Floating Knee

Excerpt

As early as 1975, the term floating knee was initially used by Blake and McBryde to describe fractures of the ipsilateral femur and tibia. Fractures can occur anywhere along the femur and the tibia and must occur in both bones to be considered a floating knee injury. The term floating knee refers to the knee joint and not necessarily the connection to either long bone. Although tibial and femur fractures are not uncommon, having injuries to both bones simultaneously on the ipsilateral limb is uncommon. Floating knee injuries are usually complex, with various mechanisms of injury, as well as often complicated treatments.

Floating knee (also known as "flail knee") injuries have been classified using various classification systems including the first classification used by Blake and McBryde, the Letts-Vincent, and the Bohn-Durbin classification systems.

Blake and McBryde first classified the injuries based on the injury sites as type I, type II-A, and II-B. Type I fractures include fractures of both shafts of the two long bones. Type II-A involves the knee joint, whereas type II-B fractures require the involvement of the hip or ankle joints.

The Letts-Vincent and the Bohn-Durbin are pediatric classification systems that first classify the region of the fracture and whether it is an open or closed fracture. Letts-Vincent classifies the fractures A-E, with Type A fractures being two closed diaphyseal fractures. Type B injuries are composed of two closed fractures with one being diaphyseal and the other metaphyseal; Type C injuries include two closed fractures with one being diaphyseal and the other epiphyseal; Type D injuries have at least one open fracture, and Type E fractures are composed of both fractures open.

Bohn-Durbin classification has three types; Type I are double shaft fractures, Type II injuries are juxta-articular, and Type III have an epiphyseal component.

Fraser et al. further classify floating knee injuries as Type I: shaft fractures of both bones without the involvement of either fracture into the knee, Type II fractures extended into the knee and were further sub-divided. Type IIa involved the tibial plateau, Type IIb included the distal femur into the knee, and type IIc involved both the tibial plateau and the distal femur within the knee joint.