Distal Femur Intraarticular Fracture in a Late Arthritic Knee Treated with Osteosynthesis and Computer Navigation Assisted Primary Total Knee Replacement: A Case Report

Abstract 

The incidence of osteoporosis and osteoarthritis is on the rise. What further complicates the scenario is a stress fracture in a weight-bearing joint such as a knee in the presence of arthritis, making the treatment challenging. Prolonged immobilization associated with osteosynthesis increases morbidity and mortality in elderly patients. Primary total knee arthroplasty (TKA) has been advocated as a treatment modality in patients with distal femoral fractures who already have painful arthritic knees. Most of these injuries get treated using a hinged prosthesis. However, there are concerns about the high rate of loosening and mechanical failure of this type of prosthesis. This report presents a distal femur intraarticular fracture nonunion in the late arthritic knee, which is a rare presentation as proximal tibia stress fractures are more common. This was treated with osteosynthesis, and computer navigation assisted primary total knee replacement using medial pivot knee in a 54-year-old male with a body mass index of 38. Based on clinical and radiographic evidence, primary total knee replacement and plate osteosynthesis are viable options for distal femur fractures with osteoarthritis using computer navigation. While limiting the number of procedures, it meets two prerequisites: early weight bearing, limiting decubitus-related complications, and early mobilization leading to patient autonomy.

Introduction 

Distal femur fractures in the elderly can occur even after low-energy trauma in patients with knee osteoarthritis. Pre-existing osteoporosis makes the treatment difficult compared to the younger population. Internal fixation is usually tricky due to osteoporosis and metaphyseal comminution. In such patients coexisting osteoarthritis of the knee complicates the issue further as the knee joint remains painful with impaired knee function even after the union. Prolonged immobilization associated with osteosynthesis increases morbidity as well as mortality in elderly patients. Stress fractures are overuse injuries of the bone. Stress fractures in the elderly are mainly due to osteoporosis, post-traumatic deformity, deformed degenerated knees, and post-knee arthroplasty. Treatment of stress fracture secondary to osteoarthritis is especially challenging because malalignment secondary to arthritic deformity leads to undue stress at the fracture site, which prevents union, fixation failure, rapid progression of arthritis, and stiffness. Concomitant osteoporosis makes the management even more difficult. The issue in treating such a patient is difficult or even impossible to achieve a stable bone reconstruction using osteosynthesis due to osteoporosis and the necessity for early functional recovery. Surgical options for these patients are Osteosynthesis in the first stage, followed by total knee arthroplasty in 2nd stage; Total knee replacement with stem extensions, and osteosynthesis in a single stage.