Pilot for Dual Implant Versus Single Implant Distal End of Femur (pDISIDE Femur)

The incidence of distal femur fractures in elderly patients continues to increase, most recently having an incidence of 8.7/100,000/year. This trend likely accompanies the aging population and the increased rates of knee arthroplasty. While these fractures are far less common than geriatric hip fractures, distal femur fractures present similar treatment challenges. Elderly distal femur fractures tend to occur in compromised hosts with poor bone mineral density. Similar to geriatric hip fractures, care emphasizes early mobilization to avoid the complications associated recumbency, including pneumonia, pressure sores, and venous thromboembolism. These patients are often unable to mobilize with restricted weight bearing, which places significant stress on the fixation construct. As a result, elderly patients with distal femur fractures can have high rates of morbidity and mortality.

Despite several prior studies reporting one year mortality greater than 20%, elderly distal femur fractures do not receive the same attention as geriatric hip fractures. These patient injuries are likely similar in terms of their age and comorbidities while having the same issues with post-operative mobility. Therefore, it makes sense that geriatric distal femur fracture patients and geriatric hip fracture patients have similar mortality rates. Investigators recently reported significantly greater in-hospital mortality in geriatric distal femur fractures as compared to geriatric hip fractures. A recent study of the US Medicare database is the largest study on geriatric distal femur fractures in the literature, and the overall mortality of 18.5% is similar to several prior studies ranging from 13-38%.

Distal femur fractures have traditionally been treated with operative fixation using either a lateral plate or an intramedullary nail. Advances in plate and nail technology allow for distal femur fractures to be stabilized with minimal soft tissue dissection. While recent studies suggest that early weight bearing can be tolerated with low failure rates, many surgeons continue to institute weight-bearing restrictions for osteopenic patients treated with operative fixation. Nonunion rates for operatively treated distal femur fractures have been reported to be as high as 20% in large series, leading to additional surgery to achieve union. These limitations with operative fixation have led surgeons to investigate the utility of supplementing the fixation with additional plates and/or nails.

Since many surgeons may not allow early weight bearing in osteopenic patients with operatively treated distal femur fractures, dual plating of the distal femur and locked plate/IMN combinations have become increasingly popular. Biomechanical studies have demonstrated increased torsional stiffness and axial stiffness in dual plate and plate/nail constructs as compared to single implant. A recent meta-analysis by other investigators has further demonstrated dual implants for distal femur fractures to have a low complication rate (5% nonunion) as compared to prior evidence of single implant fixation (0-25% nonunion).

In the recent study, authors reported a trend toward less one year mortality in patients treated with distal femoral replacement (DFR) (13.8%) as compared to operative fixation (22.6%) despite finding similar mortality rates at 90 days post-operatively. Since the complication rate was significantly greater in the DFR cohort, this one year mortality benefit is presumably related to early patient weight bearing after DFR that may not be permitted as frequently with operative fixation. Additionally, patients with a DFR may achieve more early mobility than operatively treated patients who are permitted immediate weight bearing due to enhanced stability in the DFR construct. Using dual implants to treat distal femur fractures may allow patients to achieve early mobility and similar mortality as a DFR patients, but have fewer post-surgical complications and less cost than a DFR.