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Early Results of the Less Invasive Stabilization System for Mechanically Unstable Fractures of the Distal Femur (AO/OTA Types A2, A3, C2, and C3)

Weight, Mark MD; Collinge, Cory MD

Original Article

Objectives: Historically, mechanically unstable fractures of the distal femur have been difficult to treat. Problems such as varus collapse, malunion, and nonunion frequently resulted before fixed-angle plates and indirect reduction techniques were popularized. More recently, the Less Invasive Stabilization System®, or LISS (Synthes, Paoli, PA), has been designed to combine these 2 approaches with the intended goals of achieving adequate stable fixation and early healing. Early clinical results for the femoral Less Invasive Stabilization System® have been promising. The purpose of this study is to evaluate the clinical results of patients with high energy, mechanically unstable fractures of the distal femur treated with the Less Invasive Stabilization System®.

Design: Retrospective analysis of a treatment protocol, consecutive patient series.

Setting: Busy level II trauma center.

Patients /Participants: Twenty-six patients with 27 high-energy AO/OTA types A2, A3, C2, and C3 fractures of the distal femur.

Intervention: Treatment with indirect fracture reduction and internal distal femoral fixation using the Less Invasive Stabilization System®.

Main Outcome Measurements: Clinical and radiographic assessment.

Results: Twenty-one patients with 22 fractures were available for evaluation at an average 19 months postinjury (range 12–35 months). The mechanism of injury included 12 motor vehicle collisions, 4 high falls, 5 motorcycle crashes, and 1 bicyclist struck by a car. Twenty patients had associated injuries. Six fractures were open. All fractures were comminuted; according to the AO/OTA fracture classification there were 4 A2, 3 A3, 12 C2, and 3 C3 fractures. All fractures healed without secondary surgeries at a mean of 13 weeks (range 7–16 weeks). There were no cases of failed fixation, implant breakage, or infection. Average joint line orientation relative to the femoral shaft axis (valgus) measured 99° on postoperative radiographs and 99° on final radiographs. A comparison of postoperative to healed final radiographs for each femur demonstrated no case with greater than a 3° difference in either varus or valgus. Complications included 1 mal-union where the fracture was fixed in 8° of valgus and 2 cases of external rotation between 10° and 15°. Painful hardware occurred in 4 patients, of which 3 underwent implant removal. The average knee range of motion was 5° to 114°.

Conclusions: The Less Invasive Stabilization System® allows for stable fixation and facilitates early healing in mechanically unstable high-energy fractures of the distal femur. There were no patients with fixation failure, varus collapse, or nonunion in this “at-risk” population. This treatment safely allows for immediate postoperative initiation of joint mobility and the progression of weight bearing with early radiographic signs of healing.

From the Harris Methodist Hospital-Fort Worth and Fort Worth Affiliated Hospitals/John Peter Smith Orthopaedic Surgery Residency, Fort Worth, TX.

Accepted for publication April 28, 2004.

The implants discussed in this manuscript have been 510K approved by the US Federal Drug Administration.

No direct financial or other support has been provided to the authors from the makers of the implants discussed in this manuscript.

Reprints: Cory Collinge, MD, 800 5th Street, Suite 500, Fort Worth, TX 76104 (e-mail:

© 2004 Lippincott Williams & Wilkins, Inc.