Fixation of periprosthetic femur fractures with the less invasive stabilization system (LISS) - a new minimally invasive treatment with locked fixed-angle screws

The Less Invasive Stabilization System (LISS) is a minimally invasive technique indicated for fixation of periprosthetic fractures. This new system allows percutaneous placement of cortical-shaft screws and fixation of the facture with fixed-angle locked screws with minimal surgical exposure of the mostly osteoporotic bone and without disturbance of the existing total joint replacement. Immediate range-of-motion excercises are begun postoperatively. A retrospective clinical review of 5 patients (2 total hip arthroplasties, 3 total knee arthroplasties) was performed to describe indications, surgical technique, intra- and postoperative complications and patient follow-up. Indications are periprosthetic distal femur fractures, per- and supracondyiar fractures. Contraindications are none, except existing medical comorbidities. Extraarticular fractures were treated via stab incisions over the lateral femoral condyle. Fractures with intraarticular displacement were fixed via an anterolateral parapatellar approach to the knee joint. After anatomic reduction of femoral condyles, articular fragments are fixed with Kirschner wires, followed by closed reduction aligning the articular fragments controlling length, axis and rotation. The LISS is introduced proximally under the M. vastus lateralis along the femur. It is fixed with self-drilling cortical shaft screws, locked fixed-angle screws both proximally and distally. Range-of-motion exercises are begun on the second day postoperatively. Time to full weight bearing averaged 6-8 weeks depending on clinical and radiological findings. Benefits of the LISS technique include the minimally invasive approach with increased primary stability using monocortical fixings thus eliminating the need for spongiosaplasty and blood transfusion. Disadvantages of the percutaneous placement of the LISS include malplacement on the femur, proximal screw pull-out and postoperative rotational and axial malalignment.