PURPOSE OF THE STUDY

Simultaneous ipsilateral femoral and tibial fractures cause a floating knee. Treatment of such patients is complicated by fat-embolism syndrome (12 per cent), local soft tissue damage, ipsilateral knee ligament tear (5 to 39 per cent) and delayed shortening or torsional deformity. Our study aimed to determine the frequency of complaints about the knee and to study the causes of malunion.

MATERIAL AND METHODS

Twenty-four patients with floating knee were treated between 1987 and 1992. Comminution was assessed according to Winquist et al. Associated soft tissue damage was assessed according to Gustilo et al. The grade III open fractures were always treated by external fixation. Intra-medullary nailing was always performed after reaming.

RESULTS

One patient died and eighteen were reviewed. Fat-embolism syndrome occurred in three cases, one superficial infection occurred in femoral plating, nine deep infection occurred in tibial fracture: 7 for grade II and III open fracture treated by external fixation and one after nailing of a grade I open fracture. Malunion occurred in five patients: 2 shortening, 2 external rotational femoral deformity of 15 and 35 degrees, one shortening associated with external rotational femoral deformity of 30 degrees. Error in comminution evaluation was the leading cause of these malunions. Non-union occurred in 2 femoral and one tibial fracture. These complications were treated by decortication and osseous grafting. Four patients had a late diagnosis of ipsilateral ligamentous injury: antero and posterior in three and lateral isolated in one. Eighteen patients were reviewed. Results were excellent in 4, good in 7 and poor in 7. The seven poor results were: 1 amputation, four patients with ligamentous injury and 2 of the 5 malunions.

DISCUSSION

Clinical evidence of fat embolism has been reported after reaming of fractured long bones. Reaming led to an increase in pulmonary artery pressure and in pulmonary free fatty acids. Reaming in the same time femoral and tibial diaphysis increased this kind of complication. We performed femoral and tibial fixation during the same operating time: first the femur and after the tibia. Tibial open grade III fractures were fixed first by external fixation. Ipsilateral femoral and tibial nailing increase malunion: shortening and rotational malunion. This problem can be reduced but not eliminated by using locking nails: the error was established during the operation. Distal femoral fraction gives better torsional control. Fractures in the distal segment of the femur are particularly prone to the development of axial malignement. In this series, malunion occurred in three cases. Knee effusion in patient with ipsilateral femoral and tibial fracture should not be ignored. It may indicate meniscal or articular pathology, or ligament disruption. If there is suspicion of ligament injury, a supracondylar femoral fraction is recommended for nailing. After femoral and tibial fixation, the knee must be examined clinically. Early surgical repair of peripheral tears is advocated. Repair of an anterior or posterior ligament without proximal or distal avulsion may not be warranted.

CONCLUSION

Simultaneous ipsilaterla femoral and tibial fracture, or so called floating knee, occurs in patients who are involved in a high-velocity injury. Knee instability is however the major cause of poor results.