Use of the Less Invasive Stabilization System (LISS) in patients with distal femoral (AO33) fractures:: a prospective multicenter study

Introduction The Less Invasive Stabilization System (LISS) is an internal fixator that can be inserted percutaneously by means of a minimally invasive surgical approach. This paper presents the use of this system exclusively in patients with AO33 distal femoral fractures, a group in which fracture management is often complicated by multiple trauma and soft-tissue damage. Materials and methods A series of 62 patients (mean age 52 years) with 66 AO33A or C fractures received the LISS implant and were followed prospectively for 12 months. Assessments included the radiographic evaluation of implant placement and healing, measurement of valgus/varus and sagittal joint malalignment, and the assessment of weight-bearing capacity and range of motion. Results The mean duration of surgery was 85 min (range 40-135 min) for 33A fractures and 149 min (range 50-300 min) for 33C fractures. Postoperative radiographic assessments showed that the LISS implant was positioned correctly in 59 cases (89%). Assessment of valgus/varus alignment showed correct axial alignment in 49 cases (74%), a deviation of 5-10 degrees in 13 cases, and a 10-20 degrees deviation in 1 case. Correct sagittal alignment was observed in 56 cases (85%), 5-10 degrees malalignment in 5 cases, and 10-20 degrees in 2 cases. During the course of the 1-year follow-up, 8 patients (9 fractures) died; 2 other patients were not available for follow-up. Complete fracture healing was achieved in 85% of the followed-up patients. Forty-eight patients were capable of full weight-bearing. After fracture healing, maximum flexion of the injured limb was on average 80% of the range of the uninjured limb. An extension deficit of more than 5 degrees was measured in 3 cases. Of the 62 patients, 14 underwent further operations during the course of follow-up. Of these, 6 required bone grafting and 3 refixation of the implant due to implant loosening. Deep infections requiring several debridements occurred in 2 patients. No complications relating solely to the implant were observed. Conclusion The LISS showed good overall results in the treatment of these difficult fractures. It is a good alternative to conventional extramedullary and intramedullary stabilizing techniques, especially in more complex fracture situations.