Session IV - Femur

Prospective Clinical Trial of the Less Invasive Stabilization (L.I.S.S.) for Supracondylar Femur Fractures

Philip J. Kregor, MD; James P. Stannard, MD; Peter A. Cole, MD; Michael Zlowodski, MD; Jorge A. Alonzo, MD, University of Mississippi Medical Center, Jackson, MS

Purpose: The Less Invasive Stabilization System (L.I.S.S.) is currently in clinical trials for treatment of A.O./O.T.A. 33A and 33C distal femoral fractures. Its characteristics include an outrigger device that allows percutaneous placement of self-drilling cortical shaft screws, locked fixed-angle screws both proximally and distally, and the ability for submuscular fixator placement. A prospective clinical review of patients with supracondylar and supracondylar/ intracondylar femur fractures treated with the L.I.S.S. was performed to define the efficacy, indications, advantages/disadvantages, and complications associated with its use.

Methods: A prospective database was established for review of patients treated with the L.I.S.S. From 4/97 until 3/99, all patients at two university Level I trauma centers with A.O./ O.T.A. 33 A1-A3 and 33 C1-C3 were treated with the L.I.S.S. In addition, it has been utilized in very distal A.O./O.T.A. 32 fractures. Patient demographics, fracture characteristics, surgical technique, and patient follow-up are being documented in an ongoing study. Sixty-one patients with an average follow-up of 6 months (1-22 months) have been studied.

The surgical technique is based on traditional anatomic reduction of the articular surface (if applicable), closed manipulation of the metaphyseal/diaphyseal component of the fracture, submuscular sliding of the L.I.S.S. fixator without disturbance of the metaphyseal/diaphyseal soft-tissue fracture environment, and percutaneous shaft screw placement.

Results: Sixty-two acute fractures (24 right, 38 left) in 61 patients (31 F, 30 M) were treated with the L.I.SS.. Of the 62 fractures, there were 4 periprosthetic fractures above total knee arthoplasties, and 1 pathologic fracture. Twenty-eight patients had isolated injuries. The average age of the patients was 50 years (18-90), with a bimodal distribution: 39 patients < 60 years, and 22 patients > 60 years. The mechanism of injury was: 28 motor vehicle collisions, 18 falls, 6 pedestrian versus motor vehicles, 5 ballistic injuries, and 2 motorcycle accidents. 48 A.O./O.T.A. 33, 5 A.O./O.T.A. 32 (distal femoral shaft), and 9 combined A.O./O.T.A. 33/32 fractures were treated. Of the 57 A.O./O.T.A. 33 injuries, there were 4 A1, 7 A2, 14 A3, 7 C1, 9 C2, and 16 C3 fractures. Twenty-one open (2 Gustilo Grade I, 9 Grade II, and 9 Grade IIIA, and 1 Grade IIIB), and 41 closed fractures were treated. Primary fixation within 24 hours of the injury was performed in 22 cases, and provisional stabilization with splinting or spanning external fixation was performed in 40 cases. The surgical approach utilized was: 33 standard anterolateral, 22 lateral parapatellar approach, 4 extension of traumatic wounds, and 3 formal lateral approach. Twenty-nine 13-hole, thirty 9-hole, and three 5-hole fixtures, with 3-6 proximal screws, and 4-7 distal screws were utilized. One acute bone grafting was performed for significant metaphyseal bone loss. Average surgical time was 200 minutes, with average time for placement of the LISS fixator of 59 minutes.

There were eight cases of malposition (5 anterior, 3 posterior) of the fixator on the exact lateral aspect of the femoral shaft. In three cases this was deemed clinically unacceptable, and was changed intra-operatively. Intra-operative complications included one broken K-wire. Postoperative reductions revealed deformities of: hyperextension > 5 degrees in 4 cases, valgus deformity > 5 degrees in 2 cases, shortening > 1 cm in 3 cases (1 desired shortening), and an external rotation deformity > 10 degrees in 2 cases.

Fracture complications include nine cases of decreased range-of-motion requiring surgical intervention (5 Judet quadriceptoplasties, 3 arthroscopic debridements, and 1 manipulation under anesthesia). Most of these cases were characterized by exuberant metaphyseal callus formation. With one bone grafting performed at 5 months, all fractures healed, with an average time to full weight bearing of 13 weeks. One acute infection, and one infection at the time of bone grafting were encountered. Average range-of-motion was 3 degrees (range -5 to 30) of extension, to 110 (range 70-135) of flexion. One failure of fixation via proximal screw pullout, and two cases of proximal screw loosening were seen. No cases of varus collapse and/or distal femoral condyle screw loosening was seen.

Discussion: Surgical treatment of supracondylar/intracondylar distal femoral fractures (33 A and C) remains a significant surgical challenge, with high complication rates. Adverse events include infection, decreased range-of-motion, need for bone grafting, malunion, and nonunion. Emphasis on preservation of osseous vascularity utilizing indirect reduction techniques has led to increased union rates without bone grafting. (1) Recent advances in submuscular plate applications utilizing existing plate constructs appear to offer considerable advantages, especially with regard to lowering infection and need for bone grafting. (2) A particular clinical problem is loss of fixation of the distal femoral fragment, especially in osteoporotic bone and/or with use of the condylar buttress plate. Loss of distal fixation and/or toggling of distal screws can lead to varus angulation and/or fracture fixation failure. Different modalities have been utilized to combat fixation failure in the distal femoral fragment. Recently, the L.I.S.S. (Less Invasive Stabilization System) internal fixation system has been developed to provide multiple, fixed-angle locked screws, and can be best thought of as an"internal" external fixator. An advantage of the submuscular plating, especially in 33 C3 fractures, is the ability to use the lateral parapatellar approach to optimally visualize the articular surface and slide the plate in a submuscular manner.

Significant and early callus formation was observed in the fractures analyzed. This may contribute to decreased knee motion. Early surgical intervention was performed in an attempt to maximize eventual range-of-motion. Eventual range-of-motion was limited in a select group of patients (n=9), who were characterized by delayed reconstruction secondary to multi-system trauma, associated extensor mechanism injury, head injury, and/or infection (n=1). Postoperative reduction quality was acceptable and may be improved with further refinement of closed reduction techniques and/or reduction aids. Of particular note, no loss of fixation in the distal femoral condyles was observed, despite the treatment of 22 patients older than 60 years.

Conclusion: L.I.S.S. stabilization of distal femoral fractures utilizing closed reduction techniques for the shaft component is associated with acceptable union rates and eventual range-of-motion. Advantages appear to include high union rates without bone grafting (97%), low infection (3%), and maintenance of distal femoral fixation (100%) in a population characterized by either high-energy trauma or low-energy trauma in osteoporotic patients. Disadvantages may include decreased range-of-motion secondary to excessive metaphyseal callus formation and difficulties with closed reduction techniques.

References: 1. Bolhofner BR, et al. Journal of Orthopaedic Trauma 10(6): 372-7, 1996. 2. Krettek C, et al. Injury Supplement(I): 20-30, 1997.