Fixation of distal femoral fractures with the Less Invasive Stabilization System: a minimally invasive treatment with locked fixed-angle screws.

Background: The Less Invasive Stabilization System (LISS) is an internal fixator, which combines closed reduction of the diaphysis or metaphysis of distal femur fractures with locked unicortical screw fixation.

Methods: In a retrospective consecutive study, 50 patients with Association for the Study of the Problems of Internal Fixation/Orthopaedic Trauma Association (AO/OTA) type 33-A1 to 33-C3 fractures were treated with the LISS between January 1999 and December 2003. Final results were assessed using the functional score of Neer after a median follow-up of 29 months (15-48 months).

Results: Fifteen male and 16 female patients were followed up. The mean age was 49 years (17-90 years). Deep wound infection was seen in one patient (3%) and malpositioning with cutting-out of the proximal screws was in two patients (6%). All other fractures healed uneventfully without bone graft requirements after a mean of 12 weeks (7-20 weeks). A revised osteosynthesis was performed for correction of a valgus deformity of 20 degrees after 4 months. There was no difference in leg length exceeding 2 cm. One patient had a valgus deformity of 10 degrees combined with a rotational deformity of 10 degrees. Range of motion of the knee joint was >120 degrees in 15 patients (48%); 12 (39%) had a range of motion between 90 degrees and 120 degrees and 4 (13%) between 70 degrees and 90 degrees. The function according to the Neer score was excellent in 15 (48%), good in 10 patients (32%), and fair in 6 patients (20%). The mean Neer score was 80 (60-100).

Conclusions: The LISS promotes early mobilization and rapid rates of bony and clinical healing without bone grafting with low rates of infection.