been conducted in children. Data from available studies show that findings observed in children are comparable to those in adults in terms of the mechanism of fracture, the incidence of associated major injuries, and the complexity of treatment.
• Epiphyseal injury can adversely affect open growth plates, predisposing a child to limb-length discrepancy and angular deformities.

Management 

In adults, all floating knee injuries must be addressed with early anatomic reconstruction and stable surgical stabilization of both fractures. The goal is to allow for early joint mobilization.

• In children, especially those younger than 10 years, treatment of ipsilateral