Floating knee: a modified Fraser's classification and the results of a series of 28 cases

This work aims to design a modified Fraser's classification and report the clinical outcomes of a series of 28 floating knees.

Between January 2006 and December 2009, 31 consecutive patients with 31 floating knees were treated at the Affiliated Hospital of Nantong University. In total, 28 cases were available for analysis. The floating knees were classified based on a modified Fraser's classification. Twelve cases were temporarily stabilised by an external fixator. Definitive fixation was performed for tibia and femur fractures using either nailing or plating. Functional outcomes were assessed according to the criteria established by Kalstrom and Olerud. The patients were followed up for a mean of 29 months (range, 12-60 months).

The floating knees were classified as three types: type I, extra-articular fracture; type II, articular surface involved; and type III, patella involved. Type II injuries were subdivided into type IIA injury (articular simple) and type IIB injury (articular complex). According to the modified classification, there were 11 cases of type I, 2 cases of type IIA, 8 cases of type IIB and 7 cases of type III injury. Complications were found in seven cases, including three cases of infection, two cases of knee instability and two cases of knee stiffness. The functional outcomes were 7 excellent, 13 good, 5 acceptable and 3 poor. The excellent or good rate was 91% (10/11) in type I, 100% (2/2) in type IIA, 63% (5/8) in type IIB and 43% (3/7) in type III injuries.

The modified Fraser's classification provides a more reliable basis for surgeons to monitor results and compare treatment results with other surgeons. According to the modified classification, the results of type IIA injury appeared to be comparable to those of type I injury. Type IIB and type III injuries represent the fracture types with the worst prognosis.